Macroevolutionary Scale Research Articles

Ecological diversification of sea catfishes is accompanied by genome-wide signatures of positive selection

Habitat transitions have shaped the evolutionary trajectory of many clades. Sea catfishes (Ariidae) have repeatedly undergone ecological transitions, including colonizing freshwaters from marine environments, leading to an adaptive radiation in Australia and New Guinea alongside non-radiating freshwater lineages elsewhere. Here, we generate and analyze one long-read reference genome and 66 short-read whole genome assemblies, in conjunction with genomic data for 54 additional species. We investigate how three major ecological transitions have shaped genomic variation among ariids over their ~ 50 million-year evolutionary history. Our results show that relatively younger freshwater lineages exhibit a higher incidence of positive selection than their more ancient marine counterparts. They also display a larger disparity in body shapes, a trend that correlates with a heightened occurrence of positive selection on genes associated with body size and elongation. Although positive selection in the Australia and New Guinea radiation does not stand out compared to non-radiating lineages overall, selection across the prolactin gene family during the marine-to-freshwater transition suggests that strong osmoregulatory adaptations may have facilitated their colonization and radiation. Our findings underscore the significant role of selection in shaping the genome and organismal traits in response to habitat shifts across macroevolutionary scales.

Evolution of avian foot morphology through anatomical network analysis

Avian evolution led to morphological adaptive variations in feet. Diverse foot types are accompanied by a diverse muscle system, allowing birds to adopt different primary lifestyles, and to display various locomotor and manipulative skills. We provide insights of evolutionary and functional significance on the avian foot architecture through Anatomical Network Analysis, a methodology focused on connectivity patterns of anatomical parts. Here, we show that: (1) anatomical parts largely conserved in living birds and already present in ancestral dinosaurs exhibit the highest connectivity degree, (2) there is no link between the more complex foot networks and the ability to perform more specialized skills or a higher number of different tasks, (3) there is a trend towards the simplification of foot networks on a macroevolutionary scale within birds, and (4) foot networks are phylogenetically constrained and conserved in all birds despite their foot type diversity, probably due to stabilizing selection.

Trophic guilds differ in blood glucose concentrations: a phylogenetic comparative analysis in birds.

Glucose is a central metabolic compound used as an energy source across all animal taxa. There is high interspecific variation in glucose concentration between taxa, the origin and the consequence of which remain largely unknown. Nutrition may affect glucose concentrations because carbohydrate content of different food sources may determine the importance of metabolic pathways in the organism. Birds sustain high glucose concentrations that may entail the risks of oxidative damage. We collected glucose concentration and life-history data from 202 bird species from 171 scientific publications, classified them into seven trophic guilds and analysed the data with a phylogenetically controlled model. We show that glucose concentration is negatively associated with body weight and is significantly associated with trophic guilds with a moderate phylogenetic signal. After controlling for allometry, glucose concentrations were highest in carnivorous birds, which rely on high rates of gluconeogenesis to maintain their glycaemia, and lowest in frugivorous/nectarivorous species, which take in carbohydrates directly. However, trophic guilds with different glucose concentrations did not differ in lifespan. These results link nutritional ecology to physiology and suggest that at the macroevolutionary scale, species requiring constantly elevated glucose concentrations may have additional adaptations to avoid the risks associated with high glycaemia.

Exploring the Macroevolutionary Signature of Asymmetric Inheritance at Speciation.

Popular comparative phylogenetic models such as Brownian Motion, Ornstein-Ulhenbeck, and their extensions, assume that, at speciation, a trait value is inherited identically by two descendant species. This assumption contrasts with models of speciation at a micro-evolutionary scale where descendants' phenotypic distributions are sub-samples of the ancestral distribution. Different speciation mechanisms can lead to a displacement of the ancestral phenotypic mean among descendants and an asymmetric inheritance of the ancestral phenotypic variance. In contrast, even macro-evolutionary models that account for intraspecific variance assume symmetrically conserved inheritance of ancestral phenotypic distribution at speciation. Here we develop an Asymmetric Brownian Motion model (ABM) that relaxes the assumption of symmetric and conserved inheritance of the ancestral distribution at the time of speciation. The ABM jointly models the evolution of both intra- and inter-specific phenotypic variation. It also infers the mode of phenotypic inheritance at speciation, which can range from a symmetric and conserved inheritance, where descendants inherit the ancestral distribution, to an asymmetric and displaced inheritance, where descendants inherit divergent phenotypic means and variances. To demonstrate this model, we analyze the evolution of beak morphology in Darwin finches, finding evidence of displacement at speciation. The ABM model helps to bridge micro- and macro-evolutionary models of trait evolution by providing a more robust framework for testing the effects of ecological speciation, character displacement, and niche partitioning on trait evolution at the macro-evolutionary scale.

'Drifting' Buchnera genomes track the microevolutionary trajectories of their aphid hosts.

Evolution of Buchnera-aphid host symbioses is often studied among species at macroevolutionary scales. Investigations within species offer a different perspective about how eco-evolutionary processes shape patterns of genetic variation at microevolutionary scales. Our study leverages new and publicly available whole-genome sequencing data to study Buchnera-aphid host evolution in Myzus persicae, the peach potato aphid, a globally invasive and polyphagous pest. Across 43 different asexual, clonally reproducing isofemale strains, we examined patterns of genomic covariation between Buchnera and their aphid host and considered the distribution of mutations in protein-coding regions of the Buchnera genome. We found Buchnera polymorphisms within aphid strains, suggesting the presence of genetically different Buchnera strains within the same clonal lineage. Genetic distance between pairs of Buchnera samples was positively correlated to genetic distance between their aphid hosts, indicating shared evolutionary histories. However, there was no segregation of genetic variation for both M. persicae and Buchnera with plant host (Brassicaceae and non-tobacco Solanaceae) and no associations between genetic and geographic distance at global or regional spatial scales. Abundance patterns of non-synonymous mutations were similar to synonymous mutations in the Buchnera genome, and both mutation classes had similar site frequency spectra. We hypothesize that a predominance of neutral processes results in the Buchnera of M. persicae to simply 'drift' with the evolutionary trajectory of their aphid hosts. Our study presents a unique microevolutionary characterization of Buchnera-aphid host genomic covariation across multiple aphid clones. This provides a new perspective on the eco-evolutionary processes generating and maintaining polymorphisms in a major pest aphid species and its obligate primary endosymbiont.

Detecting diversifying selection for a trait from within and between-species genotypes and phenotypes.

To quantify selection acting on a trait, methods have been developed using either within or between-species variation. However, methods using within-species variation do not integrate the changes at the macroevolutionary scale. Conversely, current methods using between-species variation usually discard within-species variation, thus not accounting for processes at the micro-evolutionary scale. The main goal of this study is to define a neutrality index for a quantitative trait, by combining withinand between-species variation. This neutrality index integrates nucleotide polymorphism and divergence for normalizing trait variation. As such, it does not require estimation of population size nor of time of speciation for normalization. Our index can be used to seek deviation from the null model of neutral evolution, and test for diversifying selection. Applied to brain mass and body mass at the mammalian scale, we show that brain mass is under diversifying selection. Finally, we show that our test is not sensitive to the assumption that population sizes, mutation rates and generation time are constant across the phylogeny, and automatically adjust for it.

Odd-Paired is Involved in Morphological Divergence of Snail-Feeding Beetles.

Body shape and size diversity and their evolutionary rates correlate with species richness at the macroevolutionary scale. However, the molecular genetic mechanisms underlying the morphological diversification across related species are poorly understood. In beetles, which account for one-fourth of the known species, adaptation to different trophic niches through morphological diversification appears to have contributed to species radiation. Here, we explored the key genes for the morphological divergence of the slender to stout body shape related to divergent feeding methods on large to small snails within the genus Carabus. We show that the zinc-finger transcription factor encoded by odd-paired (opa) controls morphological variation in the snail-feeding ground beetle Carabus blaptoides. Specifically, opa was identified as the gene underlying the slender to stout morphological difference between subspecies through genetic mapping and functional analysis via gene knockdown. Further analyses revealed that changes in opa cis-regulatory sequences likely contributed to the differences in body shape and size between C. blaptoides subspecies. Among opa cis-regulatory sequences, single nucleotide polymorphisms on the transcription factor binding sites may be associated with the morphological differences between C. blaptoides subspecies. opa was highly conserved in a wide range of taxa, especially in beetles. Therefore, opa may play an important role in adaptive morphological divergence in beetles.

Coevolution with hosts underpins speciation in brood-parasitic cuckoos.

Coevolution between interacting species is thought to increase biodiversity, but evidence linking microevolutionary processes to macroevolutionary patterns is scarce. We leveraged two decades of behavioral research coupled with historical DNA analysis to reveal that coevolution with hosts underpins speciation in brood-parasitic bronze-cuckoos. At a macroevolutionary scale, we show that highly virulent brood-parasitic taxa have higher speciation rates and are more likely to speciate in sympatry than less-virulent and nonparasitic relatives. We reveal the microevolutionary process underlying speciation: Hosts reject cuckoo nestlings, which selects for mimetic cuckoo nestling morphology. Where cuckoos exploit multiple hosts, selection for mimicry drives genetic and phenotypic divergence corresponding to host preference, even in sympatry. Our work elucidates perhaps the most common, but poorly characterized, evolutionary process driving biological diversification.

Dine and dash: how trophic ecology and migration shape functional locomotory traits in clupeiform fishes

Abstract Understanding how interactions between multiple selective forces influence traits at the macroevolutionary scale is key to understanding adaptive landscapes. Diadromy, an extreme form of migration between marine and freshwater environments, is thought to require locomotory traits conducive to long-distance migration. Yet, other selective forces, such as predator avoidance, habitat use, and prey acquisition, are also likely to shape locomotory adaptation in fishes. We examined how diadromy and trophic ecology together influenced locomotory trait diversity across Clupeiformes, a clade of fishes containing high trophic diversity and numerous transitions to diadromy. We found that both diadromy and trophic ecology influenced the pattern and pace of trait evolution. Diadromous taxa rapidly evolved traits characterized by high cruising efficiency, but the extent to which diadromous and non-diadromous taxa differed depended on their trophic ecology. Macropredators showed greater differences in locomotory traits between diadromous and non-diadromous taxa than phytodetritivores and micropredators, suggesting that traits conducive to migration might be most costly to consumers of evasive prey. This work shows that simultaneously characterizing the roles of multiple ecological or life-history factors in phenotypic evolution can bring the topography of adaptive landscapes into sharper focus and provide a more holistic view of the forces driving patterns of trait evolution.

Phenotypic plasticity in tropical butterflies is linked to climatic seasonality on a macroevolutionary scale.

Phenotypic plasticity can be adaptive in fluctuating environments by providing rapid environment-phenotype matching and this applies particularly in seasonal environments. African Bicyclus butterflies have repeatedly colonized seasonal savannahs from ancestral forests around the late Miocene, and many species now exhibit seasonal polyphenism. On a macroevolutionary scale, it can be expected that savannah species will exhibit higher plasticity because of experiencing stronger environmental seasonality than forest species. We quantified seasonality using environmental niche modeling and surveyed the degree of plasticity in a key wing pattern element (eyespot size) using museum specimens. We showed that species occurring in highly seasonal environments display strong plasticity, while species in less seasonal or aseasonal environments exhibit surprisingly variable degrees of plasticity, including strong to no plasticity. Furthermore, eyespot size plasticity has a moderate phylogenetic signal and the ancestral Bicyclus likely exhibited some degree of plasticity. We propose hypotheses to explain the range of plasticity patterns seen in less seasonal environments and generate testable predictions for the evolution of plasticity in Bicyclus. Our study provides one of the most compelling cases showing links between seasonality and phenotypic plasticity on a macroevolutionary scale and the potential role of plasticity in facilitating the colonization of novel environments.

Evolution of intraspecific floral variation in a generalist-specialist pollination system.

Intraspecific processes impact macroevolutionary patterns through individual variation, selection, and ecological specialisation. According to the niche variation hypothesis, the broader ecological niche of gen- eralist species results in an increased morphological variation among individuals, either because they are constituted of diversified specialised individuals each exploiting a fraction of the species' niche, or because they are constituted of true generalist individuals that experience relaxed selection. To test this hypoth- esis, we surveyed the individual floral morphology of species of Antillean Gesneriaceae, a group that has transitioned between specialisation for hummingbird pollination and generalisation multiple times throughout its evolutionary history. We characterised the profiles of corollas using geometric morpho- metrics and compared the intraspecific shape variance of specialists and generalists in a phylogenetic context. We used three approaches that differently accounted for the high dimensionality of morphologi- cal traits, the ancestral reconstruction of pollination syndromes over time, and the error associated with the estimation of the intraspecific variance. Our findings provide partial support for the niche variation hypothesis. If considering the whole shape in the analysis corroborated this idea, decomposing the shape into principal components indicated that not all aspects of the corolla exhibit the same pattern of vari- ation. Specifically, pollination generalists tend to display greater intraspecific variation than specialists in terms of tubularity, but not of curvature. Accounting for the error in the variance estimation also reduced the support for the hypothesis, suggesting that larger sample sizes may be required to reach stronger conclusions. This study emphasises the reciprocal influence between plants and their pollinators on floral morphology at different biodiversity scales, and suggests that ecological strategies of species can affect patterns of morphological variation at macroevolutionary scales.

Divergence and reticulation in the Mexican white oaks: ecological and phylogenomic evidence on species limits and phylogenetic networks in the Quercus laeta complex (Fagaceae).

Introgressive hybridization poses a challenge to taxonomic and phylogenetic understanding of taxa, particularly when there are high numbers of co-occurring, intercrossable species. The genus Quercus exemplifies this situation. Oaks are highly diverse in sympatry and cross freely, creating syngameons of interfertile species. Although a well-resolved, dated phylogeny is available for the American oak clade, evolutionary relationships within many of the more recently derived clades remain to be defined, particularly for the young and exceptionally diverse Mexican white oak clade. Here, we adopted an approach bridging micro- and macroevolutionary scales to resolve evolutionary relationships in a rapidly diversifying clade endemic to Mexico. Ecological data and sequences of 155 low-copy nuclear genes were used to identify distinct lineages within the Quercus laeta complex. Concatenated and coalescent approaches were used to assess the phylogenetic placement of these lineages relative to the Mexican white oak clade. Phylogenetic network methods were applied to evaluate the timing and genomic significance of recent or historical introgression among lineages. The Q. laeta complex comprises six well-supported lineages, each restricted geographically and with mostly divergent climatic niches. Species trees corroborated that the different lineages are more closely related to other species of Mexican white oaks than to each other, suggesting that this complex is polyphyletic. Phylogenetic networks estimated events of ancient introgression that involved the ancestors of three present-day Q. laeta lineages. The Q. laeta complex is a morphologically and ecologically related group of species rather than a clade. Currently, oak phylogenetics is at a turning point, at which it is necessary to integrate phylogenetics and ecology in broad regional samples to figure out species boundaries. Our study illuminates one of the more complicated of the Mexican white oak groups and lays groundwork for further taxonomic study.

Intercontinental dispersal and niche fidelity drive 50 million years of global diversification in Vertigo land snails

AbstractAimWe aimed to understand how biogeographical processes and moisture niche ecology contributed to the spatio‐temporal diversification dynamics in the land snail genus Vertigo.LocationGlobal (North America, Europe, Asia, Africa).Time PeriodCenozoic era.Major Taxa StudiedMinute terrestrial snails of the genus Vertigo.MethodsWe reconstructed a time‐calibrated phylogeny of 94 Vertigo taxa (~85% of all known extant species) based on mitochondrial and nuclear DNA data. Leveraging this phylogeny with distributional and ecological data from >7000 populations, we performed biogeographic and ecological modelling to investigate evolutionary mechanisms of global Vertigo diversification.ResultsVertigo has diversified since the Early Eocene, ca. 47.6 Ma (95% HPD = 46.0–52.7), with its six subgenera originating from the Late Eocene (30.2–48.7 Ma) to the Early Miocene (13.3–23.0 Ma). Species diversity accumulated linearly, with a slight increase 35–30 and 25–20 Ma, coinciding with the emergence of most subgenera and northern hemisphere cooling, respectively. Biogeographic modelling indicated that most diversification events occurred in sympatry (no range modification), but that rare founder events drove global diversification. Soil moisture conditions, a major variable defining Vertigo niches, displayed significant phylogenetic signal, but varied less among subgenera relative to within. Shifts in biogeographical ranges and moisture niches (or the absence thereof) were significantly associated at macroevolutionary scales, with most niche shifts upon sympatric cladogenesis and hardly any upon founder‐event speciation.Main ConclusionsOur results indicate that ecological shifts in soil moisture niches occasionally drove cladogenesis in sympatry and anagenetic range extensions, but that long‐distance dispersal was mainly successful in the absence of such shifts. A combination of neutral (founder events and drift) and selective mechanisms (adaptive habitat shifts) has determined the macroevolutionary success of Vertigo. Our results imply that species with high niche fidelity or fewer opportunities for long‐distance dispersal will be more vulnerable to future anthropogenic stressors.

Highly dynamic evolution of the chemosensory system driven by gene gain and loss across subterranean beetles

Chemical cues in subterranean habitats differ highly from those on the surface due to the contrasting environmental conditions, such as absolute darkness, high humidity or food scarcity. Subterranean animals underwent changes to their sensory systems to facilitate the perception of essential stimuli for underground lifestyles. Despite representing unique systems to understand biological adaptation, the genomic basis of chemosensation across cave-dwelling species remains unexplored from a macroevolutionary perspective. Here, we explore the evolution of chemoreception in three beetle tribes that underwent at least six independent transitions to the underground, through a phylogenomics spyglass. Our findings suggest that the chemosensory gene repertoire varies dramatically between species. Overall, no parallel changes in the net rate of evolution of chemosensory gene families were detected prior, during, or after the habitat shift among subterranean lineages. Contrarily, we found evidence of lineage-specific changes within surface and subterranean lineages. However, our results reveal key duplications and losses shared between some of the lineages transitioning to the underground, including the loss of sugar receptors and gene duplications of the highly conserved ionotropic receptors IR25a and IR8a, involved in thermal and humidity sensing among other olfactory roles in insects. These duplications were detected both in independent subterranean lineages and their surface relatives, suggesting parallel evolution of these genes across lineages giving rise to cave-dwelling species. Overall, our results shed light on the genomic basis of chemoreception in subterranean beetles and contribute to our understanding of the genomic underpinnings of adaptation to the subterranean lifestyle at a macroevolutionary scale.

Evolutionary and ecological trends in the Neotropical cycad genus Dioon (Zamiaceae): An example of success of evolutionary stasis

AbstractCycads represent an example of the success of evolutionary stasis. Despite their early origin, they survived multiple events of mass extinction and diversified in modern tropical ecosystems during the Cenozoic without major changes in their morphology. What factors have allowed their persistence and diversification despite their conservative nature? We reviewed documentation on the micro‐ and macro‐evolutionary processes involved in the diversification of the Neotropical genus Dioon. Dioon comprises 18 species from varied habitats in Mexico and Honduras, and serves as a model to understand the patterns of cycad diversification. Here, we synthesize evidence reached from different fields, especially biogeography, phylogenetics, population ecology, and speciation, to propose a mechanism that can explain the current patterns of biodiversity in Dioon. At the macroevolutionary scale, a Paleogene origin for Dioon is more likely than an alternative hypothesis of a Neogene origin. Dioon lineages have dispersed along with the expansion of tropical forests throughout main mountain chains. Subsequently, climate change, and particularly aridification, promoted the fragmentation of the tropical forests, allowing the main Dioon clades to evolve in isolation at distinct biogeographic regimes. At the microevolutionary scale, low seed dispersal capability, stochastic demographic processes, and niche conservatism restrict the lineages to isolate themselves at narrow habitats, promoting local adaptation in populations. Local adaptation seems to be a process achieved through many generations under stabilizing selection. Altogether, these processes shaped the diversification in Dioon. This review attempts to stimulate further research on cycads and other biological groups that have diversified despite their apparent evolutionary stasis.

Anti-predator defences are linked with high levels of genetic differentiation in frogs.

Predator-prey interactions have been suggested as drivers of diversity in different lineages, and the presence of anti-predator defences in some clades is linked to higher rates of diversification. Warning signals are some of the most widespread defences in the animal world, and there is evidence of higher diversification rates in aposematic lineages. The mechanisms behind such species richness, however, are still unclear. Here, we test whether lineages that use aposematism as anti-predator defence exhibit higher levels of genetic differentiation between populations, leading to increased opportunities for divergence. We collated from the literature more than 3000 pairwise genetic differentiation values across more than 700 populations from over 60 amphibian species. We find evidence that over short geographical distances, populations of species of aposematic lineages exhibit greater genetic divergence relative to species that are not aposematic. Our results support a scenario where the use of warning signals could restrict gene flow, and suggest that anti-predator defences could impact divergence between populations and potentially have effects at a macro-evolutionary scale.

Dental Dynamics: A Fast New Tool for Quantifying Tooth and Jaw Biomechanics in 3D Slicer.

Teeth reveal how organisms interact with their environment. Biologists have long looked at the diverse form and function of teeth to study the evolution of feeding, fighting, and development. The exponential rise in the quantity and accessibility of computed tomography (CT) data has enabled morphologists to study teeth at finer resolutions and larger macroevolutionary scales. Measuring tooth function is no easy task, in fact, much of our mechanical understanding is derived from dental shape. Categorical descriptors of tooth shape such as morphological homodonty and heterodonty, overlook nuances in function by reducing tooth diversity for comparative analysis. The functional homodonty method quantitatively assesses the functional diversity of whole dentitions from tooth shape. This method uses tooth surface area and position to calculate the transmission of stress and estimates a threshold for functionally homodont teeth through bootstrapping and clustering techniques. However, some vertebrates have hundreds or thousands of teeth and measuring the shape and function of every individual tooth can be a painstaking task. Here, we present Dental Dynamics, a module for 3D Slicer that allows for the fast and precise quantification of dentitions and jaws. The tool automates the calculation of several tooth traits classically used to describe form and function (i.e., aspect ratio, mechanical advantage, force, etc.). To demonstrate the usefulness of our module we used Dental Dynamics to quantify 780 teeth across 20 salamanders that exhibit diverse ecologies. We coupled these data with the functional homodonty method to investigate the hypothesis that arboreal Aneides salamanders have novel tooth functions. Dental Dynamics provides a new and fast way to measure teeth and increases the accessibility of the functional homodonty method. We hope Dental Dynamics will encourage further theoretical and methodological development for quantifying and studying teeth.

Songbirds avoid the oxidative stress costs of high blood glucose levels: a comparative study.

Chronically high blood glucose levels (hyperglycaemia) can compromise healthy ageing and lifespan at the individual level. Elevated oxidative stress can play a central role in hyperglycaemia-induced pathologies. Nevertheless, the lifespan of birds shows no species-level association with blood glucose. This suggests that the potential pathologies of high blood glucose levels can be avoided by adaptations in oxidative physiology at the macroevolutionary scale. However, this hypothesis remains unexplored. Here, we examined this hypothesis using comparative analyses controlled for phylogeny, allometry and fecundity based on data from 51 songbird species (681 individuals with blood glucose data and 1021 individuals with oxidative state data). We measured blood glucose at baseline and after stress stimulus and computed glucose stress reactivity as the magnitude of change between the two time points. We also measured three parameters of non-enzymatic antioxidants (uric acid, total antioxidants and glutathione) and a marker of oxidative lipid damage (malondialdehyde). We found no clear evidence for blood glucose concentration being correlated with either antioxidant or lipid damage levels at the macroevolutionary scale, as opposed to the hypothesis postulating that high blood glucose levels entail oxidative costs. The only exception was the moderate evidence for species with a stronger stress-induced increase in blood glucose concentration evolving moderately lower investment into antioxidant defence (uric acid and glutathione). Neither baseline nor stress-induced glucose levels were associated with oxidative physiology. Our findings support the hypothesis that birds evolved adaptations preventing the (glyc)oxidative costs of high blood glucose observed at the within-species level. Such adaptations may explain the decoupled evolution of glycaemia and lifespan in birds and possibly the paradoxical combination of long lifespan and high blood glucose levels relative to mammals.

Carrion converging: Skull shape predicts feeding ecology in vultures

AbstractThe link between skull shape and dietary ecology in birds at macroevolutionary scales has recently been called into question by analyses of 3D shape that reveal that cranial anatomy is mainly influenced by other factors such as allometry. It is still unknown whether this form‐function disconnect also exists at smaller evolutionary scales, for example within specialized ecological guilds. Vultures are a diverse guild of 23 extant species in two families (Accipitridae and Cathartidae) that exhibit evolutionary convergence as a result of highly specialized feeding ecology. Vultures are the only known obligate scavengers among vertebrates and are usually grouped together under this single dietary category, but within this specialized diet there are three distinct, species‐specific feeding strategies termed ripper, gulper, and scrapper. We use three‐dimensional geometric morphometrics to quantify the relative contributions of feeding ecology, allometry, and phylogeny on vulture skull shape, along with several non‐vulture raptors of similar size, range and ecology. Families show clear separation in shape, but phylogenetic signal is comparatively weak (Kmult = 0.33). Taking into account the influence of phylogeny, skull shape is not significantly correlated with either skull size or feeding type, but there are examples of strong, significant convergence and parallel shape evolution across feeding groups. Furthermore, skull shape performs strongly in predicting feeding ecology in a phylogenetic discriminant function analysis. These findings highlight the importance of detailed assessment of feeding behavior in studies of ecomorphology, rather than broader dietary categories alone, and reveal that ecology can be readily inferred from form given appropriate information.

Evaluating modularity in the hominine skull related to feeding biomechanics.

Modular architecture of traits in complex organisms can be important for morphological evolution at micro- and sometimes macroevolutionary scales as it may influence the tempo and direction of changes to groups of traits that are essential for particular functions, including food acquisition and processing. We tested several distinct hypotheses about craniofacial modularity in the hominine skull in relation to feeding biomechanics. First, we formulated hypothesized functional modules for craniofacial traits reflecting specific demands of feeding biomechanics (e.g., masseter leverage/gape or tooth crown mechanics) in Homo sapiens, Pan troglodytes, and Gorilla gorilla. Then, the pattern and strength of modular signal was quantified by the covariance ratio coefficient and compared across groups using covariance ratio effect size. Hierarchical clustering analysis was then conducted to examine whether a priori-defined functional modules correspond to empirically recovered clusters. There was statistical support for most a priori-defined functional modules in the cranium and half of the functional modules in the mandible. Modularity signal was similar in the cranium and mandible, and across the three taxa. Despite a similar strength of modularity, the empirically recovered clusters do not map perfectly onto our priori functional modules, indicating that further work is needed to refine our hypothesized functional modules. The results suggest that modular structure of traits in association with feeding biomechanics were mostly shared with humans and the two African apes. Thus, conserved patterns of functional modularity may have facilitated evolutionary changes to the skull during human evolution.