Testing the link between phenotypic evolution and speciation: an integrated paleontological and phylogenetic analysis

1. The punctuated equilibrium model predicts that phenotypic change is concentrated into pulses associated with speciation, with little change otherwise accruing in established lineages. Paleontological tests of this model have generally lacked an adequate phylogenetic and modeling framework, whereas tests relying on extant populations lack direct constraints on the evolutionary dynamics within lineages. 2. The present study extends a modeling approach developed in comparative studies and applies it to a clade with a rich fossil record, the deep-sea ostracode genus Poseidonamicus. Using a phylogenetic framework and an independent set of shape traits plus body size, a model was fit that allows estimation of anagenetic (within-lineage) evolution, cladogenetic (speciational) change, and geographic variation within species. 3. Maximum-likelihood parameter estimates suggested dominantly speciational change for only one or two shape traits, depending on model assumptions. For the remaining sh...