Search

We present a short review of the biology, diagnostic characteristics, and invasiveness of the Oriental hornet, Vespa orientalis . We also performed an analysis of the shape of the forewings (geometric morphometrics) of different geographic groups along their native distribution and their potential geographical distribution using the MaxEnt entropy modeling. Our results show a wide potential expansion range of the species, including an increase in environmentally suitable areas in Europe, Asia, and Africa but more especially the Western Hemisphere, where the species was recently introduced. The geometric morphometric analysis of the forewings shows that there are three different morphogroups: one distributed along the Mediterranean coast of Europe and the Middle East (MEDI), another along the Arabian Peninsula and Western Asia but excluding the Mediterranean coast (MEAS), and one more in northern Africa north of the Sahara and south of the Mediterranean coast (AFRI), all of which show differences in their potential distribution as a result of the pressure from the different environments and which will also determine the capacity of the different morphogroups to successfully invade new habitats., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Smith-Pardo, Altamiranda-Saavedra and Polly.)

Objectives Evolutionary changes in hominin social complexity have been associated with increases in absolute brain size. The temporal lobes are nestled in the middle cranial fossae (MCF) of the skull, the dimensions of which allow estimation of temporal lobe volume (TLV) in extant and fossil taxa. Materials and Methods The main aim of this study is to determine where along the hominid phylogeny, major temporal lobe size transitions occurred. We used computed tomography (CT) scans of crania, 3D photogrammetry data, and laser surface scans of endocranial casts to measure seven MCF metrics in 11 extant anthropoid taxa using multiple regressions to estimate TLV in 5 extant hominids and 10 fossil hominins. Phylogenetic comparative methods mapped temporal lobe size, brain size, and temporal lobe proportions onto phylogenetic trees broadly for Hominidae and specifically for Hominini. Results Extant Homo sapiens were not an outlier in relative brain size, temporal lobe size, or proportions of the temporal lobes, but some proportions within the lobe were uniquely altered. The most notable changes in relative temporal lobe size and proportions saw a decrease in relative temporal lobe size and proportions in the genus Pan compared to other extant great apes and fossil hominins while there was a relative increase in the temporal lobe width and length in Australopithecus-Paranthropus clade compared to the genus Homo and other extant great apes including modern humans. Discussion We do not find support for the social brain, environmental or functional craniology hypotheses alone but think it prudent to consider the implications of cerebral reorganization between the temporal lobes and other regions of the brain within the context of these hypotheses and with future investigation is warranted., (© 2024 The Author(s). American Journal of Biological Anthropology published by Wiley Periodicals LLC.)

Tests of phenotypic convergence can provide evidence of adaptive evolution, and the popularity of such studies has grown in recent years due to the development of novel, quantitative methods for identifying and measuring convergence. These methods include the commonly applied C1-C4 measures of Stayton (2015a), which measure morphological distances between lineages, and Ornstein-Uhlenbeck (OU) model-fitting analyses, which test whether lineages converged on shared adaptive peaks. We test the performance of C-measures and other convergence measures under various evolutionary scenarios and reveal a critical issue with C-measures: they often misidentify divergent lineages as convergent. We address this issue by developing novel convergence measures-Ct1-Ct4-measures-that calculate distances between lineages at specific points in time, minimizing the possibility of misidentifying divergent taxa as convergent. Ct-measures are most appropriate when focal lineages are of the same or similar geologic ages (e.g., extant taxa), meaning that the lineages' evolutionary histories include considerable overlap in time. Beyond C-measures, we find that all convergence measures are influenced by the position of focal taxa in phenotypic space, with morphological outliers often statistically more likely to be measured as strongly convergent. Further, we mimic scenarios in which researchers assess convergence using OU models with a priori regime assignments (e.g., classifying taxa by ecological traits) and find that multiple-regime OU models with phenotypically divergent lineages assigned to a shared selective regime often outperform simpler models. This highlights that model support for these multiple-regime OU models should not be assumed to always reflect convergence among focal lineages of a shared regime. Our new Ct1-Ct4-measures provide researchers with an improved comparative tool, but we emphasize that all available convergence measures are imperfect, and researchers should recognize the limitations of these methods and use multiple lines of evidence to test convergence hypotheses., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Society for the Study of Evolution (SSE). All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Parallel laser photogrammetry (PLP), which consists of attaching two or three parallel laser beams at a known inter-beam distance to a camera, can be used to collect morphological measurements of organisms noninvasively. The lasers project onto the photo being taken, and because the inter-beam distance is known, they act as a scale for image analysis programs like ImageJ. Traditionally, this method has been used to measure larger morphological traits (e.g., limb length, crown-rump length) to serve as proxies for overall body size, whereas applications to smaller anatomical features remain limited. To that end, we used PLP to measure the testes of 18 free-living mantled howler monkeys (Alouatta palliata) at La Selva Biological Station, Costa Rica. We tested whether this method could reliably measure this relatively small and globular morphology, and whether it could detect differences among individuals. We tested reliability in three ways: within-photo (coefficient of variation [CV] = 4.7%), between-photo (CV = 5.5%), and interobserver (intraclass correlation = 0.92). We found an average volume of 36.2 cm 3 and a range of 16.4-54.4 cm 3 , indicating variation in testes size between individuals. Furthermore, these sizes are consistent with a previous study that collected measurements by hand, suggesting that PLP is a useful method for making noninvasive measurements of testes., (© 2024 The Authors. American Journal of Primatology published by Wiley Periodicals LLC.)

Objectives: Two decades ago, Rilling and Seligman, hereafter abbreviated to RAS Study, suggested modern humans had relatively larger temporal lobes for brain size compared to other anthropoids. Despite many subsequent studies drawing conclusions about the evolutionary implications for the emergence of unique cerebral specializations in Homo sapiens, no re-assessment has occurred using updated methodologies., Methods: We reassessed the association between right temporal lobe volume (TLV) and right hemisphere volume (HV) in the anthropoid brain. In a sample compiled de novo by us, T1-weighted in vivo Magnetic Resonance Imaging (MRI) scans of 11 extant anthropoid species were calculated by-voxel from the MRI and the raw data from RAS Study directly compared to our sample. Phylogenetic Generalized Least-Squares (PGLS) regression and trait-mapping using Blomberg's K (kappa) tested the correlation between HV and TLV accounting for anthropoid phylogeny, while bootstrapped PGLS regressions tested difference in slopes and intercepts between monkey and ape subsamples., Results: PGLS regressions indicated statistically significant correlations (r 2  < 0.99; p ≤ 0.0001) between TLV and HV with moderate influence from phylogeny (K ≤ 0.42). Bootstrapped PGLS regression did not show statistically significant differences in slopes between monkeys and apes but did for intercepts. In our sample, human TLV was not larger than expected for anthropoids., Discussion: Updated imaging, increased sample size and advanced statistical analyses did not find statistically significant results that modern humans possessed a disproportionately large temporal lobe volume compared to the general anthropoid trend. This has important implications for human and non-human primate brain evolution., (© 2023 The Authors. American Journal of Biological Anthropology published by Wiley Periodicals LLC.)

We are in a modern biodiversity crisis that will restructure community compositions and ecological functions globally. Large mammals, important contributors to ecosystem function, have been affected directly by purposeful extermination and indirectly by climate and land-use changes, yet functional turnover is rarely assessed on a global scale using metrics based on functional traits. Using ecometrics, the study of functional trait distributions and functional turnover, we examine the relationship between vegetation cover and locomotor traits for artiodactyl and carnivoran communities. We show that the ability to detect a functional relationship is strengthened when locomotor traits of both primary consumers (artiodactyls, n = 157 species) and secondary consumers (carnivorans, n = 138 species) are combined into one trophically integrated ecometric model. Overall, locomotor traits of 81% of communities accurately estimate vegetation cover, establishing the advantage of trophically integrated ecometric models over single-group models (58 to 65% correct). We develop an innovative approach within the ecometrics framework, using ecometric anomalies to evaluate mismatches in model estimates and observed values and provide more nuance for understanding relationships between functional traits and vegetation cover. We apply our integrated model to five paleontological sites to illustrate mismatches in the past and today and to demonstrate the utility of the model for paleovegetation interpretations. Observed changes in community traits and their associated vegetations across space and over time demonstrate the strong, rapid effect of environmental filtering on community traits. Ultimately, our trophically integrated ecometric model captures the cascading interactions between taxa, traits, and changing environments.

This article investigates a form of rank deficiency in phenotypic covariance matrices derived from geometric morphometric data, and its impact on measures of phenotypic integration. We first define a type of rank deficiency based on information theory then demonstrate that this deficiency impairs the performance of phenotypic integration metrics in a model system. Lastly, we propose methods to treat for this information rank deficiency. Our first goal is to establish how the rank of a typical geometric morphometric covariance matrix relates to the information entropy of its eigenvalue spectrum. This requires clear definitions of matrix rank, of which we define three: the full matrix rank (equal to the number of input variables), the mathematical rank (the number of nonzero eigenvalues), and the information rank or "effective rank" (equal to the number of nonredundant eigenvalues). We demonstrate that effective rank deficiency arises from a combination of methodological factors-Generalized Procrustes analysis, use of the correlation matrix, and insufficient sample size-as well as phenotypic covariance. Secondly, we use dire wolf jaws to document how differences in effective rank deficiency bias two metrics used to measure phenotypic integration. The eigenvalue variance characterizes the integration change incorrectly, and the standardized generalized variance lacks the sensitivity needed to detect subtle changes in integration. Both metrics are impacted by the inclusion of many small, but nonzero, eigenvalues arising from a lack of information in the covariance matrix, a problem that usually becomes more pronounced as the number of landmarks increases. We propose a new metric for phenotypic integration that combines the standardized generalized variance with information entropy. This metric is equivalent to the standardized generalized variance but calculated only from those eigenvalues that carry nonredundant information. It is the standardized generalized variance scaled to the effective rank of the eigenvalue spectrum. We demonstrate that this metric successfully detects the shift of integration in our dire wolf sample. Our third goal is to generalize the new metric to compare data sets with different sample sizes and numbers of variables. We develop a standardization for matrix information based on data permutation then demonstrate that Smilodon jaws are more integrated than dire wolf jaws. Finally, we describe how our information entropy-based measure allows phenotypic integration to be compared in dense semilandmark data sets without bias, allowing characterization of the information content of any given shape, a quantity we term "latent dispersion". [Canis dirus; Dire wolf; effective dispersion; effective rank; geometric morphometrics; information entropy; latent dispersion; modularity and integration; phenotypic integration; relative dispersion.]., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Society of Systematic Biologists.)

A boom in technological advancements over the last two decades has driven a surge in both the diversity and power of analytical tools available to biomechanical and functional morphology research. However, in order to adequately investigate each of these dense datasets, one must often consider only one functional narrative at a time. There is more to each organism than any one of these form-function relationships. Joint performance landscapes determined by maximum likelihood are a valuable tool that can be used to synthesize our understanding of these multiple functional hypotheses to further explore an organism's ecology. We present an example framework for applying these tools to such a problem using the morphological transition of ammonoids from the Middle Triassic to the Early Jurassic. Across this time interval, morphospace occupation shifts from a broad occupation across Westermann Morphospace to a dense occupation of a region emphasizing an exposed umbilicus and modest frontal profile. The hydrodynamic capacities and limitations of the shell have seen intense scrutiny as a likely explanation of this transition. However, conflicting interpretations of hydrodynamic performance remain despite this scrutiny, with scant offerings of alternative explanations. Our analysis finds that hydrodynamic measures of performance do little to explain the shift in morphological occupation, highlighting a need for a more robust investigation of alternative functional hypotheses that are often intellectually set aside. With this we show a framework for consolidating the current understanding of the form-function relationships in an organism, and assess when they are insufficiently characterizing the dynamics those data are being used to explain. We aim to encourage the broader adoption of this framework and these ideas as a foundation to bring the field close to comprehensive synthesis and reconstruction of organisms., (© The Author(s) 2022. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology.)

Many seasonally breeding animals exhibit a threshold day length (critical photoperiod; CPP) for gonadal growth, and populations breeding at higher latitudes typically have a higher CPP. Much less is known about latitudinal variation in CPP in migratory population that winter away from their breeding range and must time their reproduction to match favorable conditions at their destination. To address the relationship between migration, breeding latitude, and CPP, we held two closely related songbird populations in a common environment. One population is resident (Junco hyemalis carolinensis), the other winters in sympatry with the residents but migrates north to breed (Junco hyemalis hyemalis). We gradually increased photoperiod and measured indices of readiness to migrate (fat score, body mass) and breed (cloacal protuberance volume, baseline testosterone, and gonadotropin releasing hormone challenged testosterone). To estimate breeding latitude, we measured hydrogen isotopes in feathers grown the preceding year. As we predicted, we found a higher CPP in migrants than residents, and a higher CPP among migrants deriving from higher as opposed to lower latitudes. Migrants also terminated breeding earlier than residents, indicating a shorter breeding season. To our knowledge, this is a first demonstration of latitudinal variation in CPP-dependent reproductive timing in bird populations that co-exist in the non-breeding season but breed at different latitudes. We conclude that bird populations appear to exhibit local adaptation in reproductive timing by relying on differential CPP response that is predictive of future conditions on the breeding ground., (Published by Elsevier Inc.)

The kinetic skull is a key innovation that allowed snakes to capture, manipulate, and swallow prey exclusively using their heads using the coordinated movement of eight bones. Despite these unique feeding behaviors, patterns of evolutionary integration and modularity within the feeding bones of snakes in a phylogenetic framework have yet to be addressed. Here, we use a dataset of 60 μCT-scanned skulls and high-density geometric morphometric methods to address the origin and patterns of variation and integration in the feeding bones of aquatic-foraging snakes. By comparing alternate superimposition protocols allowing us to analyze the entire kinetic feeding system simultaneously, we find that the feeding bones are highly integrated, driven predominantly by functional selective pressures. The most supported pattern of modularity contains four modules, each associated with distinct functional roles: the mandible, the palatopterygoid arch, the maxilla, and the suspensorium. Further, the morphological disparity of each bone is not linked to its magnitude of integration, indicating that integration within the feeding system does not strongly constrain morphological evolution, and that adequate biomechanical solutions to a wide range of feeding ecologies and behaviors are readily evolvable within the constraint due to integration in the snake feeding system., (© 2020 The Authors. Evolution © 2020 The Society for the Study of Evolution.)

Functional tradeoffs are often viewed as constraints on phenotypic evolution, but they can also facilitate evolution across the suboptimal valleys separating performance peaks. I explore this process by reviewing a previously published model of how disruptive selection from competing functional demands defines an intermediate performance optimum for morphological systems that cannot simultaneously be optimized for all of the functional roles they must play. Because of the inherent tradeoffs in such a system, its optimal morphology in any particular environmental context will usually be intermediate between the performance peaks of the competing functions. The proportional contribution of each functional demand can be estimated by maximum likelihood from empirically observed morphologies, including complex ones measured with multivariate geometric morphometrics, using this model. The resulting tradeoff weight can be mapped onto a phylogenetic tree to study how the performance optimum has shifted across a functional landscape circumscribed by the function-specific performance peaks. This model of tradeoff evolution is sharply different from one in which a multipeak Ornstein-Uhlenbeck (OU) model is applied to a set of morphologies and a phylogenetic tree to estimate how many separate performance optima exist. The multi-peak OU approach assumes that each branch is pushed toward one of two or more performance peaks that exist simultaneously and are separated by valleys of poor performance, whereas the model discussed here assumes that each branch tracks a single optimal performance peak that wanders through morphospace as the balance of functional demands shifts. That the movements of this net performance peak emerge from changing frequencies of selection events from opposing functional demands are illustrated using a series of computational simulations. These simulations show how functional tradeoffs can carry evolution across putative performance valleys: even though intermediate morphologies may not perform optimally for any one function, they may represent the optimal solution in any environment in which an organism experiences competing functional demands., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.)

Objectives: We investigate the suitability of middle cranial fossa (MCF) size as a proxy for temporal lobe volume (TLV), examining the strength of the association between TLV and MCF metrics and assess the reliability predicting TLV in fossil anthropoids. The temporal lobe of the primate brain is a multimodal association cortex involved in long-term memory, auditory, and visual processing with unique specializations in modern humans for language comprehension. The MCF is the bony counterpart for the temporal lobe providing inferences for fossil hominin temporal lobe evolution. We now investigate whether the MCF is a suitable proxy for the temporal lobe., Methods: A sample of 23 anthropoid species (n = 232, including 13 fossil species) from computed tomography (CT) scans of ex vivo crania and magnetic resonance imaging (MRI) of the in vivo brain were generated into three-dimensional (3D) virtual models. Seven linear metrics were digitally measured on the right MCF with right TLV calculated from in vivo MRI., Results: Regression analyses produced statistically significant correlations between TLV and all MCF metrics (r ≥ 0.85; p ≤ 0.0009) with TLV predictions within ±1 standard error and three MCF metrics (posterior-width, mid-length, and mid-width) the most reliable predictors of TLV with only one metric weakly associated with TLV., Discussion: These findings indicate a strong association between the MCF and TLV, provide reliable predictors of fossil TLV that were previously unattainable, allow the inclusion of fragmentary fossil material, and enable inferences into the emergence of modern human temporal lobe morphology., (© 2020 Wiley Periodicals, Inc.)

Phylogenetic comparative methods use tree topology, branch lengths, and models of phenotypic change to take into account nonindependence in statistical analysis. However, these methods normally assume that trees and models are known without error. Approaches relying on evolutionary regimes also assume specific distributions of character states across a tree, which often result from ancestral state reconstructions that are subject to uncertainty. Several methods have been proposed to deal with some of these sources of uncertainty, but approaches accounting for all of them are less common. Here, we show how Bayesian statistics facilitates this task while relaxing the homogeneous rate assumption of the well-known phylogenetic generalized least squares (PGLS) framework. This Bayesian formulation allows uncertainty about phylogeny, evolutionary regimes, or other statistical parameters to be taken into account for studies as simple as testing for coevolution in two traits or as complex as testing whether bursts of phenotypic change are associated with evolutionary shifts in intertrait correlations. A mixture of validation approaches indicates that the approach has good inferential properties and predictive performance. We provide suggestions for implementation and show its usefulness by exploring the coevolution of ankle posture and forefoot proportions in Carnivora., (© 2019 The Authors. Evolution © 2019 The Society for the Study of Evolution.)

The field of comparative morphology has entered a new phase with the rapid generation of high-resolution three-dimensional (3D) data. With freely available 3D data of thousands of species, methods for quantifying morphology that harness this rich phenotypic information are quickly emerging. Among these techniques, high-density geometric morphometric approaches provide a powerful and versatile framework to robustly characterize shape and phenotypic integration, the covariances among morphological traits. These methods are particularly useful for analyses of complex structures and across disparate taxa, which may share few landmarks of unambiguous homology. However, high-density geometric morphometrics also brings challenges, for example, with statistical, but not biological, covariances imposed by placement and sliding of semilandmarks and registration methods such as Procrustes superimposition. Here, we present simulations and case studies of high-density datasets for squamates, birds, and caecilians that exemplify the promise and challenges of high-dimensional analyses of phenotypic integration and modularity. We assess: (1) the relative merits of "big" high-density geometric morphometrics data over traditional shape data; (2) the impact of Procrustes superimposition on analyses of integration and modularity; and (3) differences in patterns of integration between analyses using high-density geometric morphometrics and those using discrete landmarks. We demonstrate that for many skull regions, 20-30 landmarks and/or semilandmarks are needed to accurately characterize their shape variation, and landmark-only analyses do a particularly poor job of capturing shape variation in vault and rostrum bones. Procrustes superimposition can mask modularity, especially when landmarks covary in parallel directions, but this effect decreases with more biologically complex covariance patterns. The directional effect of landmark variation on the position of the centroid affects recovery of covariance patterns more than landmark number does. Landmark-only and landmark-plus-sliding-semilandmark analyses of integration are generally congruent in overall pattern of integration, but landmark-only analyses tend to show higher integration between adjacent bones, especially when landmarks placed on the sutures between bones introduces a boundary bias. Allometry may be a stronger influence on patterns of integration in landmark-only analyses, which show stronger integration prior to removal of allometric effects compared to analyses including semilandmarks. High-density geometric morphometrics has its challenges and drawbacks, but our analyses of simulated and empirical datasets demonstrate that these potential issues are unlikely to obscure genuine biological signal. Rather, high-density geometric morphometric data exceed traditional landmark-based methods in characterization of morphology and allow more nuanced comparisons across disparate taxa. Combined with the rapid increases in 3D data availability, high-density morphometric approaches have immense potential to propel a new class of studies of comparative morphology and phenotypic integration., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology.)

2 H/ 1 H ratios in animal biomass reflect isotopic input from food and water. A 10-week controlled laboratory study raised 48 mice divided in two generations (8 mothers Mus musculus and their offspring). The mice were divided into four groups based on the combination of 2 H, 13 C, 15 N-enriched and non-enriched food and water. Glycine, the most common amino acid in bone collagen, carried the 2 H, 13 C, 15 N-isotopic spike in food. ANOVA data analysis indicated that hydrogen in food accounted for ∼81 % of the hydrogen isotope inventory in collagen whereas drinking water hydrogen contributed ∼17 %. Air humidity contributed an unspecified amount. Additionally, we monitored 13 C and 15 N-enrichment in bone collagen and found strong linear correlations with the 2 H-enrichment. The experiments with food and water indicate two biosynthetic pathways, namely (i) de novo creation of non-essential amino acids using hydrogen from water, and (ii) the integration of essential and non-essential amino acids from food. The lower rate of isotope uptake in mothers' collagen relative to their offspring indicates incomplete bone collagen turnover after ten weeks. The variance of hydrogen stable isotope ratios within the same cohort may limit its usefulness as a single sample proxy for archaeological or palaeoenvironmental research.

In Table 1 of this article, the descriptions of landmarks 14, 15, and 36 are incorrect. Landmarks 14 and 36 should read "Posterior extremity of occipital condyle along margin of foramen magnum" and landmark 15 should read "Opisthion". A correct version of Table 2 appears in the Author Correction associated with this article; the error has not been fixed in the original article.

A unique characteristic of mammals is a vertebral column with anatomically distinct regions, but when and how this trait evolved remains unknown. We reconstructed vertebral regions and their morphological disparity in the extinct forerunners of mammals, the nonmammalian synapsids, to elucidate the evolution of mammalian axial differentiation. Mapping patterns of regionalization and disparity (heterogeneity) across amniotes reveals that both traits increased during synapsid evolution. However, the onset of regionalization predates increased heterogeneity. On the basis of inferred homology patterns, we propose a "pectoral-first" hypothesis for region acquisition, whereby evolutionary shifts in forelimb function in nonmammalian therapsids drove increasing vertebral modularity prior to differentiation of the vertebral column for specialized functions in mammals., (Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Conservation of species and ecosystems is increasingly difficult because anthropogenic impacts are pervasive and accelerating. Under this rapid global change, maximizing conservation success requires a paradigm shift from maintaining ecosystems in idealized past states toward facilitating their adaptive and functional capacities, even as species ebb and flow individually. Developing effective strategies under this new paradigm will require deeper understanding of the long-term dynamics that govern ecosystem persistence and reconciliation of conflicts among approaches to conserving historical versus novel ecosystems. Integrating emerging information from conservation biology, paleobiology, and the Earth sciences is an important step forward on the path to success. Maintaining nature in all its aspects will also entail immediately addressing the overarching threats of growing human population, overconsumption, pollution, and climate change., (Copyright © 2017, American Association for the Advancement of Science.)

The large brain and small postcanine teeth of modern humans are among our most distinctive features, and trends in their evolution are well studied within the hominin clade. Classic accounts hypothesize that larger brains and smaller teeth coevolved because behavioral changes associated with increased brain size allowed a subsequent dental reduction. However, recent studies have found mismatches between trends in brain enlargement and posterior tooth size reduction in some hominin species. We use a multiple-variance Brownian motion approach in association with evolutionary simulations to measure the tempo and mode of the evolution of endocranial and dental size and shape within the hominin clade. We show that hominin postcanine teeth have evolved at a relatively consistent neutral rate, whereas brain size evolved at comparatively more heterogeneous rates that cannot be explained by a neutral model, with rapid pulses in the branches leading to later Homo species. Brain reorganization shows evidence of elevated rates only much later in hominin evolution, suggesting that fast-evolving traits such as the acquisition of a globular shape may be the result of direct or indirect selection for functional or structural traits typical of modern humans., Competing Interests: The authors declare no conflict of interest.

Developmental constraints can have significant influence on the magnitude and direction of evolutionary change, and many studies have demonstrated that these effects are manifested on macroevolutionary scales. Phenotypic integration, or the strong interactions among traits, has been similarly invoked as a major influence on morphological variation, and many studies have demonstrated that trait integration changes through ontogeny, in many cases decreasing with age. Here, we unify these perspectives in a case study of the ontogeny of the mammalian cranium, focusing on a comparison between marsupials and placentals. Marsupials are born at an extremely altricial state, requiring, in most cases, the use of the forelimbs to climb to the pouch, and, in all cases, an extended period of continuous suckling, during which most of their development occurs. Previous work has shown that marsupials are less disparate in adult cranial form than are placentals, particularly in the oral apparatus, and in forelimb ontogeny and adult morphology, presumably due to functional selection pressures on these two systems during early postnatal development. Using phenotypic trajectory analysis to quantify prenatal and early postnatal cranial ontogeny in 10 species of therian mammals, we demonstrate that this pattern of limited variation is also apparent in the development of the oral apparatus of marsupials, relative to placentals, but not in the skull more generally. Combined with the observation that marsupials show extremely high integration of the oral apparatus in early postnatal ontogeny, while other cranial regions show similar levels of integration to that observed in placentals, we suggest that high integration may compound the effects of the functional constraints for continuous suckling to ultimately limit the ontogenetic and adult disparity of the marsupial oral apparatus throughout their evolutionary history., (© The Author 2016. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology.)

Competing Interests: The author declares no conflict of interest.

Fossils and other paleontological information can improve phylogenetic comparative method estimates of phenotypic evolution and generate hypotheses related to species diversification. Here, we use fossil information to calibrate ancestral reconstructions of suitable climate for Sceloporus lizards in North America. Integrating data from the fossil record, general circulation models of paleoclimate during the Miocene, climate envelope modeling, and phylogenetic comparative methods provides a geographically and temporally explicit species distribution model of Sceloporus-suitable habitat through time. We provide evidence to support the historic biogeographic hypothesis of Sceloporus diversification in warm North American deserts and suggest a relatively recent Sceloporus invasion into Mexico around 6 Ma. We use a physiological model to map extinction risk. We suggest that the number of hours of restriction to a thermal refuge limited Sceloporus from inhabiting Mexico until the climate cooled enough to provide suitable habitat at approximately 6 Ma. If the future climate returns to the hotter climates of the past, Mexico, the place of highest modern Sceloporus richness, will no longer provide suitable habitats for Sceloporus to survive and reproduce.

Fossils provide the principal basis for temporal calibrations, which are critical to the accuracy of divergence dating analyses. Translating fossil data into minimum and maximum bounds for calibrations is the most important-often least appreciated-step of divergence dating. Properly justified calibrations require the synthesis of phylogenetic, paleontological, and geological evidence and can be difficult for nonspecialists to formulate. The dynamic nature of the fossil record (e.g., new discoveries, taxonomic revisions, updates of global or local stratigraphy) requires that calibration data be updated continually lest they become obsolete. Here, we announce the Fossil Calibration Database (http://fossilcalibrations.org), a new open-access resource providing vetted fossil calibrations to the scientific community. Calibrations accessioned into this database are based on individual fossil specimens and follow best practices for phylogenetic justification and geochronological constraint. The associated Fossil Calibration Series, a calibration-themed publication series at Palaeontologia Electronica, will serve as a key pipeline for peer-reviewed calibrations to enter the database., (© The Author(s) 2015. Published by Oxford University Press, on behalf of the Society of Systematic Biologists. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Our understanding of the evolution of the dentition has been transformed by advances in the developmental biology, genetics, and functional morphology of teeth, as well as the methods available for studying tooth form and function. The hierarchical complexity of dental developmental genetics combined with dynamic effects of cells and tissues during development allow for substantial, rapid, and potentially non-linear evolutionary changes. Studies of selection on tooth function in the wild and evolutionary functional comparisons both suggest that tooth function and adaptation to diets are the most important factors guiding the evolution of teeth, yet selection against random changes that produce malocclusions (selectional drift) may be an equally important factor in groups with tribosphenic dentitions. These advances are critically reviewed here.

Hox genes regulate regionalization of the axial skeleton in vertebrates, and changes in their expression have been proposed to be a fundamental mechanism driving the evolution of new body forms. The origin of the snake-like body form, with its deregionalized pre-cloacal axial skeleton, has been explained as either homogenization of Hox gene expression domains, or retention of standard vertebrate Hox domains with alteration of downstream expression that suppresses development of distinct regions. Both models assume a highly regionalized ancestor, but the extent of deregionalization of the primaxial domain (vertebrae, dorsal ribs) of the skeleton in snake-like body forms has never been analysed. Here we combine geometric morphometrics and maximum-likelihood analysis to show that the pre-cloacal primaxial domain of elongate, limb-reduced lizards and snakes is not deregionalized compared with limbed taxa, and that the phylogenetic structure of primaxial morphology in reptiles does not support a loss of regionalization in the evolution of snakes. We demonstrate that morphometric regional boundaries correspond to mapped gene expression domains in snakes, suggesting that their primaxial domain is patterned by a normally functional Hox code. Comparison of primaxial osteology in fossil and modern amniotes with Hox gene distributions within Amniota indicates that a functional, sequentially expressed Hox code patterned a subtle morphological gradient along the anterior-posterior axis in stem members of amniote clades and extant lizards, including snakes. The highly regionalized skeletons of extant archosaurs and mammals result from independent evolution in the Hox code and do not represent ancestral conditions for clades with snake-like body forms. The developmental origin of snakes is best explained by decoupling of the primaxial and abaxial domains and by increases in somite number, not by changes in the function of primaxial Hox genes.

Phenotypic integration is a pervasive characteristic of organisms. Numerous analyses have demonstrated that patterns of phenotypic integration are conserved across large clades, but that significant variation also exists. For example, heterochronic shifts related to different mammalian reproductive strategies are reflected in postcranial skeletal integration and in coordination of bone ossification. Phenotypic integration and modularity have been hypothesized to shape morphological evolution, and we extended simulations to confirm that trait integration can influence both the trajectory and magnitude of response to selection. We further demonstrate that phenotypic integration can produce both more and less disparate organisms than would be expected under random walk models by repartitioning variance in preferred directions. This effect can also be expected to favour homoplasy and convergent evolution. New empirical analyses of the carnivoran cranium show that rates of evolution, in contrast, are not strongly influenced by phenotypic integration and show little relationship to morphological disparity, suggesting that phenotypic integration may shape the direction of evolutionary change, but not necessarily the speed of it. Nonetheless, phenotypic integration is problematic for morphological clocks and should be incorporated more widely into models that seek to accurately reconstruct both trait and organismal evolution.

A central problem in paleoanthropology is the identity of the last common ancestor of Neanderthals and modern humans ([N-MH]LCA). Recently developed analytical techniques now allow this problem to be addressed using a probabilistic morphological framework. This study provides a quantitative reconstruction of the expected dental morphology of the [N-MH]LCA and an assessment of whether known fossil species are compatible with this ancestral position. We show that no known fossil species is a suitable candidate for being the [N-MH]LCA and that all late Early and Middle Pleistocene taxa from Europe have Neanderthal dental affinities, pointing to the existence of a European clade originated around 1 Ma. These results are incongruent with younger molecular divergence estimates and suggest at least one of the following must be true: (i) European fossils and the [N-MH]LCA selectively retained primitive dental traits; (ii) molecular estimates of the divergence between Neanderthals and modern humans are underestimated; or (iii) phenotypic divergence and speciation between both species were decoupled such that phenotypic differentiation, at least in dental morphology, predated speciation.

The climatic cycles of the Quaternary, during which global mean annual temperatures have regularly changed by 5-10°C, provide a special opportunity for studying the rate, magnitude, and effects of geographic responses to changing climates. During the Quaternary, high- and mid-latitude species were extirpated from regions that were covered by ice or otherwise became unsuitable, persisting in refugial retreats where the environment was compatible with their tolerances. In this study we combine modern geographic range data, phylogeny, Pleistocene paleoclimatic models, and isotopic records of changes in global mean annual temperature, to produce a temporally continuous model of geographic changes in potential habitat for 59 species of North American turtles over the past 320 Ka (three full glacial-interglacial cycles). These paleophylogeographic models indicate the areas where past climates were compatible with the modern ranges of the species and serve as hypotheses for how their geographic ranges would have changed in response to Quaternary climate cycles. We test these hypotheses against physiological, genetic, taxonomic and fossil evidence, and we then use them to measure the effects of Quaternary climate cycles on species distributions. Patterns of range expansion, contraction, and fragmentation in the models are strongly congruent with (i) phylogeographic differentiation; (ii) morphological variation; (iii) physiological tolerances; and (iv) intraspecific genetic variability. Modern species with significant interspecific differentiation have geographic ranges that strongly fluctuated and repeatedly fragmented throughout the Quaternary. Modern species with low genetic diversity have geographic distributions that were highly variable and at times exceedingly small in the past. Our results reveal the potential for paleophylogeographic models to (i) reconstruct past geographic range modifications, (ii) identify geographic processes that result in genetic bottlenecks; and (iii) predict threats due to anthropogenic climate change in the future.

Fossil discoveries over the past 30 years have radically transformed traditional views of Mesozoic mammal evolution. In addition, recent research provides a more detailed account of the Cretaceous diversification of flowering plants. Here, we examine patterns of morphological disparity and functional morphology associated with diet in early mammals. Two analyses were performed: (i) an examination of diversity based on functional dental type rather than higher-level taxonomy, and (ii) a morphometric analysis of jaws, which made use of modern analogues, to assess changes in mammalian morphological and dietary disparity. Results demonstrate a decline in diversity of molar types during the mid-Cretaceous as abundances of triconodonts, symmetrodonts, docodonts and eupantotherians diminished. Multituberculates experience a turnover in functional molar types during the mid-Cretaceous and a shift towards plant-dominated diets during the late Late Cretaceous. Although therians undergo a taxonomic expansion coinciding with the angiosperm radiation, they display small body sizes and a low level of morphological disparity, suggesting an evolutionary shift favouring small insectivores. It is concluded that during the mid-Cretaceous, the period of rapid angiosperm radiation, mammals experienced both a decrease in morphological disparity and a functional shift in dietary morphology that were probably related to changing ecosystems.

Sorex araneus, the Common shrew, is a species with more than 70 karyotypic races, many of which form parapatric hybrid zones, making it a model for studying chromosomal speciation. Hybrids between races have reduced fitness, but microsatellite markers have demonstrated considerable gene flow between them, calling into question whether the chromosomal barriers actually do contribute to genetic divergence. We studied phenotypic clines across two hybrid zones with especially complex heterozygotes. Hybrids between the Novosibirsk and Tomsk races produce chains of nine and three chromosomes at meiosis, and hybrids between the Moscow and Seliger races produce chains of eleven. Our goal was to determine whether phenotypes show evidence of reduced gene flow at hybrid zones. We used maximum likelihood to fit tanh cline models to geometric shape data and found that phenotypic clines in skulls and mandibles across these zones had similar centers and widths as chromosomal clines. The amount of phenotypic differentiation across the zones is greater than expected if it were dissipating due to unrestricted gene flow given the amount of time since contact, but it is less than expected to have accumulated from drift during allopatric separation in glacial refugia. Only if heritability is very low, Ne very high, and the time spent in allopatry very short, will the differences we observe be large enough to match the expectation of drift. Our results therefore suggest that phenotypic differentiation has been lost through gene flow since post-glacial secondary contact, but not as quickly as would be expected if there was free gene flow across the hybrid zones. The chromosomal tension zones are confirmed to be partial barriers that prevent differentiated races from becoming phenotypically homogenous.

Facial length is one of the best known examples of heterochrony. Changes in the timing of facial growth have been invoked as a mechanism for the origin of our short human face from our long-faced extinct relatives. Such heterochronic changes arguably permit great evolutionary flexibility, allowing the mammalian face to be remodelled simply by modifying postnatal growth. Here we present new data that show that this mechanism is significantly constrained by adult size. Small mammals are more brachycephalic (short faced) than large ones, despite the putative independence between adult size and facial length. This pattern holds across four phenotypic lineages: antelopes, fruit bats, tree squirrels and mongooses. Despite the apparent flexibility of facial heterochrony, growth of the face is linked to absolute size and introduces what seems to be a loose but clade-wide mammalian constraint on head shape.

As the most common and best preserved remains in the fossil record, teeth are central to our understanding of evolution. However, many evolutionary analyses based on dental traits overlook the constraints that limit dental evolution. These constraints are diverse, ranging from developmental interactions between the individual elements of a homologous series (the whole dentition) to functional constraints related to occlusion. This study evaluates morphological integration in the hominin dentition and its effect on dental evolution in an extensive sample of Plio- and Pleistocene hominin teeth using geometric morphometrics and phylogenetic comparative methods. Results reveal that premolars and molars display significant levels of covariation; that integration is stronger in the mandibular dentition than in the maxillary dentition; and that antagonist teeth, especially first molars, are strongly integrated. Results also show an association of morphological integration and evolution. Stasis is observed in elements with strong functional and/or developmental interactions, namely in first molars. Alternatively, directional evolution (and weaker integration) occurs in the elements with marginal roles in occlusion and mastication, probably in response to other direct or indirect selective pressures. This study points to the need to reevaluate hypotheses about hominin evolution based on dental characters, given the complex scenario in which teeth evolve., (© 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.)

Background: Efficient gene expression involves a trade-off between (i) premature termination of protein synthesis; and (ii) readthrough, where the ribosome fails to dissociate at the terminal stop. Sense codons that are similar in sequence to stop codons are more susceptible to nonsense mutation, and are also likely to be more susceptible to transcriptional or translational errors causing premature termination. We therefore expect this trade-off to be influenced by the number of stop codons in the genetic code. Although genetic codes are highly constrained, stop codon number appears to be their most volatile feature., Results: In the human genome, codons readily mutable to stops are underrepresented in coding sequences. We construct a simple mathematical model based on the relative likelihoods of premature termination and readthrough. When readthrough occurs, the resultant protein has a tail of amino acid residues incorrectly added to the C-terminus. Our results depend strongly on the number of stop codons in the genetic code. When the code has more stop codons, premature termination is relatively more likely, particularly for longer genes. When the code has fewer stop codons, the length of the tail added by readthrough will, on average, be longer, and thus more deleterious. Comparative analysis of taxa with a range of stop codon numbers suggests that genomes whose code includes more stop codons have shorter coding sequences., Conclusions: We suggest that the differing trade-offs presented by alternative genetic codes may result in differences in genome structure. More speculatively, multiple stop codons may mitigate readthrough, counteracting the disadvantage of a higher rate of nonsense mutation. This could help explain the puzzling overrepresentation of stop codons in the canonical genetic code and most variants.

Climate change research is increasingly focusing on the dynamics among species, ecosystems and climates. Better data about the historical behaviours of these dynamics are urgently needed. Such data are already available from ecology, archaeology, palaeontology and geology, but their integration into climate change research is hampered by differences in their temporal and geographical scales. One productive way to unite data across scales is the study of functional morphological traits, which can form a common denominator for studying interactions between species and climate across taxa, across ecosystems, across space and through time-an approach we call 'ecometrics'. The sampling methods that have become established in palaeontology to standardize over different scales can be synthesized with tools from community ecology and climate change biology to improve our understanding of the dynamics among species, ecosystems, climates and earth systems over time. Developing these approaches into an integrative climate change biology will help enrich our understanding of the changes our modern world is undergoing.

Mean annual temperature reported by the Intergovernmental Panel on Climate Change increases at least 1.1°C to 6.4°C over the next 90 years. In context, a change in climate of 6°C is approximately the difference between the mean annual temperature of the Last Glacial Maximum (LGM) and our current warm interglacial. Species have been responding to changing climate throughout Earth's history and their previous biological responses can inform our expectations for future climate change. Here we synthesize geological evidence in the form of stable oxygen isotopes, general circulation paleoclimate models, species' evolutionary relatedness, and species' geographic distributions. We use the stable oxygen isotope record to develop a series of temporally high-resolution paleoclimate reconstructions spanning the Middle Pleistocene to Recent, which we use to map ancestral climatic envelope reconstructions for North American rattlesnakes. A simple linear interpolation between current climate and a general circulation paleoclimate model of the LGM using stable oxygen isotope ratios provides good estimates of paleoclimate at other time periods. We use geologically informed rates of change derived from these reconstructions to predict magnitudes and rates of change in species' suitable habitat over the next century. Our approach to modeling the past suitable habitat of species is general and can be adopted by others. We use multiple lines of evidence of past climate (isotopes and climate models), phylogenetic topology (to correct the models for long-term changes in the suitable habitat of a species), and the fossil record, however sparse, to cross check the models. Our models indicate the annual rate of displacement in a clade of rattlesnakes over the next century will be 2 to 3 orders of magnitude greater (430-2,420 m/yr) than it has been on average for the past 320 ky (2.3 m/yr).

We outline here an approach for understanding the biology of climate change, one that integrates data at multiple spatial and temporal scales. Taxon-free trait analysis, or "ecometrics," is based on the idea that the distribution in a community of ecomorphological traits such as tooth structure, limb proportions, body mass, leaf shape, incubation temperature, claw shape, any aspect of anatomy or physiology can be measured across some subset of the organisms in a community. Regardless of temporal or spatial scale, traits are the means by which organisms interact with their environment, biotic and abiotic. Ecometrics measures these interactions by focusing on traits which are easily measurable, whose structure is closely related to their function, and whose function interacts directly with local environment. Ecometric trait distributions are thus a comparatively universal metric for exploring systems dynamics at all scales. The main challenge now is to move beyond investigating how future climate change will affect the distribution of organisms and how it will impact ecosystem services and to shift the perspective to ask how biotic systems interact with changing climate in general, and how climate change affects the interactions within and between the components of the whole biotic-physical system. We believe that it is possible to provide believable, quantitative answers to these questions. Because of this we have initiated an IUBS program iCCB (integrative Climate Change Biology)., (© 2010 ISZS, Blackwell Publishing and IOZ/CAS.)

Background: Although variation provides the raw material for natural selection and evolution, few empirical data exist about the factors controlling morphological variation. Because developmental constraints on variation are expected to act by influencing trait correlations, studies of modularity offer promising approaches that quantify and summarize patterns of trait relationships. Modules, highly-correlated and semi-autonomous sets of traits, are observed at many levels of biological organization, from genes to colonies. The evolutionary significance of modularity is considerable, with potential effects including constraining the variation of individual traits, circumventing pleiotropy and canalization, and facilitating the transformation of functional structures. Despite these important consequences, there has been little empirical study of how modularity influences morphological evolution on a macroevolutionary scale. Here, we conduct the first morphometric analysis of modularity and disparity in two clades of placental mammals, Primates and Carnivora, and test if trait integration within modules constrains or facilitates morphological evolution., Principal Findings: We used both randomization methods and direct comparisons of landmark variance to compare disparity in the six cranial modules identified in previous studies. The cranial base, a highly-integrated module, showed significantly low disparity in Primates and low landmark variance in both Primates and Carnivora. The vault, zygomatic-pterygoid and orbit modules, characterized by low trait integration, displayed significantly high disparity within Carnivora. 14 of 24 results from analyses of disparity show no significant relationship between module integration and morphological disparity. Of the ten significant or marginally significant results, eight support the hypothesis that integration within modules constrains morphological evolution in the placental skull. Only the molar module, a highly-integrated and functionally important module, showed significantly high disparity in Carnivora, in support of the facilitation hypothesis., Conclusions: This analysis of within-module disparity suggested that strong integration of traits had little influence on morphological evolution over large time scales. However, where significant results were found, the primary effect of strong integration of traits was to constrain morphological variation. Thus, within Primates and Carnivora, there was some support for the hypothesis that integration of traits within cranial modules limits morphological evolution, presumably by limiting the variation of individual traits.

The largest extant snakes live in the tropics of South America and southeast Asia where high temperatures facilitate the evolution of large body sizes among air-breathing animals whose body temperatures are dependant on ambient environmental temperatures (poikilothermy). Very little is known about ancient tropical terrestrial ecosystems, limiting our understanding of the evolution of giant snakes and their relationship to climate in the past. Here we describe a boid snake from the oldest known neotropical rainforest fauna from the Cerrejón Formation (58-60 Myr ago) in northeastern Colombia. We estimate a body length of 13 m and a mass of 1,135 kg, making it the largest known snake. The maximum size of poikilothermic animals at a given temperature is limited by metabolic rate, and a snake of this size would require a minimum mean annual temperature of 30-34 degrees C to survive. This estimate is consistent with hypotheses of hot Palaeocene neotropics with high concentrations of atmospheric CO(2) based on climate models. Comparison of palaeotemperature estimates from the equator to those from South American mid-latitudes indicates a relatively steep temperature gradient during the early Palaeogene greenhouse, similar to that of today. Depositional environments and faunal composition of the Cerrejón Formation indicate an anaconda-like ecology for the giant snake, and an earliest Cenozoic origin of neotropical vertebrate faunas.

Aim: To compare the phenotypic appearance of the skull bones and teeth of wild type C57BL/6J mice with that of diabetic leptin-deficient (ob/ob) and diabetic leptin receptordeficient (db/db) mice used as models for diabetes., Study Design and Methods: Skulls were extracted from the carcasses of mice belonging to wild-type C57B/6J mice, db/db mice on a C57BLKS/J background, and ob/ob mice on a C57B/6J background. After removal of overlying tissue, the skulls and mandibles were then left to dehydrate and examined for phenotypic variations in structure and wear., Results: Bone surfaces of the skulls of wild type mice had a whiter and smoother surface compared with a yellowish colour with a grainy texture in the two mutant strains. The frontal, parietal and occipital bones were translucent in the two mutant strains. Breakages of the zygomatic arches and mandibles were more common in the ob/ob and db/db mice than in the wild type mice. Half of the teeth of the db/db mice and 90% teeth of the ob/ob mice showed considerable wear compared with marginal wear in the wild type mice., Conclusions: These observations suggested that the teeth of the two diabetic mutant strains are exhibiting considerable signs of hypomineralization with increased fragility and decreased bone thickness.

The Vancouver Island marmot is the most endangered mammal of Canada. Factors which have brought this population to the verge of extinction have not yet been fully elucidated, but the effects of deforestation and habitat fragmentation on survival rates, as well as those of variation in rainfall, temperature, snowpack depth and snowmelt strongly suggest that marmots on the island are struggling to keep pace with environmental changes. Genetic analyses, however, seem to indicate that the Vancouver Island marmot may merely represent a melanistic population of its parental species on the mainland. Were it not for its black pelage colour, it is unlikely that it would have attracted much attention as a conservation priority. Our study uses three-dimensional coordinates of cranial landmarks to further assess phenotypic differentiation of the Vancouver Island marmot. A pattern of strong interspecific divergence and low intraspecific variation was found which is consistent with aspects of drift-driven models of speciation. However, the magnitude of shape differences relative to the putatively neutral substitutions in synonymous sites of cytochrome b is too large for being compatible with a simple neutral model. A combination of bottlenecks and selective pressures due to natural and human-induced changes in the environment may offer a parsimonious explanation for the large phenotypic differentiation observed in the species. Our study exemplifies the usefulness of a multidisciplinary approach to the study of biological diversity for a better understanding of evolutionary models and to discover aspects of diversity that may be undetected by using only a few genetic markers to characterize population divergence and uniqueness.

This study reports on the molecular phylogenetics of ground squirrels, genus Spermophilus, in Turkey using cytochrome b (1140bp), part of the D-loop and flanking tRNAs (572bp), X chromosome (867-1051bp) and Y chromosome (983-989bp) DNA sequences. Individuals also were characterized by karyotype and with geometric morphometric analyses of mandibles and skulls. Two hundred fourteen individuals from 91 localities were studied. All the data support the recognition of a new species in SW Anatolia: the Taurus ground squirrel Spermophilus taurensis sp. nov. The new species has a small distribution in the Taurus Mountains in an area that is a hotspot for biodiversity. Molecular clock analysis suggests that the new species diverged from the European ground squirrel, Spermophilus citellus, about 2.5 million years ago and that the ancestor of these two species diverged from the widespread Anatolian ground squirrel, Spermophilus xanthoprymnus, about 5 million years ago. Morphometric differentiation in skull and mandible shape among the three species is incomplete, but statistically significant. S. xanthoprymnus is subdivided into five cytochrome b phylogroups and we use these data to infer the location of glacial refugia where the species lived during the last glacial maximum. This study illustrates the potential of combined molecular and morphometric studies to uncover new Anatolian species and to reconstruct their phylogeographic history. The new species is important for squirrel taxonomy and for understanding Eurasian mammal evolution.