The first 50Myr of dinosaur evolution: macroevolutionary pattern and morphological disparity

The evolutionary radiation of dinosaurs in the Late Triassic and Early Jurassic was a pivotal event in the Earth's history but is poorly understood, as previous studies have focused on vague driving mechanisms and have not untangled different macroevolutionary components (origination, diversity, abundance and disparity). We calculate the morphological disparity (morphospace occupation) of dinosaurs throughout the Late Triassic and Early Jurassic and present new measures of taxonomic diversity. Crurotarsan archosaurs, the primary dinosaur 'competitors', were significantly more disparate than dinosaurs throughout the Triassic, but underwent a devastating extinction at the Triassic-Jurassic boundary. However, dinosaur disparity showed only a slight non-significant increase after this event, arguing against the hypothesis of ecological release-driven morphospace expansion in the Early Jurassic. Instead, the main jump in dinosaur disparity occurred between the Carnian and Norian stages of the Triassic. Conversely, dinosaur diversity shows a steady increase over this time, and measures of diversification and faunal abundance indicate that the Early Jurassic was a key episode in dinosaur evolution. Thus, different aspects of the dinosaur radiation (diversity, disparity and abundance) were decoupled, and the overall macroevolutionary pattern of the first 50Myr of dinosaur evolution is more complex than often considered.     

Diversity versus disparity and the radiation of modern cetaceans

Modern whales are frequently described as an adaptive radiation spurred by either the evolution of various key innovations (such as baleen or echolocation) or ecological opportunity following the demise of archaic whales. Recent analyses of diversification rate shifts on molecular phylogenies raise doubts about this interpretation since they find no evidence of increased speciation rates during the early evolution of modern taxa. However, one of the central predictions of ecological adaptive radiation is rapid phenotypic diversification, and the tempo of phenotypic evolution has yet to be quantified in cetaceans. Using a time-calibrated molecular phylogeny of extant cetaceans and a morphological dataset on size, we find evidence that cetacean lineages partitioned size niches early in the evolutionary history of neocetes and that changes in cetacean size are consistent with shifts in dietary strategy. We conclude that the signature of adaptive radiations may be retained within morphological traits even after equilibrium diversity has been reached and high extinction or fluctuations in net diversification have erased any signature of an early burst of diversification in the structure of the phylogeny.     

Morphological disparity as a biodiversity metric in lower bathyal and abyssal gastropod assemblages

Studies of deep-sea biodiversity focus almost exclusively on geographic patterns of alpha-diversity. Few include the morphological or ecological properties of species that indicate their actual roles in community assembly. Here, we explore morphological disparity of shell architecture in gastropods from lower bathyal and abyssal environments of the western North Atlantic as a new dimension of deep-sea biodiversity. The lower bathyal-abyssal transition parallels a gradient of decreasing species diversity with depth and distance from land. Morphological disparity measures how the variety of body plans in a taxon fills a morphospace. We examine disparity in shell form by constructing both empirical (eigenshape analysis) and theoretical (Schindel's modification of Raup's model) morphospaces. The two approaches provide very consistent results. The centroids of lower bathyal and abyssal morphospaces are statistically indistinguishable. The absolute volumes of lower bathyal morphospaces exceed those of the abyss; however, when the volumes are standardized to a common number of species they are not significantly different. The abyssal morphospaces are simply more sparsely occupied. In terms of the variety of basic shell types, abyssal species show the same disparity values as random subsets of the lower bathyal fauna. Abyssal species possess no evident evolutionary innovation. There are, however, conspicuous changes in the relative abundance of shell forms between the two assemblages. The lower bathyal fauna contains a fairly equable mix of species abundances, trophic modes, and shell types. The abyssal group is numerically dominated by species that are deposit feeders with compact unsculptured shells.     

Differences in mandibular disparity between extant and extinct species of metatherian and placental carnivore clades

There are a number of studies relating to skull morphology differences within the carnivoran clades of both placentals and metatherians. It is difficult to compare these studies because of differences in taxonomic sampling, for example some include fossil taxa while others include non‐carnivoran placentals. As a consequence, we studied mandible morphology in a broad range of both extant and extinct carnivorous species, including Carnivora, Marsupialia and Sparassodonta to test for differences between these clades. We used geometric morphometrics and two disparity indexes, the variance and Procrustes distances mean. When including fossil species, we found no significant differences for both disparities in some analyses, except after the exclusion of the sabretooth morphotype. This can be explained by the extreme morphology of this morphotype, which increases the variance and reduces the disparity effect of the other species in the analyses. Using Procrustes distances, we found significant differences in disparity distances between Carnivora and Metatheria for most of the analyses. We also found significant differences using the variance index in some analyses. The mandibular disparity in Carnivora is greater than in carnivorous metatherian mammals for most of the cases and this can be related with differences in evolutionary history and constraints of both groups. The pattern found in the mandible is similar to that found in the face of the skull but was not observed in the braincase, due to differences in skull function and mandible function.     

The patterns and modes of the evolution of disparity in Mesozoic birds

The origin of birds from non-avian theropod dinosaurs is one of the greatest transitions in evolution. Shortly after diverging from other theropods in the Late Jurassic, Mesozoic birds diversified into two major clades—the Enantiornithes and Ornithuromorpha—acquiring many features previously considered unique to the crown group along the way. Here, we present a comparative phylogenetic study of the patterns and modes of Mesozoic bird skeletal morphology and limb proportions. Our results show that the major Mesozoic avian groups are distinctive in discrete character space, but constrained in a morphospace defined by limb proportions. The Enantiornithines, despite being the most speciose group of Mesozoic birds, are much less morphologically disparate than their sister clade, the Ornithuromorpha—the clade that gave rise to living birds, showing disparity and diversity were decoupled in avian history. This relatively low disparity suggests that diversification of enantiornithines was characterized in exhausting fine morphologies, whereas ornithuromorphs continuously explored a broader array of morphologies and ecological opportunities. We suggest this clade-specific evolutionary versatility contributed to their sole survival of the end-Cretaceous mass extinction.     

First evidence of brachiopod diversification after the end-Triassic extinction from the pre-Pliensbachian Internal Subbetic platform (South-Iberian Paleomargin)

Lower Jurassic brachiopods are widely known in the External Betic Zone. Their occurrence was so far virtually restricted to the easternmost Subbetic Zone where they underwent a diversity burst and radiation event during the late Sinemurian–early Pliensbachian interval, leading to a bloom in brachiopod diversity from the early Pliensbachian onwards. Taxonomical and paleobiogeographical analyses performed in a newly recorded assemblage from the most offshore areas of the Subbetic Basin (Granada province, Spain) reveals that this diversification event occurred earlier than expected hitherto, probably in the Turneri–Obtusum chronozones, as similarly observed in the most intra-Tethyan basins such as the Northern Calcareous Alps and Transdanubian Ranges, illustrating the recovery of the background conditions for the establishment of diversified brachiopod communities after the end-Triassic extinction event. A new rhynchonellide species, Alebusirhynchia vorosi nov. sp., is formally described among the ten different taxa recorded for the first time in this area. The Mediterranean paleobiogeographical affinities revealed by the brachiopod assemblage emphasizes that the onset of the Mediterranean/Euro-Boreal bioprovinciality and the initial brachiopod diversification in the pre-Pliensbachian Internal Subbetic platform took place earlier in the Sinemurian as well, following the Euro-Boreal monotypic record previously reported in this region.     

Decoupling of morphological disparity and taxic diversity during the adaptive radiation of anomodont therapsids

Adaptive radiations are central to macroevolutionary theory. Whether triggered by acquisition of new traits or ecological opportunities arising from mass extinctions, it is debated whether adaptive radiations are marked by initial expansion of taxic diversity or of morphological disparity (the range of anatomical form). If a group rediversifies following a mass extinction, it is said to have passed through a macroevolutionary bottleneck, and the loss of taxic or phylogenetic diversity may limit the amount of morphological novelty that it can subsequently generate. Anomodont therapsids, a diverse clade of Permian and Triassic herbivorous tetrapods, passed through a bottleneck during the end-Permian mass extinction. Their taxic diversity increased during the Permian, declined significantly at the Permo–Triassic boundary and rebounded during the Middle Triassic before the clade''s final extinction at the end of the Triassic. By sharp contrast, disparity declined steadily during most of anomodont history. Our results highlight three main aspects of adaptive radiations: (i) diversity and disparity are generally decoupled; (ii) models of radiations following mass extinctions may differ from those triggered by other causes (e.g. trait acquisition); and (iii) the bottleneck caused by a mass extinction means that a clade can emerge lacking its original potential for generating morphological variety.     

Ecomorphological diversification following continental colonization in muroid rodents (Rodentia: Muroidea)

The emergence of exceptionally diverse clades is often attributed to ecological opportunity. For example, the exceptional diversity in the most diverse superfamily of mammals, muroid rodents, has been explained in terms of multiple independent adaptive radiations. If multiple ecological opportunity events are responsible for generating muroid diversity, we expect to find evidence of these lineages ecologically diversifying following dispersal into new biogeographical areas. In the present study, we tested the trait‐based predictions of ecological opportunity using data on body size, appendages, and elevation in combination with previously published data on biogeographical transitions and a time‐calibrated molecular phylogeny. We identified weak to no support of early ecological diversification following the initial colonizations of all continental regions, based on multiple tests, including node height tests, disparity through time plots, evolutionary model comparison, and Bayesian analysis of macroevolutionary mixtures. Clades identified with increased diversification rates, not associated with geographical transitions, also did not show patterns of phenotypic divergence predicted by ecological opportunity, which suggests that phylogenetic diversity and phenotypic disparity may be decoupled in muroids. These results indicate that shifts in diversification rates and biogeographically‐mediated ecological opportunity are poor predictors of phenotypic diversity patterns in muroids.     

Bathymetric patterns of morphological disparity in deep-sea gastropods from the western North Atlantic basin

Understanding patterns of species richness requires knowledge of the individual roles species play in community structure. Here, I use gastropod shells as a source of information about both their ecological and their evolutionary functions in generating bathymetric gradients of diversity. Specifically, morphological disparity of shell architecture in deep-sea gastropods is evaluated over a depth gradient in the western North Atlantic by constructing an empirical morphospace based on an eigenshape analysis. Morphological disparity is quantified by calculating the centroid, total range, and dispersion of the morphospace at each station along the depth gradient. The results indicate that local faunas are drawn from a regional pool with the same variance but that average dissimilarity in forms reflects the number of species in the sample. The range of the morphospace at local scales is also less than at regional scales, resulting from the variability of the morphospace centroid over depth. Although the position of the morphospace changes with depth, morphological disparity remains unaffected. Despite the lack of bathymetric patterns in variance, patterns in nearest neighbor distance persist. The findings suggest the importance of interacting ecological and evolutionary processes at varying spatiotemporal scales for both morphological disparity and species richness.     

Decoupling of taxonomic diversity and morphological disparity during decline of the Cambrian trilobite family Pterocephaliidae

Although discordance between taxonomic diversity and morphological disparity is common, little is known about the underlying dynamics that drive this decoupling. Early in the history of the Cambrian trilobite family Pterocephaliidae, there was an increase in taxonomic diversity and morphological diversity. As taxonomic diversity declined in the later history of the clade, range of variation stayed high and disparity continued to increase. However, per‐branch rates of morphological evolution estimated from a recent phylogeny decreased with time. Neither within‐trait nor within‐species variation increased or decreased, suggesting that the declining rates of morphological evolution were more likely related to ecological opportunity or niche partitioning, rather than increasing intrinsic constraints. This is further supported by evidence for increased biofacies associations throughout the time period. Thus, the high disparity seen at low taxonomic diversity late in the history of this clade was due to extinction – either random or targeting mean forms – rather than increased rates of morphological evolution. This pattern also provides a scenario that could account for instances of low taxonomic diversity but high morphological disparity in modern groups.     

Phylogeny,extinction and conservation: embracing uncertainties in a time of urgency

Evolutionary studies have played a fundamental role in our understanding of life, but until recently, they had only a relatively modest involvement in addressing conservation issues. The main goal of the present discussion meeting issue is to offer a platform to present the available methods allowing the integration of phylogenetic and extinction risk data in conservation planning. Here, we identify the main knowledge gaps in biodiversity science, which include incomplete sampling, reconstruction biases in phylogenetic analyses, partly known species distribution ranges, and the difficulty in producing conservation assessments for all known species, not to mention that much of the effective biological diversity remains to be discovered. Given the impact that human activities have on biodiversity and the urgency with which we need to address these issues, imperfect assumptions need to be sanctioned and surrogates used in the race to salvage as much as possible of our natural and evolutionary heritage. We discuss some aspects of the uncertainties found in biodiversity science, such as the ideal surrogates for biodiversity, the gaps in our knowledge and the numerous available phylogenetic diversity-based methods. We also introduce a series of cases studies that demonstrate how evolutionary biology can effectively contribute to biodiversity conservation science.     

Morphological diversity of Old World rats and mice (Rodentia, Muridae) mandible in relation with phylogeny and adaptation

The respective roles of the phylogenetic and ecological components in an adaptive radiation are tested on a sample of Old World rats and mice (Muridae, Murinae). Phylogeny was established on nuclear and mitochondrial genes and reconstructed by maximum likelihood and Bayesian methods. This phylogeny is congruent with previous larger scale ones recently published, but includes some new results: Bandicota and Nesokia are sister taxa and Micromys would be closely related to the Rattus group. The ecological diversification is investigated through one factor, the diet, and the mandible outline provides the morphological marker. Elliptic and radial Fourier transforms are used for quantifying size and shape differences among species. Univariate size and shape parameters indicate that phylogeny is more influential on size than diet, and the reverse occurs for shape and robust patterns are recognized by multivariate analyses of the data sets provided by the Fourier methods. Omnivorous and herbivorous groups are well separated despite some overlapping, as well as are other Murinae with a specialized diet (insects, seeds). Phylogeny is also influential as shown by the segregation of several groups (Praomys, Arvicanthini, Rattus, Apodemus). Allometric shape variation was investigated, and although present it does not overwhelm effects of either phylogeny or diet. Massive mandibles characterize herbivorous Murinae and slender mandibles, the insectivorous ones. A strong angular process relative to the coronoid process characterizes seedeaters, and the reverse characterized Murinae with a diet based largely on animal matter. Such changes in morphology are clearly in relation with the functioning of the mandible, and with the forces required by the nature of the food: the need of a stronger occlusal force in herbivorous species would explain massive mandibles, and an increase of the grasping and piercing function of incisors in insectivorous species would explain slender mandibles.     

Morphological variability in time and space: an example of patterns within buchiid bivalves (Bivalvia,Buchiidae)

Abstract: We studied morphological variation of the bivalve Buchia over its geographical and temporal range. Buchia was widely distributed during the Late Jurassic and Early Cretaceous, and, while previous quantitative studies have shown that species are characterized by large amounts of variation, there have been no prior attempts to measure how morphology varies geographically. We employed traditional morphometric techniques using nine linear/angular measurements on 1855 buchiid shells from eight localities taken from widely separated, but mostly coeval, sections across its range. Principal component and canonical variate analyses indicate that geographical morphospace of buchiids varied significantly, but we did not find evidence of a latitudinal gradient in shell shape. The amount of variation between localities was similar to the amount of variation between species, indicating the importance of geographical effects on morphology. Disparity (morphological diversity within a taxon, calculated by the sum of variances) and diversity (number of species) were calculated for each location and time period (age). Disparity and diversity reached ultimate lows just before the genus’ extinction in the Hauterivian, and is suggestive that extinction was morphologically selective. We did not find significant trends for either metric, but there were discordances throughout its temporal range. Latitudinal trends of disparity and diversity within Buchia are not apparent. This research adds to the growing body of work on geographical variation and is a preliminary step to understanding the nature and variation of buchiid species and of biodiversity in general.     

Evolution and the latitudinal diversity gradient: speciation, extinction and biogeography

A latitudinal gradient in biodiversity has existed since before the time of the dinosaurs, yet how and why this gradient arose remains unresolved. Here we review two major hypotheses for the origin of the latitudinal diversity gradient. The time and area hypothesis holds that tropical climates are older and historically larger, allowing more opportunity for diversification. This hypothesis is supported by observations that temperate taxa are often younger than, and nested within, tropical taxa, and that diversity is positively correlated with the age and area of geographical regions. The diversification rate hypothesis holds that tropical regions diversify faster due to higher rates of speciation (caused by increased opportunities for the evolution of reproductive isolation, or faster molecular evolution, or the increased importance of biotic interactions), or due to lower extinction rates. There is phylogenetic evidence for higher rates of diversification in tropical clades, and palaeontological data demonstrate higher rates of origination for tropical taxa, but mixed evidence for latitudinal differences in extinction rates. Studies of latitudinal variation in incipient speciation also suggest faster speciation in the tropics. Distinguishing the roles of history, speciation and extinction in the origin of the latitudinal gradient represents a major challenge to future research.     

Tempo and mode in the evolution of morphological disparity in the Neotropical fern genus Pleopeltis

Species diversity and morphological disparity are two measures to examine the diversity of life. Evidence based on the fossil record suggests a complex relation between these two parameters of biodiversity including frequent decoupling of their assembly through time. However, rather few studies explored the correlation of these two measurements by studying extant plant species. This study was designed to explore the accumulation of morphological disparity of the derived Neotropical fern genus Pleopeltis. To explore the relationship of species diversity and morphological disparity, we employed several approaches including divergence time estimates based on DNA sequence variation, reconstruction of character state changes based on a morphological matrix comprising 41 discrete characters, and exploration of the phylomorphospace. Accumulation of species diversity and morphological disparity was found to be concordant although the assumption of independence was not rejected for the accumulation of genetic and morphological variation. The phylomorphospace reconstruction provided further evidence for clade‐specific morphospace expansion that imply developmental pathways and competition among clades as major factors shaping the assembly of morphological disparity over time.     

Testing for unequal rates of morphological diversification in the absence of a detailed phylogeny: a case study from Characiform fishes

This study develops the random phylogenies rate test (RAPRATE), a likelihood method that simulates morphological evolution along randomly generated phylogenies, and uses it to determine whether a considerable difference in morphological diversity between two sister clades of South American fishes should be taken as evidence of differing rates of morphological change or lineage turnover. Despite identical ages of origin, similar species richness, and sympatric geographic distributions, the morphological and ecological diversity of the superfamily Anostomoidea exceeds that of the Curimatoidea. The test shows with 90% confidence (using variance among species as the measure of morphological diversity) or 99% confidence (using volume of occupied morphospace) that the rate of morphological change per unit time in the Anostomoidea likely exceeded that of the Curimatoidea. Variation in the rate of lineage turnover (speciation and extinction rates) is not found to affect greatly the morphological diversity of simulated clades and is not a likely explanation of the observed difference in morphological diversity in this case study. Though a 17% or greater delay in the onset of diversification in the Curimatoidea remains a possible alternative explanation of unequal morphological diversification, further simulations suggest that two clades drawn from the possible treespace of the Anostomoidea and Curimatoidea will rarely differ so greatly in the onset of diversification. Several uniquely derived morphological and ecological features of the Anostomoidea and Curimatoidea may have accelerated or decelerated their rate of morphological change, including a marked lengthening of the quadrate that may have relaxed structural constraints on the evolution of the anostomoid jaw.     

Integrating biogeography,threat and evolutionary data to explore extinction crisis in the taxonomic group of cycads

Will the ongoing extinction crisis cause a severe loss of evolutionary information accumulated over millions of years on the tree of life? This question has been largely explored, particularly for vertebrates and angiosperms. However, no equivalent effort has been devoted to gymnosperms. Here, we address this question focusing on cycads, the gymnosperm group exhibiting the highest proportion of threatened species in the plant kingdom. We assembled the first complete phylogeny of cycads and assessed how species loss under three scenarios would impact the cycad tree of life. These scenarios are as follows: (1) All top 50% of evolutionarily distinct (ED ) species are lost; (2) all threatened species are lost; and (3) only all threatened species in each IUCN category are lost. Finally, we analyzed the biogeographical pattern of cycad diversity hotspots and tested for gaps in the current global conservation network. First, we showed that threatened species are not significantly clustered on the cycad tree of life. Second, we showed that the loss of all vulnerable or endangered species does not depart significantly from random loss. In contrast, the loss of all top 50% ED , all threatened or all critically endangered species, would result in a greater loss of PD (Phylogenetic Diversity) than expected. To inform conservation decisions, we defined five hotpots of diversity, and depending on the diversity metric used, these hotspots are located in Southern Africa, Australia, Indo‐Pacific, and Mexico and all are found within protected areas. We conclude that the phylogenetic diversity accumulated over millions of years in the cycad tree of life would not survive the current extinction crisis. As such, prioritizing efforts based on ED and concentrating efforts on critically endangered species particularly in southern Africa, Australia, Indo‐Pacific, and Mexico are required to safeguarding the evolutionary diversity in the cycad tree of life.     

巴里坤盐湖退化区土壤微生物群落结构及生态功能分析

【目的】微生物是湖泊生态系统的重要组成部分,参与碳、氮和硫等元素的生物地球化学循环过程,其群落组成和功能对环境的稳定性和可持续性至关重要。然而,新疆的部分湖泊出现退化和盐渍化等问题,微生物如何响应湖泊退化值得研究。【方法】本研究基于16S rRNA基因的扩增子高通量测序,对巴里坤盐湖退化区域的土壤微生物群落结构进行分析,同时对微生物的潜在生态学功能进行预测。【结果】本研究发现,假单胞菌门(Pseudomonadota)、绿弯菌门(Chloroflexota)和拟杆菌门(Bacteroidota)是巴里坤盐湖退化生境中的优势类群。在轻度退化阶段,脱硫菌门(Desulfobacterota)和弯曲杆菌门(Campylobacterota)是主要类群,但随着湖泊退化程度加剧,这些类群急剧减少甚至消失;在极度退化阶段,酸杆菌门(Acidobacteriota)和浮霉菌门(Planctomycetota)等类群逐渐占据主导地位。基于BugBase对氧的需求进行预测,结果发现好氧类群主要是放线菌门(Actinomycetota)、假单胞菌门(Pseudomonadota)和绿弯菌门(Chlorof...     

Morphological and functional diversity of the mandible in suckermouth armored catfishes (Siluriformes: Loricariidae)

We examined the mandibles of 377 individuals representing 25 species, 12 genera, 5 tribes, and 2 subfamilies of the Loricariidae, a species‐rich radiation of detritivorous–herbivorous neotropical freshwater fishes distinguished by having a ventral oral disk and jaws specialized for surface attachment and benthic feeding. Loricariid mandibles are transversely oriented and bilaterally independent, each rotating predominantly around its long axis, although rotational axes likely vary with mandibular geometry. On each mandible, we measured three traditional and three novel morphological parameters chosen primarily for their functional relevance. Five parameters were linear distances and three of these were analogous to traditional teleost in‐ and out‐levers for mandibular adduction. The sixth parameter was insertion area of the combined adductor mandibulae muscle (AM_area), which correlated with adductor mandibulae volume across a subset of taxa and is interpreted as being proportional to maximum force deliverable to the mandible. Multivariate analysis revealed distributions of phylogenetically diagnosed taxonomic groupings in mandibular morphospace that are consistent with an evolutionary pattern of basal niche conservatism giving rise to multiple adaptive radiations within nested clades. Correspondence between mandibular geometry and function was explored using a 3D model of spatial relationships among measured parameters, potential forces, and axes of rotation. By combining the model with known loricariid jaw kinematics, we developed explicit hypotheses for how individual parameters might relate to each other during kinesis. We hypothesize that the ratio [AM_area/tooth row length²] predicts interspecific variation in the magnitude of force entering the mandible per unit of substrate contacted during feeding. Other newly proposed metrics are hypothesized to predict variation in aspects of mandibular mechanical advantage that may be specific to Loricariidae and perhaps shared with other herbivorous and detritivorous fishes. 2011. © 2011Wiley Periodicals, Inc.