Dispersal and population structure at different spatial scales in the subterranean rodent Ctenomys australis

Abstract

BackgroundThe population genetic structure of subterranean rodent species is strongly affected by demographic (e.g. rates of dispersal and social structure) and stochastic factors (e.g. random genetic drift among subpopulations and habitat fragmentation). In particular, gene flow estimates at different spatial scales are essential to understand genetic differentiation among populations of a species living in a highly fragmented landscape. Ctenomys australis (the sand dune tuco-tuco) is a territorial subterranean rodent that inhabits a relatively secure, permanently sealed burrow system, occurring in sand dune habitats on the coastal landscape in the south-east of Buenos Aires province, Argentina. Currently, this habitat is threatened by urban development and forestry and, therefore, the survival of this endemic species is at risk. Here, we assess population genetic structure and patterns of dispersal among individuals of this species at different spatial scales using 8 polymorphic microsatellite loci. Furthermore, we evaluate the relative importance of sex and habitat configuration in modulating the dispersal patterns at these geographical scales.ResultsOur results show that dispersal in C. australis is not restricted at regional spatial scales (~ 4 km). Assignment tests revealed significant population substructure within the study area, providing support for the presence of two subpopulations from three original sampling sites. Finally, male-biased dispersal was found in the Western side of our study area, but in the Eastern side no apparent philopatric pattern was found, suggesting that in a more continuous habitat males might move longer distances than females.ConclusionsOverall, the assignment-based approaches were able to detect population substructure at fine geographical scales. Additionally, the maintenance of a significant genetic structure at regional (~ 4 km) and small (less than 1 km) spatial scales despite apparently moderate to high levels of gene flow between local sampling sites could not be explained simply by the linear distance among them. On the whole, our results support the hypothesis that males disperse more frequently than females; however they do not provide support for strict philopatry within females.

Population structure and landscape genetics in the endangered subterranean rodent Ctenomys porteousi

“…Levels of microsatellite variability in C. porteousi were slightly higher compared with other species of the genus Ctenomys. Although the mean number of alleles per locus (12.1) was higher than reported in previous studies in tucotucos, the number of alleles per population showed a similar range of values (see Lacey 2001;Wlasiuk et al 2003;El Jundi and Freitas 2004;Gava and de Freitas 2004;Cutrera et al 2006;Fernández-Stolz et al 2007;Gonçalves and de Freitas 2009;Mirol et al 2010;Mora et al 2010). …”

“…This pattern was reported in tuco-tucos by many authors (see Wlasiuk et al 2003;Mora et al 2006 and2007;Fernández-Stolz et al 2007;Gonçalves and de Freitas 2009), even at fine spatial scale when only small habitat discontinuities separate local populations (Mora et al 2010). Our results for C. porteousi conforms to this scenario, perhaps reinforced by the fact that each sampling site was located in a different habitat patch, surrounded by non suitable habitat (Mapelli and Kittlein 2009).…”

“…Since significant deviations were not associated to any loci in particular and that previous studies in other Ctenomys species using these loci did not detect physical linkage (see Wlasiuk et al 2003;Cutrera et al 2005;Mora et al 2010;Mirol et al 2010), we considered these eight loci as independent markers.…”

“…These habitat restrictions determine, in general, discontinued distributions (El Jundi and Freitas 2004;Mora et al 2006Mora et al , 2007. As a consequence, tuco-tucos are commonly grouped in small demes with low genetic variation and high interpopulation divergence, showing strong population structure sustained by low rates of migration and gene flow (Wlasiuk et al 2003;Fernández-Stolz et al 2007; Kittlein and Gaggiotti 2008;Mora et al 2010). A clear example is provided in Mapelli et al (2011) who detected strong population structure in C. porteousi using mitochondrial markers.…”

Landform and surface attributes for prediction of rodent burrows in the Western Usambara Mountains, Tanzania

“…There is a rich literature on the survey of rodent burrows and the way they relate to landforms and surface attributes (Reichman & Smith, 1990;Goyal & Ghosh, 1993;Randall, 1993;Laundre & Reynolds, 1993;Davidson et al, 2008;Mora et al, 2010;Naderi et al, 2011). Most of these works have focused on rodents' survival and soil suitability for burrowing.…”