The effect of historical legacy on adaptation: do closely related species respond to the environment in the same way?
- evolutionary history;
- structural equation model
The many documented examples of parallel and convergent evolution in similar environments are strong evidence for the role of natural selection in the evolution of trait variation. However, species may respond to selection in different ways; idiosyncrasies of their evolutionary history may affect how different species respond to the same selective pressure. To determine whether evolutionary history affects trait-environment associations in a recently diverged lineage, we investigated within-species trait-environment associations in the white proteas, a closely related monophyletic group. We first used manovas to determine the relative importance of shared response to selection, evolutionary history and unique responses to selection on trait variation. We found that on average, similar associations to the environment across species explained trait variation, but that the species had different mean trait values. We also detected species-specific associations of traits with the environmental gradients. To identify the traits associated uniquely with the environment, we used a structural equation model. Our analysis showed that the species differed in how their traits were associated with each of the environmental variables. Further, in the cases of two root traits (root mass and root length/mass ratio), two species differed in the direction of their associations (e.g. populations in one species had heavier roots in warmer areas, and populations in the other species had lighter roots in warmer areas). Our study shows that even in a closely related group of species, evolutionary history may have an effect on both the size and direction of adaptations to the environment.
1Of course, it's not really my Protea. It's one that Jane and Rachel did all of the work for and that they were kind enough to let me help with. It's also not the only paper I've been part of in the last year and a half. It's only the last Protea paper of which I've been part.
2By “in the pipeline” I mean that one has been accepted pending very minor revisions in Oecologia and that we're less than two weeks away from submitting the second to PLoS One.