Variation In Body Size Research Articles

A country‐wide examination of effects of urbanization on common birds

AbstractUrbanization forms one of the most drastic alterations of the environment and poses a major threat to wildlife. The human–induced modifications of the landscape may affect individual's fitness resulting in population declines. Research on how urbanization affects fitness traits has shown mixed results. However, studies typically contrasted data from a single species from few urban and non‐urban sites collected over short timeframes. Examining multiple species across a broad urbanization gradient enables a more robust comparison and understanding of how different species are impacted by urbanization‐knowledge crucial for generating population predictions, which are essential for conservation management. Here, we use data from a nation‐wide citizen science project to examine variation in survival and relative body mass and size (wing length) of common passerine birds, collected along an urbanization gradient in the Netherlands over an 8‐year period. Urbanization was measured as the distance from the city's border and the proportion of impervious surface area. Although the overall association between urbanization and survival was slightly negative, there was support for lower survival closer to the city in three species (chiffchaff Phylloscopus collybita, European robin Erithacus rubecula, European greenfinch Chloris chloris) and higher survival closer to the city in two (great tit Parus major and house sparrow Passer domesticus) of the 11 species examined. The contrasting survival successes among species suggest that ongoing urbanization may lead to shifts in community structure and loss of biodiversity. Impacts of urbanization on relative mass and size also exhibited varying effects, albeit less pronounced, and these effects were not correlated with the effects on survival. This implies that body mass and size cannot be used as indicators for urban‐associated patterns of survival. Our results further imply that effective conservation management targeting bird communities should involve a range of diverse actions, as focusing on single measures is unlikely to simultaneously impact multiple species due to the variation in responses to urbanization.

Demographic insights for the endangered Apennine yellow-bellied toad in the Pollino National Park (Southern Italy). A five-year Capture-Mark-Recapture study

Investigating population structure, parameters, and growth over time is vital for conserving endangered taxa like the Apennine yellow-bellied toad (Bombina variegata pachypus) in Italy. The Apennine yellow-bellied toad faces habitat loss or degradation, disease, and climate change threats. Our study delves into the population dynamics of this endemic amphibian by monitoring populations in two breeding sites within the Pollino National Park (Southern Italy) using a five-year Capture-Mark-Recapture (CMR) approach. With a particular emphasis on demographic parameters such as population size, detectability, survival, temporary emigration probability, and body condition index, the research aims to contribute to understanding population dynamics and inform conservation efforts. We used two CMR models to estimate these parameters: Jolly-Seber with POPAN parametrisation and Pollock's robust design with Huggins' estimator. Results showed variation in body size between males and females, challenging previous findings in south-central Italy. For both populations, demographic data indicate high annual adult survival, fidelity to the breeding areas, support for no movement, and minimal trap response. Abundance over the years reveals a slight decline in one site and a gradual increase in the other. The estimated maximum population size indicated ∼ 92 animals in one population and ∼ 70 in the other one. Despite the high conservation concern for the Apennine yellow-bellied toad, there remains a dearth of quantitative information on demographic aspects in Southern Italy. The findings underscore the importance of protected areas in biodiversity conservation and contribute to understanding the B. v. pachypus conservation status, suggesting that small, isolated populations may be vulnerable to unpredictable fluctuations, inbreeding depression, and extinction risks. Additionally, the research emphasises the importance of long-term CMR studies to gain insights into population dynamics and develop effective conservation strategies and management practices, particularly in the face of climate changes that may impact both the endemic taxon and its habitat.

Geographic Variation in Body Size and Hematology of the Slate-Colored Coot (Fulica ardesiaca) along the Andes of Peru

Geographic Variation in Body Size and Hematology of the Slate-Colored Coot (Fulica ardesiaca) along the Andes of Peru

Ecogeographic rules in a common Neotropical treefrog: No clinal variation along a mountain range

AbstractBody and limb size are associated with many aspects of the biology of animals. Geographic variation in morphological traits has often been investigated through ecogeographical rules. Bergmann's rule posits an inverse relationship between body size and temperature in homeotherms, while Allen's rule posits that endothermic animals inhabiting colder climates have relatively shorter protruding parts (e.g., limbs) in comparison to populations from warmer climates. However, the applicability and validity of these rules in poikilotherms are currently contentious. In this study, we aimed to test predictions of Bergmann's and Allen's rules in populations of the Neotropical frog Boana platanera. We analysed 142 adult male museum specimens from 17 localities along a mountain range in western Venezuela. We obtained six external morphological measurements and assessed the correlation of body size and limb size with temperature data for each locality. Our results were contrary to the expectations but consistent with previous studies. All this together indicates that exceptions to the Bergmann's and Allen's rules are frequent and idiosyncratic in anurans. We discuss alternative hypotheses that could explain geographic variation of body and limb size in future studies.

Using a common morphometric-based method to sex a migratory bird along its entire flyway despite geographical and temporal variations in body size and sexual size dimorphism

Using a common morphometric-based method to sex a migratory bird along its entire flyway despite geographical and temporal variations in body size and sexual size dimorphism

Physiology Evolves Convergently but Lags Behind Warming inCities.

Cities, through the generation of urban heat islands, provide a venue for exploring contemporary convergent evolution to climatic warming. We quantified how repeatable the evolution of heat tolerance, cold tolerance, and body size was among diverse lineages in response to urban heat islands. Our study revealed significant shifts toward higher heat tolerance and diminished cold tolerance among urban populations. We further found that the magnitude of trait divergence was significantly and positively associated with the magnitude of the urban heat island, suggesting that temperature played a major role in the observed divergence in thermal tolerance. Despite these trends, the magnitude of trait responses lagged behind environmental warming. Heat tolerance responses exhibited a deficit of 0.84°C for every 1°C increase in warming, suggesting limits on adaptive evolution and consequent adaptational lags. Other moderators were predictive of greater divergence in heat tolerance, including lower baseline tolerance and greater divergence in body size. Although terrestrial species did not exhibit systematic shifts toward larger or smaller body size, aquatic species exhibited significant shifts toward smaller body size in urban habitats. Our study demonstrates how cities can be used to address long-standing questions in evolutionary biology regarding the repeatability of evolution. Importantly, this work also shows how cities can be used as forecasting tools by quantifying adaptational lags and by developing trait-based associations with responses to contemporary warming.

Study of defensive behavior of a venomous snake as a new approach to understand snakebite

Snakebites affect millions of people worldwide. The majority of research and management about snakebites focus on venom and antivenom, with less attention given to snake ecology. The fundamental factor in snakebites is the snakes’ defensive biting behavior. Herein we examine the effects of environmental variables (temperature, time of day, and human stimulus) and biological variables (sex and body size) on the biting behavior of a medically significant pit viper species in Brazil, Bothrops jararaca (Viperidae), and associate it with the epidemiology of snakebites. Through experimental simulations of encounters between humans and snakes, we obtained behavioral models applicable to epidemiological situations in the State of São Paulo, Brazil. We found a significant overlap between behavioral, morphological, environmental, and epidemiological data. Variables that increase snakebites in epidemiological data also enhance the tendency of snakes to bite defensively, resulting in snakebites. We propose that snakebite incidents are influenced by environmental and morphological factors, affecting the behavior of snakes and the proportion of incidents. Thus, investigating behavior of snakes related to snakebite incidents is a valuable tool for a better understanding of the epidemiology of these events, helping the prediction and, thus, prevention of snakebites.

Bumble bee diet breadth increases with local abundance and phenophase duration, not intraspecific variation in body size

Patterns of abundance across space and time, and intraspecific variation in body size, are two species attributes known to influence diet breadth and the structure of interaction networks. Yet, the relative influence of these attributes on diet breadth is often assumed to be equal among taxonomic groups, and the relationship between intraspecific variation in body size on interaction patterns is frequently neglected. We observed bee–flower interactions in multiple locations across Montana, USA, for two growing seasons and measured spatial and temporal patterns of abundance, along with interspecific and intraspecific variation in body size for prevalent species. We predicted that the association between spatial and temporal patterns of abundance and intraspecific variation in body size, and diet breadth, would be stronger for bumble bee compared to non-bumble bee species, because species with flexible diets and long activity periods can interact with more food items. Bumble bees had higher local abundance, occurred in many local communities, more intraspecific variation in body size, and longer phenophases compared to non-bumble bee species, but only local abundance and phenophase duration had a stronger positive association with the diet breadth of bumble bee compared to non-bumble bee species. Communities with a higher proportion of bumble bees also had higher intraspecific variation in body size at the network-level, and network-level intraspecific variation in body size was positively correlated with diet generalization. Our findings highlight that the association between species attributes and diet breadth changes depending on the taxonomic group, with implications for the structure of interaction networks.

Plant mass variations of Leymus chinensis (Poaceae) and their relationships with environmental factors on a large-scale gradient, northeastern China.

Body size (or mass) variations and their relationships with environmental variability have been well documented for many species at the local scale, while the effects of climate, combined with soil nutrients, on plant mass in large-scale gradient remain unclear. Herein, detailed surveys were conducted to investigate plant mass (PM, aboveground mass per plant) variations of Leymus chinensis and their relationship with environmental factors (e.g., climate, soil nutrient, and microbial diversity) at 18 wild sites along a large-scale gradient from 114 to 124° E in northeastern China. Based on site-by-site analyses, the plant mass of the species varied significantly from east to west along the gradient. It initially increased, peaking at middle sites, and then dropped with the increase of drought in both dry and rainy seasons. Plant mass at the eastern end was almost equal to that at the western end and was equivalent to 1/2 and 1/3 of middle sites. The average plant mass in the rainy season was about 50% greater than that in the dry season (F 1,1078 = 489.80, p < .001). The effects of environmental variables on plant mass differed in dry and rainy seasons. Mean annual temperature and temperature seasonality were the critical restrictions of plant mass in the dry season, while temperature and precipitation seasonality and soil resources (total C, Mn, Zn) had significant impacts in the rainy season (p < .05). In general, plant mass had not dropped linearly with the increase of drought along large-scale gradient, suggesting that precipitation decrease was not the critical restriction regulating the growth and settlement of the species.

Variability in intermediate predator hatching does not alter top-down effects of top predators

Variability in phenological shifts (seasonal changes in biological events) has become more common with climate change. As phenological variability increases due to climatic factors, species interactions within diverse communities can be affected. Shifts in hatching phenology can lead to body size variability that can alter species interactions, especially within and across trophic levels in complex food webs. To understand the effects of hatching phenology and food web complexity on prey communities, we conducted an experiment with ectotherms from ponds by manipulating hatching synchrony of a prey species across three dates and food web complexity. We hypothesized that predation on prey would be highest in the lowest synchrony treatment due to predator satiation effects in high synchrony additions. Food webs with top predators present had the lowest survival rates for prey compared to other food webs. Prey size at metamorphosis was also highest in the top predator food webs, suggesting a thinning effect. Hatching synchrony treatments did not have a significant impact on prey survival or size at metamorphosis except in treatments where intermediate and top predators were absent. Overall, our results show that top-down effects of predators may be enough to suppress the influence of phenological shifts in prey.

Inconsistent effects of environmental variations on body size and density of pillbugs, Armadillidium vulgare (Latreille, 1804) (Isopoda, Oniscidea) in urban green spaces

Inconsistent effects of environmental variations on body size and density of pillbugs, Armadillidium vulgare (Latreille, 1804) (Isopoda, Oniscidea) in urban green spaces

Natural body size variation in seabirds provides a fundamental challenge for flight height determination by single-camera photogrammetry: a comment on Humphries et al. (2023)

Natural body size variation in seabirds provides a fundamental challenge for flight height determination by single-camera photogrammetry: a comment on Humphries et al. (2023)

Response to: “Natural body size variation in seabirds provides a fundamental challenge for flight height determination by single-camera photogrammetry”

Response to: “Natural body size variation in seabirds provides a fundamental challenge for flight height determination by single-camera photogrammetry”

Occurrence of giant migratory locust Locusta migratoria (Acrididae) on Tsushima Island, Japan

This study focused on the populations of Locusta migratoria (Linnaeus, 1758) on Tsushima Island, Japan, which exhibited the largest mean adult body size when compared to other populations from various climatic regions. Certain individuals, designated as “giant locusts,” displayed exceptionally large sizes, with females and males identified when with head widths surpassing 10.5 mm and 8.0 mm, respectively. The maximum weight recorded for a giant locust was 8.9 g, in contrast to other examined females with the maximum weight ranging from 3.1 to 5.5 g. Notably, giant females exhibited the ability to yield larger egg pods and progeny compared to their counterparts. A positive correlation emerged between body size of adult females and the number of ovarioles. To explore the potential heritability of body size, selection experiments were conducted across two generations. A significant impact of selection on adult body size was apparent at LD 12:12h, whereas this effect was not evident at LD 16:8h. Furthermore, crossing experiments showed that body size at hatching closely resembled that of the female parent or demonstrated dimensions intermediary between the two parents, suggesting a complex genetic basis for the observed body size variations. This study provides no evidence of genetic differentiation between the giant locusts and the other locusts on this island.

Genetic insight into a polygenic trait using a novel genome-wide association approach in a wild amphibian population.

Body size variation is central in the evolution of life-history traits in amphibians, but the underlying genetic architecture of this complex trait is still largely unknown. Herein, we studied the genetic basis of body size and fecundity of the alternative morphotypes in a wild population of the Greek smooth newt (Lissotriton graecus). By combining a genome-wide association approach with linkage disequilibrium network analysis, we were able to identify clusters of highly correlated loci thus maximizing sequence data for downstream analysis. The putatively associated variants explained 12.8% to 44.5% of the total phenotypic variation in body size and were mapped to genes with functional roles in the regulation of gene expression and cell cycle processes. Our study is the first to provide insights into the genetic basis of complex traits in newts and provides a useful tool to identify loci potentially involved in fitness-related traits in small data sets from natural populations in non-model species.

Variation in Ventral Coloration Pattern and Aposematism in Tropical Warty Newts.

Aposematic coloration plays a crucial role in animal defense, and it is shaped by a complex interplay of factors such as physiological limitations and sexual and natural selection. Warty newts within the genus Paramesotriton exhibit significant variation in ventral coloration. In this study, we quantified the percentage of red ventral area to investigate aposematic ventral coloration in Paramesotriton deloustali and P. guangxiensis across eight populations in northern Vietnam. To assess the interaction between predators and the aposematic signals, we conducted experiments employing three types of clay replicas of newts: dorsal, red ventral, and black ventral models. Our findings revealed a significant variation in the red ventral area among different populations. Additionally, a significant correlation was detected between the red ventral area of the newt and the annual temperature range. In clay model experiments, a significant difference in predator attack rates was observed between dorsal and ventral clay models. Interestingly, there was no significant difference in attack rates between red and black ventral types. Our study suggested that the variation in the red ventral area of warty newts is probably influenced by multiple factors, including genetic constraints, sex, ambient environment, and diet. Furthermore, our results supported the effectiveness of displaying aposematic coloration as an antipredator defense mechanism in warty newts. However, variations in body size and the pressure of mammal predation might not play a significant role in determining aposematic coloration.

Rolling with the punches—How competition shapes the morphology of small passerines on small islands

AbstractAimWallacea is a global biodiversity hotspot and Sulawesi is the largest island in this region, notable for a high proportion of endemic species. The Wakatobi archipelago, off the southeastern peninsular arm of Sulawesi, is home to several endemic bird species. Although islands are known to influence the morphology of their resident species, competitive interactions also exert strong influences on morphology. Here, we consider the contributions of both islands and competitors on two morphological traits of two bird species in a small passerine guild found on the Wakatobi islands.LocationWakatobi archipelago, Sulawesi Tenggara, Indonesia.TaxonWakatobi White‐eye (Zosterops flavissimus) and Wakatobi Sunbird (Cinnyris infrenatus).MethodsWorking with morphological measures (from netting studies), population density metrics (from transect surveys) and fundamental data from islands (area, distance from mainland and elevation), we investigated (by means of multiple linear regression) which terms best explained variation in the body size and bill size of two small passerine birds endemic to the Wakatobi islands.ResultsBoth island metrics and competitor presence/density were useful in describing the variation in body size of both bird species. However, only competitor presence/density was useful in describing variation in bill size of the birds. The best models describing variation in these traits included terms representing both interspecific and intraspecific competition.Main ConclusionsOur findings indicate that simple island metrics may be useful in predicting some of the variation in some functional traits of island species. However, in this example, simple island metrics were insufficient to explain the full variation in body size of endemic birds across the Wakatobi archipelago and were of no use in predicting the variation in their bill size. As bill morphology frequently dictates diet and feeding niche, it is a trait which may determine population divergence and speciation. If simple island metrics fail to describe such diversification, it is surely important to capture that information in other ways.

Phenotypes of predator individuals underpin contrasting ecosystem effects

Abstract Intraspecific variability has implications for our understanding of ecosystem functioning. Yet, beyond ontogenetic variation in body size, we know little about how phenotypic differences between individuals modulate ecosystem functioning. We addressed this question empirically within a forested stream, by studying the ecosystem effects triggered by conspecific predatory dragonfly larvae that varied in sex, body shape, behaviour and growth rate. With the help of stream enclosures, we were able to evaluate how different predator phenotypes drive cascading effects on litter‐dwelling prey, fungal biomass and leaf litter decomposition, in uncontrolled natural conditions. Some individual predators increased leaf litter standing stocks and fungal biomass compared to controls (without dragonfly larvae added), but others had the opposite effect. These contrasting effects were repeatable between the two runs of our experiment. Phenotypic effects were related to the sex and the position of individuals along a life history—behavioural continuum, and were possibly mediated by differential top‐down control of prey, or by inter‐individual variability in non‐consumptive effects. Several phenotypic dimensions are likely to mediate individual variability in predator effects on ecosystem processes, even in a complex and stochastic natural context such as a forested stream. We invite further investigations that seek to understand the mechanisms (e.g., non‐consumptive effects) driving individual variability in predator effects on ecosystem processes.

Intra and interspecific variation in thermal performance and critical limits in anurans from southern Chile

The relationship between temperature and performance can be illustrated through a thermal performance curve (TPC), which has proven useful in describing various aspects of ectotherms' thermal ecology and evolution. The parameters of the TPC can vary geographically due to large-scale variations in environmental conditions. However, only some studies have attempted to quantify how thermal performance varies over relatively small spatial scales, even in the same location or consistently among individuals within a species. Here, we quantified individual and species variation in thermal sensitivity of locomotor performance in five amphibia Eupsophus species found in the temperate rainforests of southern Chile and compared their estimates against co-occurring species that exhibit a substantially more extensive distributional range. We measured critical thermal limits and jumping performance under five different temperatures. Our results suggest that thermal responses are relatively conserved along the phylogeny, as the locomotor performance and thermal windows for activity remained narrow in Eupsophus species when compared against results observed for Batrachyla taeniata and Rhinella spinulosa. Additionally, we found significant individual differences in locomotor performance within most species, with individual consistency in performance observed across varied temperatures. Further analyses explored the influence of body size on locomotor performance and critical thermal limits within and between species. Our results suggest a trade-off scenario between thermal tolerance breadth and locomotor performance, where species exhibiting broader thermal ranges might have compromised performance. Interestingly, these traits seem partly mediated by body size variations, raising questions about potential ecological implications.

Functional Traits Drive the Changes in Diversity and Composition of Benthic Invertebrate Communities in Response to Hydrological Regulation

Of all the environmental elements that influence the biological communities of rivers, water flow characteristics are undoubtedly the most important. Unfortunately, natural hydrological characteristics are increasingly threatened by human activities, especially in alpine or high mountain areas where there are numerous hydropower plants. In this study, we analysed the impact of hydrological alterations on the macroinvertebrate community of a lowland river in NW Italy. Specifically, we analysed the macroinvertebrate communities of an unaffected site by comparing them with those of a site subject to hydrological alteration. We adopted an approach that is not only taxonomic but also functional, allowing us to study a component of biodiversity that is generally less known. Our results show that the flow-altered site hosted a benthic community with lower species and functional diversity than the control site. Interestingly, we also detected a number of significant differences between the summer and autumn samples. In particular, examination of community-weighted mean (CWM) trait values reveals significant variation in body size, voltinism, substrate, locomotion, feeding habits and other traits between sites and seasons. The integration of taxonomic and functional approaches provides a comprehensive understanding of how human-induced hydrological variations can affect aquatic biodiversity and ecological functions.