Changing environments and genetic variation: inbreeding does not compromise short-term physiological responses

Selfing plant lineages are surprisingly widespread and successful in a broad range of environments, despite showing reduced genetic diversity, which is predicted to reduce long-term evolutionary potential. However, short-term capacity to respond appropriately to new conditions might not require high levels of standing genetic variation. The purpose of this study was to directly test whether mating system variation and its associated changes in genetic variability in natural populations affected responses to short-term environmental challenges. We compared relative fitness and metabolome profiles of naturally outbreeding (genetically diverse) and inbreeding (genetically depauperate) populations of a long-lived perennial plant, Arabidopsis lyrata, under constant growth chamber conditions and an outdoor common garden environment outside its native range. We found no effect of mating system on survival or reproductive output, although several phenological traits showed different associations with latitude for outcrossing and inbreeding populations. Natural inbreeding had no effect on the plasticity of physiological responses, using either multivariate approaches or analysis of variation in individual metabolites. Moreover, while both growing environment and time significantly affected the relative abundance of individual metabolites, inbreeding populations responded similarly to outbreeding populations, suggesting physiological adaptation to the outdoor environment, regardless of mating system. We conclude that low genetic diversity in naturally inbred populations may not compromise fitness or short-term capacity for appropriate physiological responses to environmental change. The absence of natural costs of inbreeding could help to explain the global success of clonal or asexual mating strategies for adapting to a wide range of environments.