Lack of adaptation from standing genetic variation despite the presence of putatively adaptive alleles in introduced sweet vernal grass (Anthoxanthum odoratum).

Population genetic theory predicts that the availability of appropriate standing genetic variation should facilitate rapid evolution when species are introduced to new environments. However, few tests of rapid evolution have been paired with empirical surveys for the presence of previously identified adaptive genetic variants in natural populations. In this study, we examined local adaptation to soil Al toxicity in the introduced range of sweet vernal grass (Anthoxanthum odoratum), and we genotyped populations for the presence of Al tolerance alleles previously identified at the long-term ecological Park Grass Experiment (PGE, Harpenden, UK) in the species native range. We found that markers associated with Al tolerance at the PGE were present at appreciable frequency in introduced populations. Despite this, there was no strong evidence of local adaptation to soil Al toxicity among populations. Populations demonstrated significantly different intrinsic root growth rates in the absence of Al. This suggests that selection on correlated root growth traits may constrain the ability of populations to evolve significantly different root growth responses to Al. Our results demonstrate that genotype-phenotype associations may differ substantially between the native and introduced parts of a species range and that adaptive alleles from a native species range may not necessarily promote phenotypic differentiation in the introduced range.