Strong evidence for positive and negative correlational selection revealed by recreating ancestral variation
Waterman, Robin et al. (2022), Strong evidence for positive and negative correlational selection revealed by recreating ancestral variation, Dryad, Dataset, https://doi.org/10.5061/dryad.02v6wwq6g
The study of adaptation helps explain the incredible diversity of life and predict future evolution. Yet the process of adaptation can be difficult to observe due to limited phenotypic variation in contemporary populations. Furthermore, in plants, the scarcity of male fitness estimates has made it difficult to both understand adaptation and evaluate theoretical predictions on sexual conflict. We addressed both issues in our study of two anther position traits in wild radish (Raphanus raphanistrum): anther exsertion (long filament length − corolla tube length) and anther separation (long filament length − short filament length). These traits affect pollination efficiency and are of particular interest due to the unusually high correlations among their component traits. We measured selection in the field through both male and female fitness on wild radish plants from populations artificially selected to recreate ancestral variation in either anther exsertion or separation. We found strong evidence for stabilizing selection on anther exsertion and disruptive selection on anther separation, indicating positive and negative correlational selection on the component traits. Intermediate levels of exsertion are likely an adaptation to best contact small bees, but the function of anther separation is less clear. Finally, we found little evidence for conflicts between male and female function. Future studies in other species with multiple stamen types and mechanistic studies investigating pollen placement on pollinators should elucidate the adaptive function of anther separation.
National Science Foundation, Award: DEB 9903880
National Science Foundation, Award: DEB 0108354
National Science Foundation, Award: DBI 0638591
National Science Foundation, Award: DEB 0919452