Patterns of Adaptation of Crop Genetic Resources Conserved in Situ in Centers of Diversity.

Landraces cultivated in centers of crop diversity result from past and contemporary patterns of natural and farmer-mediated evolutionary forces. Successful in situ conservation of crop genetic resources depends on continuity of these evolutionary processes. Climate change is projected to affect agricultural production, yet analyses of impacts on in situ conservation of crop genetic diversity have been absent. This, despite the fact that landraces grown across naturally varying landscapes can provide an excellent system for understanding traits, such as temperature tolerance, that will be essential for further adaptation to climate change. Thus, here we do three things. First, we explore how crop landraces may respond to alterations in climate by reviewing the roles that phenotypic plasticity, evolution, and gene flow might play in sustaining production, as well as the ways that erosion of genetic diversity could ensue if landrace populations or entire races lose productivity. Second, we clarify how the outcome of climate change for any given crop in a given region will depend on the distribution of genetic variation that affects fitness, patterns of climate change, and farmer responses. Third, provide empirical examples of how this might operate using landraces of maize grown in southern Mexico along altitudinal and environmental gradients. Results from reciprocal common garden studies of maize landraces from along these gradients elucidate future responses to climate. Based on their productivity in lower altitude gardens, highland maize landraces do not appear to express the plasticity necessary to sustain productivity under climate change. Yet they may be able to evolve in response to altered conditions. Understanding patterns of adaptive diversity from the population to the landscape scale is essential to clarify how landraces conserved in situ will continue to evolve and how to minimize genetic erosion of these essential natural resources.