the euteleostei or euteleosts is a clade of bony fishes within the teleostei that evolved some 240 million years ago .

it is divided into the protacanthopterygii ( including the salmon and dragonfish ) and the neoteleostei ( including the lanternfish , lizardfish , oarfish , and the acanthopterygii ) .

the cladogram is based on near et al. ( 2012 ) and betancur-rodriguez et al. 2016 .

they explored the phylogeny and divergence times of every major lineage , analysing the dna sequences of 9 unlinked genes .

they calibrated ( set actual values for ) branching times in this tree from 36 reliable measurements of absolute time from the fossil record .

euteleostei

( 27 ) euteleostei . mrca : lepidogalaxias , takifugu . hard minimum age : 149 ma . 95 % soft maximum age : 260 ma . prior setting : uniform distribution ( crown calibration ) . calibration source : broughton et al . [ 2 ] .
davis mp . evolutionary relationships of the aulopiformes ( euteleostei : cyclosquamata ) : a molecular and total evidence approach . in : nelson js , schultze hp , wilson mvh , editors . origin and phylogenetic interrelationships of teleosts . 2010 . münchen , germany : verlag dr . friedrich pfeil . pp . 317 - 336 .
with regard to the relationships of early euteleosts , our phylogenetic analyses support several results from previous molecular studies and a new result that places galaxiidae as the sister lineage of neoteleostei ( without stomiiforms ) [ bs = 95 % , bpp = 1 . 00 ( fig . 1 , and figs . s1 and s2 ) ] . lineages previously treated as “protacanthopterygians” ( 3 ) are polyphyletic in the molecular phylogeny because the alepocephaliforms ( slickheads ) are resolved in a clade containing clupeomorphs ( anchovies and herrings ) and ostariophysians ( catfish and minnows ) [ bs = 94 % , bpp = 1 . 00 ( 21 , 33 ) ] , the enigmatic freshwater australian species lepidogalaxias salamandroides is the sister lineage to all other euteleostei ( 15 , 23 ) [ bs = 100 % , bpp = 1 . 00 ( fig . 1 , and figs . s1 and s2 ) ] , salmonids ( trouts and salmon ) and esociforms ( pikes and mudminnows ) are resolved as a clade [ bs = 100 % , bpp = 1 . 00 ( 21 , 23 ) ] , and there is strong support for a clade containing stomiiforms ( dragonfishes ) , osmeriforms ( smelts ) , and retropinnids ( southern smelts ) [ bs = 100 % , bpp = 1 . 00 ( 23 ) ] . although most of these relationships were reflected in the species tree , lepidogalaxias was resolved as the sister lineage of galaxiidae ( fig . s3 ) . however , only one of the two gene trees ( rag1 ) that sampled both lepidogalaxias and galaxiidae resolved these lineages as sharing a common ancestor . the phylogenetic resolution of these early euteleost lineages using morphology is thought to have been hampered by a mosaic of highly modified and ancestral character states ( 3 , 13 ) . the relationships inferred in our trees provide a phylogenetic framework to investigate the evolution of morphological character state changes , which have proven difficult to use in the inference of relationships among early diverging euteleost lineages ( e . g . , ref . 34 ) .
edited by david m . hillis , university of texas , austin , tx , and approved july 19 , 2012 ( received for review april 22 , 2012 )
ray - finned fishes make up half of all living vertebrate species . nearly all ray - finned fishes are teleosts , which include most commercially important fish species , several model organisms for genomics and developmental biology , and the dominant component of marine and freshwater vertebrate faunas . despite the economic and scientific importance of ray - finned fishes , the lack of a single comprehensive phylogeny with corresponding divergence - time estimates has limited our understanding of the evolution and diversification of this radiation . our analyses , which use multiple nuclear gene sequences in conjunction with 36 fossil age constraints , result in a well - supported phylogeny of all major ray - finned fish lineages and molecular age estimates that are generally consistent with the fossil record . this phylogeny informs three long - standing problems : specifically identifying elopomorphs ( eels and tarpons ) as the sister lineage of all other teleosts , providing a unique hypothesis on the radiation of early euteleosts , and offering a promising strategy for resolution of the “bush at the top of the tree” that includes percomorphs and other spiny - finned teleosts . contrasting our divergence time estimates with studies using a single nuclear gene or whole mitochondrial genomes , we find that the former underestimates ages of the oldest ray - finned fish divergences , but the latter dramatically overestimates ages for derived teleost lineages . our time - calibrated phylogeny reveals that much of the diversification leading to extant groups of teleosts occurred between the late mesozoic and early cenozoic , identifying this period as the “second age of fishes . ”
ray - finned fishes ( actinopterygii ) are one of the most successful radiations in the long evolutionary history of vertebrates , yet despite the rapid progress toward reconstructing the vertebrate tree of life , only 5 % of the ray - finned fish phylogeny is resolved with strong support ( 1 ) . actinopterygii contains more than 30 , 000 species ( 2 ) , with all but 50 being teleosts ( 3 ) . compared with other large vertebrate radiations , such as mammals ( 4 ) or birds ( 5 ) , a general consensus on the phylogenetic relationships and timing of diversification among the major actinopterygian and teleost lineages is lacking ( 3 , 6 , 7 ) . this uncertainty about relationships has prevented the development of a comprehensive time - calibrated phylogeny of ray - finned fishes , which is necessary to understand macroevolutionary processes that underlie their diversity .
) , and unlike other clades of vertebrates , there has been no comprehensive effort to resolve the phylogeny of actinopterygians and teleosts using molecular data that sample multiple nuclear genes and include taxa that span the major lineages . despite the long history of using morphological data in the phylogenetics of ray - finned fishes , there are several areas of uncertainty and disagreement regarding some of the most fundamental relationships . first , there are two competing hypotheses on the phylogenetic relationships that reflect the earliest diversification of teleosts : either the osteoglossomorpha [ bony tongues (
) ] are the sister lineage of all other teleosts . second , the relationships of lower euteleosts ( e . g . , salmons , smelts , pikes , slickheads , and galaxiids ) , or “protacanthopterygians , ” has changed frequently as a result of phylogenetic analyses of different morphological datasets (
) to label the percomorpha as the “bush at the top of the [ teleost ] tree . ”
applications of molecular data to these three long - standing questions in teleost phylogenetics have yielded mixed results . for example , analyses of nuclear and mtdna gene sequences have supported all three possible relationships among osteoglossomorphs , elopomorphs , and all other teleosts [ i . e . , clupeocephalans (
we investigated phylogenetic relationships and divergence times of all major lineages of actinopterygii and teleostei using dna sequences of nine unlinked protein - coding nuclear genes sampled from 232 species . we used 36 well - justified absolute time calibrations from the fossil record of ray - finned fishes in relaxed - molecular clock analyses to estimate divergence times . phylogenies resulting from these analyses were well resolved , the majority of phylogenetic inferences were supported with strong node support values , were robust to inferences using new “species tree” methods , and provide a comprehensive molecular perspective on areas of long - standing disagreement and uncertainty in the relationships of teleost fishes . divergence times estimated from relaxed - molecular clock analyses yield a comprehensive time - scale of actinopterygian diversification that is remarkably close to ages inferred from the fossil record .
maximum - likelihood analyses of the nine nuclear gene dataset resolved 89 % of the 232 nodes in the actinopterygian phylogeny with bootstrap replicate scores ( bs ) ≥70 % and the phylogenies inferred using the bayesian method had 91 % of the nodes strongly supported posterior probabilities ( bpp ) ≥ 0 . 95 ( fig . 1 , and figs . s1 and s2 ) . relationships of nonteleostean actinopterygians were consistent with traditional morphologically - based inferences ( 6 ) with polypterids ( bichirs and ropefish ) resolved as the sister lineage of all other actinopterygians ( actinopteri ) in the relaxed - clock analysis ( fig . 1 ) . in addition , acipenseriformes ( sturgeons and paddlefishes ) were the sister lineage of neopterygii with strong support ( bs = 100 % , bpp = 1 . 00 ) , and holostei ( bowfin and gars ) was resolved as the sister lineage of teleosts [ bs = 100 % , bpp = 1 . 00 ( fig . 1 , and figs . s1 and s2 ) ] . these results contrast with earlier molecular studies that either resolved acipenseriforms and holosteans as an “ancient - fish” clade ( 31 ) or acipenseriforms and polypteriforms as a weakly supported clade ( 32 ) .
actinopterygian time - calibrated phylogeny based on nine nuclear genes and 36 fossil age constraints . bars represent the posterior distribution of divergence - time estimates . gray bars identify nodes supported with bpp ≥ 0 . 95 , and white bars mark nodes with bpp < 0 . 95 . nodes with age priors taken from the fossil record are marked with a “c . ” for full details on calibration see materials and methods and fig . s2 . the time - calibrated tree is scaled to the geological time scale with absolute time given in millions of years .
our results provide resolution to three of the most compelling questions in teleost phylogenetics . the molecular phylogeny resulted in the strongly supported position ( bs = 97 % , bpp = 1 . 00 ) of elopomorphs as the sister lineage of all other teleosts ( fig . 1 , and figs . s1 and s2 ) . this result is also strongly supported in a species tree analysis , which accounts for potential discordance among individual gene histories , with a bootstrap proportion of 100 % ( fig . s3 ) . evidence for osteoglossomorpha as the sister lineage of all other teleosts was based on the presence of a single character state in the caudal fin skeleton ( 9 , 10 ) . on the other hand , the hypothesis that elopomorpha is the sister lineage of all other teleosts was based on eight derived character - state changes identified from optimization of a matrix containing 135 discretely coded morphological characters ( 11 ) . our results strongly support the latter hypothesis , illustrating agreement between phylogenetic inferences from a robust morphological data matrix and our densely sampled nuclear gene dna sequence dataset .
one of the most important problems in vertebrate phylogenetics is the resolution of the major lineages of percomorpha . the phylogeny confirms several results presented in previous molecular analyses , including the resolution of ophidiiforms ( cusk eels ) and batrachoidids ( toadfish ) as early diverging percomorphs (
posterior distribution of molecular age estimates and patterns of calibration sharing across studies of ray - finned fish phylogeny . ( a ) posterior distribution of molecular age estimates , in millions of years , for 14 actinopterygian lineages , resulting from analyses of whole mtdna genomes ( blue ) , the rag1 nuclear gene ( orange ) , the rag1 nuclear gene using the calibrations from this study ( yellow ) , and the nine nuclear gene dataset presented in this study ( green ) . the circle represents the mean of the posterior estimate and the whiskers mark the upper and lower 95 % highest posterior density of the age estimates . gray boxes mark the oldest fossils for a given lineage , those with dashed lines were used as calibration age priors ( see materials and methods ) and those with solid black lines were not used as age calibrations . line drawings of ray - finned fish species are based on photographs of specimens housed at the peabody museum of natural history , yale university , new haven , ct . ( b ) frequency of calibrations shared between this study and those using whole mtdna genomes ( blue ) and the rag1 nuclear gene ( orange ) binned by the age of the fossil calibration in millions of years ( ma ) .
despite the apparent gap in the fossil record for early crown–group teleosts , we find that most major teleost lineages originated in a period spanning the late mesozoic into the early cenozoic ( figs . 1 and 2 a ) , which corresponds to patterns apparent in the fossil record ( 39 ) . we identify this interval as the “second age of fishes . ” the devonian age of fishes is characterized by the presence of all major vertebrate lineages referred to as “fishes , ” both living and extinct [ e . g . , ostracoderms , placoderms , acanthodians , chondrichthyans , and so forth ( 40 ) ] . although this period in time appears to mark the origin of crown actinopterygii ( figs . 1 and 2 a ) , it does not correspond to the divergence of the major lineages that comprise the bulk of living actinopterygian biodiversity . instead , the second age of fishes represents the interval in geologic time where these species - rich lineages ( e . g . , otophysians and acanthomorphs ) originated and eventually flourished , becoming the dominant vertebrate component of marine and freshwater habitats .
ray - finned fishes include half of the entire species richness of vertebrates ( 2 , 3 ) , but had ranked last , by a wide margin , in the degree of phylogenetic resolution offered by available dna sequence and genomic resources ( 1 ) . our phylogeny , based on a multilocus dataset , provides robust resolution and strong support across all major lineages of ray - finned fishes and teleosts . additionally , our divergence time estimates reconcile inferences from paleontology with those obtained from other studies that used molecular methods , providing a molecular time scale that is more consistent with ages implied by the fossil record . this comprehensive molecular perspective on the evolutionary diversification of one - half of all vertebrate species provides dna sequence data and calibration information from which to integrate resolution of clades at lower taxonomic levels ( e . g . , families ) and estimate ages of actinopterygian lineages that lack a fossil record .
standard phenol - chloroform extraction protocol or qiagen dneasy blood and tissue kits were used to isolate dna from tissue biopsies sampled from 232 ray - finned fish species ( table s2 ) . previously published pcr primers were used to amplify and sequence an exon from each of nine nuclear genes [ glyt , myh6 , plagl2 , ptr , rag1 , sh3px3 , sreb2 , tbr1 , and zic1 ( 22 , 41 ) ] . the genes were aligned by eye using the inferred amino acid sequences . no frame mutations or dna substitutions that resulted in stop codons were observed in the aligned dna sequences . the combined nine - gene dataset contained 7 , 587 base pairs .
twenty - seven data partitions were designated that corresponded to the three separate codon positions for each of the nine genes . a gtr + g substitution model was used in a portioned maximum - likelihood analysis using the computer program raxml 7 . 2 . 6 ( 42 ) run with the –d option . support for nodes in the raxml tree was assessed with a thorough bootstrap analysis ( option –f i ) with 1 , 000 replicates .
a species tree was inferred using gene tree parsimony implemented in the computer program igtp ( 43 ) . individual gene trees estimated using raxml were used as input files . several rooting strategies were used . the individual gene trees were rooted using erpetoichthys calabaricus or polypterus ornatipinnis , except in three cases when these species were not sampled for a specific gene . in these cases the individual gene trees were rooted using scaphirhynchus platorynchus , amia calva , or atractosteus spatula . a heuristic search using randomized hill climbing was performed to find the species tree that minimized the reconciliation cost for deep coalescence . this search was bootstrapped by performing it 100 times and bootstrap proportions for the resulting species trees were calculated using sumtrees in the dendropy package ( 44 ) .
for each fossil calibration prior , we identify the calibrated node in the ray - fin fish phylogeny , list the taxa that represent the first occurrence of the lineage in the fossil record , describe the character states that justify the phylogenetic placement of the fossil taxon , provide information on the stratigraphy of the rock formations bearing the fossil , give the absolute age estimate for the fossil , outline the prior age setting in the beast relaxed - clock analysis , and provide any additional notes on the calibration ( si text ) . each calibration is numbered and the phylogenetic placement of the calibration is highlighted in fig . s2 .
we thank t . - y . cheng and k . - t . shao of the biodiversity research museum , academia sinica ; j . friel of the cornell university museum of vertebrates ; p . a . hastings and h . j . walker of the scripps institution of oceanography ; k . p . maslenikov and t . w . pietsch of the burke museum of natural history and culture , university of washington ; and a . c . bentley and e . o . wiley of the biodiversity institute of the university of kansas for generous gifts of tissue specimens . j . s . albert , j . w . armbruster , l . bernatchez , t . m . berra , c . p . burridge , c . d . hulsey , s . lavoué , j . g . lundberg , m . miya , n . merret , p . j . unmack , k . watanabe , j . m . waters provided additional specimens ; c . m . bossu , r . c . harrington , p . r . hollingsworth , c . d . hulsey , b . p . keck , and the staff of the carribean research management of biodiversity biological research station in curaçao provided assistance in sampling expeditions ; gregory watkins - colwell assisted with museum collections . k . l . ilves provided insight on taxon sampling . this research was supported by the peabody museum of natural history and national science foundation grants deb - 0444842 , deb - 0716155 , deb - 0717009 , deb - 0732642 , ant - 0839007 , deb - 1060869 , deb - 1061806 , and deb - 1061981 ( to w . l . s . , p . c . w . , and t . j . n . ) ; and natural environment research council grant nerc ne / i005536 / 1 ( to m . f . ) .
author contributions : t . j . n . , r . i . e . , a . d . , j . a . m . , m . p . d . , p . c . w . , m . f . , and w . l . s . designed research ; t . j . n . , r . i . e . , a . d . , k . l . k . , p . c . w . , m . f . , and w . l . s . performed research ; t . j . n . , r . i . e . , a . d . , m . f . , and w . l . s . analyzed data ; and t . j . n . , r . i . e . , a . d . , j . a . m . , p . c . w . , m . f . , and w . l . s . wrote the paper .
data deposition : the sequence reported in this paper has been deposited in the genbank database ( accession no . jx190073 – jx191369 ) .
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researchers used field data from 2012 to 2015 to study mortality and allele frequency changes in the sea star pisaster ochraceus during a mass mortality event in northcentral california , and found that surviving adult and juvenile sea stars experienced 81 % mortality and allele shifts , according to the authors .
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a study of cognitive ability in norwegian males born from 1962 to 1991 suggests that environmental factors rather than changing genetic composition of families likely account for most of the change in norwegian population iq .
the mathematical tools behind recent gerrymandering cases have brought a modicum of precision into the political arena—but this rigor hasn’t always been enough to spur policy changes .
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betancur - r . r , broughton re , wiley eo , carpenter k , lópez ja , li c , holcroft ni , arcila d , sanciangco m , cureton ii jc , zhang f , buser t , campbell ma , ballesteros ja , roa - varon a , willis s , borden wc , rowley t , reneau pc , hough dj , lu g , grande t , arratia g , ortí g . the tree of life and a new classification of bony fishes . plos currents tree of life . 2013 apr 18 . edition 1 . doi : 10 . 1371 / currents . tol . 53ba26640df0ccaee75bb165c8c26288 .
department of biological sciences , the george washington university , washington , dc , usa .
oklahoma biological survey and department of biology , university of oklahoma , norman , ok , usa .
biodiversity institute and department of ecology & evolutionary biology , university of kansas , lawrence , ks , usa , biologist at the university of kansas .
department of biological sciences , old dominion university , norfolk , virginia , u . s . a . , international union for conservation of nature .
fishes , university of alaska fairbanks , fairbanks , alaska , united states of america , university of alaska museum .
key laboratory of exploration and utilization of aquatic genetic resources , shanghai ocean university , ministry of education , shanghai 201306 , china .
science division , johnson county community college , overland park , kansas , usa .
department of biological sciences , old dominion university , norfolk , virginia , usa .
department of biology and oklahoma biological survey , university of oklahoma , norman , oklahoma , usa .
department of biology and oklahoma biologcial survey , university of oklahoma , norman , ok , usa , ph . d . student .
department of biology and wildlife , university of alaska fairbanks , fairbanks , ak , usa .
department of biological sciences , the george washington university , washington , dc , united states .
department of biological sciences , george washington university , washington , dc , usa , research assistant .
school of biological sciences , university of nebraska - lincoln , lincoln , ne , usa .
biology , university of nebraska - omaha , omaha , nebraska , united states .
department of biological sciences , florida a & m university , tallahassee , fl , usa .
systematics and ecology and biodiversity institute , university of kansas , lawrence , kansas , usa , courtesy research professor and associated researcher .
this work was supported by nsf awards deb - 0732988 ( to reb ) , deb - 0732838 , deb - 1019308 ( to go and cl ) , deb - 0732819 ( eow ) , deb 0732589 ( tg ) , deb - 0732894 ( kc ) , deb 0963767 ( jal ) , and deb - 0732969 ( gl ) ; gwu selective excellence in diversity of life program ( to rbr ) ; leading academic discipline project of shanghai municipal education commission , project number s30701 ( cl ) . the biodiversity institute , university of kansas , provided financial support for the collection used in this study .
our view of the phylogeny and classification of bony fishes is rapidly changing under the influence of molecular phylogenetic studies based on larger and more taxonomically comprehensive datasets . classification schemes displayed in widely used text books on fish biodiversity ( e . g . , 2 , 3 ) have been based on loosely formulated syntheses ( supertrees ) and community consensus views of largely disconnected studies . the phylogenetic structure underpinning such classifications has many areas that are notably unresolved and poorly known , providing weak or no justification for many groups that , although formally recognized , are implicitly known to be polyphyletic ( e . g . percoids , perciforms , scorpaeniforms ) . a comprehensive phylogenetic tree for all major groups of fishes has been elusive because explicit analyses including representatives across their diversity have never been accomplished . detailed morphological cladistic investigations of fish relationships have typically focused on lower taxonomic scales and few attempts to synthesize morphology at higher taxonomic levels proved to be challenging and met limited success ( e . g . , 4 ) . a recent effort to systematically collect morphological synapomorphies from published records for all currently recognized groups resulted in the first teleost classification based on monophyletic groups 5 . this effort , however , did not produce a global phylogenetic hypothesis . similarly , molecular analyses have been limited and many times conflicting in terms of genetic coverage and taxonomic sampling .
this study is the main product of the euteleost tree of life project ( etol ) . a total of 21 molecular markers with a genome - wide distribution were examined , the majority of which were developed by etol using a genomic screen pipeline 25 . this pipeline compared the danio rerio and takifugu rubripes genomes to identify single - copy genes with long exons ( > 800 bp ) and divergence levels suggesting they evolve at rates appropriate for phylogenetic resolution among distantly related taxa . exons markers were sequenced from 11 nuclear genes previously published by our group ( kiaa1239 , ficd , myh6 , panx2 , plagl2 , ptchd4 ( = ptr ) , ripk4 , sidkey , snx33 ( = sh3px3 ) , tbr1b ( = tbr1 ) , and zic1 ) and three additional markers , including one intron ( hoxc6a ) and two exons ( svep1 , and vcpip ) , were newly developed for this study using the same approach . sequence data from seven additional markers , including etol markers ( enc1 , gtdc2 ( = glyt ) , and gpr85 ( = sreb2 ) ) or markers developed by others ( 16s mtdna , rag1 , rag2 , and rh ) , were generated for our previous studies ( e . g . , 25 , 26 , 27 , 28 , 66 , 96 ) or obtained from ncbi , ensembl , or other genomic databases .
fish diversity is represented in the phylogenetic data matrix by a sample of 1410 bony fish species ( of ca . 31000 51 ) plus four tetrapod species and two chondrichthyan outgroups ( total 1416 terminals ) . the taxonomic sampling of bony fishes consists of 1093 genera ( of ca . 4300 ) , 369 families ( of 502 ; see below ) , and all traditionally recognized orders ( e . g . , 5 ) . our taxonomic sampling emphasizes representation of percomorph groups , with 1037 ( of > 15000 ) species in 201 families . all scientific names were checked against the catalog of fishes 51 . a complete list of material examined is given in table s1 .
* 1st and 2nd are primers for the first and nested / seminested ( optional ) rounds of pcr , respectively .
contigs were assembled from forward and reverse sequences using codoncode aligner v3 . 5 . 4 ( codoncode corporation ) , sequencher v4 ( gene codes corporation ) , or geneious pro v4 . 5 ( biomatters ltd . ) . exon markers were aligned individually based on their underlying reading frame in translatorx 52 using the mafft aligner 53 . the hoxc6a and 16s sequences were aligned with mafft v6 . 9 53 using 1000 iterations and the genafpair algorithm . because nested pcr is highly prone to cross - contamination , we vetted the data by visually inspecting individual gene trees estimated with the geneious tree builder algorithm in geneious . to qualitatively assess gene - tree congruence , the final gene alignments were analyzed under maximum likelihood ( ml ) in raxml using ten independent runs for each ; exon alignments were partitioned by codon position . alternative approaches to analyze combined data based on species - tree methods that account for gene - tree heterogeneity due to lineage sorting ( e . g . , 54 , 55 , 56 , 57 ) could not be applied to this dataset due to high proportion of missing data ( see results ) .
individual genes were concatenated using sequencematrix v1 . 7 . 8 58 or geneious . two datasets were assembled and analyzed separately , one including all 1416 taxa with sequence data from three genes or more ( 3 + dataset ) and a subset including 1020 taxa with sequence data from seven genes or more ( 7 + dataset ) . analyses of the 3 + dataset were performed under maximum likelihood ( ml ) using two partitioning schemes , a simple one determined arbitrarily with 5 data partitions ( 3 codon positions across all exons plus 16s and hoxc6a ) , and a more complex scheme with 24 partitions ( a combination of codon positions and individual genes plus 16s and hoxc6a ) indicated by partitionfinder 59 . to make the partitionfinder analysis scalable , a representative subset of 201 taxa was run under the bayesian information criterion 59 . the 7 + dataset was analyzed with the 24 - partition scheme only . analyses for both datasets and partition schemes were conducted in raxml using 30 independent replicates under the gtrgamma model . nodal support was assessed using the rapid bootstrapping algorithm of raxml with 1000 replicates estimated under the gtrcat model 60 , and the collection of sample trees was used to draw the bibartition frequencies on the optimal tree . all raxml analyses were conducted in the cipres portal v3 . 1 .
for comparison purposes , the 3 + dataset was also analyzed under implied - weighted parsimony 61 . the optimal tree search and bootstrap trees were set to run independently . gaps were treated as missing characters and all parsimony uninformative characters were ignored . a relatively mild value of k ( 20 ) was chosen arbitrarily due to computational limitations to explore sensitivity of the nodes to other weighting functions . tree searches were performed in tnt 1 . 1 63 using a driven - search strategy combining the following tree - search algorithms : ratchet , drift , sectorial searches and tree fusion . the exhaustiveness of the search parameters was self - adjusted every 2 hits of the current best score . to maximize tree - space exploration , the final searches implemented tree - bisection - reconnection ( tbr ) . a strict consensus of nine equally optimal trees ( length 407187 steps ; fit 7309 . 19 ) was computed . bootstrap search strategies were relaxed to ten random addition sequences and tbr , saving only one tree per replicate ( 1000 replicates ) ; bootstrap bipartition frequencies were drawn on the consensus tree .
the complete tree with 1416 taxa was time - calibrated under penalized likelihood ( pl 67 ) with treepl 69 . the pl model , which assumes rate autocorrelation , has been shown to perform poorly in simulation studies resulting in high stochastic error of divergence time estimates 70 . to ameliorate this problem , mean highest posterior density estimates of clade ages obtained with the subset in beast were imposed as fixed secondary calibrations for the pl analysis , rather than using primary calibrations with minimum and maximum age constrains . a total of 126 secondary calibrations were used for this analysis , including the ages obtained for all major groups in the tree as well as the nodes near which primary calibrations were defined . the rate smoothing parameter was set to 10 based on the cross - validation procedure and the χ 2 test in treepl ( four smoothing values between 1 and 1000 were compared ) .
based on the topology obtained ( figs . 1 - 10 , s1 ) we propose a new classification for ordinal and subordinal groups of bony fishes and subsequently discuss some of the most significant findings .
fig . 1 : main phylogenetic hypothesis of bony fish groups collapsed to depict higher - level clades .
the phylogenetic tree was estimated in raxml using the 3 + dataset ( 1416 taxa ) and 24 partitions with divergence times estimated under pl using 126 fixed secondary calibrations from the beast analysis ( see fig . 11 ) . terminal clades are either orders or supraordinal taxa with multiple orders included . values in parentheses indicate number of families examined . see also figs . 3 - 10 for relationship details on selected percomorph clades . the complete phylogeny with bootstrap support values and names for supraordinal taxa is in fig . s1 ) .
fish illustrations were obtained from fishes of the world ( nelson [ 2 ] ) and are reproduced with permission of john wiley & sons , inc . .
fig . 2 : sensitivity analyses for selected clades obtained in this study ( shown in figs . 1 , 3 - 10 ) and for selected alternative hypotheses .
for each case , we assess support from individual gene trees ( indicating whether the group was obtained ) or from the concatenated data sets ( indicating whether the group was obtained and showing boostrap support ) . for some gene trees , monophyletic groups ignore a few rogue taxa falling outside . n / a : insufficient taxonomic sampling to test hypothesis . 1 excluding gymnotiformes ( e . g . , saitoh et al . 77 ) ; 2 stomiatii ; 3 stiassny and moore 75 ; 4 nelson 2 and wiley and johnson 5 ; 5 shan and gras 47 ; 6 patterson and rosen 78 ; 7 arratia 79 ; 8 fink and fink 80 ; 9 nelson 81 ; 10 olney et al . 82 ; 11 johnson and patterson 4 ; 12 miya et al . 8 ; 13 johnson 83 ; 14 kaufman and liem 84 ; 15 gill 85 ; 16 acanthuriformes sensu tyler et al . 86 ( i . e . , acanthuriformes sensu stricto 87 plus scatophagidae and siganidae ) ; 17 jordan 88
the nomenclatural arrangement presented in appendix 2 builds on the existing classification by wiley and johnson 5 and intends to preserve names and taxonomic composition of groups whenever possible . however , adjustments are made to recognize new well - supported molecular clades , many of which also have been obtained by previous molecular studies ( several examples discussed below ) . order - level or supraordinal taxa are erected ( new ) or resurrected on the basis of well - supported clades only ( > 90 % bootstrap values ) . current taxon names supported by previous molecular or morphological studies are retained if congruent with our results , even if bootstrap support is low ( e . g . , osteoglossocephalai sensu arratia 79 with only 38 % bootstrap ) . in some cases , ordinal or subordinal taxa that were not monophyletic in our analysis are also validated , as long as the incongruence is not supported by strong bootstrap values . examples include the suborder blennioidei ( not monophyletic here but monophyletic in wainwright et al . 31 ) and the order pleuronectiformes ( not monophyletic here but monophyletic in betancur - r . et al . 28 ) .
our results ( appendix 2 ) invite comparison to the recent classification of wiley and johnson 5 based on morphological evidence gleamed from many investigators . of 123 clades recognized by them , 70 ( 56 . 9 % ) are congruent with bootstrap values > 95 % obtained in this study . five of these 70 clades are included in our sample by only one family and thus their monophyly is not critically tested . another six clades ( 4 . 9 % ) are congruent but are supported by lower bootstrap values ; seven additional clades ( 5 . 7 % ) are monotypic . forty clades ( 32 . 5 % ) are incongruent , with some being grossly polyphyletic in our tree . notable examples are protacanthopterygii , smegmamorpharia , and labriformes . others are incongruent based on exclusion of subclades and are rendered monophyletic in our classification by the addition or removal of smaller clades . examples include stomiatii ( inclusion of osmeriformes sensu stricto ) , otomorpha ( inclusion of alepocephaliformes ) , neoteleostei ( removal of stomiatiformes ) , and lampridiformes ( removal of stylephorus ) .
there is considerable consensus between morphology and the interrelationships of major clades . for example , the major cohorts of living teleosts and their interrelationships are congruent with the listing convention employed by wiley and johnson 5 ; this is also true within many of the major clades ( e . g . relationships within elopomorpha ) . but there is also incongruence . for example , relationships among early - branching acanthomorph groups differ considerably from previous morphological hypotheses ( e . g . , johnson and patterson 4 ) with lampridiforms , percopsiforms , zeiforms and gadiforms branching off basally relative to polymixiiforms . more explicit tests of new and alternative phylogenetic hypotheses based on multiple analyses of our dataset are presented in fig . 2 .
the following sections highlight some of the salient features of this global phylogeny and classification of bony fishes , especially in reference to well - established relationships and newly found clades among the euteleosts . we do not attempt to provide a complete account of all taxonomic issues , but to give some perspective and contrast to discuss the evidence supporting novel and established taxa .
our analyses support several recent hypotheses based on molecular data that contradict the consensus based on morphology 2 , 5 relative to the composition of “protacanthopterygians . ” although our results fall short of resolving with confidence circumscription and relationships among taxa in this group ( hence protacathopterygii is a sedis mutabilis taxon in our proposed classification ) , some relationships are well supported and consistent with previous studies ( fig . 1 ) . first , is the hypothesis that alepocephalid fishes ( slickheads ) have affinities within otomorpha , instead of argentiformes , as proposed by johnson and patterson 4 . this result was first proposed on the basis of mitogenomic data 10 , 41 , 100 , 101 and recently corroborated with a subset of the nuclear markers used in this study 29 . second , is the sister group relationship of osmeriformes and stomiatiformes ( = stomiiformes ) , first proposed by lópez et al . 21 based on mtdna and rag1 sequence data . finally , the position of lepidogalaxias at the base of the euteleosts rendering galaxiidae non - monophyletic also was proposed previously 102 , 29 and supported by our data ( see also fig . 2 ) .
a corollary of the increased resolution of percomorph relationships is the demise of the smegmamorpharia sensu johnson and patterson 4 ( see also wiley and johnson 5 ; fig . 2 ) . elements included in this supraordinal taxon are now scattered throughout the molecular phylogeny , placed within many of the newly found clades with high bootstrap support . for example , the pygmy sunfishes ( elassoma ) are back with the other sunfishes ( centrarchids ) , as suggested by earlier classifications and recently confirmed by molecules 30 . centrarchids plus elassomatids are placed here in the resurrected order centrarchiformes ( within percomorpharia , fig . 9 ) . mugiliforms ( mullets ) and atherinomorphs ( silversides , needlefishes , halfbeaks , guppies and allies ) are placed within ovalentariae ( fig . 8 ) . the swamp eels and spiny eels ( order synbranchiformes , suborders synbranchoidei and mastacembeloidei ) are placed with confidence in anabantomorphariae ( fig . 5 ) , together with armored sticklebacks ( indostomidae ) , one of the 11 families previously included in the order gasterosteiformes . the polyphyly of gasterosteiformes ( another large clade assigned to smegmamorpha ) was first pointed out by mitogenomic evidence 12 . our results place the sticklebacks , tubesnouts and sand eels ( previously assigned to gasterosteoidei ) in our newly defined perciformes ( suborder cottioidei ; fig . 10 ) and the rest of the families previously assigned to the suborder syngnathoidei were relocated to our newly defined order syngnathiformes within the scombrimorpharia ( fig . 4 , see below ) .
phylogenetic resolution within five newly discovered clades , however , will require additional study . relationships within syngnathiformes , scombriformes , carangimorphariae , ovalentariae , and percomorpharia may be challenging to recover given the rapid radiation and diversification of these clades .
based on a phylogeny estimated with four mitochondrial markers , thacker 33 resurrected the order gobiiformes , to accommodate three suborders : gobioidei ( gobies and sleepers ) , kurtidoidei ( nurseryfish ) , and apogonoidei ( including apogonids and pempherids ) . previous molecular studies have shown affinities between gobioids , apogonids , kurtids and , to some extent , pempherids and dactylopterids 8 , 11 , 16 . there is also morphological evidence supporting a close relationship between gobids and apogonids 108 , 109 as well as between kurtids and apogonids 110 . our results provide partial support for the gobiiformes sensu thacker 33 but we treat it here as a supraordinal group ( gobiomorpharia ) . a major difference is that our hypothesis segregates the family pempheridae ( sweepers ) to its own order ( pempheriformes , together with glaucosomatidae ) , within percomorpharia ( figs . 1 , 3 , 9 ) .
fig . 3 : detailed relationships among orders and families of gobiomorpharia ( see also fig . 1 ) .
fish illustrations were obtained from fishes of the world ( nelson [ 2 ] ) and are reproduced with permission of john wiley & sons , inc .
scombrimorpharia : sea horses and tunas are close relatives ( figs . 1 , 4 and 5 )
one of the most unanticipated new percomorph clades is the scombrimorpharia , grouping such disparate fishes as seahorses and tunas . this clade includes the newly circumscribed orders syngnathiformes ( fig . 4 ) and scombriformes ( fig . 5 ) . not surprisingly , a close relationship among taxa contained within this group , including syngnathids , mullids , callionymids , dactylopterids , scombrids , stromateids , an others , has never been proposed on morphological grounds . the syngnathiformes , as defined here ( fig . 4 ) , comprises mostly tropical marine reef - dwellers , traditionally placed in three distinct percomorph orders , including gasterosteiformes ( syngnathids ) , “perciformes” ( mullids and callionymids ) and “scorpaeniformes” ( dactylopterids ) . recent molecular studies have emphasized the non - monophyly of scorpaeniformes 74 . we have noted above the dissolution of gasterosteiformes 12 and , as discussed below , we provide a restricted definition for perciformes that includes many scorpaeniform taxa ( fig . 10 ) .
fig . 4 : detailed relationships among families of syngnathiformes ( see also fig . 1 ) .
our new order scombriformes ( fig . 5 ) includes most of the families previously grouped in the perciform suborder scombroidei 2 or the order scombriformes 5 , except for the barracudas ( sphyraenidae ) and the billfishes and swordfishes ( here placed in their own order , istiophoriformes ) . sphyraenidae and istiophoriformes are now firmly placed within carangimorphariae ( fig . 7 ) together with disparate taxa such as remoras ( echeneidae ) , archer fishes ( toxotidae ) , jacks ( carangidae ) , flatfishes ( pleuronectiformes ) , and others ( see below ) . because billfishes and tunas are not closely related as previously suggested by anatomical studies 83 ( fig . 2 ) , the new hypothesis implies that endothermy has evolved at least twice independently in teleosts 111 , 112 . this new circumscription of scombriformes also comprises families belonging to multiple orders in previous classifications , such as stromateiformes ( centrolophidae , nomeidae , ariommatidae , stromateidae ) , trachiniformes ( chiasmodontidae ) , icosteiformes ( icosteidae ) , and perciformes ( bramidae , pomatomidae , and caristiidae ) . despite the disparate morphology among members of scombriformes , most are offshore fishes that inhabit pelagic and / or deep - sea waters .
fig . 5 : detailed relationships among families of scombriformes ( see also fig . 1 ) .
another major percomorph group proposed here is the series carangimorpharia , including three subseries : anabantomorphariae , carangimorphariae , and ovalentariae ( fig . 1 ) . species in anabantomorphariae include representatives placed in three separate orders by wiley and johnson 5 : synbranchiformes ( swamp eels ) , gasterosteiformes ( indostomus , the armored stickleback ) , and anabantiformes ( gouramis ) ( fig . 6 ) . while the first two orders belonged to the smegmamorpharia 4 , 5 , the anabantiformes were placed as incertae sedis in percomorphacea 5 . the monophyly of anabantomorphariae has also been supported on the basis of mitogenomics 8 , 11 , 12 and nuclear markers 28 . a remarkable condition shared by members of this novel grouping is their mostly freshwater origin and restriction to africa and south east asia ( although some members in the family synbranchidae occur in mexico , and central and south america ) . most are able to occupy marginal , stagnant waters due to their capacity to tolerate anoxia and to obtain oxygen directly from the air . anabantiforms have a suprabranchial organ and synbranchids have suprabranchial pouches with respiratory function .
fig . 6 : detailed relationships among orders and families of anabantomorphariae ( see also fig . 1 ) .
a close affinity between other seemingly disparate groups , including barracudas , swordfishes , jacks , flatfishes , and others , has been well established by recent molecular studies 10 , 16 , 19 , 24 , 27 , 28 , 112 ( fig . 7 ) . this higher - level group has been referred to as ‘‘clade l’’ sensu chen et al . 19 or carangimorpha by li et al . 24 ( see also 27 , 28 ) . in looking for possible anatomical synapomorphies uniting flatfishes , billfishes , and carangids , little et al . 112 found that most taxa share a relatively low number of vertebrae , have multiple dorsal pterygiophores inserting before the second neural spine , and lack supraneurals , among others . however , according to friedman 113 , some of these characters are symplesiomorphies while others are absent in the remaining carangimorph groups . it thus seems paradoxical that despite the apparent lack of morphological synapomorphies for carangimorphs there is a strong molecular signal supporting their monophyly , whereas the opposite is true for pleuronectiforms 28 . for additional insights and discussion on carangimorphariae we refer the reader to recent studies 24 , 27 , 28 , 112 , 113 .
fig . 7 : detailed relationships among orders and families of carangimorphariae ( see also fig . 1 ) .
values in parentheses indicate number of genera examined ( see also betancur - r . et al . 28 ) .
ovalentariae is one of the most spectacular percomorph radiations , including more than 5000 species in some 44 families , grouping seemingly distinct groups such as cichlids , mullets , blennies , and atherinomorphs ( atheriniforms , beloniforms , and cyprinodontiforms ) . this clade was first found on the basis of mitogenomic evidence 8 , 12 and later confirmed with nuclear sequence data 23 , 24 , 26 , 31 . our results suggest that this group can be divided into four subgroups ( superorders ) , two of which already existed ( atherninomorphae and mugilomorphae ) and two that are new : ( i ) cichlomorphae ( cichlidae plus pholidichthyidae ) and ( ii ) blennimorphae ( blennioids plus clingfishes , jawfishes and basslets ) . many families in ovalentariae , however , remain incertae sedis ( e . g . , embiotocidae and pseudochromidae ) . two different studies have coined a name for this group ; first stiassnyiformes by li et al . 24 and , more recently , ovalentaria by wainwright et al . 31 for their characteristic demersal , adhesive eggs with chorionic filaments ( lost secondarily in some groups ) . an interesting implication of this phylogenetic hypothesis is that the pharyngeal jaw apparatus ( pharyngognathy ) , present in many members of this clade ( e . g . , cichlidae , pomacentridae , hemiramphidae ) , has evolved multiple times in percomorphs 31 . we refer the reader to wainwright et al . 31 for additional discussion on ovalentariae .
fig . 8 : detailed relationships among orders and families of ovalentariae ( see also fig . 1 ) .
values in parentheses indicate number of genera examined ( see also wainwright et al . 31 ) . many clades lacking taxonomic annotations on nodes are incertae sedis taxa ( for details , see classification ) .
percomorpharia is by far the largest percomorph clade , including 11 orders with some of the most prominent ones such as perciformes , labriformes , lophiiformes , and tetraodontiformes . at least 151 families ( 105 examined ) belong in percomorpharia , including three of the top ten most diverse families of fishes ( i . e . , labridae , serranidae , and scorpaenidae ) 2 . more than one third ( 514 ) of the species in our bony fish phylogeny are placed in this clade . previous molecular studies obtained monophyletic groups with a combination of taxa here assigned to percomorpharia , but with far more limited sampling ( e . g . , 8 , 11 , 16 , 74 ) . although most family - level and ordinal groups within percomorpharia receive high bootstrap support , interrelationships among them are largely unresolved ( hence , the new bush at the top ; fig . 9 ) . several of these groups are newly proposed or resurrected orders under new circumscription ( e . g . , uranoscopiformes , ephippiformes , pempheriformes ) . our new arrangement removes anglerfishes ( lophiiformes ) from paracanthomorphacea , as was suggested by previous classifications 78 , and places them close to tetraodontiforms , caproids , acanthuriforms , chaetodontids , pomacanthids , ephippids and others ( see also 87 , 114 , 115 ) . the largest group within percomorpharia is the order perciformes .
fig . 9 : detailed relationships among orders and families of percomorpharia ( the new bush at the top ; see also fig . 1 ) .
values in parentheses indicate number of genera examined in each terminal family or number of families and genera , respectively , in each terminal order . see also fig . 10 for expanded relationships on perciform groups . many clades lacking taxonomic annotations on nodes are incertae sedis taxa ( for details , see classification ) .
for the first time , a monophyletic definition of perciformes can be recovered from phylogenetic analysis of a comprehensive taxon sampling . the new circumscription of perciformes reduces significantly the number of included taxa , while retaining remarkable diversity that can be organized into several suborders and infraorders . nelson’s classification 2 included 160 families in perciformes , making it the largest order of all vertebrates . our definition indicates unambiguous membership for 38 families and uncertain membership for an additional 42 that were not examined in our study but that have been assigned to either “perciformes” ( 10 ) , “scorpaeniformes” ( 14 ) , cottiformes ( 8 ) , or trachiniformes ( 1 ) in previous classifications 2 , 5 . hence , the maximum possible number of families in the newly defined perciformes is reduced to 71 . this number is closer to the 90 families proposed by wiley and johnson 5 for their perciformes , but with a very different composition .
for a long time , perciformes has been regarded as a “taxonomic waste basket” 2 , 5 with ‘‘percoids’’ scattered throughout percomorpha and no clear phylogenetic distinction among percoidei , perciformes , and percomorpha 74 . earlier molecular studies lacked sufficient sampling to resolve phylogenetic questions among “percoids , ” but close relationships among groupers ( serranidae ) , perches ( percidae ) , sticklebacks ( gasterosteidae ) , searobins ( triglidae ) , icefishes ( notothenioidei ) , sculpins ( cottoidei ) , eelpouts ( zoarcoidei ) and scorpionfishes ( scorpaenoidei ) have been obtained in one form or another , and in different combinations , by several authors 16 , 19 , 20 , 23 , 24 , 29 , 74 , 116 . all of these taxa are included in our definition of perciformes ( fig . 10 ) .
within perciformes , we tentatively propose suborders ( notothenioidei , scorpaenoidei , trigloidei , cottoidei ) for clades with high support that also represent some well - established groups , but two incertae sedis ( percophidae and platycephalidae ) , and several unexamined families remain unclassified . additional taxon sampling and more data are needed to resolve interrelationships among these taxa . four suborders / infraorders were recognized as separate orders by wiley and johnson 5 : percoidei , scorpaenoidei , cottioidei , and gasterosteales ( an infraorder of cottioidei ) .


anelosimus eximius is a species of social spider in the genus anelosimus , native to the lesser antilles and the area from panama to argentina .

colonies can comprise several thousand individuals .

anelosimus eximius are classified as a social spider species because they engage in shared brood care and cooperate to capture prey within their web , which allows them to capture prey much larger than a single individual would be able to .

their webs do not capture a lot of prey , but the prey that are caught are significantly larger than most prey captured in the webs of other individual social or antisocial spider species .

thus , their techniques provide more nutrients than other social spider colonies may obtain .

these techniques are most efficient in anelosimus eximius colonies of about 1,000 individuals .

the sociality of anelosimus eximius aids in the increased fitness of the species .

one potential cost of sociality in anelosimus eximius is that they produce fewer egg sacs .

however , each egg sac holds more individual offspring than most arachnid egg sacs would normally hold .

thus , the benefits seem to outweigh the costs .

it is difficult to explain how sociality has evolved from a typically solitary animal .

one trait that has facilitated this shift is the lack of discrimination against foreign offspring .

it has also been questioned whether the alloparental behavior of anelosimus eximius was an ancestral trait or if the species had to overcome discrimination in order to gain their trait of sociality .

through studies on social and sub-social species that observed reactions to foreign offspring , scientists discovered that the species did not need to overcome discrimination ; both sub-social and social species of arachnids showed no discrimination towards foreign offspring .

anelosimus eximius

colony size and individual fitness in the social spider anelosimus eximius . - pubmed - ncbi
exploratory recruitment plasticity in a social spider ( anelosimus eximius ) . - pubmed - ncbi
smith , d . 1986 . population genetics of anelosimus eximius ( araneae , theridiidae ) .
view image of anelosimus eximius are social spiders ( credit : aaron pomerantz / perunature . com )
view image of anelosimus eximius live in dense colonies ( credit : aaron pomerantz / perunature . com )
view image of anelosimus eximius colonies can be massive ( credit : bernard dupont , cc by 2 . 0 )
aviles , l . 1986 . sex - ratio bias and possible group selection in the social spider anelosimus eximius .
vollrath , f . 1985 . eusociality and extraordinary sex ratios in the spider anelosimus eximius ( araneae : theridiidae .
nentwig , w . 1985 . social spiders catch larger prey : a study of anelosimus eximius ( araneae : theridiidae .
aviles , l . , p . tufino . 1998 . colony size and individual fitness in the social spider anelosimus eximius .
vollrath , f . 1986 . environment , reproduction and the sex ratio of the social spider anelosimus eximius ( araneae , theridiidae ) .
saffre , f . , a . mailleux , j . deneubourg . 2000 . exploratory recruitment plasticity in a social spider ( anelosimus eximius ) .
ebert , d . 1998 . behavioral asymmetry in relation to body weight and hunger in the tropical social spider anelosimus eximius ( araneae , theridiidae ) .
vakanas , g . , k . bertrand . 2001 . coordination of behavioral sequences between individuals during prey capture in a social spider , anelosimus eximius .
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to cite this page : carrell , s . 2016 .
anelosimus eximius
( on - line ) , animal diversity web . accessed july 09 , 2018 at urltoken
agnarsson i ( 2006 ) a revision of the new world eximius lineage of anelosimus ( araneae , theridiidae ) and a phylogenetic analysis using worldwide exemplars . zool j linnean soc 146 ( 4 ) : 453–593
settepani , v . , l . grinsted , j . granfeldt , j . jensen , t . bilde . 2013 . task specialization in two social spiders , stegodyphus sarasinorum ( eresidae ) and anelosimus eximius ( theridiidae ) .
a . eximius is perhaps the best known of the social spiders , but that is not saying much .
fowler , h . , e . venticinque . 1996 . interference competition and scavenging by crematogaster ants ( hymenoptera : formicidae ) associated with the webs of the social spider anelosimus eximius ( araneae : theridiidae ) in the central amazon .
view image of this bee got stuck in an a . eximius colony ( credit : aaron pomerantz / perunature . com )
in species like a . eximius , spiders are essentially clones . brothers and sisters mate with each other , generation after generation , so that colonies become highly inbred .
these two processes together help to explain why a . eximius colonies tend to be found in clusters , sometimes as many as 40 related colonies within just a few kilometres .
among the thousands of species of spiders ( 40 , 000 arachnids ) , there are only about 23 species that live in social groups . anelosimus eximius is most commonly found in south american countries from panama to argentina . the massive spider webs that are created by these spiders can contain spiders in excess of 50 , 000 with females outnumbering men 10 to 1 .
these spiders , like a . eximius with its massive funnel pits of doom , may superficially seem to behave like social insects . but in truth they could hardly be more different .
aviles , l . , w . maddison . 1991 . when is the sex ratio biased in social spiders ? : chromosome studies of embryos and male meiosis in anelosimus species ( araneae , therididae ) .
majer , m . , i . agnarsson , j . scenning , j . bilde . 2013 . social spiders of the genus anelosimus occur in wetter , more productive environments than non - social species .
anelosimus eximius is a species of spider that is also known as “social spider” because it socializes with its fellow spiders and builds colossal spider webs that have the potential of reaching up to 25 feet ( 7 . 6m ) in height and 5ft ( 1 . 5m ) in width . according to the journal of arachnology , this brazilian spider species is a very cooperative and group - living spider .
viera c , ghione s , costa , fg ( 2007 ) mechanisms underlying egg - sac opening in the subsocial spider anelosimus cf . studiosus ( araneae theridiidae ) . ethol evol ecol 19 ( 1 ) : 61–67
anelosimus eximius , the species i encountered in the rainforest , is not the only kind of social spider in the world , but it does construct the biggest webs . some can reach more than 25ft ( 7 . 6m ) feet long and 5ft ( 1 . 5m ) wide . a web that size could contain as many as 50 , 000 individual spiders . that is a lot of legs , eyes and fangs .
but these cases aside , social spiders just about always build webs . and most of these webs have complex , three - dimensional structures , like the cone - shaped a . eximius webs i encountered in the jungle .
a . eximius was first discovered more than a century ago by a french arachnologist named eugène simon . more social spiders have been discovered since . one was found as recently as 2006 , in ecuador , by entomologist leticia avilés .
for example , an a . eximius colony contains adult males and females as well as youngsters , but the majority of spiders on the web are females . in the early 1980s , researchers found that males comprise only between 5 % and 22 % of any colony ' s populace .
a . eximius was first discovered more than a century ago by a french arachnologist named eugène simon . an interesting advantage that these social spiders acquire by building giant webs is that they can capture prey which can be much larger in size than what a solitary spider would have been able to catch . these communal spiders work together to build , maintain and clean their webs .
exploratory recruitment was investigated in an artificial experimental set - up on location in french guyana . groups of 200 freshly collected spiders of the neotropical social theridiid anelosimus eximius were released on an open circular surface and offered a choice between two accessible shelters . results indicated that a clear - cut collective decision was not always reached , unlike what we found using a different set - up in another set of experiments . simulations were conducted using available information in order to explore the potential causes for this difference . theoretical projections fit experimental data and strongly suggest that variability in the collective response results from a combination between modifications of the environment ' s properties and alteration of the recruitment procedure . multiple variants of the theoretical set - up ( including external bias ) are investigated and emphasize plasticity in the collective response . new experimental studies are suggested and adaptative value of exploratory recruitment in social spiders is briefly discussed .
funding was provided by a natural sciences and engineering research council of canada ( nserc ) discovery grant to l . a ( 261354 - 2008 rgpi ) . k . s . was additionally supported by an nserc canada graduate scholarship ( master’s ) award ( 2009–2010 ) . the staff of simbioe and el ministerio del ambiente de ecuador assisted greatly with logistics and obtaining permits . the associates of reserva ecólogica antisana , estacion biológica jatun sacha , and bellavista cloudforest reserve all provided fantastic general assistance and field support . maurico vega and gabriel iturralde provided valuable field and spider identification assistance . members of the zoology department at ubc provided valuable comments on the manuscript . two anonymous reviewers provided many detailed suggestions that improved the manuscript greatly .
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department of ecology and evolutionary biology , university of arizona , tucson , arizona 85721 , usa .
it is like a scene from a horror film : spider webs several metres wide that are home to thousands of spiders . why did these spiders turn social ?
eight legs , eight eyes and a pair of venomous fangs – the average spider is so well - equipped that it ' s easy to see why arachnophobes are terrified . but there is one saving grace : at least spiders are solitary , so they are usually encountered in small numbers .
but then i found myself trudging along a muddy path in the peruvian amazon jungle , face to face with a spider colony several thousand strong . their funnel - shaped web arched from tree to tree , a structure containing too many of the creepy crawlies to count .
these were spiders but not as i knew them : they appeared to function as a society , just like ants or bees .
most spiders are indeed lone wolves , but a scant handful have evolved a level of sociality to rival ant colonies , bee hives , or even primate societies .
sociality shows up in at least seven spider families . in all we know of around 25 social species among the 45 , 000 described spider species on the planet . sociality evolved at least a dozen separate times among them .
while the details vary from species to species among the social spiders , many of their features are similar .
communal spiders work together to build , maintain , and clean their webs . they cooperate in capturing prey , and dine together when they snare a large feast .
the females feed their offspring by vomiting up food for them , just like mother birds . they even regurgitate food for juveniles other than their own . in other words , they work together to care for the youngest in the colony . it is a sort of spider day - care .
nearby colonies tend to be related to each other , because new colonies form in one of two ways .
sometimes , a large web is broken in half , perhaps by heavy rainfall or falling branches , or even a falling monkey . in its place , two smaller colonies are left behind .
other times , individual females will strike out on their own , setting up a new web . eventually other dispersing females will join the group ; perhaps ones who tried to set up their own webs but failed . survival is more likely in groups , after all .
gregarious arachnids are not much studied – perhaps because so few of them exist in the first place .
my students know more about social spiders than your average arachnologist ,
says linda rayor , an entomologist at cornell university in ithaca , new york , who studies australia ' s social huntsman spiders .
most animals are solitary ,
she tells me ,
whether you ' re looking at mammals , or birds , or whatever . social behaviour in otherwise solitary animals is cool .
as i watched the social spiders go about their day deep in the jungle , a bee found itself stuck in the giant web . suddenly , dozens of the eight - legged predators descended en masse onto the struggling black - and - yellow striped insect . it was impossible to see through the writhing mass of tiny spider legs , but one thing was certain : that bee was done for .
if death by one spider seems bad enough , it must be nothing compared to an attack by a whole swarm of them .
the first spider , the proto - spider , was probably solitary . so the spiders that gave rise to today ' s truly social species must have been too . but then they did something remarkable : they turned sub - social : they learned to tolerate each other , at least for a time – even if they did not exactly enjoy hanging out in groups .
that early tolerance could have come about as a result of parental care . in some spiders alive today , that is just defending an egg sac , but in others – the ones that are poised to evolve sociality – it looks more familiar to our mammal brains .
in those species , females provide food and protection for their developing offspring , and occasionally even to other juveniles . in some species , mothers even make the ultimate sacrifice , allowing themselves in their last moments to become a meal for their brood . sub - social spiders can still be cannibals , after all .
they ' re the spiders that already have cooperation as juveniles ,
says arachnologist jonathan pruitt of the university of california , santa barbara .
but as they mature , they become intolerant of each other .
in other words , juvenile tolerance alone is not enough to turn spiders fully social . the environment in which the spiders live also has to be right . researchers have discovered three ecological elements that often lead to cooperative living among arachnids .
solitary spiders living in places where it is difficult to subdue large or more profitable prey alone may eventually figure out that it is in their interest to work together . it is a smaller step from tolerance to cooperation than from aggression to cooperation .
another common feature is heavy rain . rain does not have to be frequent , but when it is really intense , it has the potential to seriously damage spider webs . when a tempest takes out the web and threatens a spider ' s survival , the ones with just a glimmer of social behaviour might fare just a little better than their isolationist peers .
as a result , some have hypothesised that rough weather favours cooperation , since in those conditions it is the spiders that share the task of maintaining and repairing their webs that fare best .
many hands make light work of web repair ,
says pruitt .
then there is the web itself . there are only a couple of instances in which spiders that do not build webs have evolved to be sub - social . these web - less social spiders , living in places like the australian deserts or in african scrub habitat , have to cope with unusual circumstances – like enormous prey or particularly aggressive raiding ants .
pruitt thinks that could be a simple matter of mechanics . it is easier for two spiders just on the cusp of evolving sociality to join their webs together if they exist in three dimensions than if they weave flatter , two - dimensional ones , like charlotte ' s eponymous web .
some combination of tolerance , prey size , rough weather , and web geometry combine to create the perfect storm for social behaviour to emerge in spiders .
add in the fact that it is easier to defend yourself against predators in a group , and that communal webs offer spiders the relative safety of staying in one place rather than risking travelling away from the web onto which you are born to live somewhere else , and for some species , cooperation is a good deal .
bees and ants sort into separate castes . some are workers , some are soldiers ( or drones ) , and then there is a reproductive class . those not included in the reproductive class are sterile ; they could not reproduce even if they wanted to .
social spiders , meanwhile , are more egalitarian . anyone can do any job , and all are capable of reproduction .
view image of driver ants are divided into strict castes ( credit : redmond o . durrell / alamy stock photo )
it is not that spider societies do not rely on the division of labour . it is just that those roles are not strictly governed as they are for the social insects .
and while some female social spiders do not wind up reproducing , it is not because they are physically or genetically incapable . instead , it is usually just because they have not lived successful enough lives . it takes a lot of nutrition to make a few hundred spider babies , and a spider that does not have a rich enough diet is not really up to the task .
instead , roles in spider colonies are usually sorted on the basis of age and sex . researchers are increasingly coming to realise that social spiders also sort themselves according to their individual personalities .
they ' re incredibly well organised ,
says pruitt .
by paying close attention to individual spiders , he and others have discovered that certain spiders are more likely to spend their days attacking predators , while others are more likely to repair the webs , help keep parasites away , clean the web , rear the young , and so on .
spider vocations are intimately tied to their efficiency at those vocations ,
he says .
though it is not yet clear whether those skills develop through experience or because of innate aptitude , some spiders are clearly in the construction business , some are hunters , others are on janitorial duty , and still others offer childcare services .
since adolescent spiders do not go off in search of new colonies , there is no influx of new genetic material . for that reason , some suspect that spider personalities develop as a result of early life experiences , not genetics .
in spite of a lack of genetic diversity , they exhibit this exquisite diversity in terms of their personalities ,
pruitt says .
view image of stegodyphus sarasinorum spiders have personalities ( credit : dinesh rao , cc by 2 . 0 )
in 2013 , he and his colleagues looked at a social spider called stegodyphus sarasinorum , native to india , sri lanka , and nepal . they found that individual personality traits predict which job each spider performs .
s . sarasinorum is found in dry scrubland . but like the spiders i found in the rainforests of peru , these arachnids work cooperatively to build and maintain their webs and to capture food .
using tiny dabs of paint applied to the spiders , pruitt and his team were able to track 40 from each of two different wild colonies . individuals that were bolder were more likely to be involved in attacking prey – but other characteristics , like body size or a spider ' s level of aggression , did not factor into their vocation .
responding to stimuli from a prey caught in the web elicits different responses according to a set of individual characteristics ,
they concluded .
in other words , social spiders have distinct personalities , which in turn help to define their roles in the community .
in a way , that is not so different from human societies . bold , risk - taking people might be more likely to wind up fighting fires or enrolling in a police academy , while the more calculating , deliberative types wind up as lawyers or architects .
despite lacking a backbone , invertebrates like insects and arachnids lend themselves well to studying complex social behaviour .
when it comes to a behaviour that any sort of animal can do , insects [ and arachnids ] can do it , if not do it better ,
says entomologist phil torres .
after all , they have been evolving on our planet for a lot longer than any bird or mammal has .
sometimes , as many as 40 colonies can be found within a distance of 1 km . to put that into perspective , check out the below image
in the below picture , a colonized spider web was discovered in a north texas park in 2007 . the people in the below picture - mike mccord , left , and freddie gowin - the lake tawokoni state park rangers , monitor a giant communal spider web at the park .
in 2013 in santo antonio da platina , brazil , these spider webs housing large quantities of spiders were eradicated by strong winds that detached the webs from their anchors , thereby , carrying the spiders and their ruined home to new sites . this event led to a “spider rain” in which people in santo antonio da platina observed spiders raining from the sky .
within the built colonies , roles are segregated for all the spiders - males and females alike . some work as “warriors” - those who act as predators and attack the prey - while some work to clean and maintain the webs .
social spiders are likely to have evolved from subsocial ancestors via the subsocial route .
it has been suggested that the transition from subsocial to social living requires a change in three behavioural traits : from premating dispersal ( wherein juveniles are dispersed from the colonies before breeding ) to postmating dispersal ( wherein juveniles are dispersed from the colonies after breeding ) , from outbreeding to inbreeding mating system , and from maternal care to cooperative breeding .
romanian workers accidentally discover 5 . 5 million - year - old sealed cave teeming with freakish , bizarre looking creatures .
information on the south american social spider is currently being researched and written and will appear here shortly .
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published online 4 august 2008 | nature | doi : 10 . 1038 / news . 2008 . 1007
for many people it ' s the ultimate nightmare : thousands of spiders collaborating to form a well organized society . a new study published this week in
reveals how colonies of one spider species grow to an enormous size , and the surprising factors that ultimately limit their expansion .
spiders are usually thought of as lone hunters . however , a few dozen species do live cooperatively , building collective webs and sharing food - gathering and child care between them . one example is the neotropical species
researchers based in the university of arizona , tucson , and university of british columbia , vancouver , have now examined colonies of the spiders in the jatun sacha biological reserve and cuyabeno nature reserve in ecuador , measuring the sizes of colonies and recording the prey captured in their communal webs .
the team discovered that as colonies grew larger , they actually caught fewer prey per spider than smaller colonies . to explain this , they turned to allometry , the study of the relationship between size and shape in biology . this is usually applied to single organisms , but the researchers found that it was equally relevant for the whole colony of spiders .
as the number of occupants grows , the volume of the webs they construct increases - but the surface - area - to - volume ratio declines . the area of web is the all - important determinant of numbers of prey caught , so bigger colonies catch proportionally fewer prey items .
at first , researcher leticia avilés was puzzled by the finding : “it begged the question of why the spiders lived in groups in the first place . ”
but she and her colleagues found a factor that compensated for the numbers effect . when they estimated the biomass – the dry weight - of prey caught , they found that larger webs spun by bigger colonies are able to capture larger prey items . larger portion sizes compensated for the falling number of prey - at least , up to a certain point .
combining both of these factors , they found that the amount of food available for each spider peaked in colonies containing around 500 spiders . “previous work had shown that social spiders are able to capture prey several times their body size . no previous work , however , had shown the relationship between colony size and the number and size of insects captured or between colony size and biomass captured per capita , ” notes avilés .
it was previously known that above a certain size the colonies break up , with the occupants dispersing to form new colonies . this research now seems to provide an explanation . although the study found many colonies larger than the optimum size , none was found with more than 9 , 000 spiders . below this size the occupants are better off staying put than starting a new , much smaller colony .
this is an exciting new perspective for thinking about how social web - spinning spiders have evolved ,
says todd blackledge at the university of akron , ohio , who studies web - weaving spiders .
in the past the focus has been on the genetic effects of inbreeding in colonies . this tells us a lot more about the ecological factors governing colony size .
is a social spider found in the neotropical region , specifically in central and south america . in particular , it inhabits as far north as panama and then sthrough eastern ecuador to peru . this spider is found patchily in locations such as suriname as well as eastern and southern brazil . colonies can also be found on islands such as trinidad and the lesser antilles .
is found in the lowland rainforest . in particular , this social spider is found in the interior forest floor and forest edge . therefore this species of spider is rarely ever found in the canopy levels of the rain forest . typically , they are found in cleared areas or around tree falls . the webs can be found as low as a meter off the ground to 20 meters in the canopy .
colonies decrease in web area size altitude decreases . according to volrath ( 1986 ) , this is due to seasons generally being harsher at lower altitudes and damaging the webs .
( majer , et al . , 2013 ; smith , 1986 ; vollrath , 1986 )
size can range from 4 . 4 to 6 millimeters . guevara and aviles ( 2011 ) report the female weight ranges from 2 . 55 to 11 . 82 mg . females are reported to be larger in weight and length than males although no specific measurements have been published for males . the size and weight of juvenile spiders have not yet been recorded in any published studies .
the social spider , like other arachnids , begins as an egg . here in this first stage , the spider goes through its first molt . the incubation period within the egg sac is 20 to 30 days . after the first molt the spiders emerge from the egg sacs . after emerging the social spiders then go through 5 to 6 developmental stages , depending on sex . each time period in between molts is numbered as an instar , or stage . the third instar is when the spiders begin to take part in colony duties . the males reach reproductive maturity in their 5th instar while females reach reproductive maturity in their 6th instar . reaching these maturity stages can take up to 2 to 3 months .
males can attract females through patterned vibrations with the strings that make up their web , as well as visual cues , such as swaying of the legs . in addition males can lay down a scent of pheromones on a line of thread to direct the female towards them . in some cases , the males use both methods of vibration and pheromone communication .
in most cases males seek out the female because the females stay with the nest to invest in the web and eggs . this social spider is considered polygynandrous .
is aseasonal , meaning the spiders do not have a particular season . furthermore , the social spider can breed more than once in its life span . depending on the resource factor , such as food , each egg sac can carry 17 to 53 eggs . the eggs hatch after an incubation period of 20 to 30 days .
females reach maturity in the 6th instar while males mature in the 5th instar . when spiders reach their 3rd instar they become involved in colony tasks , such as hunting , maintenance , and mating .
aviles ( 1986 ) suggests that both parents invest an equal amount in the offspring . however , according to vollrath ( 1985 ) , females invest significantly more into the young . vollrath says the males contribute little to nothing beyond the mating process .
the spiderlings are cared for by the female until the 3rd instar . the female protects , feeds , and hunts for the young . the adult social spiders invest in the spiderlings until they can interact in colony duties .
according to avilés ( 1986 ) , female spiders have an average life span of 76 ± 13 days while males have an average of 71 ± 13 days . the maximum lifespan of sexes are close in range . a single female was reported to have lived 94 - 103 days in the wild , while there are recordings of three males living 103 ± 13 days in the wild . these spiders are not kept in captivity .
these particular social spiders perform tasks that are shared through the colony . the tasks include web maintenance and construction , brood care , defenses , along with attacking prey for when insects hit their trap . furthermore , the spiders cooperate when capturing the trapped insects . according to settepani et al . ( 2013 ) , these tasks are often separated by age and sex . females after the third instar are more likely to perform the colony tasks as well as hunt . researchers believe
performs these tasks to be more efficient in the idea of maintaining a successful colony .
the social spiders are sedentary . emigration is very rare . however , according to smith and hagen ( 1996 ) , when the spiders do relocate it occurs when the nests are by the roadside . this may be due to the nests being more open or vulnerable to trucks driving or having less cover from the weather .
( agnarrson , 2005 ; kim , et al . , 2005 ; powers and aviles , 2007 ; settepani , et al . , 2013 ; smith and hagen , 1996 )
home range and territory size is the size of their web . rarely , does
travel out of its own web . therefore its home range is a 3 - d area with the range of volume from 0 . 0001 to 1 , 000 meters cubed .
nentwig ( 1985 ) records area of the social spiders ' webs being from 20 to 28 meters squared .
according to vakanas and bertrand ( 2001 ) and kraft and cookson ( 2012 ) , there is no observable direct communication between the spiders . however , there does appear to be organization and cooperation , leading to the ability to catch larger prey . the spiders appear to adjust their behavior to match the situation or the prey .
in terms of perception , these social spiders perceive their surroundings through their web . the span of their web acts as a visual perception of depth of their environment .
utilizes the strings by vibration of the legs and abdomen to communicate with another spider . in addition , they can also communicate through attaching pheromones to threads for sexual communication .
creates its web to act as a net trap . above their main net they have a vertical non - stick web . this part acts as a net to trap and cause insects to fall into a bowl shaped nest below to be bombarded by the thousands of spiders ( vollrath , 1986 ) . although they are small organisms this technique allows them to catch much larger prey . reported by nentwig ( 1994 ) , the diet of
was studied in two sites . the first was cerro galera , panama where their prey - capture made up of 19 . 9 % of formicoidea ( ants ) , 17 . 8 % of coleoptera ( beetles ) , 17 . 2 % of heteroptera ( true bugs ) , and 12 . 7 % of blattodea ( roaches ) . the second was el valle , panama where their diet composed of 9 . 1 % of formicoidea , 35 . 0 % of coleoptera , 10 . 6 % of heteroptera , and 10 . 6 % of blattodea . the authors concluded that the spiders are consuming these groups in larger percentages than what is naturally available .
, the spider has kleptoparasites that thrive within their web . these are organisms that are also referred to as food stealers . the social spiders ' main kleptoparaiste is
. according to cangialosi ( 1990 ) due to the parasitic spiders , the social spiders can lose up to 26 % of their food resource . consequently , the social spiders address this problem through avoiding , tolerating , and fighting off the kleptoparasites .
the conservation status of this spider has not yet been reported . this spider is not recognized by the iucn red list , is not protected by cites , and is not federally or state listed . because no scientific publications suggest its populations are in peril , no conservation measures are currently in place .
skyler carrell ( author ) , radford university , karen powers ( editor ) , radford university , april tingle ( editor ) , radford university , emily clark ( editor ) , radford university , cari mcgregor ( editor ) , radford university , jacob vaught ( editor ) , radford university .
living in the southern part of the new world . in other words , central and south america .
having body symmetry such that the animal can be divided in one plane into two mirror - image halves . animals with bilateral symmetry have dorsal and ventral sides , as well as anterior and posterior ends . synapomorphy of the bilateria .
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies . more specifically refers to a group of organisms in which members act as specialized subunits ( a continuous , modular society ) - as in clonal organisms .
offspring are produced in more than one group ( litters , clutches , etc . ) and across multiple seasons ( or other periods hospitable to reproduction ) . iteroparous animals must , by definition , survive over multiple seasons ( or periodic condition changes ) .
the area in which the animal is naturally found , the region in which it is endemic .
reproduction in which eggs are released by the female ; development of offspring occurs outside the mother ' s body .
the kind of polygamy in which a female pairs with several males , each of which also pairs with several different females .
rainforests , both temperate and tropical , are dominated by trees often forming a closed canopy with little light reaching the ground . epiphytes and climbing plants are also abundant . precipitation is typically not limiting , but may be somewhat seasonal .
a wetland area that may be permanently or intermittently covered in water , often dominated by woody vegetation .
the region of the earth that surrounds the equator , from 23 . 5 degrees north to 23 . 5 degrees south .
2014 .
iucn red list
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salomon , m . , d . mayntz , y . lubin . 2008 . colony nutrition skews reproduction in a social spider .
yip , e . , l . rayor . 2013 . the influence of siblings on body condition in a social spider : is prey sharing cooperation or competition ? .
disclaimer : the animal diversity web is an educational resource written largely by and for college students . adw doesn ' t cover all species in the world , nor does it include all the latest scientific information about organisms we describe . though we edit our accounts for accuracy , we cannot guarantee all information in those accounts . while adw staff and contributors provide references to books and websites that we believe are reputable , we cannot necessarily endorse the contents of references beyond our control .
this material is based upon work supported by the national science foundation grants drl 0089283 , drl 0628151 , due 0633095 , drl 0918590 , and due 1122742 . additional support has come from the marisla foundation , um college of literature , science , and the arts , museum of zoology , and information and technology services .
center for nonlinear phenomena and complex systems , université libre de bruxelles , c . p . 231 , bvd , du triomphe , brussels , b - 1050 , belgium .