Seasonal Migration, Speciation, and Morphological Convergence in the Genus Catharus (Turdidae)

Abstract

Abstract The effects of seasonal migration on evolutionary change within lineages is poorly understood, in terms of both differentiation (cladogenesis) and specialization (anagenesis). Regarding differentiation, two contradictory hypotheses exist: Seasonal migration counters differentiation; or it can stimulate differentiation by exposing lineages to new environments. Regarding specialization, the morphological consequences of a migratory life history have not been well explored. We examined these issues by reconstructing morphological and molecular phylogenies of the genus Catharus (Turdidae), a group of forest-dwelling, New World thrushes traditionally considered to include a small “species flock” of Nearctic-Neotropic migrants. DNA sequence data (2,920–3,027 base pairs) do not support traditional taxonomy, and morphological characters conflicted with these data. Results suggest that long-distance seasonal migration arose independently four times in Catharus sensu lato (including Hylocichla mustelina). Correlated morphological evolution occurred among several characters in these lineages, and these shared traits may stem from ecological conditions in Nearctic forests. Migración Estacional, Especiación y Convergencia Morfológica en el Género Catharus (Turdidae)