Unexpectedly high genetic diversity in a rare and endangered seabird in the Hawaiian Archipelago

Abstract

Seabirds in the order of Procellariiformes have one of the highest proportions of threatened species of any avian order. Species undergoing recovery may be predicted to have a genetic signature of a bottleneck, low genetic diversity, or higher rates of inbreeding. The Hawaiian Band-rumped Storm Petrel (‘Akē‘akē; Hydrobates castro), a long-lived philopatric seabird, suffered massive population declines resulting in its listing under the Endangered Species Act in 2016 as federally Endangered. We used high-throughput sequencing to assess patterns of genetic diversity and potential for inbreeding in remaining populations in the Hawaiian Islands. We compared a total of 24 individuals, including both historical and modern samples, collected from breeding colonies or downed individuals found on the islands of Kaua‘i, O‘ahu, Maui, and the Big Island of Hawai‘i. Genetic analyses revealed little differentiation between breeding colonies on Kaua‘i and the Big Island colonies. Although small sample sizes limit inferences regarding other island colonies, downed individuals from O‘ahu and Maui did not assign to known breeding colonies, suggesting the existence of an additional distinct breeding population. The maintenance of genetic diversity in future generations is an important consideration for conservation management. This study provides a baseline of population structure for the remaining nesting colonies that could inform potential translocations of the Endangered H. castro.

Extreme philopatry and genetic diversification at unprecedented scales in a seabird

“…The ‘seabird paradox,’ or the contradiction between the high vagility of seabirds and their apparent reluctance to disperse among breeding sites 19 , has drawn attention to the scale of population genetic differentiation, the mechanisms driving differentiation, and the implications these factors have for seabird conservation 4 . The scale of population genetic structure varies extensively among studied seabird species, down to extremely small spatial and temporal distances 20 – 22 , although the scale to which we observed population structure in the Barau’s Petrel is finer and more robust than has previously been recognized or explored (Table 4 ). The three indices of genetic differentiation highlighted that the Barau’s Petrel colonies constitute clear and distinct genetic populations each containing a proportion of unique genetic material, despite being separated by only 5 km.…”

Diverging Genetic Structure of Coexisting Populations of the Black Storm-Petrel and the Least Storm-Petrel in the Gulf of California

“…In some species of the Procellariiformes group, the patterns of genetic diversity have been explained as the consequence of either ecological (current) and/or evolutionary (historical) events (Antaky et al, 2020;Silva et al, 2016). In the first case, low diversity was associated with intense predation pressure observed in the Atlantic populations of Oceanodroma leucorhoa (Leach's Storm-Petrel), while high diversity was observed in the Pacific populations, which in turn were subject to less intense predation pressure (Bicknell et al, 2012).…”

“…Silva et al (2016) found evidence of genetic differentiation also using mitochondrial control region. The most recent study by Antaky et al (2020) (which used high-throughput sequencing) reported high levels of genetic diversity, with little differentiation between breeding colonies of the Hawaiian Band-rumped Storm-Petrel (Oceanodroma castro). Most of these examples found either strong and moderate evidence of genetic structure at large scales and regional scales, respectively (Antaky et al, 2020;Bicknell et al, 2012;Cagnon et al, 2004;Silva et al, 2016;Smith et al, 2007).…”

“…The most recent study by Antaky et al (2020) (which used high-throughput sequencing) reported high levels of genetic diversity, with little differentiation between breeding colonies of the Hawaiian Band-rumped Storm-Petrel (Oceanodroma castro). Most of these examples found either strong and moderate evidence of genetic structure at large scales and regional scales, respectively (Antaky et al, 2020;Bicknell et al, 2012;Cagnon et al, 2004;Silva et al, 2016;Smith et al, 2007). Although studies such as the one by Silva et al (2016) considered populations in the eastern Pacific near tropical American continent, none has been performed close to the coasts in this area.…”

“…(2016) found evidence of genetic differentiation also using mitochondrial control region. The most recent study by Antaky et al. (2020) (which used high-throughput sequencing) reported high levels of genetic diversity, with little differentiation between breeding colonies of the Hawaiian Band-rumped Storm-Petrel ( Oceanodroma castro ).…”