Ecogeographic variation of body size in the spectacled salamanders (Salamandrina): influence of genetic structure and local factors

Abstract

Aim The patterns and causes of ecogeographical body size variation in ectotherms remain controversial. In amphibians, recent genetic studies are leading to the discovery of many cryptic species. We analysed the relationships between body size and climate for a salamander (Salamandrina) that was recently separated into two sibling species, to evaluate how ignoring interspecific and intraspecific genetic structure may affect the conclusions of ecogeographical studies. We also considered the potential effects of factors acting at a local scale.Location Thirty-four populations covering the whole range of Salamandrina, which is endemic to peninsular Italy.Methods We pooled original data and data from the literature to obtain information on the snout-vent length (SVL) of 3850 Salamandrina females; we obtained high-resolution climatic data from the sampled localities. We used an information-theoretic approach to evaluate the roles of climate, genetic features (mitochondrial haplogroup identity) and characteristics of aquatic oviposition sites. We repeated our analyses three times: in the first analysis we ignored genetic data on intraspecific and interspecific variation; in the second one we considered the recently discovered differences between the two sibling species; in the third one we included information on intraspecific genetic structure within Salamandrina perspicillata (for Salamandrina terdigitata the sample size was too small to perform intraspecific analyses).Results If genetic information was ignored, our analysis suggested the existence of a relationship between SVL and climatic variables, with populations of large body size in areas with high precipitation and high thermal range. If species identity was included in the analysis, the role of climatic features was much weaker. When intraspecific genetic differences were also considered, no climatic feature had an effect. In all analyses, local factors were important and explained a large proportion of the variation; populations spawning in still water had a larger body size.Main conclusions An imperfect knowledge of species boundaries, or overlooking the intraspecific genetic variation can strongly affect the results of analyses of body size variation. Furthermore, local factors can be more important than the large-scale parameters traditionally considered, particularly in species with a small range.

Sex‐dependent implications of primary productivity and conspecific density on geographical body size variation in a newt: disentangling local, large scale and genetic factors

“…Mean SVL is commonly used in studies on geographical body size variation of urodele amphibians at the intraspecific level (e.g. Ficetola et al ., ; Romano & Ficetola, ), and hence results are comparable with previous findings. We also performed Pearson's correlations between mean SVL of females and males and assessed the sexual dimorphism in body size by fitting a linear mixed model with mean SVL as dependent variable, sex as a fixed factor, and population as a random factor.…”

“…Finally, we used the Akaike information criterion (AIC) (Burnham & Anderson, ) for model selection to corroborate the results of PLSR models (Galván & Rey Benayas, ), and provide results comparable with previous studies (e.g. Ficetola et al ., ; Romano & Ficetola, ). We ran generalized‐linear models (GLM) with predictors with VIP > 1 and fitted all possible models, and calculated their second‐order AIC (AICc) and weight AIC (AICw) scores.…”

Courtship behaviour, mating season and male sexual interference in Salamandrina perspicillata (Savi, 1821)

“…In recent years, some aspects of the natural history, distribution, biology, biogeography, ecology and behaviour of Salamandrina, and of S. perspicillata in particular, have been elucidated (e.g., Della Rocca, Vignoli and Bologna, 2005;Angelini, Antonelli and Utzeri, 2008;Romano, Forcina and Barbanera, 2008;Romano and Ficetola, 2010). However, knowledge is still very fragmented with regard to many aspects of their reproductive behaviour (in particular courtship stages C and D; see Salthe, 1967, and mating season in the wild).…”

Ecological correlates and determinants in the geographical variation of deer morphology

“…However, these rules do not exclude other eVects. Size patterns can covary with multiple factors (Romano and Ficetola 2010). When multiple factors are selected as explanatory variables for body size variation, we may gain insight into the underlying cause of the variation.…”

“…Thus, comprehensive studies that simultaneously analyze multiple factors are required. However, such studies have not been performed for ungulates (see the following studies for other taxonomic groups: Yom-Tov and GeVen 2006;Meiri et al 2007;Blois et al 2008;Romano and Ficetola 2010).…”