Broad‐scale patterns of body size in squamate reptiles of Europe and North America

Abstract

Aim To document geographical interspecific patterns of body size of European and North American squamate reptile assemblages and explore the relationship between body size patterns and environmental gradients. Location North America and western Europe. Methods We processed distribution maps for native species of squamate reptiles to document interspecific spatial variation of body size at a grain size of 110 × 110 km. We also examined seven environmental variables linked to four hypotheses possibly influencing body size gradients. We used simple and multiple regression, evaluated using information theory, to identify the set of models best supported by the data. Results Europe is characterized by clear latitudinal trends in body size, whereas geographical variation in body size in North America is complex. There is a consistent association of mean body size with measures of ambient energy in both regions, although lizards increase in size northwards whereas snakes show the opposite pattern. Our best models accounted for almost 60% of the variation in body size of lizards and snakes within Europe, but the proportions of variance explained in North America were less than 20%. Main conclusions Although body size influences the energy balance of thermoregulating ectotherms, inconsistent biogeographical patterns and contrasting associations with energy in lizards and snakes suggest that no single mechanism can explain variation of reptile body size in the northern temperate zone.

Species richness, hotspots, and the scale dependence of range maps in ecology and conservation

“…At coarser spatial resolutions, the spatial richness patterns generated by rangemap and atlas data become increasingly congruent (Figs. [3][4][5], with the correlation coefficient between the two spatial patterns Ն0.97 for both regions at 2°resolution. These results parallel the findings of Graham and Hijmans (17), who found a higher correlation between richness maps created using different methodologies at coarser resolutions.…”

“…A growing number of studies is concerned with continentalto-global scale patterns of biodiversity (1)(2)(3)(4) or summary patterns of species' ecological traits such as body size (5) and range size (6,7). At similarly broad scales, many conservation studies are examining the richness of rare or threatened taxa (8)(9)(10)(11) and their distribution in relation to existing reserve networks (12)(13)(14).…”

A test of Allen's rule in ectotherms: the case of two south American Melanopline Grasshoppers (Orthoptera: Acrididae) with partially overlapping geographic ranges

“…Precipitation data were also taken from Cramer and Leemans (2001). A further hypothesis pertaining body size clines is that of Rosenzweig (1968), who proposes that body size is positively correlated with primary productivity and with some correlates as actual (AET) and potential (PET) evapotranspiration (Olalla-Tárraga et al 2006. AET, an estimator of primary productivity (calculated by the Thornthwaite formula), PET, a measure of ambient energy (calculated by the Priestley-Taylor equation), and Water Balance (WB) were obtained for each locality.…”

Untangling Intra- and Interspecific Effects on Body Size Clines Reveals Divergent Processes Structuring Convergent Patterns in Anolis Lizards

“…The pattern was described as an interspecific cline manifested in homeothermic animals (Bergmann 1847;James 1970); the proposed mechanism underlying this pattern was the conservation of heat through a smaller surface area-to-volume ratio in largerbodied animals. More recently, however, the rule (sensu lato) has been extended to include intraspecific size clines and ectothermic organisms, especially squamates (Rensch 1938;Ashton and Feldman 2003;de Queiroz and Ashton 2004;Olalla-Tárraga et al 2006) and insects (Chown and Gaston 2010;Shelomi 2012). As empirical studies accumulated, new interpretations of the mechanisms underlying Bergmann's cline emerged.…”