Evolution was once assumed to only occur slowly over long time scales, but many recent studies have found that rapid adaptation (adaptation that occurs on an ecological timescale) can occur across a wide range of taxa and in many biological contexts, and can potentially alter the outcomes of ecological interactions and ecosystem-level processes. Rapid adaptation is also hypothesized to influence the establishment of species in new habitats, as evolutionary theory predicts that rapid adaptation can have important demographic consequences for colonizing populations. However, there is little empirical evidence to support this prediction. I combined a reciprocal transplant experiment with a resurrection experiment to compare populations of the annual legume Chamaecrista fasciculata planted 6 years ago in replicated prairie restorations to each other and to their original source population. I examined whether evolutionary changes had occurred in these recently established populations, whether these changes were predicted by estimates of selection, and whether plant populations showed signs of local adaptation.
Results/Conclusions
I found evidence for evolutionary change in recently established populations of Chamaecrista, with extant populations differing in phenology, root nodule production, and height from their original source population. These changes were for the most part predicted by estimates of selection, with extant Chamaecrista populations showing shifts in trait values corresponding to the direction of selection. Extant populations also showed sign of local adaptation, with higher fitness than the original source population. This suggests that rapid adaptation can occur in recently established populations; further analysis will indicate whether this adaptation influences population growth rates in ways that affect establishment.