biomechanical consequences of rapid evolution in the polar bear lineage生物力学北极熊的快速进化谱系的后果.pdfVIP

Biomechanical Consequences of Rapid Evolution in the Polar Bear Lineage 1 2 3 1 1 Graham J. Slater *, Borja Figueirido , Leeann Louis , Paul Yang , Blaire Van Valkenburgh ´ 1 Department of Ecology and Evolutionary Biology, University of California Los Angeles, Los Angeles, California, United States of America, 2 Departamento de Ecologıa y ´ ´ ´ ´ ´ Geologıa, Area de Paleontologıa, Facultad de Ciencias, Universidad de Malaga, Campus Universitario de Teatinos, Malaga, Spain, 3 Cornell University Museum of Vertebrates, Ithaca, New York, United States of America Abstract The polar bear is the only living ursid with a fully carnivorous diet. Despite a number of well-documented craniodental adaptations for a diet of seal flesh and blubber, molecular and paleontological data indicate that this morphologically distinct species evolved less than a million years ago from the omnivorous brown bear. To better understand the evolution of this dietary specialization, we used phylogenetic tests to estimate the rate of morphological specialization in polar bears. We then used finite element analysis (FEA) to compare the limits of feeding performance in the polar bear skull to that of the phylogenetically and geographically close brown bear. Results indicate that extremely rapid evolution of semi-aquatic adaptations and dietary specialization in the polar bear lineage produced a cranial morphology that is weaker than that of brown bear