Isolation of microsatellite loci in Akodon azarae (Muridae, Sigmodontinae) and cross-amplification in other Akodontini species

Abstract

Fragmentation of natural habitats is an increasing problem worldwide, having profound consequences on the genetic and demographic structure of natural populations (Mech and Hallet 2001). A representative example of a fragmentation process occurs in central Argentina, an area of approximately 500,000 km2 formerly occupied by prairies, but currently consisting almost exclusively of crops and livestock pastures separated by fencelines, roads and railroads, along which native and introduced weeds grow: the "border" habitats. One of the most important components of the fauna in this region are rodents of the subfamily Sigmodontinae, a highly speciose group of mostly South American distribution, assembled in seven different tribes (Reig 1984). Three of the most abundant Sigmodontine species in agroecosystems of central Argentina are Calomys musculinus and C. venustus (tribe Phyllotini), and Akodon azarae, pertaining to the tribe Akodontini, the second most important according to the number of species (Reig 1984). Previous studies have established that these species differ in several ecological and behavioural characteristics like habitat use (A. azarae and C. venustus preferentially use borders while C. musculinus inhabits both borders and crop fields;Mills et al. 1992; Polop and Sabattini 1993; Busch et al. 1997), space use (home range size vary by sex and breeding period in A. azarae and C. musculinus, and by population abundance in C. venustus; Priotto and Steinmann 1999; Priotto et al. 2002), mating system (promiscuous/polygynous in C. venustus and A. azarae and promiscuous in C. musculinus; Priotto and Steinmann 1999; Priotto et al. 2002; Steinmann et al. 2009) and competition (A. azarae is competitively dominant over C. musculinus; Busch et al. 2005). On these bases, it is predictable that these species will differentially perceive landscape fragmentation. Our research interest focusses on comparing the movement and the genetic structure of their populations in agroecosystems, as a model to assess the genetic consequences of fragmentation on the fauna of the region. The development of codominant microsatellite DNA markers are an invaluable tool for studying fine-scale genetic differences. For this purpose we already isolated and characterized nine microsatellite loci in C. musculinus that also amplify in C. venustus (Chiappero et al. 2005, 2011). As part of our studies on population structure at a small spatial scale, we describe here results of the isolation and characterization of 10 microsatellite loci in A. azarae. We also investigated if the polymorphic primers developed amplify in other species of the tribe Akodontini. This is, to our knowledge, the first report of microsatellite loci designed for the genus Akodon. Since this taxon has nearly 40 species distributed throughout South America from Colombia to southern Argentina and Chile, occupying a wide variety of habitats from 0 to 5000 m above sea level (Redford and Eisenberg 1984), our work has a potential utility for population genetic studies in the genus.