bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aggression and RHP in the Northern Swordtail Fish, Xiphophorus cortezi: The Relationship Between Size and Contest Dynamics in Male–Male Competition
Authors: Moretz Jason A. 
Published: December 2003

AbstractCurrent theory predicts that contest outcome, as well as decisions on whether to initiate a contest, escalate during a contest or retreat are decided by asymmetries in resource holding potential (RHP) and/or expected payoffs between contestants. In this investigation, dyadic contests were staged between male swordtail fish (Xiphophorus cortezi) where individuals were paired based on cumulative fight records and were ranked at the end of the trials in order to approximate RHP. Size was the only asymmetry that I did not attempt to control for and as a result, I was able to determine the relationships between size, contest initiation, escalation and outcome. Individuals changed their contest initiation strategy based on their size relative to that of their opponents, and contrary to predictions, the smaller of the two males in each contest was more likely to initiate the conflict than was the larger male. However, the larger of the two males was more likely to win and standard length proved to be a moderate predictor of an individual's final rank. Regardless of size, initiators fared poorly, winning only 31% of the contests. In instances where the smaller males won the contests, they were no more likely to initiate the encounter than was the larger male. However, when small males did win, fights lasted longer, suggesting that in some cases smaller males may be able to outlast their opponents.
The Occurrence and Context of the Shaking Signal in Honey Bees (Apis mellifera) Exploiting Natural Food Sources
Authors: Biesmeijer Jacobus C. 
Published: December 2003

AbstractThis study reports on the occurrence of the shaking signal during a honey bee forager's life‐time while it visits natural food sources. Experienced foragers and dance followers accounted for more than 93% of the shaking signals. Foraging success triggered shaking directly, during the next return to the hive, and indirectly, on the morning of the next day. Shaking occurred most often after the first foraging successes of the day and frequently following the first foraging success after a spell of bad weather. These findings confirm several hypotheses that predict that individual foraging success underlies colony‐level patterns in shaking activity. Some results do not fit the previously suggested messages of the shaking signal. Therefore, I propose that the shaking signal has the very broad message: ‘reassess your current activity’. This message can explain the wide range of contexts that trigger shaking while it acknowledges that the meaning of the signal depends entirely on the context of the recipient.
Unexpected patterns of genetic structuring among locations but not colour morphs inAcropora nasuta(Cnidaria; Scleractinia)
Authors: Mackenzie J. B. , Munday P. L. , Willis B. L. , Miller D. J. , Van Oppen M. J. H. 
Published: December 2003

AbstractSymbiotic relationships have contributed greatly to the evolution and maintenance of biological diversity. On the Great Barrier Reef, species of obligate coral‐dwelling fishes (genusGobiodon) coexist by selectively recruiting to colonies ofAcropora nasutathat differ in branch‐tip colour. In this study, we investigate genetic variability among sympatric populations of two colour morphs ofA. nasuta(‘blue‐tip’ and ‘brown‐tip’) living in symbiosis with two fish species,Gobiodon histrioandG. quinquestrigatus,respectively, to determine whether gobies are selecting between intraspecific colour polymorphisms or cryptic coral species. We also examine genetic differentiation among coral populations containing both these colour morphs that are separated by metres between local sites, tens of kilometres across the continental shelf and hundreds of kilometres along the Great Barrier Reef. We use three nuclear DNA loci, two of which we present here for the first time forAcropora. No significant genetic differentiation was detected between sympatric colour morphs at these three loci. Hence, symbiotic gobies are selecting among colour morphs ofA. nasuta, rather than cryptic species. Significant genetic geographical structuring was observed among populations, independent of colour, at regional (i.e. latitudinal separation by < 500 km) and cross‐shelf (< 50 km) scales, alongside relative homogeneity between local populations on within reef scales (< 5 km). This contrasts with the reported absence of large‐scale genetic structuring inA. valida, which is a member of the same species group asA. nasuta. Apparent differences in biogeographical structuring between species within theA. nasutagroup emphasize the need for comparative sampling across both spatial (i.e. within reefs, between reefs and between regions) and taxonomic scales (i.e. within and between closely related species).
Circum Black Sea phylogeography of Barbus freshwater fishes: divergence in the Pontic glacial refugium
Authors: Kotlík P. , Bogutskaya N. G. , Ekmekçi F. G. 
Published: December 2003

AbstractWe used DNA sequence variation at the mitochondrial cytochrome b gene (1141 bp) to assess the phylogeography of Barbus fishes in the Black Sea region. Our aim was to test whether the recent (≈ 22 000–7500 years ago) freshwater phase of the Black Sea was a conduit for gene flow among freshwater fishes that today are found in streams entering the saltwater Black Sea. Deep phylogeographical breaks suggestive of allopatric divergence were observed between four regional groups of populations. Coalescent simulation used to distinguish between this and an alternative scenario that the phylogeographical structure was due to random lineage sorting showed that the contemporary populations were unlikely (P < 0.001) to have been founded by a single ancestral population. Divergences between the lineages (0.86–2.54%) were dated to the Middle to Late Pleistocene using distances and a molecular clock corrected for superimposed substitutions. Taken together, this evidence suggests that multiple refugial populations survived over several later glaciations in the vicinity of the Black Sea. This Pontic refugium served as the primary source for the postglacial expansion throughout Europe as far as the Atlantic basin. However, only one of the phylogeographical lineages contributed to this dispersion, whereas the others remain restricted to the Black Sea region and followed independent evolutionary trajectories.
Phylogeographical history of the spongeCrambe crambe(Porifera, Poecilosclerida): range expansion and recent invasion of the Macaronesian islands from the Mediterranean Sea
Authors: Duran S. , Giribet G. , Turon X. 
Published: December 2003

AbstractWe studied sequence variation in the nuclear ribosomal internal transcribed spacers (ITS‐1 and ITS‐2) in 111 individuals from 11 populations/localities of the spongeCrambe crambeacross the core species range in the western Mediterranean Sea and Atlantic Ocean. We report the first confirmed instance of intragenomic variation in sponges. Phylogeographical, nested clade and population genetic analyses were used to elucidate the species’ evolutionary history. The study revealed highly structured populations affected by restricted gene flow and isolation‐by‐distance. A contiguous range expansion in the whole distribution area of the sponge was inferred. Phylogenetic analyses indicate a recent origin of most sequence types that could be explained by a recent origin of the species or a by recent bottleneck event in the studied area. A recent expansion of the distribution range to the Macaronesian region from the Mediterranean Sea was also detected, suggesting thatC. crambewas recently introduced from the Mediterranean Sea to the Atlantic Ocean via human‐mediated transport, and that the pattern observed is not the result of a natural biogeographical relationship between these zones.
Population genetic structure of the sugar beet cyst nematode Heterodera schachtii: a gonochoristic and amphimictic species with highly inbred but weakly differentiated populations
Authors: Plantard O. , Porte C. 
Published: December 2003

AbstractThe sugar beet cyst nematode Heterodera schachtii is a soil‐dwelling phytoparasitic nematode that feeds on beet roots. It is an important pest in most sugar beet growing areas, and better knowledge of its genetic variability is an important step to preserve the durability of resistant sugar beet varieties. The population genetic structure of this species in northern France was studied using five microsatellite markers. A hierarchical sampling design was used to investigate spatial structuring at the scale of the region, the field and the plant. Multilocus genotypes were obtained for single individual second‐stage larvae, using only one individual per cyst in order to avoid the analysis of closely allied individuals (larvae from the same cyst share at least the same mother). A consistent trend of heterozygote deficit at all loci was observed at all spatial scales. Heterozygote deficit at the level of individual plants argues against its generation through a Wahlund effect. Inbreeding could be due to very limited active dispersal of larvae in the soil, favouring mating between siblings, such as larvae emerging from the same cyst. Such behaviour could have important consequences for the evolution of virulence in increasing the production of homozygous virulent individuals. Moreover, an analysis of molecular variance (amova) reveals that only 1.6% of the genetic variability is observed among regions, 3.7% among fields of the same region and 94.6% within fields. The very low level of genetic differentiation among fields is also indicated by low values of FST (≤ 0.105) even for fields 150 km apart. We suggest that long‐distance gene flows occur due to passive transport of cysts by human activities, water or wind. As such mechanisms of gene flow would involve cysts and not larvae, the strong signals of inbreeding observed at the local scale should not be disrupted. To our knowledge, this study constitutes the first investigation of the genetic structure of a phytoparasitic nematode based on neutral codominant genetic markers scored in single individuals.
Mitochondrial DNA variation in North American populations of Daphnia obtusa: continentalism or cryptic endemism?
Authors: Penton E. H. , Hebert P. D. N. , Crease T. J. 
Published: December 2003

AbstractThe morphological stasis of many freshwater crustaceans has resulted in the prior delineation of cosmopolitan species and has been explained by their capacity for long‐distance dispersal. This study examines the phylogeography of Daphnia obtusa, a cladoceran thought to be widespread in North America. However, sequence variation of the mitochondrial cytochrome c oxidase subunit I gene indicates that this taxon is composed of two morphologically cryptic species, designated D. obtusa NA1 and NA2. NA2 is restricted to the east, whereas NA1 is broadly distributed across the United States, and is subdivided into four phylogroups that show weak genetic differentiation over broad geographical areas, which likely reflects recent long‐distance dispersal. The current distributions of the four phylogroups in NA1 can be explained by recent range expansion from different refugia following the last Pleistocene glacial advance. Interestingly, the mitochondrial phylogroups identified in this study do not correspond to lineages detected in a previous allozyme analysis. However, the latter groups are associated with a habitat shift suggesting that natural selection may have played a role in their divergence. The results of this and previous studies illustrate the complicated biogeographical history of freshwater cladocerans.
Extensive sharing of chloroplast haplotypes among European birches indicates hybridization among Betula pendula, B. pubescens and B. nana
Authors: Palme A. E. , Su Q. , Palsson S. , Lascoux M. 
Published: December 2003

AbstractExtensive sharing of chloroplast haplotypes among the silver birch, Betula pendula Roth., the downy birch, B. pubescens Ehrh., and the dwarf birch, B. nana L., was discovered using polymerase chain reaction–restriction fragment length polymporphism markers. The geographical component of the genetic variation was stronger than the species component: the species were not significantly different while 11% of the variation could be attributed to differentiation between the two main regions studied, Scandinavia and western Russia. All haplotypes occurring in more than 2% of the individuals were shared among the species and the introgression ratios were quite large: 0.79 between B. pubescens and B. pendula and 0.67 between B. pubescens and B. nana. The data also indicate that B. pendula individuals are more similar to sympatric B. pubescens than to B. pendula individuals from nearby forests. However, this trend is not as pronounced when B. pubescens is considered, suggesting that introgression is not symmetrical. The haplotype sharing among the three Betula species is most likely caused by hybridization and subsequent cytoplasmic introgression.
Speciation of Iberian diving beetles in Pleistocene refugia (Coleoptera, Dytiscidae)
Authors: Ribera Ignacio , Vogler Alfried P. 
Published: December 2003

AbstractThe Mediterranean basin is an area of high diversity and endemicity, but the age and origin of its fauna are still largely unknown. Here we use species‐level phylogenies based on ≈ 1300 base pairs of the genes 16S rRNA and cytochrome oxidase I to establish the relationships of 27 of the 34 endemic Iberian species of diving beetles in the family Dytiscidae, and to investigate their level of divergence. Using a molecular clock approach, 18–19 of these species were estimated to be of Pleistocene origin, with four to six of them from the Late Pleistocene (≈ 100 000 years). A second, lower speciation frequency peak was assigned to Late Miocene or Early Pliocene. Analysis of the distributional ranges showed that endemic species placed in the tip nodes of the trees are significantly more likely to be allopatric with their sisters than endemic species at lower node levels. Allopatric sister species are also significantly younger than sympatric clades, in agreement with an allopatric mode of speciation and limited subsequent range movement. These results strongly suggest that for some taxa Iberian populations were isolated during the Pleistocene long enough to speciate, and apparently did not expand their ranges to recolonize areas north of the Pyrenees. This is in contradiction to observations from fossil beetles in areas further north, which document large range movements associated with the Pleistocene glacial cycles hypothesized to suppress population isolation and allopatric speciation.
Significant reproductive skew in the facultatively polygynous antPheidole pallidula
Authors: Fournier D. , Aron S. , Keller L. 
Published: December 2003

AbstractReproductive skew — the extent to which reproduction is unevenly shared between individuals in a social group — varies greatly between and within animal species. In this study, we investigated how queens share parentage in polygynous (multiple queen) colonies of the Mediterranean antPheidole pallidula. We used highly polymorphic microsatellites markers to determine parentage of gynes (new queens), males and workers inP. pallidulafield colonies. The comparison of the genotypes of young and adult workers revealed a very low queen turnover (less than 2%). The first main finding of the study of reproductive skew in these colonies was that there was a significant departure from equal contribution of queens to gyne, male and worker production. Reproductive skew was greater for male production than for queen and worker production. There was no relationship between the magnitude of the reproductive skew and the number of reproductive queens per colony, their relatedness and the overall colony productivity, some of the factors predicted to influence the extent of reproductive skew. Finally, our study revealed for the first time a trade‐off in the relative contribution of nestmate queens to gyne and worker production. The queens contributing more to gyne production contributed significantly less to worker production.
Amplified fragment length polymorphism versus random amplified polymorphic DNA markers: clonal diversity in Saxifraga cernua
Authors: Kjølner S. , Såstad S. M. , Taberlet P. , Brochmann C. 
Published: December 2003

AbstractRandom amplified polymorphic DNA (RAPD) markers are sensitive to changes in reaction conditions and may express polymorphisms of nongenetic origin. Taxa with variable chromosome numbers are particularly challenging cases, as differences in DNA content may also influence marker reproducibility. We addressed these problems by comparing RAPD and amplified fragment length polymorphism (AFLP) analyses of clonal identity and relationships in a chromosomally variable arctic plant, the polyploid Saxifraga cernua, which has been thought to be monoclonal over large geographical distances. Fifty‐seven plants from four Greenland populations were analysed using a conservative scoring approach. In total, 26 AFLP and 32 RAPD multilocus phenotypes (putative clones) were identified, of which 21 were identical and each of the remaining five AFLP clones was split into two to three very similar RAPD clones. This minor difference can be explained by sampling error and stochastic variation. The pattern observed in Greenland corroborates our previous results from Svalbard, suggesting that rare sexual events in S. cernua are sufficient to maintain high levels of clonal diversity even at small spatial scales. We conclude that although AFLP analysis is superior in terms of efficiency, RAPDs may still be used as reliable markers in small low‐tech laboratories.
Consequences of unequal population size, asymmetric gene flow and sex‐biased dispersal on population structure in brook charr (Salvelinus fontinalis)
Authors: Fraser Dylan J. , Lippé Catherine , Bernatchez Louis 
Published: December 2003

AbstractUnravelling relationships between dispersal and population structure requires considering the impacts of assumption violations of indirect gene flow models in a given system. We combined temporal, individual and coalescent‐based analyses of microsatellite DNA variation to explore the general hypothesis that unequal effective population size (Ne), asymmetric gene flow (m) and nonrandom (sex‐biased) individual dispersal had an important effect on spatiotemporal population structuring in lake‐dwelling brook charr (Salvelinus fontinalis). This integrative examination shed light on the dichotomous structuring observed between an outlet and three tributary‐spawning populations and their potential for adaptive divergence. It revealed further that finer tributary population structuring incongruent with drainage structure has been shaped by asymmetric m from one population with a large Ne towards two populations of smaller Ne. Gene flow among the tributaries was also mediated mainly by male‐biased dispersal. However, longer distance dispersal from tributaries to the outflow was female‐biased. Spatially dependent sex‐biased dispersal may have contributed therefore to gene flow at different levels of population structuring. Our results demonstrate how dispersal and population structure may interrelate to produce spatial variation in intraspecific diversity, and are therefore relevant for conservation programmes seeking to define conservation units or predict recolonization rates of extirpated populations.
Mitochondrial control region diversity of the houbara bustard Chlamydotis undulata complex and genetic structure along the Atlantic seaboard of North Africa
Authors: Idaghdour Youssef , Broderick Damien , Korrida Amal , Chbel Faiza 
Published: December 2003

AbstractThe houbara bustard, Chlamydotis undulata, is a declining cryptic desert bird whose range extends from North Africa to Central Asia. Three subspecies are currently recognized by geographical distribution and morphology: C.u.fuertaventurae, C.u.undulata and C.u.macqueenii. We have sequenced 854 bp of mitochondrial control region from 73 birds to describe their population genetic structure with a particular sampling focus on the connectivity between C.u.fuertaventurae and C.u.undulata along the Atlantic seaboard of North Africa. Nucleotide and haplotypic diversity varied among the subspecies being highest in C.u.undulata, lowest in C.u.fuertaventurae and intermediate in C.u.macqueenii. C.u.fuertaventurae and C.u.undulata are paraphyletic and an average nucleotide divergence of 2.08% splits the later from C.u.macqueenii. We estimate that C.u.fuertaventurae and C.u.undulata split from C.u.macqueenii approximately 430 000 years ago. C.u.fuertaventurae and C.u.undulata are weakly differentiated (FST = 0.27, Nm = 1.3), indicative of a recent shared history. Archaeological evidence indicates that houbara bustards have been present on the Canary Islands for 130–170 000 years. However, our genetic data point to a more recent separation of C.u.fuertaventurae and C.u.undulata at around 20–25 000 years. Concordant archaeological, climatic opportunities for colonization and genetic data point to a scenario of: (i) initial colonization of the Canary Islands about 130 000 years ago; (ii) a period of secondary contact 19–30 000 years ago homogenizing any pre‐existing genetic structure followed by; (iii) a period of relative isolation that persists today.
Genetic consequences of Pleistocene glaciations for the tundra vole (Microtus oeconomus) in Beringia
Authors: Galbreath Kurt E. , Cook Joseph A. 
Published: December 2003

AbstractRepeated glacial events during the Pleistocene fragmented and displaced populations throughout the northern continents. Different models of the effects of these climate‐driven events predict distinct phylogeographic and population genetic outcomes for high‐latitude faunas. The role of glaciations in (i) promoting intraspecific genetic differentiation and (ii) influencing genetic diversity was tested within a phylogeographic framework using the rodent Microtus oeconomus. The spatial focus for the study was Beringia, which spans eastern Siberia and northwestern North America, and was a continental crossroads and potential high arctic refugium during glaciations. Variation in mitochondrial DNA (cytochrome b and control region; 214 individuals) and nuclear DNA (ALDH1 intron; 63 individuals) was investigated across the Beringian region. Close genetic relationships among populations on either side of the Bering Strait are consistent with a history of periodic land connections between North America and Asia. A genetic discontinuity observed in western Beringia between members of a Central Asian clade and a Beringian clade is geographically congruent with glacial advances and with phylogeographic discontinuities identified in other organisms. Divergent island populations in southern Alaska were probably initially isolated by glacial vicariance, but subsequent differentiation has resulted from insularity. Tests of the genetic effects of postglacial colonization were largely consistent with expansion accompanied by founder effect bottlenecking, which yields reduced diversity in populations from recently deglaciated areas. Evidence that populations in the Beringian clade share a history of expansion from a low‐diversity ancestral population suggests that Beringia was colonized by a small founder population from central Asia, which subsequently expanded in isolation.