Lama guanicoe (Müller 1776) body size in continental Patagonia and Tierra del Fuego

L'HEUREUX G. L

Mendoza, Mendoza

Congreso; 10th International Mammalogical Congress; 2009

Center for Science & Technology - CCT CONICET Mendoza (CRICYT), National Council of Science and Technology - CONICET, Institute for Aridlands Research - IADIZA, Biodiversity Research Group - GiB, International Federation of Mammalogists - IFM, Sociedad Ar

The estimation of body size is a relevant issue in many ecological, adaptive, and microevolutionary studies of mammals. Body size cannot be directly estimated on paleontological or modern osseous remains, but in a derivative way using measurements taken on bones whose dimensions are correlated with overall body size. In this paper we evaluate appendicular bone size differences between modern regional samples of Lama guanicoe (Müller 1976) (guanaco), the widest distributed camelid in South America. The whole sample was composed by 120 fully fused individuals drawn from three different guanaco populations from continental and insular Patagonia (Río Negro, Santa Cruz, and Tierra del Fuego), covering the latitudinal strip between 40° and 54° south lat. One hundred and sixty four humerus, 146 radioulnae, 124 femora, and 214 metapodials were measured. The obtained result show that specimens from Tierra del Fuego (54°S) are, on average, bigger than those from Santa Cruz (50-52°S) and that, in turn, the latter are bigger than those from Río Negro (40°S). Statistically, this latitudinal variation is significant for distal epiphises of long bones and for metapodials. The observed pattern is consistent with biogeographic generalizations like the Bergmann’s rule. However it is contended that factors other than local adaptation and limited rates of gene flow can account for at least part of the observed differences. Among these factors we may consider differential competition with sheeps during the last 100 years, higher predation pressure in contintental Patagonia than in Tierra del Fuego, and the so-called “island rule” that operated since the complete separation of Tierra del Fuego from the continent after the opening of the Magellan Strait during the Early Holocene..