Landscape genetics in a highly threatened environment: how relevant to ants is the physiognomic mosaic of the cerrado savanna?

The Brazilian cerrado is one of the world’s biodiversity hotspots, comprising a mosaic of vegetation physiognomies. The cerrado presents a high ant diversity, and ant genetic variation can be subjected to the influence of landscape features. Here, we investigate how the composition and configuration of a cerrado reserve (4500 ha) in SE Brazil influence dispersal and gene flow (through measures of genetic distance) in two abundant carpenter ants, Camponotus renggeri and C. rufipes. Based on landscape genetics, we evaluated the degree of permeability of different land covers on the dispersal of ant queens, males and workers, employing a genetic optimization algorithm framework. We found little genetic structure in C. renggeri, regardless of caste. By contrast, we observed the formation of clear genetic clusters in C. rufipes, mainly for workers and queens. For workers of both species, we found that genetic distance was not influenced by geographic distance or landscape composition. For queens and males of C. renggeri, geographic distance was the most important factor explaining genetic distance. For C. rufipes queens and males, however, the best model considered the effect of landscape resistance to gene flow (i.e. the cost imposed by land use and cover types), with males dispersing through human-affected areas such as roads, and queens through forested cerrado areas. Our results showed that cerrado landscape can differentially affect ant dispersal, even for closely related species, reinforcing the importance of using different castes and sexes in landscape genetics of social insects. Our study also highlights that preservation of different vegetation physiognomies of cerrado is relevant for ant dispersal performance.