Unravelling the genetic diversity and population dynamics of three Tacinga species (Cactaceae: Opuntioideae) in the Caatinga.

This article focuses on the genetic diversity, differentiation, and phylogeography of three endemic cactus species—Tacinga inamoena, Tacinga subcylindrica, and Tacinga palmadora—widely distributed in the Caatinga biogeographical region of northeastern Brazil. Using multilocus molecular markers and extensive sampling, the study found that these species diversified during the middle Pleistocene, with the Southern Sertaneja Depression identified as their ancestral area. Contrary to patterns observed in other taxa, major geographical features such as the São Francisco River and Caatinga ecoregions did not act as barriers to gene flow in these cacti, which exhibit low genetic diversity and weak population structure likely influenced by recent expansion and reproductive strategies involving both sexual and clonal propagation. The findings underscore the importance of considering species-specific biological traits when interpreting biogeographical and evolutionary processes in the Caatinga.