Meeting Abstract

LBS3.2  Friday, Jan. 4  Constraints and the scaling of evolutionary rates HARMON, LJ; Univ. of Idaho lukeh@uidaho.edu

The evolutionary dynamics of phenotypic change provide key insights into macroevolutionary processes. Analyses ranging from experimental evolution to phenotypic change in the paleontological record show that net rates of evolutionary change are greatest over the shortest time scales. Possible explanations for this pattern invoke constraints. Constant constraints within lineages, such as stabilizing selection or developmental limits to adaptation, will be have cumulative effects that are apparent only over long time scales. Alternatively, under an adaptive radiation model, constraints becoming stronger as organisms near their phenotypic optima and/or ecological space becomes filled with competitors, slowing the rate of evolution. Here we explicitly test these models and show that, across a wide range of animal taxa, models of constant constraints provide the best fit to body size evolution. These within-lineage constraints may link short-term evolutionary radiations and long-term dynamics of macroevolutionary change.