Searching for genetic evidence of demographic decline in an arctic seabird: beware of overlapping generations

Emeline Charbonnel (1, 2) , Claire Daguin-Thiébaut (3, 4) , Lucille Caradec (3, 4) , Eléonore Moittié (3, 4) , Olivier Gilg (2, 5) , Maria V. Gavrilo (6) , Hallvard Strøm (7) , Mark L. Mallory (8) , R. I. Guy Morrison (9, 10) , H. Grant Gilchrist (9, 10) , Raphaël Leblois (11) , Camille Roux (12) , Jonathan M. Yearsley (13) , Glenn Yannic (1, 2) , Thomas Broquet (3, 4)

1 LECA - Laboratoire d'Ecologie Alpine
2 GREA - Groupe de recherche en écologie arctique
3 SBR - Station biologique de Roscoff = Roscoff Marine Station
4 ADMM - Adaptation et diversité en milieu marin
5 BGS - Biogéosciences [UMR 6282]
6 AARI - Arctic and Antarctic Research Institute
7 Norwegian Polar Institute
8 Acadia University
9 Carleton University - Department of Biology, Carleton University
10 National Wildlife Research Centre
11 UMR CBGP - Centre de Biologie pour la Gestion des Populations
12 Evo-Eco-Paléo (EEP) - Évolution, Écologie et Paléontologie (Evo-Eco-Paleo) - UMR 8198
13 SBES - School of Biology and Environmental Sciences

Genetic data are useful for detecting sudden population declines in species that are difficult to study in the field. Yet this indirect approach has its own drawbacks, including population structure, mutation patterns, and generation overlap. The ivory gull (Pagophila eburnea), a long-lived Arctic seabird, is currently suffering from rapid alteration of its primary habitat (i.e., sea ice), and dramatic climatic events affecting reproduction and recruitment. However, ivory gulls live in remote areas, and it is difficult to assess the population trend of the species across its distribution. Here we present complementary microsatellite- and SNP-based genetic analyses to test a recent bottleneck genetic signal in ivory gulls over a large portion of their distribution. With attention to the potential effects of population structure, mutation patterns, and sample size, we found no significant signatures of population decline worldwide. At a finer scale, we found a significant bottleneck signal at one location in Canada. These results were compared with predictions from simulations showing how generation time and generation overlap can delay and reduce the bottleneck microsatellite heterozygosity excess signal. The consistency of the results obtained with independent methods strongly indicates that the species shows no genetic evidence of an overall decline in population size. However, drawing conclusions related to the species' population trends will require a better understanding of the effect of age structure in long-lived species. In addition, estimates of the effective global population size of ivory gulls were surprisingly low (similar to 1000 ind.), suggesting that the evolutionary potential of the species is not assured.

Domaines: Génétique des populations [q-bio.PE]

Emeline Charbonnel, Claire Daguin-Thiébaut, Lucille Caradec, Eléonore Moittié, Olivier Gilg, et al.. Searching for genetic evidence of demographic decline in an arctic seabird: beware of overlapping generations. Heredity, 2022, 128 (5), pp.364-376. ⟨10.1038/s41437-022-00515-3⟩. ⟨hal-03658284⟩