Explore the vast range of titles available.

Mammals are characterized by the complex adaptations of their dentition, which are an indication that diet has played a critical role in their evolutionary history. Although much attention has focused on diet and the adaptations of specific taxa, the role of diet in large-scale diversification patterns remains unresolved. Contradictory hypotheses have been proposed, making prediction of the expected relationship difficult. We show that net diversification rate (the cumulative effect of speciation and extinction), differs significantly among living mammals, depending upon trophic strategy. Herbivores diversify fastest, carnivores are intermediate, and omnivores are slowest. The tempo of transitions between the trophic strategies is also highly biased: the fastest rates occur into omnivory from herbivory and carnivory and the lowest transition rates are between herbivory and carnivory. Extant herbivore and carnivore diversity arose primarily through diversification within lineages, whereas omnivore diversity evolved by transitions into the strategy. The ability to specialize and subdivide the trophic niche allowed herbivores and carnivores to evolve greater diversity than omnivores.

Spiny-rayed fishes, or acanthomorphs, comprise nearly one-third of all living vertebrates. Despite their dominant role in aquatic ecosystems, the evolutionary history and tempo of acanthomorph diversification is poorly understood. We investigate the pattern of lineage diversification in acanthomorphs by using a well-resolved time-calibrated phylogeny inferred from a nuclear gene supermatrix that includes 520 acanthomorph species and 37 fossil age constraints. This phylogeny provides resolution for what has been classically referred to as the “bush at the top” of the teleost tree, and indicates acanthomorphs originated in the Early Cretaceous. Paleontological evidence suggests acanthomorphs exhibit a pulse of morphological diversification following the end Cretaceous mass extinction; however, the role of this event on the accumulation of living acanthomorph diversity remains unclear. Lineage diversification rates through time exhibit no shifts associated with the end Cretaceous mass extinction, but there is a global decrease in lineage diversification rates 50 Ma that occurs during a period when morphological disparity among fossil acanthomorphs increases sharply. Analysis of clade-specific shifts in diversification rates reveal that the hyperdiversity of living acanthomorphs is highlighted by several rapidly radiating lineages including tunas, gobies, blennies, snailfishes, and Afro-American cichlids. These lineages with high diversification rates are not associated with a single habitat type, such as coral reefs, indicating there is no single explanation for the success of acanthomorphs, as exceptional bouts of diversification have occurred across a wide array of marine and freshwater habitats.

In recent years, the fields of evolutionary biomechanics and morphology have developed into a deeply quantitative and integrative science, resulting in a much richer understanding of how structural relationships shape macroevolutionary patterns. This issue highlights new research at the conceptual and experimental cutting edge, with a special focus on applying big data approaches to classic questions in form–function evolution. As this issue illustrates, new technologies and analytical tools are facilitating the integration of biomechanics, functional morphology, and phylogenetic comparative methods to catalyze a new, more integrative discipline. Although we are at the cusp of the big data generation of organismal biology, the field is nonetheless still data-limited. This data bottleneck is primarily due to the rate-limiting steps of digitizing specimens, recording and tracking organismal movements, and extracting patterns from massive datasets. Automation and machine-learning approaches hold great promise to help data generation keep pace with ideas. As a final and important note, almost all the research presented in this issue relied on specimens—totaling the tens of thousands—provided by museum collections. Without collection, curation, and conservation of museum specimens, the future of the field is much less bright.

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.

Traits underlie organismal responses to their environment and are essential to predict community responses to environmental conditions under global change. Species differ in life‐history traits, morphometrics, diet type, reproductive characteristics and habitat utilization. Trait associations are widely analysed using phylogenetic comparative methods (PCM) to account for correlations among related species. Similarly, traits are measured for some but not all species, and missing continuous traits (e.g. growth rate) can be imputed using ‘phylogenetic trait imputation’ (PTI), based on evolutionary relatedness and trait covariance. However, PTI has not been available for categorical traits, and estimating covariance among traits without ecological constraints risks inferring implausible evolutionary mechanisms. Here, we extend previous PCM and PTI methods by (1) specifying covariance among traits as a structural equation model (SEM), and (2) incorporating associations among both continuous and categorical traits. Fitting a SEM replaces the covariance among traits with a set of linear path coefficients specifying potential evolutionary mechanisms. Estimated parameters then represent regression slopes (i.e. the average change in trait Y given an exogenous change in trait X) that can be used to calculate both direct effects (X impacts Y) and indirect effects (X impacts Z and Z impacts Y). We demonstrate phylogenetic structural‐equation mixed‐trait imputation using 33 variables representing life history, reproductive, morphological, and behavioural traits for all >32,000 described fishes worldwide. SEM coefficients suggest that one degree Celsius increase in habitat is associated with an average 3.5% increase in natural mortality (including a 1.4% indirect impact that acts via temperature effects on the growth coefficient), and an average 3.0% decrease in fecundity (via indirect impacts on maximum age and length). Cross‐validation indicates that the model explains 54%–89% of variance for withheld measurements of continuous traits and has an area under the receiver‐operator‐characteristics curve of 0.86–0.99 for categorical traits. We use imputed traits to classify all fishes into life‐history types, and confirm a phylogenetic signal in three dominant life‐history strategies in fishes. PTI using phylogenetic SEMs ensures that estimated parameters are interpretable as regression slopes, such that the inferred evolutionary relationships can be compared with long‐term evolutionary and rearing experiments.

Innovations in organismal functional morphology are thought to be a major force in shaping evolutionary patterns, with the potential to drive adaptive radiation and influence the evolutionary prospects for lineages. But the evolutionary consequences of innovation are diverse and usually do not result in adaptive radiation. What factors shape the macroevolutionary impact of innovations? We assert that little is known in general about the macroevolutionary outcomes associated with functional innovations and we discuss a framework for studying biological innovations in an evolutionary context. Innovations are novel functional mechanisms that enhance organismal performance. The ubiquity of trade-offs in functional systems means that enhanced performance on one axis often occurs at the expense of performance on another axis, such that many innovations result in an exchange of performance capabilities, rather than an expansion. Innovations may open up new resources for exploitation but their consequences for functional and ecological diversification depend heavily on the adaptive landscape around these novel resources. As an example of a broader program that we imagine, we survey five feeding innovations in labrid fishes, an exceptionally successful and ecologically diverse group of reef fishes, and explore their impact on the rate of evolution of jaw functional morphology. All of the innovations provide performance enhancements and result in changes in patterns of resource use, but most are not associated with subsequent functional diversification or substantial ecological diversification. Because selection acts on a specific performance enhancement and not on the evolutionary potential of an innovation, the enhancement of diversity may be highly serendipitous. The macroevolutionary potential of innovations depends critically on the interaction between the performance enhancement and the ecological opportunity that is exposed.

Spiny-rayed fishes (Acanthomorpha) dominate modern marine habitats and account for more than a quarter of all living vertebrate species. Previous time-calibrated phylogenies and patterns from the fossil record explain this dominance by correlating the origin of major acanthomorph lineages with the Cretaceous–Palaeogene mass extinction. Here we infer a time-calibrated phylogeny using ultraconserved elements that samples 91.4% of all acanthomorph families and investigate patterns of body shape disparity. Our results show that acanthomorph lineages steadily accumulated throughout the Cenozoic and underwent a significant expansion of among-clade morphological disparity several million years after the end-Cretaceous. These acanthomorph lineages radiated into and diversified within distinct regions of morphospace that characterize iconic lineages, including fast-swimming open-ocean predators, laterally compressed reef fishes, bottom-dwelling flatfishes, seahorses and pufferfishes. The evolutionary success of spiny-rayed fishes is the culmination of multiple species-rich and phenotypically disparate lineages independently diversifying across the globe under a wide range of ecological conditions. The authors construct a time-calibrated phylogeny spanning >90% of spiny-rayed fishes to explore patterns of body shape disparity within acanthomorphs. They find a trend of steady accumulation of lineages from the Cenozoic, with an increase in morphological disparity following the Cretaceous–Palaeogene event, facilitating the radiation of diverse morphotypes that characterize acanthomorphs’ widespread ecological success today.

Half of all artiodactyls (even-toed hoofed mammals) are threatened with extinction, around double the mammalian average. Here, using a complete species-level phylogeny, we construct a multivariate model to assess for the first time which intrinsic (biological) and extrinsic (anthropogenic and environmental) factors influence variation in extinction risk in artiodactyls. Globally artiodactyls at greatest risk live in economically less developed areas, have older weaning ages and smaller geographical ranges. Our findings suggest that identifying predictors of threat is complicated by interactions between both biological and anthropogenic factors, resulting in differential responses to threatening processes. Artiodactyl species that experience unregulated hunting live in significantly less economically developed areas than those that are not hunted; however, hunted species are more susceptible to extinction if they have slower reproductive rates (older weaning ages). In contrast, risk in non-hunted artiodactyls is unrelated to reproductive rate and more closely associated with the economic development of the region in which they live.

Host social, ecological and life history traits are predicted to influence both parasite establishment within host species and the distribution of parasites among host species. Yet only a few studies have investigated the role multiple host traits play in determining patterns of infection across diverse parasite groups. To explore the association between host traits and parasite species richness (PSR), we assembled a comprehensive database encompassing 601 parasites (including viruses, bacteria, protozoa, helminths and arthropods) reported to infect 96 species from two well- studied and diverse host clades: even- and odd-toed hoofed mammals (Artiodactyla and Perissodactyla). Comparative analyses were used to examine associations between three sets of host variables (life history and body mass, social and mating behavior, and ecological traits) and PSR for all parasites combined and for distinct parasite sub-groups. Results from a combination of phylogenetic and non-phylogenetic tests showed that PSR increased with host body size across all parasites groups. Counter to expectations, measures of parasite diversity decreased with host longevity and social group size, and associations between group size and PSR further depended on the underlying mating system of the host species. Our results suggest that body mass, longevity, and social organization influence the diversity and types of parasites reported to infect wild populations of hoofed mammals, and that multiple host and parasite traits can combine in unexpected ways to shape observed patterns.

Because teeth are the most easily preserved part of the vertebrate skeleton and are particularly morphologically variable in mammals, studies of fossil mammals rely heavily on dental morphology. Dental morphology is used both for systematics and phylogeny as well as for inferences about paleoecology, diet in particular. We analyze the influence of evolutionary history on our ability to reconstruct diet from dental morphology in the mammalian order Carnivora, and we find that much of our understanding of diet in carnivorans is dependent on the phylogenetic constraints on diet in this clade. Substantial error in estimating diet from dental morphology is present regardless of the morphological data used to make the inference, although more extensive morphological datasets are more accurate in predicting diet than more limited character sets. Unfortunately, including phylogeny in making dietary inferences actually decreases the accuracy of these predictions, showing that dietary predictions from morphology are substantially dependent on the evolutionary constraints on carnivore diet and tooth shape. The “evolutionary ratchet” that drives lineages of carnivorans to evolve greater degrees of hypercarnivory through time actually plays a role in allowing dietary inference from tooth shape, but consequently requires caution in interpreting dietary inference from the teeth fossil carnivores. These difficulties are another reminder of the differences in evolutionary tempo and mode between morphology and ecology.