Evolution in novel environments: do restored prairie populations experience strong selection?

When populations colonize new habitats, they are likely to experience
novel environmental conditions, and as a consequence may experience strong
selection. While selection and the resulting evolutionary responses may
have important implications for establishment success in colonizing
populations, few studies have estimated selection in such scenarios. Here
we examined evidence of selection in recently established plant
populations in two prairie restorations in close proximity (< 15 km
apart) using two approaches: 1) we tested for evidence of past selection
on a suite of traits in two Chamaecrista fasciculata populations by
comparing the restored populations to each other and their shared source
population in common gardens to quantify evolutionary responses and 2) we
measured selection in the field. We found evidence of past selection on
flowering time, specific leaf area, and root nodule production in one of
the populations, but detected contemporary selection on only one trait
(plant height). Our findings demonstrate that while selection can occur in
colonizing populations, resulting in significant trait differences between
restored populations in less than 6 generations, evolutionary responses
differ across even nearby populations sown with the same source
population. Because contemporary measures of selection differed from
evolutionary responses to past selection, our findings also suggest that
selection likely differs over the early stages of succession that
characterize young prairies.