Microsatellite variation in solitary and social tuco-tucos: molecular properties and population dynamics

Variation at 15 microsatellite loci was characterized for a population of t he solitary Patagonian tuco-tuco (Ctenomys haigi) and a population of group -living colonial tuco-tuco (C. sociabilis), both of which were located in t he Limay River Valley of south western Argentina. All loci examined were ch aracterized by uninterrupted di- or trinucleotide repeats in both species; seven of these loci had been isolated from C. haigi and eight had been isol ated from C. sociabilis. Across all loci. there was a significant tendency for both number of alleles and heterozygosity to be greater in C. haigi tha n in C. sociabilis. Cloning and sequencing of multiple PCR products per loc us per population revealed no significant biases in allele length, suggesti ng that this difference in variability was not due to ascertainment bias or to population-wide differences in rates of microsatellite evolution. Inste ad, differences in microsatellite variation between C. haigi and C. sociabi lis were more consistent with current demographic and suspected historical differences between these populations. In particular., interpopulation diff erences in the distribution of microsatellite allele sizes and allele frequ encies suggested that C. sociabilis has been more subject to historical red uctions in population size (e.g. population bottlenecks) than has C. haigi. These findings indicate that analyses of microsatellite structure can yiel d important insights into the population-level phenomena that contribute to diversity at these markers, including differences in population history th at continue to influence levels of genetic variability.