Meeting Abstract

103.3  Wednesday, Jan. 7  Evolution of jaw size and shape in New World tree squirrels SWIDERSKI, D.L.*; ZELDITCH, M.L.; Univ. of Michigan, Ann Arbor; Univ. of Michigan, Ann Arbor dlswider@umich.edu

Animals that differ by more than an order of magnitude in body mass might be expected to also differ in shape particularly in the shapes of functionally relevant structures like the jaws. The lineage of New World tree squirrels encompasses both 1,000 g. Sciurus niger and 100 g. Microsciurus alfari. On average, large and small members of Sciurus (e.g., S. niger vs. 400 g. S. deppei) do differ in the size and shape of the mandible, but the shape differences are slight and do not extrapolate to species of Microsciurus. Larger differences can be found among species of similar size and different ecologies. Compared to the North American S. niger, the Amazonian S. spadiceus has a deeper incisor and ramus, but a shorter molar row and smaller angular process. Similar differences distinguish S. granatensis and S. deppei, but a different combination of traits distinguishes these smaller Sciurus from similar sized Tamiasciurus hudsonicus. This diversity of morphologies and inferred evolutionary trajectories is not consistent with isometric scaling, or with a single allometric trend, but it is consistent with recently described patterns of variation in jaws of S. niger.