Abstract Genetic analyses of kinship can generate important insights into social structure, particularly for species for which direct observations of social relationships are challenging. We used molecular markers to characterize the kin structure of a population of the Río Negro tuco-tuco (Ctenomys rionegrensis), a subterranean species of rodent that is rarely observed above ground. Previous research has revealed that adults of this species engage in at least periodic episodes of burrow sharing, indicating that C. rionegrensis may not be strictly solitary. To explore the kin structure of this species, we used variability at 10 microsatellite loci to determine if (1) adults and juveniles captured at the same burrow entrance were parents and offspring and (2) kinship among adults captured together differed from that among randomly sampled pairs of individuals in our study population. Our analyses revealed that adults and juveniles captured together were not typically parents and offspring, suggesting potential mixing of litters among burrow systems. Relatedness among adults captured together did not differ from background levels of genetic similarity, providing no evidence that spatial proximity was associated with kin structure. Collectively, our findings support the hypothesis that C. rionegrensis is not strictly solitary but instead engages in burrow sharing by adults and associated litters of young.

Lineage delimitation is of extreme importance in evolutionary biology and constitutes an essential tool in basic and applied fields including conservation. We addressed the delimitation of two closely related species complexes of South American rodents of the genus Ctenomys (tuco-tucos), namely the C. pearsoni and Corrientes groups, whose relationships have been unclear or conflicting in previous phylogenetic studies. We performed a molecular phylogenetic analysis, increasing the number of representatives of each group and including sequences of three mitochondrial loci (the complete cytochrome b coding sequence, and partial regions of the cytochrome oxydase I gene and the D-loop of the control region). The trees obtained using Bayesian Inference and Maximum Parsimony methods show the Corrientes group and the C. pearsoni complex as reciprocally monophyletic sister clades, with higher values of intergroup compared to intragroup genetic distances. These results indicate that the Corrientes group and the C. pearsoni complex are differentiated lineages. The resulting tree topology is in agreement with a scenario of independent chromosomal rearrangements from the ancestral karyomorph (2n = 70 FN = 84), leading to the considerable chromosomal diversity that characterizes both groups.

La delimitación de linajes tiene una gran importancia en biología evolutiva y constituye una herramienta fundamental en disciplinas básicas y aplicadas incluyendo la conservación. Abordamos la delimitación de dos complejos de especies de roedores sudamericanos del género Ctenomys (tuco-tucos), denominados grupos C. pearsoni y Corrientes, cuyas relaciones resultaron poco claras o conflictivas en estudios filogenéticos previos. Realizamos una filogenia molecular, aumentando el número de representantes de cada grupo e incluyendo secuencias de tres marcadores mitocondriales (la secuencia completa de la región codificante del gen del citocromo b y secuencias parciales del gen de la enzima citocromo oxidasa I, y del D-loop de la región control). Los árboles obtenidos mediante métodos de inferencia bayesiana y máxima parsimonia muestran que el grupo Corrientes y el complejo C. pearsoni son grupos hermanos recíprocamente monofiléticos con mayores valores de distancias genéticas entre grupos que dentro de los grupos. Estos resultados indican que el grupo Corrientes y el complejo C. pearsoni son linajes diferenciados. La topología resultante es consistente con un escenario de fijación de reordenamientos cromosómicos independientes a partir del cariomorfo ancestral (2n = 70 NF = 84), dando origen a la considerable diversidad cromosómica que caracteriza a ambos grupos.

The allele frequencies of 10 microsatellite loci previously described for sheep as BM1314, BM6526, OarFCB128, OarHH64, OarCP20, OarHH47, OarFCB48, OarHH35, OarHH72 and BM2508 were estimated for the Uruguayan flocks. A representative sample of 101 individuals composed by the two predominant breeds (76% Corriedale and 24% Australian Merino) was used. The sample did not show a significant tendency towards substructuring, in spite of presenting some significantly different allele frequencies between races. The Corriedale sample presents three loci in which the presence of null alleles is possible. The markers were highly variable, showing between 7 and 15 alleles each. The Polymorphism Information Content Index ranged from 0.63 to 0.87 and the Exclusion Probability from 0.39 to 0.75 for a cumulative Exclusion Probability of 99.98%. These results suggest the effectiveness of this set of loci for testing genetic relatedness. This is the first report of microsatellite variation in Corriedale.