Macroevolutionary Trends Research Articles

Interpreting the historical terrestrial vertebrate biodiversity of Cayman Brac (Greater Antilles, Caribbean) through collagen fingerprinting

Cayman Brac (Cayman Islands) lies within the Caribbean Islands Biodiversity Hotspot, an epicenter of high biodiversity and endemism. However, all endemic terrestrial mammals on the Cayman Islands are now extinct, following post-1500 AD human colonization of the islands. Introduced rodents and domesticated mammals now exclusively represent this facet of terrestrial fauna on the Cayman Islands, and are a likely cause of endemic species loss on the islands. Cayman Brac has numerous caves and rock fissures that offer protection to a naturally accumulated ensemble of vertebrate sub-fossil bone remains, documenting modifications in island biodiversity through the Holocene. In this study, we showcase the first molecular faunal survey undertaken on sub-fossil remains from the Cayman Islands, using collagen fingerprinting for taxonomic identification of the cave skeletal deposits collected from a single cave system, Green Cave on Cayman Brac. Collagen type (I) extracts from 485 bone fragments were analyzed to determine faunal identity and assemblage composition. A total of 76% of the collagen fingerprint-yielding samples were mammalian in origin, 67% of which were identified as invasive murid rodents. Here, we present mass spectral biomarkers for the endemic terrestrial mammal fauna of Cayman Brac, including the extinct capromyid rodents, Capromys and Geocapromys (Rodentia: Capromyidae), alongside commentary on the composition of the sub-fossil bone assemblage between the five distinct depositional chambers that comprise Green Cave. Collagen (I) provides a key service in taxonomic identification and mapping of macroevolutionary trends, and these results suggest a pivotal role for murid rodents in the competition and extinction of terrestrial endemic mammals from the Cayman Islands.

Metabolic physiology explains macroevolutionary trends in the melanic colour system across amniotes.

Metabolism links organisms to their environment through its effects on thermoregulation, feeding behaviour and energetics. Genes involved in metabolic processes have known pleiotropic effects on some melanic colour traits. Understanding links between physiology and melanic colour is critical for understanding the role of, and potential constraints on, colour production. Despite considerable variation in metabolic rates and presumed ancestral melanic coloration in vertebrates, few studies have looked at a potential relationship between these two systems in a comparative framework. Here, we test the hypothesis that changes in melanosome shape in integumentary structures track metabolic rate variation across amniotes. Using multivariate comparative analyses and incorporating both extant and fossil taxa, we find significantly faster rates of melanosome shape evolution in taxa with high metabolic rates, as well as both colour- and clade-specific differences in the relationship between metabolic rate and melanosome shape. Phylogenetic tests recover an expansion in melanosome morphospace in maniraptoran dinosaurs, as well as rate shifts within birds (in songbirds) and mammals. These findings indicate another core phenotype influenced by metabolic changes in vertebrates. They also provide a framework for testing clade-specific gene expression patterns in the melanocortin system and may improve colour reconstructions in extinct taxa.

A Virtue Made of Necessity: Is the Increasing Hierarchical Complexity of Sexual Clades an Inevitable Outcome of Their Declining (Macro)evolutionary Potential?

The increasing maximal hierarchical complexity of organisms is one of the best-supported macroevolutionary trends. The nature and causes of this trend, as well as several accompanying macroevolutionary phenomena are, however, still unclear. In this theoretical article, we propose that the cause of this trend could be the increasing pressure of species selection, which results from the gradual decrease of (macro)evolutionary potential (i.e. the probability of producing major evolutionary innovations). As follows from the Theory of Frozen Evolution, this process is an inevitable consequence of the sorting of genes, traits, and their integrated groups (modules) based on their contextually dependent stability. In turn, this causes effectively unchangeable elements of genetic architecture to accumulate during the existence of evolutionary lineages. Although (macro)evolutionary potential can be partially restored by several processes, a profound restoration of (macro)evolutionary potential is probably possible only by means of a transition to a higher level of hierarchical complexity. However, the accumulation of contextually more stable elements continues even on this higher level. This leads to the integration of the modular character of composite organisms and a repeated pressure to increase the level of hierarchical complexity. Our model explains all components of McShea’s “Evolutionary Syndrome,” i.e. the trend of increasing the hierarchical complexity of organisms, the growth of variability among elements on the immediately lower level, and their gradual machinification. This pattern should be characteristic of sexual eukaryotes and especially their complex representatives. Our model also sheds new light on several related macroevolutionary phenomena, such as the gradual acceleration of the trend or the striking difference between pre-Neoproterozoic and Phanerozoic evolution.

Phylogeny, Macroevolutionary Trends and Historical Biogeography of Sloths: Insights From a Bayesian Morphological Clock Analysis.

Sloths, like other xenarthrans, are an extremely interesting group of mammals that, after a long history of evolution and diversification in South America, became established on islands in the Caribbean and later reached North America during the Great American Biotic Interchange. In all three regions, they were part of the impressive Pleistocene megafauna. Most taxa became extinct and only two small, distantly related tree-dwelling genera survived. Here, we incorporate several recently described genera of sloths into an assembled morphological data supermatrix and apply Bayesian inference, using phylogenetic and morphological clock methods, to 64 sloth genera. Thus, we investigate the evolution of the group in terms of the timing of divergence of different lineages and their diversity, morphological disparity and biogeographical history. The phylogeny obtained supports the existence of the commonly recognized clades for the group. Our results provide divergence time estimates for the major clades within Folivora that could not be dated with molecular methods. Lineage diversity shows an early increase, reaching a peak in the Early Miocene followed by a major drop at the end of the Santacrucian (Early Miocene). A second peak in the Late Miocene was also followed by a major drop at the end of the Huayquerian (Late Miocene). Both events show differential impact at the family level. After that, a slight Plio-Pleistocene decline was observed before the marked drop with the extinction at the end of the Pleistocene. Phenotypic evolutionary rates were high during the early history of the clade, mainly associated with Mylodontidae, but rapidly decreased to lower values around 25 Ma, whereas Megalonychidae had lower rates at the beginning followed by a steady increase, peaking during the Late Miocene and the Pliocene. Morphological disparity showed a similar trend, with an early increase, followed by a slowly increasing phase through the Late Oligocene and Early Miocene, and ending with another increase beginning at the middle of the Miocene. Biogeographic analysis showed southern South America as the most probable area of origin of the clade and the main region in which the early diversification events took place. Both Megatheriinae and Nothrotheriinae basal nodes were strongly correlated with Andean uplift events, whereas the early history of Mylodontidae is closely associated with southern South America and also shows an early occupation of the northern regions. Within Megalonychidae, our results show Choloepus as a descendant of an island dispersing ancestor and a probable re-ingression to South America by a clade that originated in Central or North America.

Fuzzy ecospace modelling

Abstract Quantitative ecospace models are a numerical approach to comparing the functional structure of different ecosystems on macroevolutionary time‐scales, by quantifying the distribution of functional ecological traits. Ecospace modelling has historically been restricted to a combination of visual interpretation and quantification via metrics such as mean sum of ranges. We argue that comparing ecosystem function in this way overlooks critical information about degrees of overlap and redundancy, and potentially misrepresents the role of “empty ecospace” in driving macroevolution. Fuzzy ecospace modelling (FEM) places conventional ecospace modelling within a fuzzy set‐theoretic framework, wherein functional groups are learned from the dataset, creating models which are sensitive to overlap and the role of empty ecospace. Fuzzy ecospace modelling is a machine learning program which quantifies functional ecological similarity, and uses this information to classify new taxa. It creates functional groups using a Gower dissimilarity coefficient‐based approach to the k‐medoids algorithm, and uses fuzzy discriminant analysis to classify the taxa present in another ecosystem into these clusters, based on minimal Gower dissimilarity with a fuzzy threshold. This has the effect of quantifying the similarity between these ecosystems in terms of their functional groups, accounting for total redundancy, partial redundancy/novelty and total novelty. By using fuzzy membership functions, FEM can classify taxa which are highly ecologically dissimilar (outliers with respect to all functional groups), taxa which are fully redundant (100% similarity to those in a given functional group) and taxa in‐between, which represent degrees of niche overlap. This can be used to compare the functional groups present in different ecosystems (as well as their degrees of overlap), and as a metric approach to comparing total ecological disparity. These results can be used to test models of the role of empty ecospace in macroevolutionary trends, or to investigate how ecosystems respond to global perturbations. Furthermore, it allows us to define numerically the concept of empty ecospace for n‐dimensional datasets. A cluster‐based approach to the quantification of ecospace allows for a numerical estimate of niche overlap, a value particularly difficult to quantify in fossil contexts.

Links between Anatomy, Systems biology, Epigenetics, etho‐eco‐morphological mismatches, evolutionary trends, and organism behavior: a unifying view of anatomical evolution

It is a puzzling paradox that eco‐morphological mismatches occur so frequently in an evolutionary process that often leads to macroevolutionary trends and in which organisms are said to be ‘designed’ for the habitats they inhabit. Here I present a new framework ‐ Organic Nonoptimal Constrained Evolution (ONCE) ‐ to address this paradox, and to explain why organisms look as they look: organisms themselves, and in particular their behavior, are the major active players of evolution. That is, within this framework, internal factors can both decrease and increase plasticity/hidden variation and therefore, together with epigenetic factors influenced by the external environment, can allows organisms to shift their behavior, for instance as a response to environmental changes. Importantly, due to behavioral persistence related to behavioral/ecological inheritance, organisms as diverse as bacteria, plants and animals help to construct their own niches, thus being crucial to direct evolution. Darwinian natural (external) selection then comes into play as a secondary ‐ but still crucial ‐ player. That is, due to organismal behavioral persistence, the random mutations/epigenetic factors that happen to be advantageous within the niches constructed by the organisms will be selected, further directing evolution and increasing the match between behavior, phenotype, and environment. This process can extend for long periods of time, leading to macroevolutionary morphological trends and further increasing this match, potentially resulting in successful phenotypic overspecialization. However, behavioral persistence, loss of plasticity due to natural selection, genetic drift, overspecialization, and internal constraints can often make it difficult for the organisms to respond behaviorally and/or anatomically to new environmental changes, resulting in potential mismatches between behavior, ecology and form, and eventually in extinction. This new framework about anatomical evolution therefore bridges the gap between ideas that have been long considered to be opposing views of biology since Aristotle, including internalism and externalism, Cuvier's vs. Geoffroy's take on form and function, Darwinism and Lamarkism, the ideas of Baldwin, Waddington and Goldschmidt, and current Evo‐Devo ideas such as a physicalist framework, niche construction and epigenetic plasticity. This talk therefore covers ‐ and aims to link ‐ areas as diverse as evolutionary developmental biology, paleontology, evolutionary biology, comparative anatomy, ecomorphology, functional anatomy, ecology, ethology, biological anthropology, evolutionary medicine and history and philosophy of biology.Support or Funding InformationNAThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Factors driving metabolic diversity in the budding yeast subphylum

BackgroundAssociations between traits are prevalent in nature, occurring across a diverse range of taxa and traits. Individual traits may co-evolve with one other, and these correlations can be driven by factors intrinsic or extrinsic to an organism. However, few studies, especially in microbes, have simultaneously investigated both across a broad taxonomic range. Here we quantify pairwise associations among 48 traits across 784 diverse yeast species of the ancient budding yeast subphylum Saccharomycotina, assessing the effects of phylogenetic history, genetics, and ecology.ResultsWe find extensive negative (traits that tend to not occur together) and positive (traits that tend to co-occur) pairwise associations among traits, as well as between traits and environments. These associations can largely be explained by the biological properties of the traits, such as overlapping biochemical pathways. The isolation environments of the yeasts explain a minor but significant component of the variance, while phylogeny (the retention of ancestral traits in descendant species) plays an even more limited role. Positive correlations are pervasive among carbon utilization traits and track with chemical structures (e.g., glucosides and sugar alcohols) and metabolic pathways, suggesting a molecular basis for the presence of suites of traits. In several cases, characterized genes from model organisms suggest that enzyme promiscuity and overlapping biochemical pathways are likely mechanisms to explain these macroevolutionary trends. Interestingly, fermentation traits are negatively correlated with the utilization of pentose sugars, which are major components of the plant biomass degraded by fungi and present major bottlenecks to the production of cellulosic biofuels. Finally, we show that mammalian pathogenic and commensal yeasts have a suite of traits that includes growth at high temperature and, surprisingly, the utilization of a narrowed panel of carbon sources.ConclusionsThese results demonstrate how both intrinsic physiological factors and extrinsic ecological factors drive the distribution of traits present in diverse organisms across macroevolutionary timescales.

Resurrecting ancestral genes in bacteria to interpret ancient biosignatures.

Two datasets, the geologic record and the genetic content of extant organisms, provide complementary insights into the history of how key molecular components have shaped or driven global environmental and macroevolutionary trends. Changes in global physico-chemical modes over time are thought to be a consistent feature of this relationship between Earth and life, as life is thought to have been optimizing protein functions for the entirety of its approximately 3.8 billion years of history on the Earth. Organismal survival depends on how well critical genetic and metabolic components can adapt to their environments, reflecting an ability to optimize efficiently to changing conditions. The geologic record provides an array of biologically independent indicators of macroscale atmospheric and oceanic composition, but provides little in the way of the exact behaviour of the molecular components that influenced the compositions of these reservoirs. By reconstructing sequences of proteins that might have been present in ancient organisms, we can downselect to a subset of possible sequences that may have been optimized to these ancient environmental conditions. How can one use modern life to reconstruct ancestral behaviours? Configurations of ancient sequences can be inferred from the diversity of extant sequences, and then resurrected in the laboratory to ascertain their biochemical attributes. One way to augment sequence-based, single-gene methods to obtain a richer and more reliable picture of the deep past, is to resurrect inferred ancestral protein sequences in living organisms, where their phenotypes can be exposed in a complex molecular-systems context, and then to link consequences of those phenotypes to biosignatures that were preserved in the independent historical repository of the geological record. As a first step beyond single-molecule reconstruction to the study of functional molecular systems, we present here the ancestral sequence reconstruction of the beta-carbonic anhydrase protein. We assess how carbonic anhydrase proteins meet our selection criteria for reconstructing ancient biosignatures in the laboratory, which we term palaeophenotype reconstruction.This article is part of the themed issue ‘Reconceptualizing the origins of life’.

A toothless dwarf dolphin (Odontoceti: Xenorophidae) points to explosive feeding diversification of modern whales (Neoceti).

Toothed whales (Odontoceti) are adapted for catching prey underwater and possess some of the most derived feeding specializations of all mammals, including the loss of milk teeth (monophyodonty), high tooth count (polydonty), and the loss of discrete tooth classes (homodonty). Many extant odontocetes possess some combination of short, broad rostra, reduced tooth counts, fleshy lips, and enlarged hyoid bones-all adaptations for suction feeding upon fishes and squid. We report a new fossil odontocete from the Oligocene (approx. 30 Ma) of South Carolina (Inermorostrum xenops, gen. et sp. nov.) that possesses adaptations for suction feeding: toothlessness and a shortened rostrum (brevirostry). Enlarged foramina on the rostrum suggest the presence of enlarged lips or perhaps vibrissae. Phylogenetic analysis firmly places Inermorostrum within the Xenorophidae, an early diverging odontocete clade typified by long-snouted, heterodont dolphins. Inermorostrum is the earliest obligate suction feeder within the Odontoceti, a feeding mode that independently evolved several times within the clade. Analysis of macroevolutionary trends in rostral shape indicate stabilizing selection around an optimum rostral shape over the course of odontocete evolution, and a post-Eocene explosion in feeding morphology, heralding the diversity of feeding behaviour among modern Odontoceti.

Regional and environmental variation in escalatory ecological trends during the Jurassic: a western Tethys hotspot for escalation?

AbstractUnderstanding the drivers of macroevolutionary trends through the Phanerozoic has been a central question in paleobiology. Increasingly important is understanding the regional and environmental variation of macroevolutionary patterns and how they are reflected at the global scale. Here we test the role of biotic interactions on regional ecological patterns during the Mesozoic marine revolution. We test for escalatory trends in Jurassic marine benthic macroinvertebrate ecosystems using occurrence data from the Paleobiology Database parsed by region and environment. The escalation hypothesis posits that taxonomic groups that could adapt to intense predation and bioturbation proliferated, whereas groups unable to adapt were reduced in diversity and abundance or driven to extinction. We tested this hypothesis in five regions during Jurassic stages and among four depositional environments in Europe. Few escalatory trends were detected, although at least one escalatory trend was observed in every region, with the greatest number and strongest trends observed in Europe. These trends include increases in shallow infauna and cementing epifauna and occurrences of facultatively mobile invertebrates and decreases in pedunculate, free-lying, and sessile epifauna. Within Europe, escalatory trends occur in shallow-water environments but also in deeper-water environments, where they are predicted not to occur. When regional trends are aggregated, trends in Europe drive the global signal. The results of this study suggest that while evidence of escalation is rare globally, it is plausible that escalation drove macroevolutionary patterns in Europe. Furthermore, these results underline the need to dissect global fossil data at the regional scale to understand global macroevolutionary dynamics.

Natural History Constrains the Macroevolution of Foot Morphology in European Plethodontid Salamanders.

The natural history of organisms can have major effects on the tempo and mode of evolution, but few examples show how unique natural histories affect rates of evolution at macroevolutionary scales. European plethodontid salamanders (Plethodontidae: Hydromantes) display a particular natural history relative to other members of the family. Hydromantes commonly occupy caves and small crevices, where they cling to the walls and ceilings. On the basis of this unique and strongly selected behavior, we test the prediction that rates of phenotypic evolution will be lower in traits associated with climbing. We find that, within Hydromantes, foot morphological traits evolve at significantly lower rates than do other phenotypic traits. Additionally, Hydromantes displays a lower rate of foot morphology evolution than does a nonclimbing genus, Plethodon. Our findings suggest that macroevolutionary trends of phenotypic diversification can be mediated by the unique behavioral responses in taxa related to particular attributes of their natural history.

Evo‐Devo, epigenetics, niche construction and the Extended Evolutionary Synthesis: crucial implications for anatomical and medical sciences in the 21st century

It is a puzzling paradox that eco‐morphological mismatches occur so frequently in an evolutionary process that often leads to macroevolutionary trends and in which organisms are said to be ‘designed’ for the habitats they inhabit. Here I present a new framework ‐ Organic Nonoptimal Constrained Evolution (ONCE) ‐ to address this paradox, and to explain why organisms look as they look: organisms themselves, and in particular their behavior, are the major active players of evolution. That is, within this framework, internal factors can both decrease and increase plasticity/hidden variation and therefore, together with epigenetic factors influenced by the external environment, can allows organisms to shift their behavior, for instance as a response to environmental changes. Importantly, due to behavioral persistence related to behavioral/ecological inheritance, organisms as diverse as bacteria, plants and animals help to construct their own niches, thus being crucial to direct evolution. Darwinian natural (external) selection then comes into play as a secondary ‐ but still crucial ‐ player. That is, due to organismal behavioral persistence, the random mutations/epigenetic factors that happen to be advantageous within the niches constructed by the organisms will be selected, further directing evolution and increasing the match between behavior, phenotype, and environment. This process can extend for long periods of time, leading to macroevolutionary trends and further increasing this match, potentially resulting in successful phenotypic overspecialization. However, behavioral persistence, loss of plasticity due to natural selection, genetic drift, overspecialization, and internal constraints can often make it difficult for the organisms to respond behaviorally and/or anatomically to new environmental changes, resulting in potential mismatches between behavior, ecology and form, and eventually in extinction. This new framework therefore bridges the gap between ideas that have been long considered to be opposing views of biology since Aristotle, including internalism and externalism, Cuvier's vs. Geoffroy's take on form and function, Darwinism and Lamarkism, the ideas of Baldwin, Waddington and Goldschmidt, and current Evo‐Devo ideas such as a physicalist framework, niche construction and epigenetic plasticity. This talk therefore covers ‐ and aims to link ‐ areas as diverse as evolutionary developmental biology, paleontology, evolutionary biology, comparative anatomy, ecomorphology, functional anatomy, ecology, ethology, biological anthropology, evolutionary medicine and history and philosophy of biology.Support or Funding InformationSupport from NSF (1516557) and American Association of Anatomists Innovations Program

Etho-Eco-Morphological Mismatches, an Overlooked Phenomenon in Ecology, Evolution and Evo-Devo That Supports ONCE (Organic Nonoptimal Constrained Evolution) and the Key Evolutionary Role of Organismal Behavior

Since ecomorphologists have started to use explicit and taxonomically-broad frameworks in studies on the relationships between form, behavior, ecology and phylogeny they have consistently reported - often against their expectations - 1) that phylogeny is a better predictor of anatomy than ecology is, and 2) many cases of etho-eco-morphological mismatches. It is puzzling that such mismatches occur frequently in an evolutionary process that often leads to macroevolutionary trends and in which organisms are said to be optimally/almost optimally 'designed' for the habitats they inhabit. Organic Nonoptimal Constrained Evolution (ONCE), a new perspective on biological evolution that is proposed here, addresses this apparent paradox, based on an extensive compilation of empirical data and broader evolutionary ideas, from Aristotle to current Evo-Devo. According to ONCE, by taking behavioral choices, and subsequently due to their behavioral persistence related to behavioral/ecological inheritance, organisms as diverse as bacteria, plants and animals help to construct their own niches and are thus the central, active players in their evolutionary history. The highly constrained character of organic evolution, including developmental constraints as well as the crucial role played by behavioral persistence, can dramatically limit the occurrence of new behavioral shifts and thus the responses to external (e.g., environmental) changes, often resulting in etho-eco-morphological mismatches and eventually in evolutionary dead-ends that may lead to extinction.

Evolutionary Relationships among Extinct and Extant Sloths: The Evidence of Mitogenomes and Retroviruses.

Macroevolutionary trends exhibited by retroviruses are complex and not entirely understood. The sloth endogenized foamy-like retrovirus (SloEFV), which demonstrates incongruence in virus–host evolution among extant sloths (Order Folivora), has not been investigated heretofore in any extinct sloth lineages and its premodern history within folivorans is therefore unknown. Determining retroviral coevolutionary trends requires a robust phylogeny of the viral host, but the highly reduced modern sloth fauna (6 species in 2 genera) does not adequately represent what was once a highly diversified clade (∼100 genera) of placental mammals. At present, the amount of molecular data available for extinct sloth taxa is limited, and analytical results based on these data tend to conflict with phylogenetic inferences made on the basis of morphological studies. To augment the molecular data set, we applied hybridization capture and next-generation Illumina sequencing to two extinct and three extant sloth species to retrieve full mitochondrial genomes (mitogenomes) from the hosts and the polymerase gene of SloEFV. The results produced a fully resolved and well-supported phylogeny that supports dividing crown families into two major clades: 1) The three-toed sloth, Bradypus, and Nothrotheriidae and 2) Megalonychidae, including the two-toed sloth, Choloepus, and Mylodontidae. Our calibrated time tree indicates that the Miocene epoch (23.5 Ma), particularly its earlier part, was an important interval for folivoran diversification. Both extant and extinct sloths demonstrate multiple complex invasions of SloEFV into the ancestral sloth germline followed by subsequent introgressions across different sloth lineages. Thus, sloth mitogenome and SloEFV evolution occurred separately and in parallel among sloths.

Lifestyle-Based Approaches Provide Insights into Body Size Variation Across Environmental Gradients in Anurans

Body size of organisms as a fitness-related phenotype has evolved in response to local conditions, often through the size-dependent thermoregulatory mechanisms. The direction and degree of this response should depend on animals’ lifestyle in terms of the preference for terrestrial or aquatic conditions, especially so for adult anurans that differ in lifestyle among species but all must maintain certain body temperatures for metabolism. It may be expected that anuran species frequently exposed to terrestrial environments characterized by fluctuant thermal conditions are more plastic in body size along thermal gradients than those highly relaying on aquatic environments where thermal conditions are relatively stable. We test this prediction using both interspecific and intraspecific data. With anurans in China as the model organisms, we show that across terrestrial species but not aquatic species, body size decreases with increasing ambient temperature. From the published literature worldwide, we summarized that more terrestrial versus fewer aquatic species follow the predicted ecogeographical size patterns. In addition, both interspecific and intraspecific data reveal that arboreal anurans do not exhibit the size cline, probably because relatively warm climates experienced by these species impose weak selective pressures on heat conservation or adaptation to tree-climbing constrains the variation in body size. Our finding highlights the importance of taking lifestyle into account when assessing macroevolutionary trends in body size for anurans in particular and ectothermic taxa in general.

Magnitude versus direction of change and the contribution of macroevolutionary trends to morphological disparity

Considerable research has been devoted to measuring rates of morphological evolution and identifying when rate differences or rate shifts have led to differences in morphological diversity (i.e. disparity) among clades. Although less frequently investigated, differences in the direction of change may also contribute to differences in disparity. These same components, namely magnitude (a function of rate and time) and direction of change, have also been used to describe morphological trends, although the direction of change is more frequently the focus of the latter. Increases in disparity are often considered as a diffusive process of volume-filling, whereas disparity patterns may just as frequently represent the sum total of trends among subclades. As a result, different trend dynamics across subclades can produce different patterns of morphological diversification at different taxonomic scales. For example, although a subclade undergoing a driven trend will not increase in disparity over time, it may contribute to an increase in disparity at more inclusive taxonomic levels. This is demonstrated in the present study using examples from post-Paleozoic echinoids and Cambrian trilobites.

Macroevolution of genome size in sarcopterygians during the water–land transition

Genome size spans over a 300-fold range among vertebrates (132pg for Protopterus aethiopicus, the marbled lungfish, and 0.35pg for Tetraodon nigroviridis, the green spotted pufferfish). While phylogenetic analysis of genome size has helped clarify how this variation evolved in multiple tetrapod groups, the ancestral tetrapod condition still remains poorly characterized, and this obscures our understanding of character state polarity and macroevolutionary trends in genome size. To address this problem, we used phylogenetic comparative methods to analyze paleohistological data from eight taxa of the Middle and Late Paleozoic to the Early Mesozoic: Eusthenopteron, Ichthyostega, Acheloma, Eryops, Trimerorhachis, Wetlugasaurus, an unidentified dissorophoid, and Chroniosaurus. Five other extinct taxa were included from previous studies to better frame our results, including Marmorerpeton, Cardiocephalus, Diplocaulus, an unidentified basal sauropsid, and Mycterosaurus. We augmented a previously reported histological and genome size data set (including data from 14 lissamphibians, three testudines, Sphenodon, five squamates, two crocodilians, 11 birds, and 22 mammals) with genome size and histological data from extant Latimeria and three extant actinopterygians. Our results suggest that all eight of the newly analyzed extinct taxa had genome sizes ranging between 3.2 and 3.9pg. These results imply that basal tetrapods had genome sizes (and underlying genomic architectures) similar to extant mammals and lepidosaurs. We find no major shifts in genome size during the tetrapod water-to-land transition. Our analysis suggests that Eusthenopteron and Ichthyostega had genome sizes well within the range of extant actinopterygians and Latimeria, despite several whole-genome duplications in actinopterygians.

Microevolutionary patterns in the common caiman predict macroevolutionary trends across extant crocodilians

Both extinct and extant crocodilians have repeatedly diversified in skull shape along a continuum, from narrow-snouted to broad-snouted phenotypes. These patterns occur with striking regularity, although it is currently unknown whether these trends also apply to microevolutionary divergence during population differentiation or the early stages of speciation. Assessing patterns of intraspecific variation within a single taxon can potentially provide insight into the processes of macroevolutionary differentiation. For example, high levels of intraspecific variation along a narrow-broad axis would be consistent with the view that cranial shapes can show predictable patterns of differentiation on relatively short timescales, and potentially scale up to explain broader macroevolutionary patterns. In the present study, we use geometric morphometric methods to characterize intraspecific cranial shape variation among groups within a single, widely distributed clade, Caiman crocodilus. We show that C. crocodilus skulls vary along a narrow/broad-snouted continuum, with different subspecies strongly clustered at distinct ends of the continuum. We quantitatively compare these microevolutionary trends with patterns of diversity at macroevolutionary scales (among all extant crocodilians). We find that morphological differences among the subspecies of C. crocodilus parallel the patterns of morphological differentiation across extant crocodilians, with the primary axes of morphological diversity being highly correlated across the two scales. We find intraspecific cranial shape variation within C. crocodilus to span variation characterized by more than half of living species. We show the main axis of intraspecific phenotypic variation to align with the principal direction of macroevolutionary diversification in crocodilian cranial shape, suggesting that mechanisms of microevolutionary divergence within species may also explain broader patterns of diversification at higher taxonomic levels.

Revision of Chlidoniopsidae Harmer, (Bryozoa: Cheilostomata) including a description of Celiopsis vici gen. and sp. nov.

AbstractThe bryozoan family Chlidoniopsidae Harmer, 1957 is reviewed in relation to a new Paleogene European fossil, Celiopsis vici new genus and new species. It differs from the type and only other genus of the family in having longer internodes with up to three zooids, shorter proximal caudae, and, more importantly, suture lines that unequally divided the umbonuloid frontal shield and basal (abfrontal) wall (and the hypostegal coelom in life) into sectors, analogous to the situation in the lepralioid-shielded Prostomariidae and Urceoliporidae. Unlike Prostomaria and Urceolipora, and like Chlidoniopsis, Celiopsis is uniserial. The suture lines in Celiopsis were lines of insertion (attachment) of epithecal membranes in life and each sector has its own longitudinal series of septular pores, sometimes doubled. Miocene to Recent Chlidoniopsis contains two species, and Eocene–Oligocene Celiopsis contains three species. The geographic distribution gives evidence of origination of the family in the Paratethys of Europe, with southeastwards migration to Australia and the tropical western Pacific. The temporal distribution suggests two macro-evolutionary trends—from multizooidal to unizooidal internodes, and from a broader area of basal wall, with a division into separate cryptocystal fields, to a narrower basal wall with no such division.

Eopolydiexodina (Middle Permian giant fusulinids) from Afghanistan: Biometry, morphometry, paleobiogeography, and end-Guadalupian events

The most spectacular macroevolutionary trend presented by the genera of schwagerinoid fusulinids, during the Pennsylvanian –Permian, is an enormous increase in size, which culminated in the Middle Permian with Eopolydiexodina. However, this potential major biogeographic marker, during the Kubergandian–early Midian time interval, is as yet hampered by its poor taxonomic characterization. Hence, Eopolydiexodina is revised here using biometric and morphometric methods applied to large collections from Afghanistan and selected taxa in the literature. These multivariate analyses consist of classical linear test parameters, as well as new area parameters acquired by computer image analysis. The Afghan species are re-defined, and some other species, occasionally described as Cimmerian, are re-discussed. These methods, combined with classical morphological analyses, also permit to conclude that the largest Eopolydiexodina of Afghanistan are microspheric specimens (probably agamonts) of E. afghanensis and E. bithynica. Two megalospheric groups of individuals (probably gamonts and schizonts) are represented in both species, as well as in E. persica and E. darvasica. Due to this presence of gamonts, agamonts and schizonts in several species, Eopolydiexodina is probably the oldest identified trimorphic genus among the large benthic foraminifers. Biostratigraphically, Eopolydiexodina appears restricted to the late Kubergandian to early Midian. The associated Afghan fusulinids (Dunbarula, Kahlerina, Afghanella, Yangchienia, Sumatrina, and Codonofusiella) allow proposing an accurate biostratigraphy of the Eopolydiexodina species in the Murgabian–Midian boundary interval. Paleobiogeographically, Eopolydiexodina was essentially located in the Laurentian and Perigondwanan borders of the Tethys. The possible presence of Eopolydiexodina in the Cimmerian Continent and in some regions of China has never been irrefutably demonstrated. This paleobiological revision of Eopolydiexodina and the biostratigraphic revision of other large Capitanian fusulinids, permit to suggest that the end-Guadalupian event is most probably a protracted succession of last appearance data of giant genera rather than an instantaneous Lilliput effect at the Capitanian/Wuchiapingian boundary.