Meeting Abstract

P1.200  Saturday, Jan. 4 15:30  Diversification, species richness and rates of morphological evolution: Squirrel jaw morphology ZELDITCH, M.L*; LI, J.; TRAN, L.A.P.; SWIDERSKI, D.L.; Univ. of Michigan, Ann Arbor zelditch@umich.edu

Whether rates of diversification and morphological evolution are related is a central question in evolutionary biology. They could be related when speciation and morphological divergence are both driven by ecological opportunity. But the relationship between them might be weak when speciation is driven by geographical opportunity and species either track their habitat or are adapted to widespread environments. Even when lineage accumulation and morphological evolution are related, that relationship could be complicated by diversity-dependence of speciation rate or morphological evolution. In particular, when species diversification rates are bounded, species richness rather than speciation rate might be a better predictor of morphological evolutionary rates. Similarly, when morphological evolution is also bounded, disparity may be more strongly related to lineage accumulation than are evolutionary rates. To examine the relationships between rates of diversification, species richness, rates of morphological evolution and morphological disparity we analyze jaw shape and size in 168 species of squirrels (Sciuridae), representing 17 monophyletic groups. We find some correlations that are high but non-significant, especially between species richness and two measures of accumulation of size and shape differences: disparity and evolutionary rates. We also find high but non-significant correlations of species richness with clade age and evolutionary rate. The correlations are not significant because of outliers. In Sciuridae, the disparity in species-poor clades is highly variable, while species-rich clades are among the least disparate. Clades that are both species rich and very disparate are unusual.