Cranial Morphology Dynamics in a Founder Population of North American Wolves

Vucetich, J; Peterson, Rolf; Sadhasivan, G

In this morphometric study, skulls of 34 adult gray wolves (Canis lupus lycaon) from Isle Royale and southern Ontario were characterized by measurements of 54 skull traits. The Isle Royale wolf population was founded from the Ontario wolf population in the late 1940s, has remained reproductively isolated ever since, and is known to have lost significant genetic diversity. Using multivariate morphological data, we tested the following hypotheses regarding the evolutionary dynamics of founder effects in wild populations: 1) Mean size of Isle Royale wolves will be larger than ONT wolves because of consistently large prey size; 2) the Isle Royale wolf population will possess less morphological variance in accordance with the hypothesis that genetic disparity is related to phenotypic disparity; 3) Isle Royale population, suffering from loss of genetic diversity, will possess greater fluctuating asymmetry (FA) due to loss of developmental stability. There is little statistical evidence suggesting that Isle Royale wolves were larger. Isle Royale wolves possessed much greater morphological variance in some traits, conforming with some theoretical models and experiments, but generally contrary to conventional understanding of population genetics. Isle Royale wolves did not exhibit greater FA, and we question the use of FA as an index of developmental instability arising from loss of genetic variability.