Life on the edge: carnivore body size variation is all over the place

Abstract

Evolutionary biologists have long been fascinated by both the ways in which species respond to ecological conditions at the edges of their geographic ranges and the way that species' body sizes evolve across their ranges. Surprisingly, though, the relationship between these two phenomena is rarely studied. Here, we examine whether carnivore body size changes from the interior of their geographic range towards the range edges. We find that within species, body size often varies strongly with distance from the range edge. However, there is no general tendency across species for size to be either larger or smaller towards the edge. There is some evidence that the smallest guild members increase in size towards their range edges, but results for the largest guild members are equivocal. Whether individuals vary in relation to the distance from the range edges often depends on the way edge and interior are defined. Neither geographic range size nor absolute body size influences the tendency of size to vary with distance from the range edge. Therefore, we suggest that the frequent significant association between body size and the position of individuals along the edge-core continuum reflects the prevalence of geographic size variation and that the distance to range edge per se does not influence size evolution in a consistent way.

Environmental Domains and Range-Limiting Mechanisms: Testing the Abundant Centre Hypothesis Using Southern African Sandhoppers

“…Alternatively, individuals tend to be larger towards higher latitudes. Populations distributed along a North-South axis therefore tend to show larger individuals near one of the edges rather than the core [66], [67]. Our results, confirmed this last tendency of larger size at higher latitudes, with A. quadrispinosa showing a ramped south distribution of size.…”

“…[15]). Some studies suggest that larger individuals occur at the core of the range (in agreement with the ACH) where the habitat is most suitable [11], [12], [66]. Alternatively, individuals tend to be larger towards higher latitudes.…”

Body size clines in the European badger and the abundant centre hypothesis

“…Furthermore, previous studies have shown a positive fit between body size variation and latitude in badgers (Meiri & Dayan, 2003; Meiri et al. , 2004), although Meiri et al. (2009) found some support for the ACH.…”

“…, 2005). Only recently, Meiri et al. (2009) showed that the relationship between body size variation and position within the range (i.e.…”

Geographic range limits of species

“…In most cases, the extent to which these are general patterns, or the circumstances under which they do and do not emerge, remain poorly understood. In this special issue, in exploring the case of spatial variations in body size using the carnivores as a study system, Meiri et al (2009) document the complexity that can arise and the importance of examining large numbers of species. Likewise, drawing on a vast dataset for species of trees in the eastern USA, Purves (2009) examines the, from an empirical perspective surprisingly neglected, pattern of change in demographic rates between the core and limit of geographic ranges.…”