Molecular systematics of cowries (Gastropoda: Cypraeidae) and diversification patterns in the tropics

This study produces a nearly comprehensive phylogeny for the marine gastropod group Cypraeidae (cowries) and uses this topology to examine diversification patterns in the tropics. The dataset is based on molecular sequence data from two mitochondrial genes and includes 210 evolutionary significant units (ESUs) from 170 recognized species (>80%). Systematics for the group is revised based on well‐supported clades, and tree topology is generally consistent with previously proposed classification schemes. Three new genera are introduced ( Cryptocypraea gen. nov , Palmulacypraea gen. nov , and Contradusta gen. nov ) and two previous genera are resurrected (Perisserosa and Eclogavena). One new tribe is proposed (Bistolidini). Topologies produced by a range of transition:transversion (Ti:Tv) weighting schemes in parsimony are pooled and evaluated using maximum likelihood criteria. Extensive geographical coverage shows persistent, large‐scale geographical structure in sister‐groups. Genetic divergence between subspecies is often equivalent or even greater than that between recognized species. Using ESUs as a metric, diversity throughout the Indo‐West Pacific (IWP) increases by 38%. Intra‐ and inter‐regional diversification patterns show that the IWP is the centre for speciation in cowries. The other major tropical regions of the world are inhabited by a predominantly relictual fauna; from a cowrie's eye‐view. Good dispersal ability begets larger ranges, increased extinction resistance and morphological stasis; whereas shorter larval duration results in smaller ranges, higher speciation rates, but also higher turnover. Larval duration and dispersal ability appear correlated with ocean productivity as taxa with longer‐lived larvae are associated with oligotrophic conditions; whereas taxa with shorter larval durations are associated with eutrophic, continental conditions. This tendency is carried to the extreme in temperate or upwelling regions where a planktonic phase is completely lost and crawl‐away larvae evolve multiple times. A strong phylogenetic trend supports these observations as lineages leading up to and including the derived Indo‐West Pacific Erroneinae clade contain taxa predominantly restricted to continental habitats and have undergone the greatest evolutionary radiations in their respective regions. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 79, 401– 459.     

几种因子对灰尖巴蜗牛翻身习性的影响

将蜗牛身体倒置并记录其恢复原状的时间来研究灰尖巴蜗牛的翻身习性,并研究蜗牛体重、环境温度、光照强度、饥饿和取食等因素对翻身时间的影响。结果表明,翻身时间随体重、光照强度和饥饿时间增加而增加,随温度升高和取食时间增加而减少。体重组Ⅳ(体重0.7～0.9g)、Ⅴ(体重0.9～1.2g)的翻身时间极显著长于体重组Ⅰ(体重0.1～0.3g)、Ⅱ(体重0.3～0.5g)、Ⅲ(体重0.5～0.7g)(P<0.01),体重组Ⅰ的翻身时间显著短于体重组Ⅲ的(P<0.05);3体重组(Ⅰ、Ⅲ、Ⅴ)在较高温度和低白炽灯光照强度(204lx)下的翻身时间显著短于较低温度和强白炽灯光照强度(493lx)下的;体重组Ⅰ、Ⅴ在长饥饿时间下的翻身时间均显著长于短饥饿时间。体重组Ⅲ、Ⅴ取食较长时间后的翻身时间都显著短于取食较短时间。     

Cryptic lineage diversity,body size divergence,and sympatry in a species complex of Australian lizards (Gehyra)

Understanding the joint evolutionary and ecological underpinnings of sympatry among close relatives remains a key challenge in biology. This problem can be addressed through joint phylogenomic and phenotypic analysis of complexes of closely related lineages within, and across, species and hence representing the speciation continuum. For a complex of tropical geckos from northern Australia—Gehyra nana and close relatives—we combine mtDNA phylogeography, exon‐capture sequencing, and morphological data to resolve independently evolving lineages and infer their divergence history and patterns of morphological evolution. Gehyra nana is found to include nine divergent lineages and is paraphyletic with four other species from the Kimberley region of north‐west Australia. Across these 13 taxa, 12 of which are restricted to rocky habitats, several lineages overlap geographically, including on the diverse Kimberley islands. Morphological evolution is dominated by body size shifts, and both body size and shape have evolved gradually across the group. However, larger body size shifts are observed among overlapping taxa than among closely related parapatric lineages of G. nana, and sympatric lineages are more divergent than expected at random. Whether elevated body size differences among sympatric lineages are due to ecological sorting or character displacement remains to be determined.     

Molecular phylogeny of the extinct cave lion Panthera leo spelaea

To reconstruct the phylogenetic position of the extinct cave lion (Panthera leo spelaea), we sequenced 1 kb of the mitochondrial cytochrome b gene from two Pleistocene cave lion DNA samples (47 and 32 ky B.P.). Phylogenetic analysis shows that the ancient sequences form a clade that is most closely related to the extant lions from Africa and Asia; at the same time, cave lions appear to be highly distinct from their living relatives. Our data show that these cave lion sequences represent lineages that were isolated from lions in Africa and Asia since their dispersal over Europe about 600 ky B.P., as they are not found among our sample of extant populations. The cave lion lineages presented here went extinct without mitochondrial descendants on other continents. The high sequence divergence in the cytochrome b gene between cave and modern lions is notable.     

Wing morphology of a new Cretaceous praying mantis solves the phylogenetic jigsaw of early‐diverging extant lineages

The extremely derived morphology and behaviour of extant praying mantises combined with a scarce record of fossil relatives introduce significant challenges to tracing their evolution from Palaeozoic stem‐dictyopterans. Extant members of Chaeteessidae, Mantoididae and Metallyticidae could be invaluable to resolving the mantodean tree, yet their inclusion in phylogenetic analyses led to conflicting hypotheses due to their highly disparate respective morphologies. In this contribution, we present Labradormantis guilbaulti gen. et sp.n. , a new fossil species described from both fore‐ and hind‐wing imprints discovered in the Redmond Mine locality (Late Cretaceous, Cenomanian, Redmond Formation; Labrador, Canada). The examination of its hind‐wing AA2* supports the hypothesis that this structure, unique to Chaeteessidae among extant mantises, is a true vein and that its occurrence represents a plesiomorphy for Mantodea. A parsimony analysis including newly coded wing‐related characters further established that L. guilbaulti gen. et sp.n. displays a unique combination of plesiomorphic and apomorphic character states that situates it within the extinct family Baissomantidae. This dataset resolved the phylogenetic relationships of early‐diverging extant lineages as (Chaeteessidae (Mantoididae (Metallyticidae, Artimantodea))), and suggested that the Eocene Lithophotina floccosa Cockerell might be a close relative of extant metallyticids. It also indicated a trend towards increased modularity within mantis fore‐wings, in contrast with a trend towards increased morphological integration in their hind‐wings, both of which are potentially associated with improved flight performance for modern mantises. This study emphasizes the importance of fossils for resolving phylogenetic relationships and for introducing transitional phenotypes to infer ancient evolutionary trends of extant derived clades.     

Systematics and evolution of the Pan‐Alcidae (Aves,Charadriiformes)

Puffins, auks and their allies in the wing‐propelled diving seabird clade Pan‐Alcidae (Charadriiformes) have been proposed to be key pelagic indicators of faunal shifts in Northern Hemisphere oceans. However, most previous phylogenetic analyses of the clade have focused only on the 23 extant alcid species. Here we undertake a combined phylogenetic analysis of all previously published molecular sequence data (～ 12 kb) and morphological data (n = 353 characters) with dense species level sampling that also includes 28 extinct taxa. We present a new estimate of the patterns of diversification in the clade based on divergence time estimates that include a previously vetted set of twelve fossil calibrations. The resultant time trees are also used in the evaluation of previously hypothesized paleoclimatic drivers of pan‐alcid evolution. Our divergence dating results estimate the split of Alcidae from its sister taxon Stercorariidae during the late Eocene (～ 35 Ma), an evolutionary hypothesis for clade origination that agrees with the fossil record and that does not require the inference of extensive ghost lineages. The extant dovekie Alle alle is identified as the sole extant member of a clade including four extinct Miocene species. Furthermore, whereas an Uria + Alle clade has been previously recovered from molecular analyses, the extinct diversity of closely related Miocepphus species yields morphological support for this clade. Our results suggest that extant alcid diversity is a function of Miocene diversification and differential extinction at the Pliocene–Pleistocene boundary. The relative timing of the Middle Miocene climatic optimum and the Pliocene–Pleistocene climatic transition and major diversification and extinction events in Pan‐Alcidae, respectively, are consistent with a potential link between major paleoclimatic events and pan‐alcid cladogenesis.     

Advantages and Limitations in the Use of Extant Xenarthrans (Mammalia) as Morphological Models for Paleobiological Reconstruction

Extant species of Xenarthra represent a severely restricted sample of the total diversity achieved by the group. Given their shared history, the extant representatives of the three major groups of xenarthrans (Cingulata, Folivora, and Vermilingua) provide a valuable basis for paleobiological inference. However, many extinct taxa are morphologically so dissimilar from their extant relatives that they suggest very different ways of life. In these cases, extinct forms do not have modern models within the group and the application of a simplistic and strict approach can produce nonsensical reconstructions. In this contribution, we evaluate the limitations of the use of extant xenarthrans as morphological models for paleobiological reconstructions. A database of linear dimensions of the appendicular skeleton of extant and extinct xenarthrans and other mammals (marsupials, carnivorans, rodents, primates, perissodactyls, artiodactyls, and proboscideans) was constructed. Exploratory analyzes were performed on general morphometric similarity between existing and extinct xenarthrans (PCA) and the accuracy of body mass estimates of extinct xenarthrans based on their close relatives and other mammals (simple and multiple linear regressions) were tested. Extinct xenarthrans occupy similar relative positions in the morphospaces as extant mammals other than their closest relatives. Most allometric equations, particularly those based only on xenarthrans, produced remarkable underestimates. This can be explained by dimensional differences (up to four orders of magnitude) and shape differences between most of the extinct and extant xenarthrans. This does not invalidate actualism and the use of analogues, but suggests the need to apply other approaches, such as mechanics, that address form-function relationships but are not necessarily based on known biological comparators.     

Taxon sampling to address an ancient rapid radiation: a supermatrix phylogeny of early brachyceran flies (Diptera)

Early diverging brachyceran fly lineages underwent a rapid radiation approximately 180 Ma, coincident in part with the origin of flowering plants. This region of the fly tree includes 25 000 described extant species with diverse ecological roles such as blood‐feeding (haematophagy), parasitoidism, predation, pollination and wood‐feeding (xylophagy). Early diverging brachyceran lineages were once considered a monophyletic group of families called Orthorrhapha, based on the shared character of a longitudinal break in the pupal skin made during the emergence of the adult. Yet other morphological and molecular evidence generally supports a paraphyletic arrangement of ‘Orthorrhapha’, with strong support for one orthorrhaphan lineage – dance flies and relatives – as the closest relative to all higher flies (Cyclorrhapha), together called Eremoneura. In order to establish a comprehensive estimate of the relationships among orthorrhaphan lineages using a thorough sample of publicly available data, we compiled and analysed a dataset including 1217 taxa representing major lineages and 20 molecular markers. Our analyses suggest that ‘Orthorrhapha’ excluding Eremoneura is not monophyletic; instead, we recover two main lineages of early brachyceran flies: Homeodactyla and Heterodactyla. Homeodactyla includes Nemestrinoidea (uniting two parasitic families Acroceridae + Nemestrinidae) as the closest relatives to the large SXT clade, comprising Stratiomyomorpha, Xylophagidae and Tabanomorpha. Heterodactyla includes Bombyliidae with a monophyletic Asiloidea (exclusive of Bombyliidae) as the closest relatives to Eremoneura. Reducing missing data, modifying the distribution of genes across taxa, and, in particular, removing rogue taxa significantly improved tree resolution and statistical support. Although our analyses rely on dense taxonomic sampling and substantial gene coverage, our results pinpoint the limited resolving power of Sanger sequencing‐era molecular phylogenetic datasets with respect to ancient, hyperdiverse radiations.     

Body mass estimation in xenarthra: A predictive equation suitable for all quadrupedal terrestrial placentals?

The Magnorder Xenarthra includes strange extinct groups, like glyptodonts, similar to large armadillos, and ground sloths, terrestrial relatives of the extant tree sloths. They have created considerable paleobiological interest in the last decades; however, the ecology of most of these species is still controversial or unknown. The body mass estimation of extinct species has great importance for paleobiological reconstructions. The commonest way to estimate body mass from fossils is through linear regression. However, if the studied species does not have similar extant relatives, the allometric pattern described by the regression could differ from those shown by the extinct group. That is the case for glyptodonts and ground sloths. Thus, stepwise multiple regression were developed including extant xenarthrans (their taxonomic relatives) and ungulates (their size and ecological relatives). Cases were weighted to maximize the taxonomic evenness. Twenty‐eight equations were obtained. The distribution of the percent of prediction error (%PE) was analyzed between taxonomic groups (Perissodactyla, Artiodactyla, and Xenarthra) and size groups (0–20 kg, 20–300 kg, and more than 300 kg). To assess the predictive power of the functions, equations were applied to species not included in the regression development [test set cross validation, (TSCV)]. Only five equations had a homogeneous %PE between the aforementioned groups. These were applied to five extinct species. A mean body mass of 80 kg was estimated for Propalaehoplophorus australis (Cingulata: Glyptodontidae), 594 kg for Scelidotherium leptocephalum (Phyllophaga: Mylodontidae), and 3,550.7 kg for Lestodon armatus (Phyllophaga: Mylodontidae). The high scatter of the body mass estimations obtained for Catonyx tarijensis (Phyllophaga: Mylodontidae) and Thalassocnus natans (Phyllophaga: Megatheriidae), probably due to different specializations, prevented us from predicting its body mass. Surprisingly, although obtained from ungulates and xenarthrans, these five selected equations were also able to predict the body mass of species from groups as different as rodents, carnivores, hyracoideans, or tubulidentates. This result suggests the presence of a complex common allometric pattern for all quadrupedal placentals. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.     

Tropical Asian species show that the Old World clade of ‘spiny solanums’ (Solanum subgenus Leptostemonum pro parte: Solanaceae) is not monophyletic

The tropical Asian taxa of the species‐rich genus Solanum (Solanaceae) have been less well studied than their highly diverse New World relatives. Most of these tropical Asian species, including the cultivated brinjal eggplant/aubergine and its wild progenitor, are part of the largest monophyletic Solanum lineage, the ‘spiny solanums’ (subgenus Leptostemonum or the Leptostemonum clade). Here we present the first phylogenetic analysis of spiny solanums that includes broad sampling of the tropical Asian species, with 42 of the 56 currently recognized species represented. Two nuclear and three plastid regions [internal transcribed spacer (ITS), waxy, ndhF‐rpL32, trnS‐trnG and trnT‐trnF] were amplified and used to reconstruct phylogenetic relationships using maximum likelihood and Bayesian methods. Our analyses show that Old World spiny solanums do not resolve in a single clade, but are part of three unrelated lineages, suggesting at least three independent introductions from the New World. We identify and describe several monophyletic groups in Old World solanums that have not been previously recognized. Some of these lineages are coherent in terms of morphology and geography, whereas others show considerable morphological variation and enigmatic distribution patterns. Tropical Asia occupies a key position in the biogeography of Old World spiny solanums, with tropical Asian taxa resolved as the closest relatives of diverse groups of species from Australia and Africa.     

Examining the phylogeny of the Australasian Lymnaeidae (Heterobranchia: Pulmonata: Gastropoda) using mitochondrial, nuclear and morphological markers

We examined the species groups relationships of the freshwater snail genus Austropeplea using mitochondrial, nuclear and morphological markers in addition to traditional methods of shell shape analysis. Based primarily on the results of a combined molecular and morphological analysis, samples of the nominal species A. tomentosa form distinct lineages. The New Zealand populations of A. tomentosa are a very distinct lineage from any of the Australian populations attributed to A. tomentosa. Furthermore, within the Australian group, three lineages, south Australia, Tasmania and eastern Australia, appear to have undergone recent and/or rapid speciation events. Samples assigned to A. lessoni were resolved as two distinct lineages, representing the eastern and northern Australian populations. Kutikina hispida was resolved within the Australian A. tomentosa clade. Molecular results for A. viridis suggests that it is also composed of at least two distinct lineages that could be treated as species. Incongruence observed between the single mitochondrial, nuclear and morphological topologies highlight the importance of using a number of different datasets in the delimitation of species-group taxa.     

Death feigning as an adaptive anti‐predator behaviour: Further evidence for its evolution from artificial selection and natural populations

Death feigning is considered to be an adaptive antipredator behaviour. Previous studies on Tribolium castaneum have shown that prey which death feign have a fitness advantage over those that do not when using a jumping spider as the predator. Whether these effects are repeatable across species or whether they can be seen in nature is, however, unknown. Therefore, the present study involved two experiments: (a) divergent artificial selection for the duration of death feigning using a related species T. freemani as prey and a predatory bug as predator, demonstrating that previous results are repeatable across both prey and predator species, and (b) comparison of the death‐feigning duration of T. castaneum populations collected from field sites with and without predatory bugs. In the first experiment, T. freemani adults from established selection regimes with longer durations of death feigning had higher survival rates and longer latency to being preyed on when they were placed with predatory bugs than the adults from regimes selected for shorter durations of death feigning. As a result, the adaptive significance of death‐feigning behaviour was demonstrated in another prey–predator system. In the second experiment, wild T. castaneum beetles from populations with predators feigned death longer than wild beetles from predator‐free populations. Combining the results from these two experiments with those from previous studies provided strong evidence that predators drive the evolution of longer death feigning.     

Directional selection in the evolution of elongated upper canines in clouded leopards and sabre‐toothed cats

Extremely developed or specialized traits such as the elongated upper canines of extinct sabre‐toothed cats are often not analogous to those of any extant species, which limits our understanding of their evolutionary cause. However, an extant species may have undergone directional selection for a similar extreme phenotype. Among living felids, the clouded leopard, Neofelis nebulosa, has exceptionally long upper canines for its body size. We hypothesized that directional selection generated the elongated upper canines of clouded leopards in a manner similar to the process in extinct sabre‐toothed cats. To test this, we developed an approach that compared the effect of directional selection among lineages in a phylogeny using a simulation of trait evolution and approximate Bayesian computation. This approach was applied to analyse the evolution of upper canine length in the Felidae phylogeny. Our analyses consistently showed directional selection favouring longer upper canines in the clouded leopard lineage and a lineage leading to the sabre‐toothed cat with the longest upper canines, Smilodon. Most of our analyses detected an effect of directional selection for longer upper canines in the lineage leading to another sabre‐toothed cat, Homotherium, although this selection may have occurred exclusively in the primitive species. In all the analyses, the clouded leopard and Smilodon lineages showed comparable directional selection. This implies that clouded leopards share a selection advantage with sabre‐toothed cats in having elongated upper canines.     

Molecules,fossils, and the origin of tetrapods

Summary Since the discovery of the coelacanth, Latimeria chalumnae, more than 50 years ago, paleontologists and comparative morphologists have debated whether coelacanths or lungfishes, two groups of lobe-finned fishes, are the closest living relatives of land vertebrates (Tetrapoda). Previously, Meyer and Wilson (1990) determined partial DNA sequences from two conservative mitochondrial genes and found support for a close relationship of lungfishes to tetrapods. We present additional DNA sequences from the 12S rRNA mitochondria gene for three species of the two lineages of lungfishes that were not represented in the first study: Protopterus annectens and Protopterus aethiopicus from Africa and Neoceratodus forsteri (kindly provided by B. Hedges and L. Maxson) from Australia. This extended data set tends to group the two lepidosirenid lungfish lineages (Lepidosiren and Protopterus) with Neoceratodus as their sister group. All lungfishes seem to be more closely related to tetrapods than the coelacanth is. This result appears to rule out the possibility that the coelacanth lineage gave rise to land vertebrates. The common ancestor of lungfishes and tetrapods might have possessed multiple morphological traits that are shared by lungfishes and tetrapods [Meyer and Wilson (1990) listed 14 such traits]. Those traits that seem to link Latimeria and tetrapods are arguably due to convergent evolution or reversals and not to common descent. In this way, the molecular tree facilitates an evolutionary interpretation of the morphological differences among the living forms. We recommended that the extinct groups of lobe-finned fishes be placed onto the molecular tree that has lungfishes and not the coelacanth more closely related to tetrapods. The placement of fossils would help to further interpret the sequence of morphological events and innovations associated with the origin of tetrapods but appears to be problematic because the quality of fossils is not always high enough, and differences among paleontologists in the interpretation of the fossils have stood in the way of a consensus opinion for the branching order among lobefinned fishes. Marshall and Schultze (1992) criticized the morphological analysis presented by Meyer and Wilson (1990) and suggest that 13 of the 14 morphological traits that support the sister group relationship of lungfishes and tetrapods are not shared derived characters. Here we present further alternative viewpoints to the ones of Marshall and Schultze (1992) from the paleontological literature. We argue that all available information (paleontological, neontological, and molecular data) and rigorous cladistic methodology should be used when relating fossils and extant taxa in a phylogenetic framework. Offprint requests to: Axel Meyer     

Host preferences in a phonotactic parasitoid of field crickets: the relative importance of host song characters

Abstract.  1. Predators, including insect parasitoids, often eavesdrop on prey signals, and as a result, predation can have important effects on the evolution of prey signalling behaviour.
2. The phonotactic parasitoid fly, Ormia ochracea , uses the calling songs of male field crickets to locate their field crickets hosts. In the western USA, this fly parasitises the variable field cricket, Gryllus lineaticeps . Previous work with one fly population suggested that female flies, like female field crickets, preferentially orient to male songs with higher chirp rates and longer chirp durations, although a limited range of male song types was used in this previous study. The current study, with a different fly population, used field-based, two-speaker choice tests to examine: (1) the effect of male chirp rate and chirp duration on fly attraction, using a natural range of song types; and (2) the relative importance of these song types in host selection by the flies.
3. Three lines of evidence suggested that chirp rate is more important than chirp duration in host selection. (a) The flies consistently preferred higher chirp rates but only sometimes preferred longer chirp durations. (b) The flies consistently preferred higher chirp rate/shorter chirp duration songs to lower chirp rate/longer chirp duration songs. (c) Preferences for longer chirp durations could be eliminated by increasing the amplitude of the less attractive song type, while preferences for higher chirp rates could only sometimes be eliminated by increasing the amplitude of the less attractive song type.
4. Fly predation may favour lower chirp rates and shorter chirp durations in G. lineaticeps , and may have resulted in stronger selection on chirp rate than on chirp duration.     

Postdispersal nepotism in male long‐tailed macaques (Macaca fascicularis)

Cooperative behaviors are promoted by kin selection if the costs to the actor are smaller than the fitness benefits to the recipient, weighted by the coefficient of relatedness. In primates, cooperation occurs primarily among female dyads. Due to male dispersal before sexual maturity in many primate species, however, it is unknown whether there are sufficient opportunities for selective tolerance and occasional coalitionary support for kin selection to favor male nepotistic support. We studied the effect of the presence of male kin on correlates of male reproductive success (residence time, duration of high dominance rank) in non‐natal male long‐tailed macaques (Macaca fascicularis). We found that “related” (i.e., related at the half‐sibling level or higher) males in a group have a significantly higher probability to remain in the non‐natal group compared to males without relatives. Moreover, males stayed longer in a group when a relative was present at group entry or joined the same group within 3 months upon arrival. Males with co‐residing relatives also maintained a high rank for longer than those without. To our knowledge, this is the first demonstration of a potential nepotistic effect on residence and rank maintenance among non‐natal males in a social system without long‐term alliances.     

Evolutionary Transitions Among Dinosaurs: Examples from the Jurassic of China

Dinosaurs have captured the popular imagination more than any other extinct group of organisms and are therefore a powerful tool in teaching evolutionary biology. Most students are familiar with a wide variety of dinosaurs and the relative suddenness of their extinction, but few are aware of the tremendous longevity of their time on Earth and the richness of their fossil record. We first review some of the best-known groups of dinosaurs and discuss how their less-specialized relatives elucidate the path through which each evolved. We then discuss our recent discovery of Yinlong downsi, a distant relative of Triceratops, and other fossils from Jurassic deposits in China to exemplify how the continuing discovery of fossils is filling out the dinosaur family tree.     

Early vertebrate evolution

Debate over the origin and evolution of vertebrates has occupied biologists and palaeontologists alike for centuries. This debate has been refined by molecular phylogenetics, which has resolved the place of vertebrates among their invertebrate chordate relatives, and that of chordates among their deuterostome relatives. The origin of vertebrates is characterized by wide‐ranging genomic, embryologic and phenotypic evolutionary change. Analyses based on living lineages suggest dramatic shifts in the tempo of evolutionary change at the origin of vertebrates and gnathostomes, coincident with whole‐genome duplication events. However, the enriched perspective provided by the fossil record demonstrates that these apparent bursts of anatomical evolution and taxic richness are an artefact of the extinction of phylogenetic intermediates whose fossil remains evidence the gradual assembly of crown gnathostome characters in particular. A more refined understanding of the timing, tempo and mode of early vertebrate evolution rests with: (1) better genome assemblies for living cyclostomes; (2) a better understanding of the anatomical characteristics of key fossil groups, especially the anaspids, thelodonts, galeaspids and pituriaspids; (3) tests of the monophyly of traditional groups; and (4) the application of divergence time methods that integrate not just molecular data from living species, but also morphological data and extinct species. The resulting framework will provide for rigorous tests of rates of character evolution and diversification, and of hypotheses of long‐term trends in ecological evolution that themselves suffer for lack of quantitative functional tests. The fossil record has been silent on the nature of the transition from jawless vertebrates to the jawed vertebrates that have dominated communities since the middle Palaeozoic. Elucidation of this most formative of episodes likely rests with the overhaul of early vertebrate systematics that we propose, but perhaps more fundamentally with fossil grades that await discovery.     

Experimental alteration of limb posture in the chicken (Gallus gallus) and its bearing on the use of birds as analogs for dinosaur locomotion

Extant birds represent the only diverse living bipeds, and can be informative for investigations into the life‐history parameters of their extinct dinosaurian relatives. However, morphological changes that occurred during early avian evolution, including the unique adoption of a nearly horizontal femoral orientation associated with a shift in center of mass (CM), suggest that caution is warranted in the use of birds as analogs for nonavian dinosaur locomotion. In this study, we fitted a group of white leghorn chickens (Gallus gallus) with a weight suspended posterior to the hip in order to examine the effects on loading and morphology. This caused a CM shift that necessitated a change in femoral posture (by 35° towards the horizontal, P < 0.001), and resulted in reorientation of the ground reaction force (GRF) vector relative to the femur (from 41° to 82°, P < 0.001). Despite similar strain magnitudes, an overall increase in torsion relative to bending (from 1.70 to 1.95 times bending, P < 0.001) was observed, which was weakly associated with a tendency for increased femoral cross‐sectional dimensions (P = 0.1). We suggest that a relative increase in torsion is consistent with a change in femoral posture towards the horizontal, since this change increases the degree to which the bone axis and the GRF vector produce mediolateral long‐axis rotation of the bone. These results support the hypothesis that a postural change during early avian evolution could underlie the allometric differences seen between bird and nonavian dinosaur femora by requiring more robust femoral dimensions in birds due to an increase in torsion. J. Morphol. 240:237–249, 1999. © 1999 Wiley‐Liss, Inc.     

The skeleton flight apparatus of North American bluebirds (Sialia): Phylogenetic thrushes or functional flycatchers?

To better understand ecological traits of organisms, one can study them from two, not necessarily mutually exclusive perspectives: how the traits evolved, and their current adaptive utility. In birds, foraging behavior and associated morphological traits generally are explained by a combination of adaptive and phylogenetic predictors. The avian skeleton and more specifically, the skeletal flight apparatus is under well‐known functional and phylogenetic constraints. This is an interesting area to partition the relative contributions of adaptive correlated evolution and phylogenetic constraint to species clustering in morphological space. A prediction of convergent evolution is that nonphylogenetic morphological clustering is a characteristic of ecological similarity. We tested this using representatives of North American birds from two clades, one with a mixture of foraging modes (Turdid thrushes, solitaires, and bluebirds) and one with more canalized foraging behaviors (Tyrannid flycatchers). Nine characters on the skeletal flight apparatus from 19 species were used to characterize the morphological space and test for ecomorphological clustering. When body size and phylogeny are considered, the three bluebird species and Townsend's solitaire cluster with the ecologically similar flycatchers rather than with their phylogenetic close relatives. Furthermore, sit‐and‐wait foragers tend to exhibit relatively long distal elements and a long keel while active ground foragers have deeper keels and a longer humerus. Distal elements, expected to be relatively shorter and more bowed in the flycatchers and bluebirds, were actually longer and narrower. A reduction of distal element mass may be more important for facilitating maneuverability than surface area for insertion of wing‐rotational musculature. J. Morphol. 274:909–917, 2013. © 2013 Wiley Periodicals, Inc.