Speaker
Description
Over the last decades, numerous studies have begun documenting the impacts of climate deregulation on species ranges. Among them, specialists, which thrive under specific environmental conditions, typically in narrow geographic ranges, are widely recognised as one of the most threatened categories. Many might rely on both their potential to adapt and on the existence of an environmental refugium to reach to avoid extinction. It is thus crucial to understand the influence of environmental conditions on the unfolding process of adaptation. Here, I study the eco-evolutionary dynamics of a sexually reproducing specialist species in a two-patch quantitative genetic model with moving optima. Aligning with previous theoretical studies, I first derive the critical environmental speed beyond which the environment changes too fast for the species persistance. This quantity reflects how much the existence of a refugium can delay extinction. Moreover, my analysis provides key quantitative insights about the sharp dynamics that arise on the path towards this refugium. I show that after an initial increase of population size, there exists a lower critical environmental speed for which the species crosses a tipping point, resulting into an abrupt habitat switch. Besides, when selection for local adaptation is relatively strong, this habitat switch passes through an evolutionary “death valley”, from where a small portion of the population can get rescued by adapting fast enough to the local conditions of the refugium. This work highlights in particular how evolutionary rescue can occur from a small standing variation in sexually reproducing species and highly fragmented environments.
