Population genetic structure in two contrasting human-altered environments of yellow pygmy rice rat Oligoryzomys flavescens.

Human activities are inducing substantial modifications to landscapes on a worldwide scale. As a result, a multitude of animal species are forced to adapt and survive within remnants of altered natural habitats rendering them more vulnerable to the impact of genetic drift. The objective of this research is to assess the degree of connectivity among Oligoryzomys flavescens, an orthohantavirus reservoir species, inhabiting two contrasting human-altered environments by means of genome-wide markers. This study was conducted in 16 sites with varying degrees of urbanization in the city of Buenos Aires and the surrounding metropolitan area, and rural localities in Buenos Aires province, Argentina. Genomic DNA was extracted from 93 specimens collected between 2017 and 2019 and a total of 2456 SNPs, obtained through ddRADseq, were analyzed. Urban sites presented more genetic differentiation, cluster structuring, larger number of private alleles and a higher number of kinship relationships than rural sites. Genetic and spatial distances were positively associated in the rural area while no association was detected in the urban one. Furthermore, our analyses detected some degree of differentiation between individuals inhabiting riparian environments of two distinct river basins and typically rural environments further from both basins. Our results suggest that the urban environment imposes greater limitations to gene flow compared to rural areas, probably due to restrictions to dispersal caused by a higher degree of isolation. This information contributes to the understanding of the potential dispersion of hantavirus among rodents and to design prevention measures to reduce the risk of their transmission to humans.