Effects of past climate on Passiflora actinia (Passifloraceae) populations and insights into future species management in the Brazilian Atlantic forest

The Brazilian Atlantic Rainforest is one of the most diverse and threatened ecoregions on the planet and displays high levels of endemism. Despite several population analyses and phylogeographical studies, the origins of its species richness and the evolutionary processes that gave rise to this diversification remain poorly understood, especially at the southern edge of the Atlantic Forest. Passiflora actinia is an indigenous species from the southern Atlantic Forest and, as such, was influenced by climatic changes during the Pleistocene. In this study, we investigated the effects of past climate changes on the genetic diversity of P. actinia, using nuclear and plastid markers. We subsequently suggest strategies for the preservation of this species in particular and the whole ecoregion in general. We employed phylogeographical methods and combined these results with past, present and future ensemble niche models. Genetic variability in P. actinia was similar to that of other species with similar geographical distributions, and geographical structuring was not observed based on either type of genetic marker. Diversification in P. actinia was dated to the Pleistocene, suggesting that climate changes could have influenced the distribution of genetic diversity in this species. Our results predicted that suitable P. actinia habitat will persist in the highlands but will be reduced in the lowlands, especially with higher greenhouse gas concentrations. Conservation efforts should focus on populations with unique genetic units and populations from areas with greater climatic instability. Habitat loss due to deforestation in the Atlantic Forest constitutes a major risk to this species, especially to small populations or those with low diversity indices.