Evidence of low within-pair genetic relatedness in a relict population of Thorn-tailed Rayadito despite long-term isolation

Investigating whether mating patterns are biased in relation to kinship in isolated populations can provide a better understanding of the occurrence of inbreeding avoidance mechanisms in wild populations. Here, we report on the genetic relatedness (r) among breeding pairs in a relict population of Thorn-tailed Rayadito (Aphrastura spinicauda) in north-central Chile that has experienced a long-term history of isolation. We used simulations based on 8 years of data to assess whether mating is random with respect to relatedness. We found that mean and median population values of pair relatedness tended to be lower than randomly generated values, suggesting that mating is not random with respect to kinship. We hypothesize that female-biased dispersal is the main mechanism reducing the likelihood of mating among kin, and that the proportion of related pairs (i.e., r > 0.125) in the study population (25%) would presumably be higher in the absence of sex-biased dispersal. The occurrence of other mechanisms such as extra-pair copulations, delayed breeding, and active inbreeding avoidance through kin discrimination cannot be dismissed and require further study.

Automated summary

This study investigates whether there is a preference for mating with kin in isolated populations of the Thorn-tailed Rayadito. The results suggest that mating is not random with respect to kinship, with breeding pairs showing lower relatedness values compared to randomly generated pairs. Female-biased dispersal is hypothesized to be the main mechanism reducing the likelihood of kin mating.