Relationship between the location of Pleistocene refugia and geographic and environmental centrality in a plant–pollinator mutualism from Patagonia

Glacial refugia are habitats where species could persist during past climate changes and they are of high conservation value due to their role as hotspots of genetic diversity. Therefore, it is relevant to understand factors that determine the distribution of these refugia across species' ranges and of their mutualists. According to the Central-Peripheral Hypothesis, as genetic diversity is highest in the geographic range centre, it is expected that refugia coincide with this centre, if the geographic and environmental centroids coincide. We proposed an integrative framework that combines genetic diversity, current and past distribution range, and the historical ecological centroid to investigate the association between Pleistocene refugia and geographic and environmental centrality in a mutualism from Patagonia. We identified a clear pattern in which genetic diversity was negatively associated with distance to the location of the environmental centroids and positively with distance to geographic centres of Centris cineraria, Calceolaria polyrhiza and their mutualistic interaction. Our results show that glacial refugia can be geographically peripheral but ecologically central and that a highly specialized mutualism would share the same refugia. Focusing on spatio-temporal dynamics of environmental centroids can contribute to better understanding aspects related to the conservation and evolution of species' populations.