TESTING BERGMANN?S RULE AND ROSENZWEIG HYPHOTESIS WITH CRANIOMETRIC STUDIES OF THE SOUTH AMERICAN SEA LION

SEPÚLVEDA, M.; OLIVA, D.; DURAN, R.; URRA, A.; PEDRAZA, SUSANA NOEMI; MAJLUF, P.; GOODALL, R. N. P.; CRESPO, ENRIQUE A.

OECOLOGIA

SPRINGER

Lugar: Berlin; Año: 2013 vol. 171 p. 809 - 817

0029-8549

We tested the validity of Bergmann?s rule and Rosenzweig?s hypothesis through the analysis of the geographical variation of the skull size of Otaria flavescens along the entire distribution range of the species (except Brazil). We quantified the size of 606 adult South American sea lion skulls, measured in seven localities of Peru, Chile, Uruguay, Argentina and the Falkland/Malvinas Islands. Geographical and environmental variables included latitude, longitude, and monthly minimum, maximum and mean air and ocean temperatures. We also included information on fish landings as a proxy of productivity. Males showed a positive relationship between condylobasal length (CBL) and latitude, and between CBL and the six temperature variables. On the contrary, females showed a negative relationship between CBL and the same variables. Finally, female skull size showed a significant and positive correlation with productivity, while males did not show any relation with this variable. The body size of males conformed to Bergmann?s rule, with larger individuals in southern localities of South America. Females followed the converse of Bergmann?s rule at the intraspecific level, but showed a positive a significant relation with productivity, thus supporting Rosenzweig?s hyphotesis. Differences in the factors that drive body size in females and males may be explained by their differences in life history strategies. Our analyses demonstrate that latitude and temperature are not exclusive in explaining spatial variation in body size, but other factors such as food availability are important as well in explaining the ecogeographical patterns found in O. flavescens.