Abstract
Aim To investigate the lineages diversification of Dolichothele exilis in the Caatinga biome and to infer geological and climatic drivers of diversification in this region. Location Caatinga, Northeast of Brazil. Taxon Dolichothele exilis (Araneae: Theraphosidae). Methods We used 96 individuals for genomic sequencing (GBS sequencing) and 39 individuals for COI mitochondrial marker sequencing. Population structure was inferred using STRUCTURE and SNMF approaches, and genetic diversity and diversification indices were calculated. A maximum likelihood phylogenetic tree was constructed with SNPs data and a Bayesian tree with mitochondrial data. To explore the demographic history, DIYABC was used, with a Random Forest (RF) classifier. Finally, we constructed Habitat Suitability models using five different algorithms to investigate present and past potential distributions. Results Analyses based on SNPs data and molecular markers revealed a fine‐scale structuring associated with the Caatinga ecoregions and a broader southwest–northeast structure presumably linked to the Chapada Diamantina Plateau and the palaeocourse of the São Francisco River. The southwest group is older and presents greater genetic diversity than the northeast lineage, which, according to demographic analyses, was originated by a founder event. Habitat suitability modelling indicated a contraction of the species' potential distribution during the Last Interglacial (ca. 130 ka) followed by expansion during the Last Glacial Maximum (ca. 21 ka). Main Conclusions The history of D. exilis lineages seems to have been complex, shaped by changes in the Caatinga landscape concomitant with climatic changes. The palaeocourse of the São Francisco River and the Chapada Diamantina Plateau seems to have shaped the species' macrostructure, whereas ecoregions were the drivers of microstructuring. This work represents the first comprehensive phylogeographic study of Theraphosidae in the Caatinga, encompassing the full distribution of the species, highlighting tarantulas as valuable model organisms for biogeographical research in the region.