Abstract: Genome sequences can reveal the extent of inbreeding in small populations. Here, we present the first genomic characterization of type D killer whales, a distinctive eco/morphotype with a circumpolar, subantarctic distribution. Effective population size is the lowest estimated from any killer whale genome and indicates a severe population bottleneck. Consequently, type D genomes show among the highest level of inbreeding reported for any mammalian species (FROH ? 0.65). Detected recombination cross-over events of different haplotypes are up to an order of magnitude rarer than in other killer whale genomes studied to date. Comparison of genomic data from a museum specimen of a type D killer whale that stranded in New Zealand in 1955, with 3 modern genomes from the Cape Horn area, reveals high covariance and identity-by-state of alleles, suggesting these genomic characteristics and demographic history are shared among geographically dispersed social groups within this morphotype. Limitations to the insights gained in this study stem from the nonindependence of the 3 closely related modern genomes, the recent coalescence time of most variation within the genomes, and the nonequilibrium population history which violates the assumptions of many model-based methods. Long-range linkage disequilibrium and extensive runs of homozygosity found in type D genomes provide the potential basis for both the distinctive morphology, and the coupling of genetic barriers to gene flow with other killer whale populations.

Abstract: In altricial species, parents brood their chicks constantly before leaving them unattended sometimes for extended periods when they become thermally independent. During this second phase, there is sometimes important inter-individual differences in parental attendance and the fitness costs and benefits of parental strategies have previously been extensively investigated. However, the impact of parental presence on offspring behaviors and stress physiology has been overlooked. Here, we examined the influence of parental presence on offspring hormonal and behavioral stress sensitivities in snow petrel chicks. We demonstrated for the first time in a wild bird species that attended chicks had lower stress-induced corticosterone levels and a lower probability to show defensive behavior compared to the alone chicks. This reduced stress sensitivity is certainly explained by the well-known link between corticosterone and nutritional status, and by the recent delivery of meals to the attended chicks and the improvement of their nutritional status. It may also be explained by the parental protection against predators or inclement weather, or/and by the psychosocial comfort of parental presence for the offspring. Overall, these results suggest that the presence of a parent in the nest reduces offspring stress sensitivity in wild birds. Further studies would now be required to disentangle the impact of nutritional status and parental presence on stress sensitivity and to better understand the potential impact of parental presence and circulating corticosterone levels on growth and cognitive development in wild birds.

Abstract:

Les milieux polaires et subpolaires ne sont pas dépourvus de parasites. Chez les manchots royaux, les ectoparasites tels que les tiques (Ixodes uriae) sont suspectés d’avoir des effets marqués sur la santé et le succès reproducteur des adultes. En utilisant un traitement expérimental réduisant drastiquement l’abondance d’ectoparasites chez des adultes reproducteurs, nous avons pu démontrer que l’infestation par les ectoparasites induit une augmentation du stress physiologique caractérisé par des taux élevés de corticostérone (glucocorticoïde) et une situation de stress oxydant. Bien que l’éradication des ectoparasites n’ait pas d’influence notable sur le succès d’éclosion des œufs ou la survie des poussins durant l’élevage, le traitement améliore visiblement la croissance des poussins jusqu’à l’émancipation, avec des effets positifs probables sur leur survie future. Il semble donc que les ectoparasites exercent une pression de sélection naturelle non-négligeable chez le manchot royal.