bluuebunny/crossref_metadata_2025 huggingface dataset:
Karyotype analysis and chromosome evolution in South American species of Lathyrus (Leguminosae)
Authors: Seijo J. Guillermo , Fernández Aveliano
Published: February 2008

The karyotypes of 10 species and one variety of South American Lathyrus were determined and compared with those obtained of five entities from the Northern Hemisphere. Although all the species have a chromosome number of 2n = 14, they could be differentiated by their karyotype formula and quantitative parameters of the karyotypes. Phenetic distance and principal component analysis showed that in spite of the differences observed among entities, they can be grouped in clusters that coincide with the taxonomic sections established by F. K. Kupicha and with the life cycle of the species. South American species form a homogeneous group and can be distinguished by the presence of a subtelocentric pair, which has a macrosatellite in the long arm, and the lack of a short metacentric pair characteristic of most species of the Northern Hemisphere. From an evolutionary point of view, variation in total chromosome length without major changes in the karyotype formula suggests that changes in the amounts of genomic DNA are proportional to the relative length of each chromosome arm and that species of Notolathyrus evolved in a concerted fashion. Variation in genome size, however, is congruent with morphological variation of some reproductive organs as well as with the life cycle and minimum generation time, as predicted by the nucleotype hypothesis.
Nuclear and cytoplasmic variation within and between EurasianLarix(Pinaceae) species
Authors: Semerikov Vladimir L. , Lascoux Martin
Published: February 2008

The genetic variation in nuclear and cytoplasmic markers was investigated in 28 populations belonging to EurasianLarixspecies (L. decidua,L. sibirica,L. gmelinii,L. olgensis, andL. kaempferi). Nuclear genetic variation was assessed at 214 AFLP loci, and both PCR‐RFLP and four microsatellite loci were used to estimate variation of the chloroplast DNA. Variation of the mitochondrial genome was measured using RFLPs. Although population differentiation at both nuclear and chloroplast markers was much weaker than at mitochondrial DNA, it nonetheless corroborated the grouping observed with mitochondrial DNA. The AFLPs led to the same population grouping as mtDNA. Notably, the presence of two ancient western and eastern groups withinL. sibiricawas confirmed and possible postglacial routes inferred. The genetic composition of the northernmostL. sibiricapopulation in our sample established that it is located at the confluence of the eastern and western recolonization routes. The joint use of the three markers also indicated that populations around Lake Baikal are hybrids betweenL. gmeliniiandL. sibirica, withL. gmeliniiprimarily acting as the pollinator. Finally, AFLP‐based estimates of nucleotide variation were an order of magnitude larger than the strikingly low estimates of nucleotide variation recently reported inPinus sylvestris.
The reproductive biology of the invasive ferns Lygodium microphyllum and L. japonicum (Schizaeaceae): implications for invasive potential
Authors: Lott Michael S. , Volin John C. , Pemberton Robert W. , Austin Daniel F.
Published: February 2008

The effect of culture system and population source on sexual expression and sporophyte production was examined for two invasive fern species in Florida, USA, Lygodium microphyllum and L. japonicum (Schizaeaceae). Both species are currently spreading through Florida. Long‐distance dispersal of ferns is thought to rely on successful intragametophytic selfing. Given the rate of spread observed in both Lygodium species, we hypothesized that both species are capable of intragametophytic selfing. To test this hypothesis, gametophytes of both species were grown in vitro as isolates, pairs, and groups. Both species were capable of intragametophytic selfing; 78% of L. microphyllum isolates produced sporophytes and over 90% of the L. japonicum isolates produced sporophytes. Lygodium microphyllum also displayed the ability to reproduce via intergametophytic crossing, facilitated by an antheridiogen pheromone. Sporophyte production was rapid across mating systems for both species, an advantage in Florida's wet and dry seasonal cycles. The high intragametophytic selfing rate achieved by both species has likely facilitated their ability to colonize and spread through Florida. The mixed mating system observed in L. microphyllum appears to give this species the ability to invade distant habitats and then adapt to local conditions.
Divergence in mycorrhizal specialization within Hexalectris spicata (Orchidaceae), a nonphotosynthetic desert orchid
Authors: Taylor D. Lee , Bruns Thomas D. , Szaro Timothy M. , Hodges Scott A.
Published: February 2008

Evidence is accumulating for specialized yet evolutionarily dynamic associations between orchids and their mycorrhizal fungi. However, the frequency of tight mycorrhizal specificity and the phylogenetic scale of changes in specificity within the Orchidaceae are presently unknown. We used microscopic observations and PCR‐based methods to address these questions in three taxa of nonphotosynthetic orchids within the Hexalectris spicata complex. Fungal ITS RFLP analysis and sequences of the ITS and nuclear LSU ribosomal gene fragments allowed us to identify the fungi colonizing 25 individuals and 50 roots. Thanatephorus ochraceus (Ceratobasidiaceae) was an occasional colonizer of mycorrhizal roots and nonmycorrhizal rhizomes. Members of the Sebacinaceae were the primary mycorrhizal fungi in every Hexalectris root and were phylogenetically intermixed with ectomycorrhizal taxa. These associates fell into six ITS RFLP types labeled B through G. Types B, C, D, and G were found in samples of H. spicata var. spicata, while only type E was found in H. spicata var. arizonica and only type F was found in H. revoluta. These results provide preliminary evidence for divergence in mycorrhizal specificity between these two closely related orchid taxa. We hypothesize that mycorrhizal interactions have contributed to the evolutionary diversification of the Orchidaceae.
Salt spray differentially affects water status, necrosis, and growth in coastal sandplain heathland species
Authors: Griffiths Megan E. , Orians Colin M.
Published: February 2008

Sandplain heathlands are disturbance‐dependent plant communities that occur infrequently in coastal areas of the northeastern United States. We hypothesize that salt spray plays a role in maintaining the composition of the heathland community by excluding salt‐intolerant species close to the ocean. We examined the distributions of Solidago nemoralis, Myrica pensylvanica, Pinus rigida, and Quercus spp. in heathlands and conducted greenhouse studies to determine whether different levels of salt spray tolerance explain patterns found in the field. We found that common heathland forb and shrub species grow closer to the ocean than successional woody species. In greenhouse experiments, these species differ in their water status, necrosis, and growth responses to salt spray. The tree species P. rigida and Q. rubra are more susceptible to salt spray than the common heathland species M. pensylvanica. Our results suggest that salt spray may prevent tree species in heathlands from growing close to the ocean and therefore might be an important factor in maintaining the characteristic community composition of these dwarf shrublands in coastal habitats.
Seedling demography in an alpine ecosystem
Authors: Forbis Tara A.
Published: February 2008

Seedling establishment has long been believed to be rare on alpine tundra because of predicted life history trade‐offs, the clonality of alpine species, and the harshness of the alpine climate. Contrary to the idea that seedlings are rare on alpine tundra, a 4‐yr demographic study of seedlings at Niwot Ridge, Colorado, USA, found seedlings at high densities, particularly in wetter plant communities. Higher germination densities were associated with higher soil moistures both across communities and across time. Mortality of seedlings was highest in the first year and decreased in subsequent years. Species' abundances differed between seedling and adult populations. Many forbs that lacked vegetative reproduction were significantly more abundant among seedling populations, and many monocots and clonal forbs were more abundant among adult populations. In a comparison with published demographic rates, seedling recruitment and mortality rates of Niwot Ridge species fell above or within rates for a wide range of perennial species. Therefore, germination and seedling establishment stages are no more limiting to sexual reproduction in alpine plants than in other perennial plants.
Incongruence between cladistic and taxonomic systems
Authors: Grant Verne
Published: February 2008

Cladistic and taxonomic treatments of the same plant group usually exhibit a mixture of congruences and incongruences. The question arises in the case of the incongruences as to which version is right and which is wrong. Many cladists believe that cladistics is a superior approach and gives the best results. There are several conceptual and methodological differences between cladistics and taxonomy that cause incongruence. One important conceptual difference is the use of different criteria for grouping: order of branching vs. similarity and difference (clades vs. taxa). Another is the policy regarding paraphyletic groups: to ban them in cladistics but ignore the ban in taxonomy. These two differences automatically lead to some incongruences. One approach is not right and the other wrong; each is operating by its own standards. However, when cladists apply the paraphyly rule to a taxonomic system and conclude that it needs revision to eliminate paraphyly, as cladists often do, they are judging the taxonomic system by a wrong standard. Several differences between the two schools in the use and handling of characters can also cause incongruence. First consider phenetic characters. Taxonomy uses a very wide range of these, whereas phenetic cladistics sets restrictions on the selection of characters, which deprive it of potentially useful evidence. Taxonomic systems generally rest on a broader empirical foundation than phenetic cladistic systems. Next, consider molecular cladistics, which is the leader in the use of DNA evidence. Two sources of incongruence between molecular cladistics and taxonomic systems can come into play here. First, the molecular evidence used in cladistics comes mainly from cytoplasmic organelles, whereas taxonomic systems are based on characters that are determined mainly by the chromosomal genome. More generally, the database in a molecular cladogram is, in itself, too narrow to serve as a foundation for an organismic classification. In cases of incongruence, the molecular evidence can be a reliable indicator of taxonomic relationships sometimes, misleading other times, and may afford no clear basis for a systematic decision. In this situation, it is helpful, indeed necessary, to integrate the molecular evidence with the phenetic evidence and bring more characters to bear on the question.
Floral ontogeny in Swartzia (Leguminosae: Papilionoideae: Swartzieae): distribution and role of the ring meristem
Authors: Tucker Shirley C.
Published: February 2008

The anomalous systematic position of Swartzieae at the base of Papilionoideae is correlated with unusual developmental features: one petal or none; a ring meristem; polystemony; heterostemony; little or no alignment of stamens as antesepalous or antepetalous; multicarpely; and absence of unidirectional order of organs except in the calyx. Symmetry is zygomorphic throughout development. Floral ontogeny of four species of Swartzia reveals five sepals are initiated successively, beginning abaxially, but intercalary growth below the separate sepals forms a tubular calyx that splits irregularly, a feature typifying the genus. A single petal is initiated adaxially or may be missing altogether (in S. sericea). The apex enlarges and forms a ring meristem concurrently with carpel initiation. Several large‐stamen primordia (2–15, according to the species) initiate first on the ring, followed by 40–150 small‐stamen primordia. The latter initiate in centrifugal order in S. aureosericea and S. laurifolia or in acropetal order in S. sericea and S. madagascariensis. While ring meristems are considered to be homologous among Neotropical species studied as well as in the African S. madagascariensis, they vary in extent, duration, order of initiation, and productivity. Swartzieae is unlikely to be ancestral to the rest of Papilionoideae, based on radically differing floral ontogeny in the two groups.
Androecium diversity and evolution in Myristicaceae (Magnoliales), with a description of a new Malagasy genus,Doyleanthusgen. nov
Authors: Sauquet Hervé
Published: February 2008

Myristicaceae (Magnoliales) consist of 20 genera and nearly 500 species of lowland rainforest trees with a pantropical distribution. They are distinctive in having small, unisexual flowers with stamens fused into a synandrium, which consists of a single whorl of sessile anthers borne around a sterile central column. With its short filaments and more complex anther phyllotaxy, the Malagasy genusMauloutchiarepresents a notable exception to this pattern. New scanning electron microscope (SEM) examinaitons ofBrochoneura,Cephalosphaera,Knema,Mauloutchia, andStaudtiaare incorporated into a broader review of androecium diversity across the family. These new results are discussed in the context of a phylogenetic study of the family, based on combined molecular and morphological data. The unusual synandrium ofMauloutchia, nested among genera with strictly sessile anthers fused to the column, appears to be secondarily derived. Furthermore, the diversity of patterns observed within the genus may be interpreted as the result of a stepwise transformation involving reappearance and elongation of filaments, increase of anther number, and modification of anther phyllotaxy. However, the question of the origin of stamen fusion in Myristicaceae remains unanswered and requires more developmental studies. Finally, a new Malagasy genus of Myristicaceae (Doyleanthus) is described, which is similar toMauloutchiain most characters but fundamentally different in androecial traits.
Natural selection on floral traits ofLobelia(Lobeliaceae): spatial and temporal variation
Authors: Caruso Christina M. , Peterson S. Brook , Ridley Caroline E.
Published: February 2008

The strength and direction of natural selection on floral traits can vary spatially and temporally because of variation in the biotic and abiotic environment. High spatial variation in selection should lead to differentiation of floral traits among populations. In contrast, high temporal variation in selection should retard the evolution of population‐specific floral phenotypes. To determine the relative importance of spatial vs. temporal variation in natural selection, we measured phenotypic selection on seven floral traits of the wildflowersLobelia cardinalisandL. siphiliticain 1999 and 2000.Lobelia cardinalisexperienced significant temporal variation in selection, whereasL. siphiliticaexperienced spatial variation in selection on the same traits. This variation in selection on floral traits was associated with spatial and temporal differences in the soil microenvironment. Although few studies of natural selection include spatial or temporal replicates, our results suggest that such replication is critical for understanding the distribution of phenotypes in nature.
Phylogenetic analyses of Cornales based on 26S rRNA and combined 26S rDNA‐MATK‐RBCLsequence data
Authors: Fan Chuanzhu , Xiang Qiu‐Yun (Jenny)
Published: February 2008

Nuclear 26S rDNA sequences were used to corroborate and test previously publishedmatK‐rbcL‐based hypotheses of phylogenetic relationships in Cornales. Sequences were generated for 53 taxa includingAlangium,Camptotheca,Cornus,Curtisia,Davidia,Diplopanax,Mastixia,Nyssa, and four families: Grubbiaceae, Hydrangeaceae, Hydrostachyaceae, and Loasaceae. Fifteen taxa from asterids were used as outgroups. The 26S rDNA sequences were initially analyzed separately and then combined withmatK‐rbcLsequences, using both parsimony and maximum likelihood methods. Eight strongly supported major clades were identified within Cornales by all analyses:Cornus,Alangium, nyssoids (Nyssa,Davidia, andCamptotheca), mastixioids (MastixiaandDiplopanax), Hydrangeaceae, Loasaceae,Grubbia‐Curtisia, andHydrostachys. However, relationships among the major lineages are not strongly supported in either 26S rDNA or combined 26S rDNA‐matK‐rbcLtopologies, except for the sister relationships betweenCornusandAlangiumand between nyssoids and mastixioids in the tree from combined data. Discrepancies in relationships among major lineages, especially the placement of the long‐branchedHydrostachys, were found between parsimony and maximum likelihood trees in all analyses. Incongruence between the 26S rDNA andmatK‐rbcLdata sets was suggested, where Hydrangeaceae was found to be largely responsible for the incongruence. The long branch ofHydrostachysrevealed in previous analyses was reduced significantly with more sampling. Maximum likelihood analysis of combined 26S rDNA‐matK‐rbcLsequences suggested thatHydrostachysmight be sister to the remainder of Cornales, thatCornus‐Alangiumare sisters, that nyssoids‐mastixioids are sisters, and that Hydrangeaceae‐Loasaceae are sisters, consistent with previous analyses ofmatK‐rbcLsequence data.
Divisestylus gen. nov. (aff. Iteaceae), a fossil saxifrage from the Late Cretaceous of New Jersey, USA
Authors: Hermsen Elizabeth J. , Gandolfo María A. , Nixon Kevin C. , Crepet William L.
Published: February 2008

Fossilized flowers and fruits from the Upper Cretaceous (Turonian, ca. 90 million years [my] before present) Raritan Formation of New Jersey are described as the new genus Divisestylus with two species, D. brevistamineus and D. longistamineus. The fossils are fusainized and three‐dimensionally preserved. Morphological characteristics suggest affinities with extant Saxifragaceae and Iteaceae, two closely related families in Saxifragales. Similarities include a pentamerous perianth, calyx fused below into a hypanthium with free sepal lobes above, haplostemonous androecium with stamens situated opposite the calyx lobes, inferior ovary, bicarpellate gynoecium, numerous ovules on axile placentas, conspicuous intrastaminal nectary ring, and capsulate fruit opening apically. The unique fusion of the gynoecium, with carpels and stigmas fused but styles free, indicates closer affinities with extant Iteaceae, whereas other characters, such as basifixed anthers in D. brevistamineus, tricolpate and striate pollen grains, and anomocytic stomata, indicate closer affinities to Saxifragaceae. Cladistic analyses utilizing molecular data from a previously published analysis and morphological data as well as morphological data alone demonstrate the fossils share a more recent common ancestor with Iteaceae than Saxifragaceae, thereby making Divisestylus the oldest fossils known with clear affinities to Iteaceae.
Age and sex‐specific rates of leaf regeneration in the Mojave Desert moss Syntrichia caninervis
Authors: Stark Lloyd R. , Nichols Lorenzo , McLetchie D. Nicholas , Smith Stanley D. , Zundel Christopher
Published: February 2008

The extremely skewed female‐biased sex ratio in the desert moss Syntrichia caninervis was investigated by assessing the regeneration capacity of detached leaves. Juvenile, green, yellow‐green, and brown leaves equating to approximately 0, 2, 6, and 12 yr of age, respectively, were detached from individuals of S. caninervis collected from 10 field populations and grown in a growth chamber for 58 d at a light intensity of 33–128 μmol · m−2 · s−1. Younger leaves (0–2 yr old) tended to have a greater viability, regenerate more quickly, extend their protonemal filaments farther, produce shoots (gametophores) more quickly, produce more shoots, and accumulate a greater biomass than older leaves (6 and 12 yr old). Among younger leaf classes, regenerating female leaves were more likely to produce a shoot than male leaves and produced more shoots than male leaves. The sexes did not differ significantly in time until protonemal emergence, linear extension of protonemata, or rate of biomass accumulation. However, protonemata of male leaves tended to emerge more quickly and produce a greater total biomass, ultimately consisting mostly of protonemata, than did female leaves. The more rapid proliferation of shoots by female leaf regenerants may help to explain the rarity of males in this species.
The phylogeny, evolution, and classification of the genus Globba and tribe Globbeae (Zingiberaceae): appendages do matter
Authors: Williams Kyle J. , Kress W. John , Manos Paul S.
Published: February 2008

The genus Globba (100 species) is one of the largest genera in the primarily tropical Zingiberaceae. Globba along with the small genera Gagnepainia, Hemiorchis, and Mantisia comprise the Globbeae, one of the two tribes of subfamily Zingiberoideae. Traditional infrageneric classification in Globba has focused on the number of anther appendages: zero, two, or four. Parsimony and Bayesian analyses were conducted on nuclear internal transcribed spacer (ITS) and plastid trnK‐matK data from a broad sampling of Globba and related genera. Results show Mantisia to be monophyletic but nested within Globba, while Hemiorchis and Gagnepainia are monophyletic genera that are sister to each other. Anther appendage number and shape, along with inflorescence and fruit morphology, are the most important characters for understanding evolutionary relationships in Globba. A new infrageneric classification system for Globba, recognizing three subgenera and seven sections is presented. The four species of Mantisia are formally transferred into Globba but retained as a distinct section. Within Globba, a notable biogeographic boundary is seen at the Isthmus of Kra in southern Thailand.
Comparative biogeography of the cytotypes of annual Microthlaspi perfoliatum (Brassicaceae) in Europe using isozymes and cpDNA data: refugia, diversity centers, and postglacial colonization
Authors: Koch Marcus , Bernhardt Karl‐Georg
Published: February 2008

In the last few years, the biogeography of many European plant species has been analyzed using molecular markers, and some consistent patterns of Pleistocenic differentiation and range fluctuations have been established. These studies mostly focused on perennial herbs or woody species, rarely considering annual taxa. This study focused on the annual Microthlaspi perfoliatum, which is distributed all over Europe and comprises three cytotypes. Morphologically, these cytotypes are hard to distinguish, although, based on molecular markers, they should be treated as two different species. Diploid and polyploid cytotypes had a different biogeographical history, with distinct glacial refugia. For the polyploids, a well‐known distribution pattern of relict areas was confirmed, with Iberia, Italy, and the Balkans serving as primary Pleistocene refugia. Secondary refuge areas have been detected in southeastern France and neighboring Switzerland, with closer affinity to the Iberian refugium than to any other region based on allozyme and cpDNA haplotype data. For the diploids, two refugia have been characterized, one of which is congruent to the secondary refugium of the polyploids in France and Switzerland. The second refuge of diploid populations is located in unglaciated lowland areas of East Austria and Croatia. Isozyme and cpDNA haplotype data favor a postglacial colonization of diploid populations into Germany from Austrian lowland areas along the Danube River as well as from Switzerland. This scenario is also true for polyploids in Germany, Belgium, and Sweden.
A phylogeny of all species of Arceuthobium (Viscaceae) using nuclear and chloroplast DNA sequences
Authors: Nickrent Daniel L. , García Miguel A. , Martín Maria P. , Mathiasen Robert L.
Published: February 2008

The genus Arceuthobium (dwarf mistletoes, Viscaceae) comprises 42 species that parasitize hosts in Pinaceae and Cupressaceae in the Old and New Worlds. Maximum parsimony analyses were conducted on two data partitions (separately and combined): nuclear ribosomal internal transcribed spacer (ITS) sequences for all 42 currently recognized species and chloroplast trnT‐L‐F sequences for 34 New World species. The Old and New World species were phylogenetically distinct using ITS, thus making subgenus Arceuthobium paraphyletic. Arceuthobium pendens and A. guatemalense comprise the basalmost clade of subgenus Vaginata, characterized by the presence of flabellate secondary branching. The trnT‐L‐F sequences, which vary widely in length depending upon taxon, contain three times less phylogenetic signal than ITS, although homoplasy for this partition is lower. Several of the clades obtained from analysis of nuclear ITS sequences are also recovered using trnT‐L‐F sequences such as A. guatemalense and A. pendens, the A. rubrum group, the A. vaginatum group, and the A. campylopodum group. The ITS + trnT‐L‐F tree is well resolved except for four internal nodes. A revised classification of the genus is discussed that recognizes only monophyletic species that are well differentiated by molecular data.
An expanded plastid DNA phylogeny of Orchidaceae and analysis of jackknife branch support strategy
Authors: Freudenstein John V. , van den Berg Cássio , Goldman Douglas H. , Kores Paul J. , Molvray Mia , Chase Mark W.
Published: February 2008

An expanded plastid DNA phylogeny for Orchidaceae was generated from sequences of rbcL and matK for representatives of all five subfamilies. The data were analyzed using equally weighted parsimony, and branch support was assessed with jackknifing. The analysis supports recognition of five subfamilies with the following relationships: (Apostasioideae (Vanilloideae (Cypripedioideae (Orchidoideae (Epidendroideae))))). Support for many tribal‐level groups within Epidendroideae is evident, but relationships among these groups remain uncertain, probably due to a rapid radiation in the subfamily that resulted in short branches along the spine of the tree. A series of experiments examined jackknife parameters and strategies to determine a reasonable balance between computational effort and results. We found that support values plateau rapidly with increased search effort. Tree bisection‐reconnection swapping in a single search replicate per jackknife replicate and saving only two trees resulted in values that were close to those obtained in the most extensive searches. Although this approach uses considerably more computational effort than less extensive (or no) swapping, the results were also distinctly better. The effect of saving a maximal number of trees in each jackknife replicate can also be pronounced and is important for representing support accurately.
Sympodial structure of spikelets in the tribe Schoeneae (Cyperaceae)
Authors: Zhang Xiufu , Wilson Karen L. , Bruhl Jeremy J.
Published: February 2008

Spikelet morphology of 250 specimens of 47 species of Schoeneae was examined using light microscopy and scanning electron microscopy. We confirmed that spikelet structure in Schoeneae is cymose with a sympodial “rachilla.” Monopodial spikelets, as described by most current literature, were not found in Schoeneae. Prophylls are not always present in sympodial spikelets and cannot be used to determine whether a spikelet is sympodial or monopodial. Spikelets of Schoeneae develop acropetally, and the uppermost glume may or may not produce a flower. The last feature may be variable within species and within individual plants, so presence or absence of this flower is not an indication of sympodial or monopodial spikelet structure in Schoeneae. Relative position of flower, glume, and axis is a reliable criterion to judge whether spikelets are sympodial or monopodial. In some species of Schoenus and in Ptilothrix, formation of the arch‐shaped base of the fertile glume relates to the shape of the inclined nodes on which the glume grows. This study highlights the need to reinvestigate spikelet structure in other tribes of Cyperaceae.
Chloroplast DNA diversity of Hieracium Pilosella (Asteraceae) introduced to New Zealand: reticulation, hybridization, and invasion
Authors: Trewick Steven A. , Morgan‐Richards Mary , Chapman Hazel M.
Published: February 2008

The European hawkweed Hieracium pilosella is a successful invader and a troublesome weed in New Zealand. The systematics of the genus Hieracium is extremely complex and contentious, probably due to recent speciation, hybridization, polyploidy, and diverse reproductive strategies. In the first chloroplast DNA survey of the group, we sequenced 285 plants (including H. pilosella and 12 other species of subgenus Pilosella) from New Zealand and Europe for 900 bp of trnL‐trnF. Eleven haplotypes were identified with much sharing among species. Three haplotypes (A, D, G) were found in seven, three, and four species, respectively, but two species (H. lactucella and H. auricula) had single, private haplotypes. Our cpDNA data for subgenus Pilosella are consistent with the group's having incomplete lineage sorting and/or recent reticulate evolution. Six haplotypes were identified in H. pilosella, four of these unique to this taxon in our sample. In New Zealand, haplotype A was common and occurred in plants of different ploidy (i.e., 4×, 5×, 6×), whereas haplotypes C, B, and M were restricted to 4×, 5×, and 6× plants, respectively. The distribution of haplotype variation suggests that some or all of the H. pilosella seeds accidentally introduced into New Zealand probably came from east Europe rather than the United Kingdom and that a minimum of four lineages were introduced. Within New Zealand, hybridization of H. pilosella with a related taxon (probably H. praealtum) has occurred at least three times, involving both obligate sexual tetraploids and facultative apomictic pentaploids of H. pilosella.
The plant tree of life: an overview and some points of view
Authors: Palmer Jeffrey D. , Soltis Douglas E. , Chase Mark W.
Published: February 2008

We provide a brief overview of this special issue on the plant tree of life, describing its history and the general nature of its articles. We then present our estimate for the overall topology and, for land plants, divergence times of the plant tree of life. We discuss several major controversies and unsolved problems in resolving portions of this tree. We conclude with a few thoughts about the prospects for obtaining a comprehensive, robustly resolved, and accurately dated plant tree of life and the importance of such a grand endeavor.
Assembling the fungal tree of life: progress, classification, and evolution of subcellular traits
Authors: Lutzoni François , Kauff Frank , Cox Cymon J. , McLaughlin David , Celio Gail , Dentinger Bryn , Padamsee Mahajabeen , Hibbett David , James Timothy Y. , Baloch Elisabeth , Grube Martin , Reeb Valérie , Hofstetter Valérie , Schoch Conrad , Arnold A. Elizabeth , Miadlikowska Jolanta , Spatafora Joseph , Johnson Desiree , Hambleton Sarah , Crockett Michael , Shoemaker Robert , Sung Gi‐Ho , Lücking Robert , Lumbsch Thorsten , O'Donnell Kerry , Binder Manfred , Diederich Paul , Ertz Damien , Gueidan Cécile , Hansen Karen , Harris Richard C. , Hosaka Kentaro , Lim Young‐Woon , Matheny Brandon , Nishida Hiromi , Pfister Don , Rogers Jack , Rossman Amy , Schmitt Imke , Sipman Harrie , Stone Jeffrey , Sugiyama Junta , Yahr Rebecca , Vilgalys Rytas
Published: February 2008

Based on an overview of progress in molecular systematics of the true fungi (Fungi/Eumycota) since 1990, little overlap was found among single‐locus data matrices, which explains why no large‐scale multilocus phylogenetic analysis had been undertaken to reveal deep relationships among fungi. As part of the project “Assembling the Fungal Tree of Life” (AFTOL), results of four Bayesian analyses are reported with complementary bootstrap assessment of phylogenetic confidence based on (1) a combined two‐locus data set (nucSSU and nucLSU rDNA) with 558 species representing all traditionally recognized fungal phyla (Ascomycota, Basidiomycota, Chytridiomycota, Zygomycota) and the Glomeromycota, (2) a combined three‐locus data set (nucSSU, nucLSU, and mitSSU rDNA) with 236 species, (3) a combined three‐locus data set (nucSSU, nucLSU rDNA, andRPB2) with 157 species, and (4) a combined four‐locus data set (nucSSU, nucLSU, mitSSU rDNA, andRPB2) with 103 species. Because of the lack of complementarity among single‐locus data sets, the last three analyses included only members of the Ascomycota and Basidiomycota. The four‐locus analysis resolved multiple deep relationships within the Ascomycota and Basidiomycota that were not revealed previously or that received only weak support in previous studies. The impact of this newly discovered phylogenetic structure on supraordinal classifications is discussed. Based on these results and reanalysis of subcellular data, current knowledge of the evolution of septal features of fungal hyphae is synthesized, and a preliminary reassessment of ascomal evolution is presented. Based on previously unpublished data and sequences from GenBank, this study provides a phylogenetic synthesis for the Fungi and a framework for future phylogenetic studies on fungi.
Diversity and evolutionary history of plastids and their hosts
Authors: Keeling Patrick J.
Published: February 2008

By synthesizing data from individual gene phylogenies, large concatenated gene trees, and other kinds of molecular, morphological, and biochemical markers, we begin to see the broad outlines of a global phylogenetic tree of eukaryotes. This tree is apparently composed of five large assemblages, or “supergroups.” Plants and algae, or more generally eukaryotes with plastids (the photosynthetic organelle of plants and algae and their nonphotosynthetic derivatives) are scattered among four of the five supergroups. This is because plastids have had a complex evolutionary history involving several endosymbiotic events that have led to their transmission from one group to another. Here, the history of the plastid and of its various hosts is reviewed with particular attention to the number and nature of the endosymbiotic events that led to the current distribution of plastids. There is accumulating evidence to support a single primary origin of plastids from a cyanobacterium (with one intriguing possible exception in the little‐studied amoeba Paulinella), followed by the diversification of glaucophytes, red and green algae, with plants evolving from green algae. Following this, some of these algae were themselves involved in secondary endosymbiotic events. The best current evidence indicates that two independent secondary endosymbioses involving green algae gave rise to euglenids and chlorarachniophytes, whereas a single endosymbiosis with a red algae gave rise to the chromalveolates, a diverse group including cryptomonads, haptophytes, heterokonts, and alveolates. Dinoflagellates (alveolates) have since taken up other algae in serial secondary and tertiary endosymbioses, raising a number of controversies over the origin of their plastids, and by extension, the recently discovered cryptic plastid of the closely related apicomplexan parasites.
Biology and systematics of heterokont and haptophyte algae
Authors: Andersen Robert A.
Published: February 2008

In this paper, I review what is currently known of phylogenetic relationships of heterokont and haptophyte algae. Heterokont algae are a monophyletic group that is classified into 17 classes and represents a diverse group of marine, freshwater, and terrestrial algae. Classes are distinguished by morphology, chloroplast pigments, ultrastructural features, and gene sequence data. Electron microscopy and molecular biology have contributed significantly to our understanding of their evolutionary relationships, but even today class relationships are poorly understood. Haptophyte algae are a second monophyletic group that consists of two classes of predominately marine phytoplankton. The closest relatives of the haptophytes are currently unknown, but recent evidence indicates they may be part of a large assemblage (chromalveolates) that includes heterokont algae and other stramenopiles, alveolates, and cryptophytes. Heterokont and haptophyte algae are important primary producers in aquatic habitats, and they are probably the primary carbon source for petroleum products (crude oil, natural gas).
Phylogeny and diversification of bryophytes
Authors: Shaw Jonathan , Renzaglia Karen
Published: February 2008

The bryophytes comprise three phyla of embryophytes that are well established to occupy the first nodes among extant lineages in the land‐plant tree of life. The three bryophyte groups (hornworts, liverworts, mosses) may not form a monophyletic clade, but they share life history features including dominant free‐living gametophytes and matrotrophic monosporangiate sporophytes. Because of their unique vegetative and reproductive innovations and their critical position in embryophyte phylogeny, studies of bryophytes are crucial to understanding the evolution of land plant morphology and genomes. This review focuses on phylogenetic relationships within each of the three divisions of bryophytes and relates morphological diversity to new insights about those relationships. Most previous work has been on the mosses, but progress on understanding the phylogeny of hornworts and liverworts is advancing at a rapid pace. Multilocus multigenome studies have been successful at resolving deep relationships within the mosses and liverworts, whereas single‐gene analyses have advanced understanding of hornwort evolution.
Molecular evidence on plant divergence times
Authors: Sanderson Michael J. , Thorne Jeffrey L. , Wikström Niklas , Bremer Kåre
Published: February 2008

Estimation of divergence times from sequence data has become increasingly feasible in recent years. Conflicts between fossil evidence and molecular dates have sparked the development of new methods for inferring divergence times, further encouraging these efforts. In this paper, available methods for estimating divergence times are reviewed, especially those geared toward handling the widespread variation in rates of molecular evolution observed among lineages. The assumptions, strengths, and weaknesses of local clock, Bayesian, and rate smoothing methods are described. The rapidly growing literature applying these methods to key divergence times in plant evolutionary history is also reviewed. These include the crown group ages of green plants, land plants, seed plants, angiosperms, and major subclades of angiosperms. Finally, attempts to infer divergence times are described in the context of two very different temporal settings: recent adaptive radiations and much more ancient biogeographic patterns.
Fossil evidence and phylogeny: the age of major angiosperm clades based on mesofossil and macrofossil evidence from Cretaceous deposits
Authors: Crepet William L. , Nixon Kevin C. , Gandolfo Maria A.
Published: February 2008

The fossil record has played an important role in the history of evolutionary thought, has aided the determination of key relationships through mosaics, and has allowed an assessment of a number of ecological hypotheses. Nonetheless, expectations that it might accurately and precisely mirror the progression of taxa through time seem optimistic in light of the many factors potentially interfering with uniform preservation. In view of these limitations, attempts to use the fossil record to corroborate phylogenetic hypotheses based on extensive comparisons among extant taxa may be misplaced. Instead we suggest a method—minimum age node mapping—for combining reliable fossil evidence with hypotheses of phylogeny. We use this methodology in conjunction with a phylogeny for angiosperms to assess timing in the history of major angiosperm clades. This method places many clades both with and without fossil records in temporal perspective, reveals discrepancies among clades in propensities for preservation, and raises some interesting questions about angiosperm evolution. By providing a context for understanding the gaps in the angiosperm fossil record this technique lends credibility and support to the remainder of the angiosperm record and to its applications in understanding a variety of aspects of angiosperm history. In effect, this methodology empowers the fossil record.
Fossils and plant phylogeny
Authors: Crane Peter R. , Herendeen Patrick , Friis Else Marie
Published: February 2008

Developing a detailed estimate of plant phylogeny is the key first step toward a more sophisticated and particularized understanding of plant evolution. At many levels in the hierarchy of plant life, it will be impossible to develop an adequate understanding of plant phylogeny without taking into account the additional diversity provided by fossil plants. This is especially the case for relatively deep divergences among extant lineages that have a long evolutionary history and in which much of the relevant diversity has been lost by extinction. In such circumstances, attempts to integrate data and interpretations from extant and fossil plants stand the best chance of success. For this to be possible, what will be required is meticulous and thorough descriptions of fossil material, thoughtful and rigorous analysis of characters, and careful comparison of extant and fossil taxa, as a basis for determining their systematic relationships.
Role of 2,4‐dichlorophenoxyacetic acid (2,4‐D) in somatic embryogenesis on cultured zygotic embryos of Arabidopsis: cell expansion, cell cycling, and morphogenesis during continuous exposure of embryos to 2,4‐D
Authors: Raghavan Val
Published: February 2008

The relationship between cell expansion and cell cycling during somatic embryogenesis was studied in cultured bent‐cotyledon‐stage zygotic embryos of a transgenic stock of Arabidopsis thaliana harboring a cyclin 1 At:β‐glucuronidase (GUS) reporter gene construct. In embryos cultured in a medium containing 2,4‐dichlorophenoxyacetic acid (2,4‐D), following a brief period of growth by cell expansion, divisions were initiated in the procambial cells facing the adaxial side at the base of the cotyledons. Cell division activity later spread to almost the entire length of the cotyledons to form a callus on which globular and heart‐shaped embryos appeared in about 10 d after culture. Anatomical and morphogenetic changes observed in cultured embryos were correlated with patterns of cell cycling by histochemical detection of GUS‐expressing cells. Although early‐stage somatic embryos did not develop further during their continued growth in the auxin‐containing medium, maturation of embryos ensued upon their transfer to an auxin‐free medium. In a small number of cultured zygotic embryos the shoot apical meristem was found to differentiate a leaf, a green tubular structure, or a somatic embryo. Contrary to the results from previous investigations, which have assigned a major role for the shoot apical meristem and cells in the axils of cotyledons in the development of somatic embryos on cultured zygotic embryos of A. thaliana, the present work shows that somatic embryos originate almost exclusively on the callus formed on the cotyledons. Other observations such as the induction of somatic embryos on cultured cotyledons and the inability of the embryo axis (consisting of the root, hypocotyl, and shoot apical meristem without the cotyledons) to form somatic embryos, reaffirm the important role of the cotyledons in somatic embryogenesis in this plant.
Cytotype segregation on regional and microgeographic scales in snow buttercups (Ranunculus adoneus: Ranunculaceae)
Authors: Baack Eric J.
Published: February 2008

Polyploid speciation is an important source of angiosperm diversity. Insights into the origin and establishment of new polyploid species may be gained by studying the distributions of ancestral and derivative cytotypes at multiple spatial scales. Diploid (2n= 16) and tetraploid (2n= 32) snow buttercups (Ranunculus adoneus: Ranunculaceae) occur in the alpine of the central and southern Rocky Mountains. Root‐tip squashes and flow cytometry were used to determine the ploidy of 1618 individuals from 35 populations. Samples from 31 of the 35 sites were entirely of one cytotype, either diploid or tetraploid. Diploid and tetraploid snow buttercups have nonoverlapping regional distributions. Where both cytotypes occur on the same site, the two are spatially segregated despite no apparent change in habitat. Triploid snow buttercups were only found at a diploid/tetraploid contact zone, while two hexaploid plants were found in tetraploid populations. Tetraploid establishment once or twice in the history of the species complex could account for the regional distribution of the two cytotypes. Habitat differentiation between cytotypes or reproductive exclusion of minority cytotypes may explain the observed segregation at both microgeographic and regional scales.
Population structure in Pseudoroegneria spicata (Poaceae: Triticeae) modeled by Bayesian clustering of AFLP genotypes
Authors: Larson Steven R. , Jones Thomas A. , Jensen Kevin B.
Published: February 2008

Pseudoroegneria spicata (Poaceae: Triticeae) is an abundant, allogamous species widely adapted to the temperate, semiarid steppe and open woodland regions of western North America. Amplified fragment length polymorphism (AFLP), model‐based Bayesian clustering, and other methods of hypothesis testing were used to investigate genetic diversity and population structure among 565 P. spicata plants from 82 localities representing much of the species distribution. Comparisons with four Asiatic Pseudoroegneria species and two North American Elymus wawawaiensis accessions demonstrate cohesiveness in P. spicata. However, P. spicata genotypes group by locality and geographic region based on genetic distance analysis. Average DNA polymorphism among P. spicata localities was significantly correlated (r = 0.58) with geographical distance. The optimum Bayesian cluster model included 21 P. spicata groups, indicating that dispersal among sampling locations was not sufficient to group genotypes into one unstructured population. Approximately 18.3% of the DNA polymorphism was partitioned among the 21 regional groups, 14.9% among localities within groups, and 66.8% within accessions. Average DNA polymorphism among Bayesian groups was correlated (r = 0.53) with the average geographic distance among Bayesian groups, which partly reflects isolation by distance. However, conspicuous regional boundaries were discernable among several divergent genetic groups.
Plant‐pollinator interactions in New Caledonia influenced by introduced honey bees
Authors: Kato Makoto , Kawakita Atsushi
Published: February 2008

The flora of New Caledonia is characterized by remarkably high species diversity, high endemicity, and an unusual abundance of archaic plant taxa. To investigate community‐level pollination mutualism in this endemic ecosystem, we observed flower visitors on 99 plant species in 42 families of various types of vegetation. Among the 95 native plant species, the most dominant pollination system was melittophily (bee‐pollinated, 46.3%), followed by phalaenophily (moth‐pollinated, 20.0%), ornithophily (bird‐pollinated, 11.6%), cantharophily (beetle‐pollinated, 8.4%), myophily (fly‐pollinated, 3.2%), chiropterophily (bat‐pollinated, 3.2%), and anemophily (wind‐pollinated, 3.2%). The prevalence of ornithophily by honeyeaters shows an ecological link to pollination mutualism in Australia. The relative dominance of phalaenophily is unique to New Caledonia, and is proposed to be related to the low diversity of the original bee fauna and the absence of long‐tongued bees. Although some archaic plants maintain archaic plant‐pollinator interactions, e.g., Zygogynum pollinated by micropterigid moths, or Hedycarya pollinated by thrips and staphylinid beetles, the most dominant organism observed on flowers was the introduced honey bee, Apis mellifera. The plant species now visited by honey bees are thought to have originally been pollinated by native solitary short‐tongued bees. Our data suggest that the unique systems of pollination mutualism in New Caledonia are now endangered by the establishment of highly invasive honey bees.