Body size divergence promotes post-zygotic reproductive isolation in centrarchids

Question: Does morphological divergence accelerate the evolution of post-zygotic reproductive isolation? Data incorporated: Estimates of divergence time between species, body size divergence, and hybrid embryo viability in the freshwater fish family Centrarchidae. Method of analysis: We estimated the age of each node in the phylogeny using penalized likelihood, calibrated with multiple fossil dates. We then regressed the average body size and hybrid viability at each phylogenetic node against the node’s age. Residuals from these regressions were compared to test for time-independent relationships between body size divergence and post-zygotic reproductive isolation. Conclusions: Morphologically divergent species tend to experience stronger post-zygotic reproductive isolation than expected given their age. These results suggest that morphological divergence between species is associated with an accelerated accumulation of genetic incompatibilities, and highlight one potential avenue by which ecological divergence may facilitate speciation.