Ecological specialization in plants occurs primarily through local adaptation to different environments. Local adaptation is widely thought to result in costly fitness trade-offs that result in maladaptation to alternative environments. However, recent studies suggest that such trade-offs are not universal. Further, there is currently a limited understanding of the molecular mechanisms responsible for fitness trade-offs associated with adaptation. Here, we review the literature on stress responses in plants to identify potential mechanisms underlying local adaptation and ecological specialization. We focus on drought, high and low temperature, flooding, herbivore, and pathogen stresses. We then synthesize our findings with recent advances in the local adaptation and plant molecular biology literature. In the process, we identify mechanisms that could cause fitness trade-offs and outline scenarios where trade-offs are not a necessary consequence of adaptation. Future studies should aim to explicitly integrate molecular mechanisms into studies of local adaptation.
Keywords: ecological specialization; gene network; hormone; trade-off.