Evolution Of Body Size Research Articles

The impact of paleoclimatic changes on body size evolution in marine fishes

Body size is an important species trait, correlating with life span, fecundity, and other ecological factors. Over Earth's geological history, climate shifts have occurred, potentially shaping body size evolution in many clades. General rules attempting to summarize body size evolution include Bergmann's rule, which states that species reach larger sizes in cooler environments and smaller sizes in warmer environments, and Cope's rule, which poses that lineages tend to increase in size over evolutionary time. Tetraodontiform fishes (including pufferfishes, boxfishes, and ocean sunfishes) provide an extraordinary clade to test these rules in ectotherms owing to their exemplary fossil record and the great disparity in body size observed among extant and fossil species. We examined Bergmann's and Cope's rules in this group by combining phylogenomic data (1,103 exon loci from 185 extant species) with 210 anatomical characters coded from both fossil and extant species. We aggregated data layers on paleoclimate and body size from the species examined, and inferred a set of time-calibrated phylogenies using tip-dating approaches for downstream comparative analyses of body size evolution by implementing models that incorporate paleoclimatic information. We found strong support for a temperature-driven model in which increasing body size over time is correlated with decreasing oceanic temperatures. On average, extant tetraodontiforms are two to three times larger than their fossil counterparts, which otherwise evolved during periods of warmer ocean temperatures. These results provide strong support for both Bergmann's and Cope's rules, trends that are less studied in marine fishes compared to terrestrial vertebrates and marine invertebrates.

Patterns of Phenotypic Evolution Associated with Marine/Freshwater Transitions in Fishes.

Evolutionary transitions between marine and freshwater ecosystems have occurred repeatedly throughout the phylogenetic history of fishes. The theory of ecological opportunity predicts that lineages that colonize species-poor regions will have greater potential for phenotypic diversification than lineages invading species-rich regions. Thus, transitions between marine and freshwaters may promote phenotypic diversification in trans-marine/freshwater fish clades. We used phylogenetic comparative methods to analyze body size data in nine major fish clades that have crossed the marine/freshwater boundary. We explored how habitat transitions, ecological opportunity, and community interactions influenced patterns of phenotypic diversity. Our analyses indicated that transitions between marine and freshwater habitats did not drive body size evolution, and there are few differences in body size between marine and freshwater lineages. We found that body size disparity in freshwater lineages is not correlated with the number of independent transitions to freshwaters. We found a positive correlation between body size disparity and overall species richness of a given area, and a negative correlation between body size disparity and diversity of closely related species. Our results indicate that the diversity of incumbent freshwater species does not restrict phenotypic diversification, but the diversity of closely related taxa can limit body size diversification. Ecological opportunity arising from colonization of novel habitats does not seem to have a major effect in the trajectory of body size evolution in trans-marine/freshwater clades. Moreover, competition with closely related taxa in freshwaters has a greater effect than competition with distantly related incumbent species.

So Volcanoes Created the Dinosaurs? A Quantitative Characterization of the Early Evolution of Terrestrial Pan-Aves

The early Mesozoic is marked by several global-scale environmental events, including the emplacement of large igneous provinces, such as the Siberian Traps, Wrangellia, and Central Atlantic Magmatic Province (CAMP). These have been hypothesised as drivers of the successful diversification of Pan-Aves, the lineage of archosaurs closer to birds than to crocodiles. We characterize here the diversification and body size evolution of terrestrial pan-avians (excluding pterosaurs) along the Triassic and Early Jurassic, using phylogenetic- and occurrence-based approaches, in an attempt to test the influence of such drivers. As diversity metrics, we quantified raw species richness and phylogenetic diversity (using time-calibrated phylogenetic trees), and net diversification rates were estimated with PyRate and the episodic fossilized-birth-death model. We have also characterised through-time patterns of body size (femoral length) and estimated body size evolutionary rates. Our results indicate that macroevolutionary shifts estimated from occurrence data are placed more recently in time than those from phylogenetic-based approaches, as shown by the higher diversity increase, diversification rates, and body size disparity of terrestrial Pan-Aves in the Carnian. This is consistent with hypotheses suggesting that the Carnian Pluvial Episode (CPE) was crucial for the early radiation of the group. Yet, phylogeny-based results show higher diversity/diversification rates for the Ladinian and Norian, suggesting a minor effect for the Carnian Pluvial Episode (CPE). We also found no meaningful shifts in diversity, diversification, or size-related metrics across the Triassic-Jurassic boundary. Even if the end-Triassic mass extinction possibly emptied ecospace, allowing dinosaur diversity to increase during the Jurassic, our results suggest that this expansion did not occur fast and homogeneously for the entire group. In fact, a sustained reduction in diversity and sub-zero net diversification rates are seen after the extinction, but macroevolutionary patterns here should be interpreted with care towards the end of the Early Jurassic, as they may be biased by an “edge effect.” Overall, few macroevolutionary shifts were consistently identified across all results, suggesting that the early diversification of terrestrial pan-avians was more nuanced and complex than anticipated.

Genome of a giant isopod, Bathynomus jamesi, provides insights into body size evolution and adaptation to deep-sea environment

BackgroundThe deep-sea may be regarded as a hostile living environment, due to low temperature, high hydrostatic pressure, and limited food and light. Isopods, a species-rich group of crustaceans, are widely distributed across different environments including the deep sea and as such are a useful model for studying adaptation, migration, and speciation. Similar to other deep-sea organisms, giant isopods have larger body size than their shallow water relatives and have large stomachs and fat bodies presumably to store organic reserves. In order to shed light on the genetic basis of these large crustaceans adapting to the oligotrophic environment of deep-sea, the high-quality genome of a deep-sea giant isopod Bathynomus jamesi was sequenced and assembled.ResultsB. jamesi has a large genome of 5.89 Gb, representing the largest sequenced crustacean genome to date. Its large genome size is mainly attributable to the remarkable proliferation of transposable elements (84%), which may enable high genome plasticity for adaptive evolution. Unlike its relatives with small body size, B. jamesi has expanded gene families related to pathways of thyroid and insulin hormone signaling that potentially contribute to its large body size. Transcriptomic analysis showed that some expanded gene families related to glycolysis and vesicular transport were specifically expressed in its digestive organs. In addition, comparative genomics and gene expression analyses in six tissues suggested that B. jamesi has inefficient lipid degradation, low basal metabolic rate, and bulk food storage, suggesting giant isopods adopt a more efficient mechanism of nutrient absorption, storage, and utilization to provide sustained energy supply for their large body size.ConclusionsTaken together, the giant isopod genome may provide a valuable resource for understanding body size evolution and adaptation mechanisms of macrobenthic organisms to deep-sea environments.

Dancing drives evolution of sexual size dimorphism in manakins.

Body size mediates life history, physiology and inter- and intra-specific interactions. Within species, sexes frequently differ in size, reflecting divergent selective pressures and/or constraints. Both sexual selection and differences in environmentally mediated reproductive constraints can drive sexual size dimorphism, but empirically testing causes of dimorphism is challenging. Manakins (Pipridae), a family of Neotropical birds comprising approximately 50 species, exhibit a broad range of size dimorphism from male- to female-biased and are distributed across gradients of precipitation and elevation. Males perform courtship displays ranging from simple hops to complex aerobatic manoeuvres. We tested associations between sexual size dimorphism and (a) agility and (b) environment, analysing morphological, behavioural and environmental data for 22 manakin species in a phylogenetic framework. Sexual dimorphism in mass was most strongly related to agility, with males being lighter than females in species performing more aerial display behaviours. However, wing and tarsus length dimorphism were more strongly associated with environmental variables, suggesting that different sources of selection act on different aspects of body size. These results highlight the strength of sexual selection in shaping morphology-even atypical patterns of dimorphism-while demonstrating the importance of constraints and ecological consequences of body size evolution.

Macroclimatic and maternal effects on the evolution of reproductive traits in lizards.

Much of life‐history theory rests on fundamental assumptions about constraints on the acquisition and allocation of energy to growth and reproduction. In general, the allocation of energy to reproduction depends on maternal size, which in turn depends on environmental factors experienced throughout the life of the mother. Here, we used phylogenetic path analyses to evaluate competing hypotheses about the environmental and maternal drivers of reproductive traits in lizards. In doing so, we discovered that precipitation, rather than temperature, has shaped the evolution of the life history. Specifically, environments with greater rainfall have enabled the evolution of larger maternal size. In turn, these larger mothers produce larger clutches of larger offspring. However, annual precipitation has a negative direct effect on offspring size, despite the positive indirect effect mediated by maternal size. Possibly, the evolution of offspring size was driven by the need to conserve water in dry environments, because small organisms are particularly sensitive to water loss. Since we found that body size variation among lizards is related to a combination of climatic factors, mainly precipitation and perhaps primary production, our study challenges previous generalizations (e.g., temperature‐size rule and Bergmann's rule) and suggests alternative mechanisms underlying the evolution of body size.

Physical constraints on thermoregulation and flight drive morphological evolution in bats

Body size and shape fundamentally determine organismal energy requirements by modulating heat and mass exchange with the environment and the costs of locomotion, thermoregulation, and maintenance. Ecologists have long used the physical linkage between morphology and energy balance to explain why the body size and shape of many organisms vary across climatic gradients, e.g., why larger endotherms are more common in colder regions. However, few modeling exercises have aimed at investigating this link from first principles. Body size evolution in bats contrasts with the patterns observed in other endotherms, probably because physical constraints on flight limit morphological adaptations. Here, we develop a biophysical model based on heat transfer and aerodynamic principles to investigate energy constraints on morphological evolution in bats. Our biophysical model predicts that the energy costs of thermoregulation and flight, respectively, impose upper and lower limits on the relationship of wing surface area to body mass (S-MR), giving rise to an optimal S-MR at which both energy costs are minimized. A comparative analysis of 278 species of bats supports the model’s prediction that S-MR evolves toward an optimal shape and that the strength of selection is higher among species experiencing greater energy demands for thermoregulation in cold climates. Our study suggests that energy costs modulate the mode of morphological evolution in bats—hence shedding light on a long-standing debate over bats’ conformity to ecogeographical patterns observed in other mammals—and offers a procedure for investigating complex macroecological patterns from first principles.

Phylogenomics of Elongate-Bodied Springtails Reveals Independent Transitions from Aboveground to Belowground Habitats in Deep Time.

Soil has become a major hotspot of biodiversity studies, yet the pattern and timing of the evolution of soil organisms are poorly known because of the scarcity of paleontological data. To overcome this limitation, we conducted a genome-based macroevolutionary study of an ancient, diversified, and widespread lineage of soil fauna, the elongate-bodied springtails (class Collembola, order Entomobryomorpha). To build the first robust backbone phylogeny of this previously refractory group, we sampled representatives of major higher taxa (6 out of 8 families, 11 out of 16 subfamilies) of the order with an emphasis on the most problematic superfamily Tomoceroidea, applied whole-genome sequencing methods, and compared the performance of different combinations of data sets (universal single-copy orthologs [USCO] vs. ultraconserved elements]) and modeling schemes. The fossil-calibrated timetree was used to reconstruct the evolution of body size, sensory organs, and pigmentation to establish a time frame of the ecomorphological divergences. The resultant trees based on different analyses were congruent in most nodes. Several discordant nodes were carefully evaluated by considering method fitness, morphological information, and topology test. The evaluation favored the well-resolved topology from analyses using USCO amino acid matrices and complex site-heterogeneous models (CATn}{}+GTR and LGn}{}+PMSF (C60)). The preferred topology supports the monophyletic superfamily Tomoceroidea as an early-diverging lineage and a sister relationship between Entomobryoidea and Isotomoidea. The family Tomoceridae was recovered as monophyletic, whereas Oncopoduridae was recovered as paraphyletic, with Harlomillsia as a sister to Tomoceridae and hence deserving a separate family status as Harlomillsiidae Yu and Zhang fam. n. Ancestral Entomobryomorpha were reconstructed as surface-living, supporting independent origins of soil-living groups across the Paleozoic–Mesozoic, and highlighting the ancient evolutionary interaction between aboveground and belowground fauna. [Collembola; phylogenomics; soil-living adaptation; whole-genome sequencing.]

Regional landscape change triggered by Andean uplift: The extinction of Sparassodonta (Mammalia, Metatheria) in South America

Sparassodonta, a Metatherian monophyletic group, was the main mammalian carnivore predator clade in South America from the Paleogene to the Early Pliocene (c. 66–3.5 Ma). However, there is still no consensus on the causes of their demise. Here, we use the fossil record and Bayesian diversification models to infer the origination and extinction rates for Sparassodonta. Then, we evaluate if their demise can be attributed to global temperature changes, Andean uplift, biotic interactions with their competitor and prey clades, and body mass evolution. That is biotic aspects in the context of the Red Queen model, abiotic aspects in the context of the Court Jester model, and an intrinsic lineage attribute. Our results show that this lineage is characterized by a positive near-zero net diversification rate indicating that the clade maintained a relatively low but stable diversity until the Middle Miocene when an increase in extinction rate drove them to decline and eventual extinction. Moreover, our results support the idea that a drastic regional landscape change triggered by the Andean uplift process affected their diversification dynamics, eventually driving them to extinction. These environmental changes could explicitly affect Sparassodonta lineages due to their ever-present vulnerability to extinction by near-zero net diversification rate and their highly specialized ecology that could have constrained adaptation to new South American landscapes. • We evaluate biotic and abiotic hypotheses to understand the causes of the Sparassodonta extinction. • We estimate the Sparassodonta macroevolutionary trajectories and evaluate their relationship with biotic and abiotic factors. • We find that Sparassodonts did not succumb to biotic interactions (competition and predation) or body size evolution. • The Sparassodonta decline resulted from the regional landscape changes during the Miocene associated with Andean uplift.

The Possible Role of Body Temperature in Modulating Brain and Body Sizes in Hominin Evolution.

Many models have posited that the concomitant evolution of large brains and body sizes in hominins was constrained by metabolic costs. In such studies, the impact of body temperature has arguably not been sufficiently addressed despite the well-established fact that the rates of most physiological processes are manifestly temperature-dependent. Hence, the potential role of body temperature in regulating the number of neurons and body size is investigated by means of a heuristic quantitative model. It is suggested that modest deviations in body temperature (i.e., by a couple of degrees Celsius) might allow for substantive changes in brain and body parameters. In particular, a higher body temperature may prove amenable to an increased number of neurons, a higher brain-to-body mass ratio and fewer hours expended on feeding activities, while the converse could apply when the temperature is lowered. Future studies should, therefore, endeavor to explore and incorporate the effects of body temperature in metabolic theories of hominin evolution, while also integrating other factors such as foraging efficiency, diet, and fire control in tandem.

No sustained increase in zooarchaeological evidence for carnivory after the appearance of Homo erectus

The appearance of Homo erectus shortly after 2.0 Ma is widely considered a turning point in human dietary evolution, with increased consumption of animal tissues driving the evolution of larger brain and body size and a reorganization of the gut. An increase in the size and number of zooarchaeological assemblages after the appearance of H. erectus is often offered as a central piece of archaeological evidence for increased carnivory in this species, but this characterization has yet to be subject to detailed scrutiny. Any widespread dietary shift leading to the acquisition of key traits in H. erectus should be persistent in the zooarchaeological record through time and can only be convincingly demonstrated by a broad-scale analysis that transcends individual sites or localities. Here, we present a quantitative synthesis of the zooarchaeological record of eastern Africa from 2.6 to 1.2 Ma. We show that several proxies for the prevalence of hominin carnivory are all strongly related to how well the fossil record has been sampled, which constrains the zooarchaeological visibility of hominin carnivory. When correcting for sampling effort, there is no sustained increase in the amount of evidence for hominin carnivory between 2.6 and 1.2 Ma. Our observations undercut evolutionary narratives linking anatomical and behavioral traits to increased meat consumption in H. erectus, suggesting that other factors are likely responsible for the appearance of its human-like traits.

Anatomical mechanism for protecting the airway in the largest animals on earth

Separation of respiratory and digestive tracts in the mammalian pharynx is critical for survival. Food must be kept out of the respiratory tract, and air must be directed into the respiratory tract when breathing.1 Cetaceans have the additional problem of feeding while underwater. Lunge-feeding baleen whales (rorquals) open the mouth while swimming at high speeds to engulf a volume of prey-laden water as large as their own body2 and experience tremendous forces as water floods the mouth. How the respiratory tract is protected in the pharynx during engulfment and while swallowing a massive slurry of tiny living prey remains unknown, despite its importance to survival. By dissecting adult and fetal fin whales, we determined that a large musculo-fatty structure passively seals the oropharyngeal channel. This "oral plug" is not observed in other animals, and its position indicates it must be shifted to allow swallowing; it is a part of the soft palate and can only shift posteriorly and dorsally. Elevation of the oral plug allows food transfer to the pharynx and protects the upper airways from food entry. The laryngeal inlet in the floor of the pharynx is sealed by laryngeal cartilages, and the muscular laryngeal sac moves upward into the laryngeal cavity, completely occluding the airway. The pharynx is dedicated to the digestive tract during swallowing, with no connection between upper and lower airways. These adaptations to facilitate swallowing were a critical development in the evolution of large body size in these, the largest animals on earth.

Novel Genomic Insights into Body Size Evolution in Cetaceans and a Resolution of Peto's Paradox.

AbstractCetaceans (whales, dolphins, and porpoises) have undergone a radical transformation from the typical terrestrial mammalian body plan to a streamlined body, while exhibiting dramatic interspecific size differences. However, the molecular mechanisms underlying the diversification of cetacean body size are largely unknown. Here, by using genomic and phenotypic data for 22 cetaceans, we performed phylogenetic genome-body size analysis and explored the genetic basis of the high diversity of body size in cetaceans. A functional enrichment analysis showed that body size-related genes in cetaceans are enriched in pathways associated with immunity, cell growth, and metabolism, suggesting that they contributed to body size diversification. Genes showing correlated evolution with body size were mainly involved in immune surveillance, tumor suppression function, and development of hypertumors. The role of these genes in tumor control resolves Peto's paradox (i.e., the lack of a correspondence between an expansion in body size and, thereby, cell number and an increased cancer incidence). Our results provide novel insights into the evolution of substantial body size variation in cetaceans.

Positive Selection and Enhancer Evolution Shaped Lifespan and Body Mass in Great Apes.

Within primates, the great apes are outliers both in terms of body size and lifespan, since they include the largest and longest-lived species in the order. Yet, the molecular bases underlying such features are poorly understood. Here, we leveraged an integrated approach to investigate multiple sources of molecular variation across primates, focusing on over 10,000 genes, including approximately 1,500 previously associated with lifespan, and additional approximately 9,000 for which an association with longevity has never been suggested. We analyzed dN/dS rates, positive selection, gene expression (RNA-seq), and gene regulation (ChIP-seq). By analyzing the correlation between dN/dS, maximum lifespan, and body mass, we identified 276 genes whose rate of evolution positively correlates with maximum lifespan in primates. Further, we identified five genes, important for tumor suppression, adaptive immunity, metastasis, and inflammation, under positive selection exclusively in the great ape lineage. RNA-seq data, generated from the liver of six species representing all the primate lineages, revealed that 8% of approximately 1,500 genes previously associated with longevity are differentially expressed in apes relative to other primates. Importantly, by integrating RNA-seq with ChIP-seq for H3K27ac (which marks active enhancers), we show that the differentially expressed longevity genes are significantly more likely than expected to be located near a novel “ape-specific” enhancer. Moreover, these particular ape-specific enhancers are enriched for young transposable elements, and specifically SINE–Vntr–Alus. In summary, we demonstrate that multiple evolutionary forces have contributed to the evolution of lifespan and body size in primates.

Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans.

Body sizes of marine amniotes span six orders of magnitude, yet the factors that governed the evolution of this diversity are largely unknown. High primary production of modern oceans is considered a prerequisite for the emergence of cetacean giants, but that condition cannot explain gigantism in Triassic ichthyosaurs. We describe the new giant ichthyosaur Cymbospondylus youngorum sp. nov. with a 2-meter-long skull from the Middle Triassic Fossil Hill Fauna of Nevada, USA, underscoring rapid size evolution despite the absence of many modern primary producers. Surprisingly, the Fossil Hill Fauna rivaled the composition of modern marine mammal faunas in terms of size range, and energy-flux models suggest that Middle Triassic marine food webs were able to support several large-bodied ichthyosaurs at high trophic levels, shortly after ichthyosaur origins.

Ecological specialization, rather than the island effect, explains morphological diversification in an ancient radiation of geckos.

Island colonists are often assumed to experience higher levels of phenotypic diversification than continental taxa. However, empirical evidence has uncovered exceptions to this 'island effect'. Here, we tested this pattern using the geckos of the genus Pristurus from continental Arabia and Africa and the Socotra Archipelago. Using a recently published phylogeny and an extensive morphological dataset, we explore the differences in phenotypic evolution between Socotran and continental taxa. Moreover, we reconstructed ancestral habitat occupancy to examine if ecological specialization is correlated with morphological change, comparing phenotypic disparity and trait evolution between habitats. We found a heterogeneous outcome of island colonization. Namely, only one of the three colonization events resulted in a body size increase. However, in general, Socotran species do not present higher levels or rates of morphological diversification than continental groups. Instead, habitat specialization explains better the body size and shape evolution in Pristurus. Particularly, the colonization of ground habitats appears as the main driver of morphological change, producing the highest disparity and evolutionary rates. Additionally, arboreal species show very similar body size and head proportions. These results reveal a determinant role of ecological mechanisms in morphological evolution and corroborate the complexity of ecomorphological dynamics in continent-island systems.

Rapid evolution of life-history traits in response to warming, predation and competition: A meta-analysis.

Although studies quantifying evolutionary change in response to the selective pressures that organisms face in the wild have demonstrated that organisms can evolve rapidly, we lack a systematic assessment of the frequency, magnitude and direction of rapid evolutionary change across taxa. To address this gap, we conducted a meta-analysis of 58 studies that document the effects of warming, predation or competition on the evolution of body size, development rate or fecundity in natural or experimental animal populations. We tested whether there was a consistent effect of any selective agent on any trait, whether the direction of these effects align with theoretical predictions, and whether the three agents select in opposing directions on any trait. Overall, we found weak effects of all three selective agents on trait evolution: none of our nine traits by selective agent combinations had an overall effect that differed from zero, only 31% of studies had a significant within-study effect, and attributes of the included studies generally did not account for between-study variation in results. One notable exception was that predation targeting adults consistently resulted in the evolution of smaller prey body size. We discuss potential causes of these generally weak responses and consider how our results inform the ongoing development of eco-evolutionary research.

The evolution of body size in termites.

Termites are social cockroaches. Because non-termite cockroaches are larger than basal termite lineages, which themselves include large termite species, it has been proposed that termites experienced a unidirectional body size reduction since they evolved eusociality. However, the validity of this hypothesis remains untested in a phylogenetic framework. Here, we reconstructed termite body size evolution using head width measurements of 1638 modern and fossil termite species. We found that the unidirectional body size reduction model was only supported by analyses excluding fossil species. Analyses including fossil species suggested that body size diversified along with speciation events and estimated that the size of the common ancestor of modern termites was comparable to that of modern species. Our analyses further revealed that body size variability among species, but not body size reduction, is associated with features attributed to advanced termite societies. Our results suggest that miniaturization took place at the origin of termites, while subsequent complexification of termite societies did not lead to further body size reduction.

Hidden Phylogenomic Signal Helps Elucidate Arsenurine Silkmoth Phylogeny and the Evolution of Body Size and Wing Shape Trade-Offs.

One of the key objectives in biological research is understanding how evolutionary processes have produced Earth's diversity. A critical step toward revealing these processes is an investigation of evolutionary tradeoffs-that is, the opposing pressures of multiple selective forces. For millennia, nocturnal moths have had to balance successful flight, as they search for mates or host plants, with evading bat predators. However, the potential for evolutionary trade-offs between wing shape and body size are poorly understood. In this study, we used phylogenomics and geometric morphometrics to examine the evolution of wing shape in the wild silkmoth subfamily Arsenurinae (Saturniidae) and evaluate potential evolutionary relationships between body size and wing shape. The phylogeny was inferred based on 782 loci from target capture data of 42 arsenurine species representing all 10 recognized genera. After detecting in our data one of the most vexing problems in phylogenetic inference-a region of a tree that possesses short branches and no "support" for relationships (i.e., a polytomy), we looked for hidden phylogenomic signal (i.e., inspecting differing phylogenetic inferences, alternative support values, quartets, and phylogenetic networks) to better illuminate the most probable generic relationships within the subfamily. We found there are putative evolutionary trade-offs between wing shape, body size, and the interaction of fore- and hindwing (HW) shape. Namely, body size tends to decrease with increasing HW length but increases as forewing (FW) shape becomes more complex. Additionally, the type of HW (i.e., tail or no tail) a lineage possesses has a significant effect on the complexity of FW shape. We outline possible selective forces driving the complex HW shapes that make Arsenurinae, and silkmoths as a whole, so charismatic. [Anchored hybrid enrichment; Arsenurinae; geometric morphometrics; Lepidoptera; phylogenomics; Saturniidae.].

Shared patterns in body size declines among crinoids during the Palaeozoic extinction events

Crinoids were among the most abundant marine benthic animals throughout the Palaeozoic, but their body size evolution has received little attention. Here, we compiled a comprehensive database on crinoid calyx biovolumes throughout the Palaeozoic. A model comparison approach revealed contrasting and complex patterns in body size dynamics between the two major crinoid clades (Camerata and Pentacrinoidea). Interestingly, two major drops in mean body size at around two mass extinction events (during the late Ordovician and the late Devonian respectively) are observed, which is reminiscent of current patterns of shrinking body size of a wide range of organisms as a result of climate change. The context of some trends (marked declines during extinctions) suggests the cardinal role of abiotic factors (dramatic climate change associated with extinctions) on crinoid body size evolution; however, other patterns (two intervals with either relative stability or steady size increase in periods between mass extinctions) are more consistent with biotic drivers.