Big in the tropics: Ecogeographical clines in peccary size reveal the converse of Bergmann’s rule

Abstract

AbstractAimBergmann's rule is an ecogeographical rule that describes a negative relationship between body size and temperature. Here, we used a multivariate measure of skull size (centroid size) as a proxy for body size to test the influence of temperature, precipitation, elevation, human influence and competition on size in Dicotyles tajacu and Tayassu pecari.LocationAmerican tropics and sub‐tropics.TaxonTayassuidae.MethodsUsing geometric morphometric methods, we measured 426 adult skulls of both peccary species from 174 different localities south of the equator and 83 in the north. We explored the effects of temperature, precipitation, altitude and human influence, controlling for spatial autocorrelation, using ordinary least squares models and the Akaike information criterion. Size differences where the species occur allopatrically or sympatrically, where competition could be a factor, were investigated using ANCOVA models.ResultsWe found that peccaries were larger in the tropics. Temperature and precipitation explained the size variation of both peccaries in the southern hemisphere, whereas human influence is a predictor of size only for T. pecari. Size variation of northern D. tajacu is mainly explained by elevation and temperature. Tayassu pecari is consistently larger than D. tajacu in both hemispheres. Peccaries did not exhibit significant shifts in either rate of change in size or size–latitude relationships between allopatric and sympatric areas.Main conclusionsGeographical variation in size of these peccaries does not support Bergmann's rule. In the tropics, precipitation and human influence appear to exert strong selective pressures on body size of peccaries, whose resource utilization patterns are shaped by group living. Size differences of the two species across the continents may contribute to their stable coexistence via interference rather than exploitative competition.