Phylogeography of the endangered ant species Atta robusta Borgmeier, 1939 (Formicidae: Myrmicinae): insights into genetic structure, demographic history, and conservation priorities
Atta robusta is a narrow endemic leaf-cutting ant restricted to restinga habitats along Brazil’s southeastern coast. Despite its conservation status, little is known about its evolutionary history and genetic structure. Here, we investigate patterns of genetic variation in A. robusta using mitochondrial (COI–IGS–tRNALeu–COII) and nuclear (EF1alpha copy one) DNA markers sampled across its known range. We assess genetic diversity and population structure and infer relationships among haplotypes using Bayesian phylogenetic analysis and haplotype network reconstruction. We detected moderate haplotype diversity (Hd = 0.7789 for mtDNA and phased Hd = 0.6737 for EF1alpha F1), significant but incomplete population differentiation (ΦST up to 0.61), and a weak to moderate pattern of isolation by distance. Bayesian analyses recovered geographically associated haplotypes with shallow genetic divergence, while nuclear marker exhibited low relative to mitochondrial data. The star-like haplotype network is compatible with multiple demographic scenarios, but neutrality tests did not provide evidence for departures from demographic equilibrium. Overall, our results indicate shallow genetic structure and incomplete spatial differentiation across the species range. These findings highlight the importance of preserving remnant restinga habitats and maintaining landscape connectivity to safeguard genetic diversity in A. robusta and other habitat-specialist ants.