Biometrics of Iberian DippersCinclus cinclus: Environmental Sources of Among-Population Variation

Abstract

Biometry of Iberian Dippers Cinclus cinclus has typically been addressed from a geographic perspective, often considering small local populations. In this work, we explored environmental correlates of among-population phenotypic variation in Dipper morphology throughout Iberia. We tested for effect of river slope, altitude, temperature and precipitation (summarized using Principal Component Analyses, PCA) on absolute and relative (controlling for tarsus length) wing length and tarsus length. We used data of 222 Dippers captured from 35 rivers in eight breeding areas in N and S Iberia. All biometric variables were larger for older birds and males, though tarsus length was not affected by age. Wing length was longer in S Iberia, even when controlling for tarsus length, All biometric variables co-varied negatively with one of the PCA components of abiotic factors, owing to large-scale environment differences between N and S Iberia (zone). The abiotic factors predicted mean tarsus length of birds within zones, with tarsus increasing with increasing river slope and decreasing temperatures and precipitation. Furthermore, Dippers from S Iberia were not larger but had longer absolute and relative wings than those from N Iberia. Altogether, these findings imply that the morphological diversification of Iberian Dippers is affected by the environment and that body size-wing length allometric relationship differs between N and S Iberia.