Ecological and social correlates of natal dispersal in female and male Thorn-tailed Rayadito (Aphrastura spinicauda) in a naturally isolated and fragmented habitat

Abstract

Sex-biased natal dispersal is predicted to be a consequence of differences in the costs and benefits of dispersal perceived by each sex. Although female-biased dispersal has been described for numerous birds in heterogeneous landscapes, studies documenting sex-related differences in the causes and consequences of natal dispersal in fragmented habitats are comparatively scarce. We used capture-mark-recapture data and genetic analyses in a population of Thorntailed Rayadito (Aphrastura spinicauda) from north-central Chile in order to investigate how the possible causes and consequences of dispersal are linked to sex-specific dispersal behavior in a naturally isolated and fragmented forest habitat. We analyzed 36 recaptured post-fledging birds to test whether female-biased dispersal reflected differential responses between sexes to potentially long-term acting selective pressures related to habitat fragmentation and high population densities. In this population, females disperse long distances (median distance: 780 m), whereas males are mostly philopatric (median distance: 85 m). Results suggest that female dispersal is possibly a response to the local density of breeding birds and mate availability, and comes without apparent reproductive costs. Inbreeding avoidance was not evident, but females may already be decreasing the probability of mating with relatives by moving away from their natal neighborhood where male kin usually remain. Our findings also indicate that male dispersal, while reduced in relation to females, can result from a tradeoff between the social benefits of settling near the natal territory and the associated costs of high breeding densities and kin competition. An increase of paternity loss was evident for males moving long distances. Follow-up studies should assess the differences in the costs and benefits of within- and between-fragment dispersal in this population.

Extrapair paternity in two populations of the socially monogamous Thorn‐tailed RayaditoAphrastura spinicauda(Passeriformes: Furnariidae)

“…We used multi‐locus genotypes for parentage analyses following the methods described in Botero‐Delgadillo et al. (2019). Analyses were performed in CERVUS version 3.0.7 (Kalinowski et al., 2007).…”

“…As described for other members of the family Furnariidae, both sexes contribute to incubation and feeding the young (Espíndola‐Hernández et al., 2017; Moreno et al., 2005, 2007). Genetic polyandry has been confirmed for rayaditos (Botero‐Delgadillo et al., 2019), but rates of EPP have not yet been quantified and described in this species. Furthermore, population differences in EPP rates may occur given marked environmental variation throughout the species’ extensive geographic range (see e.g., Ippi et al., 2011; Quirici et al., 2014).…”

Female extra‐pair behavior is not associated with reduced paternal care in Thorn‐tailed Rayadito

“…DNA extraction from blood samples and individual genotyping were carried out according to the protocol described in Botero‐Delgadillo et al. (2019). 250 birds (88 adults and 206 nestlings) were sexed using a chromosome‐linked marker (P2/P8) and genotyped at 12 polymorphic microsatellite loci.…”

“…These allelic mismatches were used to calculate the frequency of genotyping errors in CERVUS. As outlined by Botero-Delgadillo et al (2019), paternity was excluded based on the logarithm-of-odds (LOD) score and the critical Delta value (<80%), or whenever there were two or more mismatches between the social male and its putative offspring.…”

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

“…The study population inhabits a temperate forest relict in Bosque Fray Jorge National Park in north‐central Chile, breeding in tree cavities in forest fragments that are surrounded by a semi‐arid landscape (del‐Val et al, 2006 ; Figure 1 ). Although post‐glacial aridisation have caused the study population to experience a long‐term process of isolation since the end of the tertiary (Villagrán et al, 2004 ), it harbors a relatively high level of genetic diversity (observed heterozygosity, H O =0.67) and a moderate level of inbreeding (population mean inbreeding coefficient, F = 0.18), and it has been suggested that, along with historical factors, female‐biased natal dispersal could account for such level of inbreeding (Botero‐Delgadillo et al, 2019 ; Botero‐Delgadillo, Quirici, Poblete, Acevedo, et al, 2020 ; Botero‐Delgadillo, Quirici, Vásquez, et al, 2020 ).…”