Local adaptation and the consequences of being dislocated for coevolved enemies

Plants are being moved across the globe at an increasing rate both within and outside their current distributional range. Research in the past few decades has focuesd intensely on invasive exotic plant species that are moved outside their distributional range. Such invaders can have dramatic impacts on indigenous communities through altered biotic interactions with competitors, mutualists, and antagonists. But likewise, translocation within the distributional range exposes nonnative plant genotypes to interactions with nonlocally coevolved competitors, mutualists, and antagonists. A major concern in restoration ecology is that translocation of seeds from foreign seed sources introduces plant genotypes that are maladapted to local conditions and subsequently hybridize with locally adpated conspecifics, decreasing mean population fitness. Interestingly, while local adaptation of plants to their abiotic environment is well documented, warranting the concern, studies of plant local adaptation to their biotic environment have shown less unequivocal results, ranging from local adpation to local maladaptation for interactions with antagonists. A large reciprocal transplant field study by Cremieux et al., reported in this issue of New Phytologist, offers a prime example of the diversity of outcomes of altered biotic interactions that we can observe following translocation of plants within their current distributional range even within a single community. In one plant species, local plant genotypes were more resistant to the local demes of specialist antagonist than nonlocal plant genotypes, suggesting plant local adaptation to important aspects of the biotic environment. However, in another plant species, the reverse pattern was observed. The take-home message from this study is a teeth-grinder for restoration ecologists: it is hard to make a general prediction as to whether foreign seed provenances pose a risk of introducting alleles causing low biotic resistance in the restoration area or not.