Introgression and Genetic Diversity Between Two Cactophilic Drosophila (Drosophila repleta group) Species: A Case Study of an Isolated Population from the Sandstone Hills in the Southeast of Brazil.

Introgressive hybridization involves the integration of genetic material from one population into another genetically distinct population. Despite its widespread occurrence in nature, the mechanisms and consequences of introgression remain poorly understood. In this study, we examine the hypothesis that the mitochondrial gene COI from Drosophila antonietae has been introgressed into the gene pool of a specific population of D. gouveai. Additionally, we extended our analysis to include other genes associated with the COX complex, such as mitochondrial (COII) and nuclear genes (CoVa, CG9603, and levy), across various populations of both species from different locations. We estimated indices of genetic diversity, constructed haplotype networks in both mitochondrial and nuclear genes, and performed selection tests to assess the evolutionary dynamics of mitochondrial genes. Our results confirm the hypothesis of a historical secondary contact between D. gouveai and D. antonietae in the region of Analândia, SP, showing asymmetric unidirectional introgression, with signs of positive selection in the mitochondrial genes.