Population sizes of endemic songbirds on Kaua‘i have decreased by an order of magnitude over the past 10–15 years to dangerously low numbers. The primary cause appears to be the ascent of invasive mosquitoes and Plasmodium relictum, the agent of avian malaria, into elevations formerly free of introduced malarial parasites and their vectors. Given that these declines in native bird populations appear to be continuing, last resort measures to save these species from extinction, such as conservation breeding, are being implemented. Using 200–1439 SNPs from across the genome, we assessed kinship among individuals, levels of genetic variation, and extent of population decline in wild birds of the two most critically endangered Kaua‘i endemic species, the ‘akikiki (Oreomystis bairdi) and ‘akeke‘e (Loxops caeruleirostris). We found relatively high genomic diversity within individuals and little evidence of spatial population genetic structure. Populations displayed genomic signatures of declining population size, but individual inbreeding coefficients were universally negative, likely indicating inbreeding avoidance. Diversity within the founding conservation breeding population largely mirrored that in the wild, indicating that genetic variation in the conservation breeding population is representative of the wild population and suggesting that the current breeding program captures existing variation. Thus, although existing genetic diversity is likely lower than in historical populations, contemporary variation has been retained through high gene flow and inbreeding avoidance. Nonetheless, current effective population size for both species was estimated at fewer than 20 individuals, highlighting the urgency of management actions to protect these species.
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Blood samples from individuals in the conservation breeding population were collected following San Diego Zoo Wildlife Alliance IACUC 18-022. We are thankful to Carter Atkinson, U.S. Geological Survey, Pacific Island Ecosystems Research Center, for sharing blood samples collected in the Alaka‘i during the 1990s and to Katy Parise for DNA extractions. We are grateful to the Kaua‘i Forest Bird Recovery Project field crews and the San Diego Zoo Wildlife Alliance crews for their tremendous dedication to catching all the wild birds and to finding, collecting, and hatching the eggs. The establishment of the conservation breeding population was funded by the U.S. Fish and Wildlife Service, State of Hawai‘i, San Diego Zoo Wildlife Alliance, and the Mohamed Bin Zayed Species Conservation Fund. Funding to collect samples from wild individuals and for genetic analysis was in part provided by the U.S. Fish and Wildlife Service, the State of Hawai‘i, NSF DEB-1547168, Ann Beeson, and Friends of the National Zoo’s Small Grant program. We appreciate comments on the manuscript from the @CrawLab and Cadena Lab at Universidad de los Andes and from two anonymous reviewers. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
U.S. Fish and Wildlife Service, State of Hawai‘i, San Diego Zoo Wildlife Alliance, Mohamed Bin Zayed Species Conservation Fund, Friends of the National Zoo.
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Cassin-Sackett, L., Campana, M.G., McInerney, N.R. et al. Genetic structure and population history in two critically endangered Kaua‘i honeycreepers. Conserv Genet 22, 601–614 (2021). https://doi.org/10.1007/s10592-021-01382-x
- Population structure
- Conservation breeding