Data from: Commensalism facilitates gene flow in mountains: a comparison between two Rattus species

Small mammal dispersal is strongly affected by geographical barriers. However, commensal mammals may be passively transported over large distances and strong barriers by humans. This pattern should be especially apparent in topographically complex landscapes such as mountain ranges where valleys and/or peaks can limit dispersal of less vagile species. We predict that commensals would have lower genetic differentiation and higher migration rates than related non-commensals in such landscapes. We contrasted population genetic differentiation in two sympatric Rattus species (R. satarae and R. rattus) in the Western Ghats in southern India. We sampled rats from villages and adjacent forests in seven locations (20 - 640 km apart). Capture-based statistics confirmed that R. rattus is more abundant in villages, while R. satarae is found mostly in forests. Population structure analyses using ~970 bp mitochondrial control region and 17 microsatellite loci revealed higher differentiation for the non-commensal (R. satarae F-statistics = 0.420, 0.065, R. rattus F-statistics = 0.195, 0.034; mtDNA, microsatellites respectively). Clustering analyses confirm that clusters in R. satarae are more distinct and less admixed than those in R. rattus. R. satarae shows higher slope for IBD compared to R. rattus. While mode of migration estimates do not strongly suggest higher rates in R. rattus than in R. satarae, they indicate that migration over long distances could still be higher in R. rattus. We suggest that association with humans could drive the observed pattern of differentiation in commensal R. rattus, consequently impacting not only their dispersal abilities, but also their evolutionary trajectories.