Range shift and loss of genetic diversity under climate change in Caryocar brasiliense, a Neotropical tree species

Many species have suffered reduction in habitable area due to recent climate change, but few studies evaluated how these range collapses will impact genetic diversity. Here, we modeled shifts in the species’ geographical range to evaluate how genetic diversity of Caryocar brasiliense will change as a consequence of predicted climate change in the next 50 years. A total of 135 records of species occurrence were obtained to model species’ distribution based on the current environment using MAXENT and forecasting future distribution using a combination of three coupled atmospheric–oceanic global circulation models. Genetic parameters were estimated based on the polymorphism at ten microsatellite loci for 466 individuals. Our results show that climatic suitable areas for C. brasiliense will be restricted to the southernmost distribution of savanna vegetation. Genetic diversity and the number of alleles may decrease slowly if populations persist in regions up to 0.5 of environmental suitability estimated by MAXENT, but will sharply decrease above this level. Nevertheless, deviation from mutation–drift equilibrium is significant even if a small amount of local populations is lost. More climatic suitable areas in the future will be in the most disturbed regions in Brazil, and populations that will persist there are those with higher levels of inbreeding at present. This may impose several threats to the species, including the limited capacity to cope with ongoing climatic changes by adaptation and constraints to dispersal.