Data from: Morph-specific selection pressures drive phenotypic divergence in a color polymorphic bird

Abstract - There is a long tradition in using genetically based color polymorphisms in natural populations to study selection, gene flow, and other evolutionary processes. However, although there is increasing evidence for continuous variation within discrete morphs, it remains unclear how this affects selective dynamics and the persistence of color polymorphisms. Here we leverage 43 years of plumage color data from a Finnish population of tawny owls (Strix aluco) to show that two color morphs (gray and brown) each host large intra-morph continuous variation in pigmentation, which has diverged over the years: while the brown morph is on a steady trajectory toward more intense plumage pigmentation, the gray morph recently and abruptly shifted toward less pigmented plumage. Our results suggest that the drivers behind these dynamics are morph-specific: lower plumage pigmentation in the gray morph appears to be shaped by selection during periods of extreme winter, resulting in reduced standing genetic variation and thus potential to respond to selection. In the brown morph, we found an interaction between reproductive success, plumage coloration and timing of breeding, and stronger environmental effects during the pre-fledging period. Together, these findings suggest that intra-morph variation determines each morph’s response to selection pressures differently, potentially influencing their ability to track shifting phenotypic optima. Our work highlights the relevance of phenotypic variation within genetically discrete morphs for evolutionary processes, including how populations respond and adapt to environmental change. Dataset - This repository includes all data necessary to reproduce the results and figures from the paper. How to use - Check the Readme file.