Body size, developmental instability, and climate change

Multilevel Analysis of Ground Beetle Responses to Forest Management: Integrating Species Composition, Morphological Traits and Developmental Instability

This study evaluates the response of ground beetle (Coleoptera: Carabidae) assemblage to forest management practices by integrating species composition, body traits, wing morphology and developmental instability. Traditional approaches that rely on averaged identity-based descriptors often overlook phenotypic plasticity and functional trait variability, potentially masking species-specific responses to environmental changes. To address this, we applied a three-layered analytical approach to address this gap, utilising ground beetle occurrence and morphological trait data from Podyjí National Park, Czech Republic. The first layer assessed assemblage composition with ecological and dietary preferences across control, ecotone and clearing treatments using multivariate techniques. Building on species-level knowledge, the second layer analysed the interaction between coarse traits, such as wing morphology and fine-scale body traits, including body size (proxied by elytron length), head width and last abdominal sternite, to assess their relationship with the different treatments. These interactions were explored as intraspecific wing plasticity can affect functional interpretations. The third layer focused on fluctuating asymmetry as an intraindividual indicator of developmental instability, examining how ground beetles respond to environmental stressors. Our findings revealed: (i) no significant impact of habitat treatments on the presence of specialist species in the assemblage analysis; (ii) analysis of morphological traits highlights the combined influence of a coarse trait, such as wing morphology, and a fine trait, such as head width, which together contribute to the partitioning of assemblages and help distinguish differences in habitat use; and (iii) FA analysis revealed a significant positive association between the second antennal segment of specialist species and litter while displaying a negative association with Collembola. This multilevel analytical framework not only confirms ecological findings but also advances our approach to habitat and species analysis, offering deeper insights into ecosystem dynamics.

Long-term patterns of forearm asymmetry in females of three syntopic bat species and its effects on individual fitness

Fluctuating asymmetry, the non-directional deviation from bilateral symmetry resulting from developmental instability, can indicate early-life environmental stress. While fluctuating asymmetry can affect individual survival and reproductive success, its effect on fitness differs between species. Here, we analyzed up to 27 years of mark-recapture data from 894 RFID tagged individuals of three forest-living bat species in southern Germany to investigate the degree of fluctuating asymmetry in forearm length. In Bechstein's bats, Myotis bechsteinii, the species with the highest sample size, we furthermore investigated if fluctuating asymmetry has become more frequent over the study period, a time when juvenile bats have grown larger forearms in response to warmer summers. We also investigated whether fluctuating asymmetry affects individual lifespan and lifetime reproductive success in female Myotis bechsteinii. The degree of fluctuating asymmetry clearly exceeding the measurement error estimated on recaptured individuals was similar in all three species (1.8%). In female Myotis bechsteinii, the frequency of fluctuating asymmetry did not increase over the course of the study and even strong asymmetry had no effect on individual reproductive success and life expectancy. Our data suggest that fluctuating asymmetry is a poor predictor of fitness in the female Myotis bechsteinii studied, and is so far unaffected by the warming environment which is leading to larger individuals in our study population.

The estimation of additive genetic variance of body size in a wild passerine is sensitive to the method used to estimate relatedness among the individuals

Assessing additive genetic variance is a crucial step in predicting the evolutionary response of a target trait. However, the estimated genetic variance may be sensitive to the methodology used, e.g., the way relatedness is assessed among the individuals, especially in wild populations where social pedigrees can be inaccurate. To investigate this possibility, we investigated the additive genetic variance in tarsus length, a major proxy of skeletal body size in birds. The model species was the collared flycatcher (Ficedula albicollis), a socially monogamous but genetically polygamous migratory passerine. We used two relatedness matrices to estimate the genetic variance: (1) based solely on social links and (2) a genetic similarity matrix based on a large array of single-nucleotide polymorphisms (SNPs). Depending on the relatedness matrix considered, we found moderate to high additive genetic variance and heritability estimates for tarsus length. In particular, the heritability estimates were higher when obtained with the genetic similarity matrix instead of the social pedigree. Our results confirm the potential for this crucial trait to respond to selection and highlight methodological concerns when calculating additive genetic variance and heritability in phenotypic traits. We conclude that using a social pedigree instead of a genetic similarity matrix to estimate relatedness among individuals in a genetically polygamous wild population may significantly deflate the estimates of additive genetic variation.

A global assessment of Bergmann's rule in mammals and birds

Bergmann's rule states that endotherms have a large body size in high latitudes and cold climates. However, previous empirical studies have reported mixed evidence on the relationships between body size and latitude, raising the question of why some clades of endotherms follow Bergmann's rule, whereas others do not. Here, we synthesized the interspecific relationships between body size and latitude among 16,187 endothermic species (5422 mammals and 10,765 birds) using Bayesian phylogenetic generalized linear mixed models to examine the strength and magnitude of Bergmann's rule. We further assessed the effect of biological and ecological factors (i.e., body mass categories, dietary guild, winter activity, habitat openness, and climate zone) on the variations in the body mass-latitude relationships by adding an interaction term in the models. Our results revealed a generally weak but significant adherence to Bergmann's rule among all endotherms at the global scale. Despite taxonomic variation in the strength of Bergmann's rule, the body mass of species within most animal orders showed an increasing trend toward high latitudes. Generally, large-bodied, temperate species, non-hibernating mammals, and migratory and open-habitat birds tend to conform to Bergmann's rule more than their relatives do. Our results suggest that whether Bergmann's rule applies to a particular taxon is mediated by not only geographic and biological features, but also potential alternate strategies that species might have for thermoregulation. Future studies could explore the potential of integrating comprehensive trait data into phylogenetic comparative analysis to re-assess the classic ecogeographic rules on a global scale.

Transcriptomics and Selection Pressure Analysis Reveals the Influence Mechanism of PLIN1 Protein on the Development of Small Size in Min Pigs

Body size is an important biological phenotypic trait that has attracted substantial attention. Small domestic pigs can serve as excellent animal models for biomedicine and also help meet sacrificial culture needs in human societies. Although the mechanisms underlying vertebral development regulating body size variation in domestic pigs during the embryonic period have been well described, few studies have examined the genetic basis of body size variation in post embryonic developmental stages. In this study, seven candidate genes-PLIN1, LIPE, PNPLA1, SCD, FABP5, KRT10 and IVL-significantly associated with body size were identified in Min pigs, on the basis of weighted gene co-expression network analysis (WGCNA), and most of their functions were found to be associated with lipid deposition. Six candidate genes except for IVL were found to have been subjected to purifying selection. PLIN1 had the lowest ω value (0.139) and showed heterogeneous selective pressure among domestic pig lineages with different body sizes (p < 0.05). These results suggested that PLIN1 is an important genetic factor regulating lipid deposition and consequently affecting body size variation in pigs. The culture of whole pig sacrifice in Manchu during the Qing Dynasty in China might have contributed to the strong artificial domestication and selection of Hebao pigs.

Signatures of increasing environmental stress in bumblebee wings over the past century: Insights from museum specimens

Determining when animal populations have experienced stress in the past is fundamental to understanding how risk factors drive contemporary and future species' responses to environmental change. For insects, quantifying stress and associating it with environmental factors has been challenging due to a paucity of time-series data and because detectable population-level responses can show varying lag effects. One solution is to leverage historic entomological specimens to detect morphological proxies of stress experienced at the time stressors emerged, allowing us to more accurately determine population responses. Here we studied specimens of four bumblebee species, an invaluable group of insect pollinators, from five museums collected across Britain over the 20th century. We calculated the degree of fluctuating asymmetry (FA; random deviations from bilateral symmetry) between the right and left forewings as a potential proxy of developmental stress. We: (a) investigated whether baseline FA levels vary between species, and how this compares between the first and second half of the century; (b) determined the extent of FA change over the century in the four bumblebee species, and whether this followed a linear or nonlinear trend; (c) tested which annual climatic conditions correlated with increased FA in bumblebees. Species differed in their baseline FA, with FA being higher in the two species that have recently expanded their ranges in Britain. Overall, FA significantly increased over the century but followed a nonlinear trend, with the increase starting c. 1925. We found relatively warm and wet years were associated with higher FA. Collectively our findings show that FA in bumblebees increased over the 20th century and under weather conditions that will likely increase in frequency with climate change. By plotting FA trends and quantifying the contribution of annual climate conditions on past populations, we provide an important step towards improving our understanding of how environmental factors could impact future populations of wild beneficial insects.

Continent-wide patterns of song variation predicted by classical rules of biogeography

Physiological constraints related to atmospheric temperature pose a limit to body and appendage size in endothermic animals. This relationship has been summarised by two classical principles of biogeography: Bergmann's and Allen's rules. Body size may also constrain other phenotypic traits important in ecology, evolution and behaviour, and such effects have seldom been investigated at a continental scale. Through a multilevel-modelling approach, we demonstrate that continent-wide morphology of related African barbets follows predictions of Bergmann's rule, and that body size mirrors variation in song pitch, an acoustic trait important in species recognition and sexual selection. Specifically, effects on song frequency in accordance with Bergmann's rule dwarf those of acoustic adaptation at a continental scale. Our findings suggest that macroecological patterns of body size can influence phenotypic traits important in ecology and evolution, and provide a baseline for further studies on the effects of environmental change on bird song.

Phenotypic responses to climate change are significantly dampened in big-brained birds

Anthropogenic climate change is rapidly altering local environments and threatening biodiversity throughout the world. Although many wildlife responses to this phenomenon appear largely idiosyncratic, a wealth of basic research on this topic is enabling the identification of general patterns across taxa. Here, we expand those efforts by investigating how avian responses to climate change are affected by the ability to cope with ecological variation through behavioural flexibility (as measured by relative brain size). After accounting for the effects of phylogenetic uncertainty and interspecific variation in adaptive potential, we confirm that although climate warming is generally correlated with major body size reductions in North American migrants, these responses are significantly weaker in species with larger relative brain sizes. Our findings suggest that cognition can play an important role in organismal responses to global change by actively buffering individuals from the environmental effects of warming temperatures.