The geography of Aspidosperma quebracho-blanco vulnerability, an emblematic species of the South American Gran Chaco

Abstract

Aspidosperma quebracho-blanco is a key species of the Gran Chaco, one of the most threatened subtropical woodlands in South America. By combining ecological niche modeling (ENM) and population genetic analysis, we explored the impact of land use and climate change on the species distribution with the aim to map the geography of its vulnerability and to propose conservation strategies. Future climate models revealed a generalized reduction in climatic suitability for A. quebracho-blanco, as well as a tendency of suitable areas for the species to shift towards the south-southeast. Land use and land cover (LULC) analysis indicated that more than 50% of A. quebracho-blanco distribution is mainly affected by cultivated lands. The analysis of the genetic population showed that the species has moderate genetic structure and populations are clustered in three genetic groups. The ENM analyses indicated an under-representation of the species’ potential range in protected areas. These results highlight the need to prioritize the conservation and restoration of remnant populations and the expansion of protected natural areas. Therefore, using an integrative approach of the results obtained here, we identified four areas with different levels of vulnerability and proposed specific conservation strategies for each one. This work can be similarly applied in other countries that might establish common criteria in the definition of conservation strategies for tree species.