Interspecific Variation In Body Size Research Articles

Wood hardness drives nest-site selection in woodpeckers of the humid Chaco

Abstract Avian excavators (woodpeckers and other species) select nest sites based on characteristics of the nest patch, nest tree, and substrate. These characteristics could increase foraging opportunities or reduce the risk of predation, but there is also a potentially important role for wood hardness in restricting nest-site selection, a role that has been little explored and is expected to vary among species according to their ability to excavate. We examined patterns of nest-site selection in 8 woodpecker species in the humid Chaco of South America, where the dominant trees have extremely hard wood. We hypothesized that (1) wood hardness is the main factor driving selection of excavation sites, and (2) interspecific variation in body size and foraging behavior (traits frequently related to excavation ability) explain interspecific variation in the wood hardness of excavated nest substrates. From 2016 to 2019 in well-preserved forests of the Argentine Chaco, we compared nesting cavities excavated in wood (cases; n = 42) vs. potential wood substrates without cavities (matched controls) and made 187 focal observations of foraging woodpeckers. Woodpeckers selected nesting substrates with softer heartwood than potential substrates, regardless of any other characteristics of the tree or nest patch. Wood hardness around nest cavities increased with body size and the prevalence of chiseling during foraging, traits that were positively correlated. Woodpeckers often excavated in Prosopis spp. (Algarrobos) but rarely in Schinopsis balansae (Quebracho), a tree with exceptionally hard internal wood, in which cavity adopters frequently nest in non-excavated cavities. Wood hardness is critical to assessing the role of woodpeckers as cavity facilitators, understanding the costs and benefits of excavation, and interpreting excavation patterns across species and forests globally.

A comparative study of body size evolution in moths: evidence of correlated evolution with feeding and phenology-related traits.

Interspecific variation in body size is one of the most popular topics in comparative studies. Despite recent advances, little is known about the patterns and processes behind the evolution of body size in insects. Here, we used a robust data set comprising all geometrid moth species occurring in Northern Europe to examine the evolutionary associations involving body size and several life-history traits under an explicitly phylogenetic framework. We provided new insights into the interactive effects of life-history traits on body size and evidence of correlated evolution. We further established the sequence of trait evolution linking body size with the life-history traits correlated with it. We found that most (but not all) of the studied life-history traits, to some extent, influenced interspecific variation in body size, but interactive effects were uncommon. Both bi- and multivariate phylogenetic analyses indicated that larger species tend to be nocturnal flyers, overwinter in the larval stage, feed on the foliage of trees rather than herbs, and have a generalist feeding behaviour. We found evidence of correlated evolution involving body size with overwintering stage, host-plant growth form, and dietary specialization. The examination of evolutionary transitions within the correlated evolution models signalled that overwintering as larvae commonly preceded the evolution of large sizes, as did feeding on tree foliage and the generalist feeding behaviour. By showing that both body size and all life-history traits correlated with it evolve at very slow rates, we caution against uncritical attempts to propose causal explanations for respective associations based on contemporary ecological settings.

Species-specific differences in bumblebee worker body size between different elevations: Implications for pollinator community structure under climate change

Pollinator populations face growing threats from global climate change, particularly in alpine environments with rapidly rising temperatures. Understanding how bumblebees, critical alpine pollinators, respond to these temperature changes is therefore an important goal. Predicting species’ responses to climate change requires several different approaches, one of which is to compare processes at different elevations, which experience different temperature regimes. Bumblebee body size is linked to fitness through its influence on nutritional requirements and foraging capacity. It is also a highly plastic trait that depends on ecological factors such as temperature. Thus, understanding how body size varies at different elevations may help predict bumblebee fitness under climate change. We collected bumblebee workers from five species in a single growing season, at two distinct elevations in the Swiss Alps. Our study aimed to examine whether body size responses differed among species and across functional traits related to foraging and nesting. Larger body size is thought to confer an advantage under cold conditions; we therefore expected greater body size with elevation, but with species-specific relationships. Contrary to our expectation, not all species were larger at high elevations. Specifically, while two species were significantly larger at high elevation, one (Bombus terrestris) was significantly smaller at high elevation, and two showed no size differences with elevation. Additionally, interspecific variation in body size was greater at low elevations. This suggests a divergence of body size with warming, although local factors may also play a role in shaping functional traits.

Population responses to temperature in 12‐year insect time series

Abstract Considerable work has examined the distribution of species under projected climate change, but empirical data are needed to support predicting change in abundance. I analysed populations of 17 saproxylic beetle species collected twice nightly from mid‐May to mid‐October from 2004 to 2015 at lights in Shizuoka, Japan, to investigate effects of two 100‐year hot summers (2010 and 2013) and correlated changes with June, July and August maximum temperatures. The first analysis examined the effect of heat stress and the second examined how populations tracked changes in temperature. I hypothesised that the responses would be species‐specific and could be related to interspecific variation in body size, voltinism, primary food source and the strength of density dependence. Heat stress was associated with population declines of five species during the same year and five other species in the following year. Conifer feeders were more likely to decline during the same year as the heat stress. Only one species tracked variation in maximum June temperature. Larger, later emerging species were more strongly detrimentally affected by high June temperatures than smaller, early emerging species. There was no relation between the response to heat stress and tracking June temperatures across species. The influence of summer temperature on saproxylic beetles was detectable from relatively short time series and occurred in a species‐specific manner. The effect of heat stress was more readily detected than correlated changes in abundance and temperature. Short time series may help reveal the response of insect populations to changing temperatures.

Comparisons of body size for native and exotic Hymenoptera established in New Zealand

ABSTRACT Body size is a fundamental component of morphology, related to many physiological and ecological traits, and is influenced by a variety of biotic and abiotic factors. Body size may also have a role in influencing the establishment of exotic species. We compared the body size of New Zealand native species, accidentally introduced exotic species, and deliberately introduced species of Hymenoptera. Specimens in the New Zealand Arthropod Collection were used to measure body and forewing length. Linear mixed effects regression models were used to compare the overall body sizes between biostatus groups, and specifically between species within a genus and family. A total of 2231 specimens were measured from 740 species of Hymenoptera, comprising 503 native, 201 exotic, and 36 biocontrol species. There was a strong positive correlation between body length and forewing length (R 2 > 0.97). Overall, the average body size of species did not differ significantly between native and accidentally introduced exotic species, but deliberately introduced biocontrol species were significantly smaller than native species. Exotic species had greater interspecific variation in body size than either native or biocontrol species. There were no significant differences in the body sizes of native and exotic species within the same genus or same family. Levene’s tests revealed there was equal variance between biostatus groups at the genus level but unequal variance at the family level. This study provides a large dataset on a key morphological trait, body size, that can be used to further examine how morphology can be shaped by, and influence, ecological communities, and interactions between species.

The Elevation does not strongly influence interspecific variation in body size of small Tropical endotherms

Introduction: Body size is an essential trait for endotherms to face the physiological requirements of cold, so there is a tendency to large body size at high altitudes and latitudes, known as Bergmann's rule. However, the validity of this ecomorphological rule to small-bodied endotherms across altitudinal gradients is poorly known. Objective: To understand the effects of environmental variation on body size, we assessed whether interspecific variation in body size of small tropical endotherms follows Bergmann's rule along tropical altitudinal gradients. Methods: We compiled data on elevational ranges and body masses for 133 species of hummingbirds of Colombia. We then assessed the association between body mass and mid-point of the altitudinal distribution using phylogenetic generalized least squares (PGLS) analyses under different evolutionary models. Results: We found a decelerating rate of evolution for body size since the Early Burst model of evolution provided a better fit to body mass data. For elevational range, we found a slow and constant rate since Pagel's lambda model provided a better fit to the mid-point of the altitudinal distribution data. Besides, phylogenetic regression analysis indicated that body mass and the altitudinal range of hummingbirds are associated through the phylogeny, with a positive but slight association (R2= 0.036). Conclusions: We found that body mass and altitude of hummingbirds are positively related, which is in agreement with expectations under Bergmann's rule. However, this association was weaker than expected for small and non-passerine birds like hummingbirds. Thus, our results suggest that environmental changes across altitudinal gradients do not strongly influence body mass in small tropical endotherms as hummingbirds.

Geographic body size variation of a tropical anuran: effects of water deficit and precipitation seasonality on Asian common toad from southern Asia

BackgroundTwo previous studies on interspecific body size variation of anurans found that the key drivers of variation are the species’ lifestyles and the environments that they live in. To examine whether those findings apply at the intraspecific level, we conducted a study of the Asian common toad (Duttaphrynus melanostictus), a terrestrial anuran distributed in tropical regions. The body size of toads from 15 locations, covering the majority of their geographic range, and local environmental data were summarized from published literature. We used a model selection process based on an information-theoretic approach to examine the relationship between toad body size and those environmental parameters.ResultsWe found a positive correlation between the body size of the Asian common toad and the water deficit gradient, but no linkage between body size and temperature-related parameters. Furthermore, there was a positive correlation between the seasonality of precipitation and body size of females from different sampled populations.ConclusionsAs a terrestrial anuran, the Asian common toad should experience greater pressure from environmental fluctuations than aquatic species. It is mainly distributed in tropical regions where temperatures are generally warm and stable, but water availability fluctuates. Therefore, while thermal gradients are not strong enough to generate selection pressure on body size, the moisture gradient is strong enough to select for larger size in both males and females in dryer regions. Larger body size supports more efficient water conservation, a pattern in accordance with the prediction that lifestyles of different species and their local habitats determine the relationship between body size and environment. In addition, larger females occur in regions with greater seasonality in precipitation, which may happen because larger females can afford greater reproductive output in a limited reproductive season.

Ancestral biogeography and ecology of marine angelfishes (F: Pomacanthidae)

Marine angelfishes (F: Pomacanthidae) are amongst the most conspicuous reef fish families inhabiting reefs on tropical and subtropical latitudes. While being disproportionately represented in the marine ornamental fish trade, only a handful of taxonomically restricted studies explored their biogeographic history and the evolution body size and trophic guilds. Here, we reconstruct the phylogenetic history for 70 pomacanthid species (85% of nominal species), based on previously published data for three nuclear and four mitochondrial markers. We use the resulting phylogenetic framework to explore the ancestral biogeography and ecological diversification of the family. Divergence times and ancestral range estimation highlight the origins of the family most likely lie in the Central Pacific region. Vicariance among ocean basins reflects the impact of the Terminal Tethyan Event and the closure of the Isthmus of Panama in the historical biogeography of Pomacanthus and Holacanthus genera. The reconstruction also uncovers ancestral colonization pathways via the Pacific Ocean into the western Atlantic waters for Holacanthus. We confirm the Indian Ocean invasion scenario previously proposed for the “acanthops” complex (genus: Centropyge). Finally, interspecific variation in body size among clades appeared to be correlated to some degree with trophic guilds, whereby 15% of variance in body size was explained by trophic modes. This suggests that the higher ecological diversification observed in the Centropyge clade might be promoted by smaller body sizes acting as an ecological novelty allowing the expansion of the genus within available niches.

Do ecogeographical rules explain morphological variation in a diverse, Holarctic genus of small mammals?

AbstractAimWe use ecogeographical rules to understand the relationship between biogeography and morphological evolution in Sorex (Linnaeus, 1758) shrews. Specifically, we test for climatic correlations in body size (Bergmann's rule; larger species in colder habitats) and pelage brightness (Gloger's rule; darker species in more humid/warmer habitats).LocationNorth America and Eurasia (Holarctic).TaxonSorex spp. (Mammalia: Soricomorpha: Soricidae).MethodsWe compiled body size data for 51 species of Sorex and measured pelage brightness from museum specimens for 43 species. We sourced bioclimatic data across the geographical range of each species as well as specific to the museum specimen localities. For comparative purposes, we also estimated a Sorex phylogeny using existing sequence data. To test Bergmann's and Gloger's rules, we constructed phylogenetic least squares models considering latitude, altitude, and bioclimatic variables as predictors of interspecific variation in body size and pelage brightness across Sorex. We then performed these tests separately for the Palaearctic and Nearctic lineages.ResultsSorex exhibits wide variation in both body size and pelage brightness. In models of the entire genus and of the Nearctic clade, neither trait is significantly predicted by the variables tested. A decrease in pelage brightness in the Palaearctic clade is significantly predicted by increasing mean annual temperature and annual precipitation, but only when considering climatic data specific to the measured specimen localities.Main conclusionsSorex does not conform to Bergmann's rule. This result aligns with intraspecific studies suggesting Bergmann's rule is less evident in smaller taxa, but it counters others that found support for the rule in North American and European assemblages. Different patterns in pelage evolution across the Nearctic and Palaearctic clades may result from different historical climatic pressures; however, the significance of the relationship between climate and pelage evolution is dependent on the specificity of the climatic data. Sorex may be a useful focal taxon for exploring the relationship between intra‐ and interspecific ecogeographical patterns as well as the relative roles of morphological, behavioural, physiological, and life history characteristics in explaining the ability to persist in climatically challenging environments.

Shallow water ray-finned marine fishes follow Bergmann’s rule

Understanding the interspecific variation in body size across macroclimatic gradients has been of paramount importance to naturalists and biogeographers. Bergmann’s rule, which describes a trend of increasing body size polewards, is arguably the best-known ecogeographical rule in terrestrial environments but remains largely unexplored in the marine realm. In this study we tested Bergmann's rule in marine ray-finned fishes (Pisces, Actinopterygii), analyzing the relationship between body size and latitude in 5662 species. To examine possible underlying mechanisms, we adopted a cross-species approach to evaluate the association of body size with four predictors: Sea Surface Temperature, Net Primary Productivity, Salinity, and Human impact. We analyzed the relationships between body size and environmental and anthropogenic variables building mixed linear models, which considered the taxonomic structure in the data. We conducted complementary analyses dividing the data into five latitudinal bands. Actinopterygii showed a clear Bergmannian pattern, with the largest species observed in temperate regions, being the first global analysis on ray-finned fishes showing a pattern consistent with Bergmann’s rule. Sea Surface Temperature and Net Primary Productivity were the best predictors, in accordance with the time to sexual maturity and resource availability hypotheses. Our analyses based on latitudinal bands showed a differential response of body size to the environment, with temperature, salinity and human impact more strongly associated with size variation at cold environments. These results agree with previous studies on Bergmann’s rule for terrestrial ectothermic, freshwater and marine fishes. Our findings suggest that temperature rise in the ocean and growing human impact may have effects on the distribution of body size, thus altering ecosystem functioning. Fundamental differences often assumed to exist between marine and terrestrial systems are not so evidently reflected in the emergence of large-scale body size gradients.

Ornament Complexity Is Correlated with Sexual Selection: (A Comment on Raia et al., "Cope's Rule and the Universal Scaling Law of Ornament Complexity").

Raia et al. propose that the evolution of the shape and complexity of animal ornaments (e.g., deer antlers) can be explained by interspecific variation in body size and is not influenced by sexual selection. They claim to show that ornament complexity is related to body size by an 0.25-power law and argue that this finding precludes a role for sexual selection in the evolution of ornament complexity. However, their study does not test alternative hypotheses and mismeasures antler shape allometry by omitting much of the published data. We show that an index of sexual selection (sexual size dimorphism) is positively correlated with size-corrected antler complexity and that the allometric slope of complexity is substantially greater than 0.25, contra Raia et al. We conclude that sexual selection and physical constraints both affect the evolution of antler shape.

Phylogenetic analyses of gazelles reveal repeated transitions of key ecological traits and provide novel insights into the origin of the genus Gazella

African bovids are a famous example of a taxonomic group in which the correlated evolution of body size, feeding mode, gregariousness, and social organization in relation to the preferred habitat type has been investigated. A continuum has been described ranging from small-bodied, sedentary, solitary or socially monogamous, forest- or bush-dwelling, browsing species that seek shelter from predation in dense vegetation, to large-bodied, migratory, highly gregarious, grazing taxa inhabiting open savannahs and relying on flight or group-defense behaviors when facing predators. Here, we examined a geographically widespread clade within the Bovidae (the genus Gazella) that shows minimal interspecific variation in body size and asked if we could still uncover correlated changes of key ecological and behavioral traits during repeated transitions from open-land to mountain-dwelling. Our study used a multi-locus phylogeny (based on sequence variation of Cytb and six nuclear intron markers) of all extant members of the genus Gazella to infer evolutionary patterns of key ecological and behavioral traits and to estimate ancestral character states using Bayesian inference. At the base of the Gazella-phylogeny, open plains were inferred as the most likely habitat type, and three independent transitions toward mountain-dwelling were uncovered. Those shifts coincided with shifts from migratory to sedentary lifestyles. Character estimation for group size was largely congruent with movement patterns in that species forming large groups tended to be migratory, while small group size was correlated with a sedentary lifestyle. Evolutionary patterns of two other conspicuous traits (twinning ability vs. exclusive singleton births and hornless vs. horned females) did not follow this trend in the Gazella-phylogeny. Furthermore, we inferred the genus Gazella to have emerged in the Late Miocene to Pliocene (10–3Mya), and estimating ancestral ranges based on a Dispersal–Extinction–Cladogenesis model found the Middle East to be the most likely origin of the genus.

Disentangling the phylogenetic and ecological components of spider phenotypic variation.

An understanding of how the degree of phylogenetic relatedness influences the ecological similarity among species is crucial to inferring the mechanisms governing the assembly of communities. We evaluated the relative importance of spider phylogenetic relationships and ecological niche (plant morphological variables) to the variation in spider body size and shape by comparing spiders at different scales: (i) between bromeliads and dicot plants (i.e., habitat scale) and (ii) among bromeliads with distinct architectural features (i.e., microhabitat scale). We partitioned the interspecific variation in body size and shape into phylogenetic (that express trait values as expected by phylogenetic relationships among species) and ecological components (that express trait values independent of phylogenetic relationships). At the habitat scale, bromeliad spiders were larger and flatter than spiders associated with the surrounding dicots. At this scale, plant morphology sorted out close related spiders. Our results showed that spider flatness is phylogenetically clustered at the habitat scale, whereas it is phylogenetically overdispersed at the microhabitat scale, although phylogenic signal is present in both scales. Taken together, these results suggest that whereas at the habitat scale selective colonization affect spider body size and shape, at fine scales both selective colonization and adaptive evolution determine spider body shape. By partitioning the phylogenetic and ecological components of phenotypic variation, we were able to disentangle the evolutionary history of distinct spider traits and show that plant architecture plays a role in the evolution of spider body size and shape. We also discussed the relevance in considering multiple scales when studying phylogenetic community structure.

Climatic correlates of body size in European tenebrionid beetles (Coleoptera: Tenebrionidae)

Tenebrionidae are one of the largest families of beetles and are known for their adaptations to hot and dry climates. An increase in body size also increases the volume/surface area ratio, which reduces transpiration, and hence water loss. If an increase in body size is an important adaptation in tenebrionids to cope with increasing aridity, we expect a correlation between body size and climatic gradients in the major tenebrionid clades. Alternatively, we can postulate that arid climates do not drive body size evolution, but rather select, from a wider fauna containing species of any size, those that have larger bodies. In this case we expect that drier regions will host faunas that contain, on average, larger species. To test the first hypothesis, we correlated inter-specific body size variation in the main tenebrionid clades with climatic gradients in Europe. We found only weak trends. To test the second hypothesis, we regressed mean body size of European country faunas against climatic characteristics. We found a strong increase in body size in southern faunas experiencing hot and dry climates. Therefore, increase in body size is not a major adaptation in tenebrionid evolution, but climate is an important filtering factor that determines a prevalence of larger species in southern Europe.

Variation in Body Shape across Species and Populations in a Radiation of Diaptomid Copepods

Inter and intra-population variation in morphological traits, such as body size and shape, provides important insights into the ecological importance of individual natural populations. The radiation of Diaptomid species (~400 species) has apparently produced little morphological differentiation other than those in secondary sexual characteristics, suggesting sexual, rather than ecological, selection has driven speciation. This evolutionary history suggests that species, and conspecific populations, would be ecologically redundant but recent work found contrasting ecosystem effects among both species and populations. This study provides the first quantification of shape variation among species, populations, and/or sexes (beyond taxonomic illustrations and body size measurements) to gain insight into the ecological differentiation of Diaptomids. Here we quantify the shape of five Diaptomid species (family Diaptomidae) from four populations each, using morphometric landmarks on the prosome, urosome, and antennae. We partition morphological variation among species, populations, and sexes, and test for phenotype-by-environment correlations to reveal possible functional consequences of shape variation. We found that intraspecific variation was 18-35% as large as interspecific variation across all measured traits. Interspecific variation in body size and relative antennae length, the two traits showing significant sexual dimorphism, were correlated with lake size and geographic location suggesting some niche differentiation between species. Observed relationships between intraspecific morphological variation and the environment suggest that divergent selection in contrasting lakes might contribute to shape differences among local populations, but confirming this requires further analyses. Our results show that although Diaptomid species differ in their reproductive traits, they also differ in other morphological traits that might indicate ecological differences among species and populations.

Cross‐species and assemblage‐based approaches to Bergmann's rule and the biogeography of body size in Plethodon salamanders of eastern North America

Over the past few years, there has been a resurgence of interest in the investigation of spatial patterns in body size over large-scales to explore Bergmann’s rule at different phylogenetic scales across a range of taxa (Blackburn et al. 1999, Gaston et al. 2008). In its original formulation Bergmann’s rule predicts that among closely related endotherms those living in colder regions tend to be larger than those in warmer environments as a result of their reduced surface-to-volume ratios and, hence, better heat conservation (Bergmann 1847). Remarkably, the debate around the validity of this ecogeographical ‘‘rule’’ has long been fostered by the conflation of pattern (increasing body size towards colder regions) and mechanism (heat conservation) (Blackburn et al. 1999). However, there is increasing recognition that the geographical distribution of body size is markedly idiosyncratic and Bergmann’s physiological mechanism cannot explain the observed size clines everywhere (Rodriguez et al. 2008, Diniz-Filho et al. 2009). Accordingly, a differentiation has to be made between pattern and process, so that the latter is not explicitly inherent to the former. In doing such distinction we do not only spur the scientific debate around the validity of the ‘‘rule’’, but the search of alternatives to Bergmann’s original mechanism that are able to account for the observed size clines. Part of the controversy around Bergmann’s rule stems from the seminal papers of Ray (1960) and Lindsey (1966) suggesting that some ectothermic organisms display intra and interspecific body size variation as a response to environmental gradients, which apparently requires alternative explanations to the ones offered for endotherms (Cushman et al. 1993, Ashton and Feldman 2003, OlallaTarraga and Rodriguez 2007). Since then, workers have tried to identify ecological or evolutionary mechanisms accounting for body size clines in ectotherms, but we are far from a consensus on a unifying mechanism. A critical step before searching for underlying mechanisms is indeed examining what the patterns look like in nature. Because Bergmann’s rule was originally formulated for endothermic vertebrates, an abundant number of studies have reported the existence of body size gradients in mammals and birds (Ashton et al. 2000, Ashton 2002a, Rodriguez et al. 2008, Diniz-Filho et al. 2009, Olson et al. 2009), whereas the geographical variation of body size for many ectothermic organisms remains mostly unknown (but see below). Several authors have documented the patterns and explored the causes of body size variation in ectotherms at different levels of biological organization (Ashton 2002b, Belk and Houston 2002, Ashton and Feldman 2003, Blanckenhorn and Demont 2004, OlallaTarraga et al. 2006, Olalla-Tarraga and Rodriguez 2007, Adams and Church 2008). Notwithstanding, the variety of methods and terminologies involved not only prevent a comparison of results from different studies but also indicate the lack of agreement on a single standard approach to investigate Bergmann’s rule. Gaston et al. (2008) recently attempted to clear up part of the confusion by identifying three kinds of approaches to studying spatial patterns in biological traits in general and Bergmann’s rule in particular: intraspecific, interspecific and assemblage-based. They stressed that the distinction between intraand interspecific approaches seems to be clear, but there is some confusion on the methodological differences between interspecific (hereafter ‘‘cross-species’’) and assemblagebased studies. Beyond semantic considerations (e.g. the assemblage-based approach has also been termed as the ‘‘community’’, ‘‘interspecific’’ or ‘‘grid-based’’ approach) (Blackburn and Hawkins 2004, Olalla-Tarraga et al. 2006), the methodological disparities between cross-species and assemblage-based approaches may not be trivial in terms of interpreting patterns and processes (Ruggiero and Hawkins 2006). In our view, this requires particular attention. Ecography 33: 362 368, 2010 doi: 10.1111/j.1600-0587.2010.06244.x # 2010 The Authors. Journal compilation # 2010 Ecography

Interspecific variations in age and size at settlement of 8 emperor fishes (Lethrinidae) at the southern Ryukyu Islands, Japan

Molecular and otolith analyses were conducted for 173 settlement-stage larvae of emperor fishes (family Lethrinidae) collected by light traps at Ishigaki Island, southern Japan, in July and August (summer season), to (1) present diagnostic DNA markers for identification of lethrinid species and (2) compare the size and age at settlement of each species. PCR–RFLP and direct nucleotide sequencing analyses identified 8 species. Size (standard length, SL) at settlement differed significantly between species; Lethrinus ornatus (mean SL ± SD, 12.8 ± 1.5 mm), L. obsoletus (14.2 ± 0.8 mm) and L. harak (15.8 ± 1.6 mm) settled at a smaller size than L. atkinsoni (17.0 ± 1.3 mm), L. genivittatus (17.3 ± 1.0 mm), L. olivaceus (18.1 ± 0.6 mm), L. nebulosus (18.6 ± 4.2 mm), and L. sp.2 reported by Lo Galbo et al. (J Mol Evol 54:754–762, 2002) (21.7 ± 1.4 mm). Age at settlement tends to increase with settlement size; L. obsoletus (mean age ± SD, 25.6 ± 1.2 days), L. atkinsoni (26.1 ± 2.1 days) and L. ornatus (26.3 ± 2.9 days) were younger at settlement than L. nebulosus (28.4 ± 2.1 days), L. harak (29.2 ± 1.7 days), L. olivaceus (29.5 ± 1.0 days), L. genivittatus (30.5 ± 1.7 days) and L. sp.2 (31.0 ± 2.0 days). Although our study showed interspecific variation in body size and age at settlement among 8 lethrinid species, further seasonal replication is necessary to clarify the general patterns.

Climate history, human impacts and global body size of Carnivora (Mammalia: Eutheria) at multiple evolutionary scales

AbstractAim One of the longest recognized patterns in macroecology, Bergmann’s rule, describes the tendency for homeothermic animals to have larger body sizes in cooler climates than their phylogenetic relatives in warmer climates. Here we provide an integrative process‐based explanation for Bergmann’s rule at the global scale for the mammal order Carnivora.Location Global.Methods Our database comprises the body sizes of 209 species of extant terrestrial Carnivora, which were analysed using phylogenetic autocorrelation and phylogenetic eigenvector regression. The interspecific variation in body size was partitioned into phylogenetic (P) and specific (S) components, and mean P‐ and S‐components across species were correlated with environmental variables and human occupation both globally and for regions glaciated or not during the last Ice Age.Results Three‐quarters of the variation in body size can be explained by phylogenetic relationships among species, and the geographical pattern of mean values of the P‐component is the opposite of the pattern predicted by Bergmann’s rule. Partial regression revealed that at least 43% of global variation in the mean phylogenetic component is explained by current environmental factors. In contrast, the mean S‐component of body size shows large positive deviations from ancestors across the Holarctic, and negative deviations in southern South America, the Sahara Desert, and tropical Asia. There is a moderately strong relationship between the human footprint and body size in glaciated regions, explaining 19% of the variance of the mean P‐component. The relationship with the human footprint and the P‐component is much weaker in the rest of the world, and there is no relationship between human footprint and S‐component in any region.Main conclusions Bergmannian clines are stronger at higher latitudes in the Northern Hemisphere because of the continuous alternation of glacial–interglacial cycles throughout the late Pliocene and Pleistocene, which generated increased species turnover, differential colonization and more intense adaptive processes soon after glaciated areas became exposed. Our analyses provide a unified explanation for an adaptive Bergmann’s rule within species and for an interspecific trend towards larger body sizes in assemblages resulting from historical changes in climate and contemporary human impacts.

Geographic body size gradients in tropical regions: water deficit and anuran body size in the Brazilian Cerrado

A recent interspecific study found Bergmann's size clines for Holarctic anurans and proposed an explanation based on heat balance to account for the pattern. However, this analysis was limited to cold temperate regions, and exploring the patterns in warmer tropical climates may reveal other factors that also influence anuran body size variation. We address this using a Cerrado anuran database. We examine the relationship between mean body size in a grid of 1° cells and environmental predictors and test the relative support for four hypotheses using an AIC‐based model selection approach. Also, we considered three different amphibian phylogenies to partition the phylogenetic and specific components of the interspecific variation in body size using a method analogous to phylogenetic eigen vector regression (PVR). To consider the potential effects of spatial autocorrelation we use eigenvector‐based spatial filters. We found the largest species inhabiting high water deficit areas in the northeast and the smallest in the wet southwest. Our results are consistent with the water availability hypothesis which, coupled with previous findings, suggests that the major determinant of interspecific body size variation in anurans switches from energy to water towards the equator. We propose that anuran body size gradients reflect effects of reduced surface to volume ratios in larger species to control both heat and water balance.

Determinants and consequences of interspecific body size variation in tetraphyllidean tapeworms

Tetraphyllidean cestodes are cosmopolitan, remarkably host specific, and form the most speciose and diverse group of helminths infecting elasmobranchs (sharks, skates and rays). They show substantial interspecific variation in a variety of morphological traits, including body size. Tetraphyllideans represent therefore, an ideal group in which to examine the relationship between parasite body size and abundance. The individual and combined effects of host size, environmental temperature, host habitat, host environment, host physiology, and host type (all likely correlates of parasite body size) on parasite length were assessed using general linear model analyses using data from 515 tetraphyllidean cestode species (182 species were included in analyses). The relationships between tetraphyllidean cestode length and intensity and abundance of infection were assessed using simple linear regression analyses. Due to the contrasting morphologies between shark and batoid hosts, and contrasting physiologies between sharks of the Lamnidae family and other sharks, analyses were repeated in different subsets based on host morphology and physiologies ("sharks" vs. batoids) to determine the influence of these variables on adult tetraphyllidean tapeworm body size. Results presented herein indicate that host body size, environmental temperature and host habitat are relatively important variables in models explaining interspecific variations in tetraphyllidean tapeworm length. In addition, a negative relationship between tetraphyllidean body size and intensity of infection was apparent. These results suggest that space constraints and ambient temperature, via their effects on metabolism and growth, determine adult tetraphyllidean cestode size. Consequently, a trade-off between size and numbers is possibly imposed by external forces influencing host size, hence limiting physical space or other resources available to the parasites.