Genetic structure of populations of the Pampean grassland mouse, Akodon azarae, in an agroecosystem under intensive management

Abstract

Agroecosystems in central Argentina are a good example of landscape modification by human activities. We used the Pampean grassland mouse (Akodon azarae) as a biological model to assess the effects of landscape fragmentation on the genetic structure of natural populations present in the region. The species is a habitat specialist that is numerically dominant in relatively stable environments, such as remnant areas of native vegetation, stream borders, roadsides and railway banks. We used seven microsatellite loci to analyze the genetic population structure and to explore if there is sex-biased dispersal during the reproductive season at a fine geographical scale. Rodents were captured seasonally in trap lines located on roadsides in an agroecosystem of central Argentina. Values of genetic differentiation among populations and temporal patterns of spatial autocorrelation revealed that the genetic populations occupy areas larger than the sampling area. Causal modeling analyses showed that unfavorable habitats (secondary roads and crop fields)were not barriers to dispersal of Akodon azarae. The high levels of gene flow and the short duration of the low population density phase, followed by a fast recovery, would contribute to the maintenance of highly polymorphic populations. As expected for A. azarae's mating system, males were not genetically structured. However, females' spatial genetic structure varied greatly over the year, which would be related to availability and quality of habitat, and to intrasex interactions. Our work contributes to the understanding of dispersal strategies in small mammals in anthropogenically fragmented habitats like intensively managed agroecosystems.

A Bocage Landscape Restricts the Gene Flow of Pest Vole Populations

“…Depending on the landscape characteristics and the land management of each agro-ecosystem, dispersal and later reproduction can be notably affected [ 10 , 11 , 12 ]. There have been several population genetics studies on patch-dependent species aiming to better understand how agricultural landscapes determine gene flow [ 13 , 14 , 15 ]. They have shown that landscape features can both restrict and facilitate the movement of individuals in natural populations.…”

“…Studying the population connectivity of rodents in agriculture ecosystems is thus of considerable value. Several genetic studies have highlighted that dispersal is often restricted in rodent species inhabiting agro-ecosystems because of agriculture intensification and the resulting reduction in natural habitats [ 13 , 14 , 15 , 21 ]. Maintaining and increasing landscape complexity benefits multiple species at the same time by providing many different ecological niches [ 22 ].…”

Relatedness dynamics and sex-biased dispersal in a seasonal cycle of corn mice from intensively managed agroecosystems

“…The agroecosystems of central Argentina present a remarkable spatiotemporal variability due to yearly land-use activities (i.e., harvest and plow activities) ( Fraschina et al 2012 ; Serafini et al 2019 ). Therefore, they offer a particularly interesting scenario to explore the spatial and temporal distributions of wild animal genotypes in human-modified landscapes ( Chiappero et al 2016 ; Vera et al 2019 ). Argentinean agroecosystems consist of monocultures of a few crops (corn, soybean, sunflower, and wheat) surrounded by a network of roadsides, fence lines, railways, and other border habitats that keep remnants of native flora and many introduced weeds.…”