Anthropocenic refugia in Patagonia: A macrogenetic approach to safeguard plants biodiversity

Abstract

Intraspecific genetic diversity (IGD) is considered the fundamental dimension of biodiversity but is scarcely considered in planning and conservation strategies. Along the evolutionary continuum, IGD is the least analyzed biodiversity level in terms of climate change and land-use impact at regional and global scale. Here, inspired by the effect of past climatic changes shaping IGD at the community level, we evaluated how future climatic changes and current land-use may erode the mechanisms behind the flowering plant IDG patterns in the Patagonian steppe in South America, and compare them with the species richness and endemism geographical patterns. We generated a georeferenced aligned chloroplastidial DNA sequences database for 24 plant species, belonging to 13 genera, in 9 families and 6 orders (5120 chloroplastidial DNA sequences for 2815 individuals in 340 localities) along the Patagonian steppe. Also, we generated a plant species richness (SR) database for the Patagonian steppe, including a subset of endemic species richness (ERS). We tested the geographical trends and spatial concordance among metrics, and identify major risk areas and possible Anthropocene refugia areas based on future climatic changes projection for two time periods, 2041-2060 and 2081-2100, and for two Shared Socioeconomic Pathways, and current Land-use of Patagonian Steppe. Finally, we determined the value of currently protected area networks to safeguard the putative Anthropocene refugia. We observed similar geographic trends between IDG and SR/ERS that become stronger when the percentage of genetic knowledge increases in relation to RS. Human-driven changes threaten flora genetic diversity mainly in northern Patagonia, eroding the historical mechanisms that motorized the observed genetic patterns. 43% of the Patagonian steppe, mainly in the southernmost portion, could serve as Anthropocenic refugia, but only 2% of these areas overlapped with current protected areas. We provide the first wide assessment of climate change and land-use effects on IGD for the community plants of the Patagonian steppe. Considering high-risk areas predictions, and the localization of potential Anthropocenic refugia, several conservation strategies can be anticipated. The conservation of the detected genetic diversity and species-rich areas with moderate land-use and projected low climate anomaly should be prioritized, whereas high-risk areas deserve monitoring and mitigation policies.