A groundbreaking study spearheaded by the San Diego Zoo Wildlife Alliance in collaboration with the Smithsonian’s National Zoo & Conservation Biology Institute delivers unprecedented insights into the genomics of Hawai‘i’s critically endangered honeycreepers. This research provides a profound understanding of how genetic factors influence the survival prospects of these unique native birds amidst an overwhelming extinction crisis. Of approximately 60 historically documented species, only 17 remain today, with most experiencing catastrophic declines fueled primarily by avian malaria spread by invasive mosquitoes. The findings, unveiled in the renowned journal Current Biology, emphasize that although the critically endangered ‘akeke‘e faces imminent extinction, targeted and urgent conservation interventions could still reverse this trajectory.
The genetic underpinnings of the remaining honeycreepers are revealing. Lead author Christopher Kyriazis, Ph.D., a postdoctoral researcher with the San Diego Zoo Wildlife Alliance, highlights that the last survivors harbor significant genetic diversity. This was somewhat unexpected given the severe bottleneck many of these populations have endured. The genomic data provide vital clues about how these birds might respond to environmental threats and assist in refining recovery strategies. Genetic diversity is typically linked with increased resilience and adaptive potential, but the study also underscores the precarious balance this biodiversity holds as inbreeding becomes a rising concern when populations shrink markedly.
Among the greatest challenges is the relentless advance of avian malaria, a parasitic disease vectored by non-native mosquitoes. Climate change-driven warming has facilitated the upward migration of these disease carriers into higher elevations that historically served as refuges for honeycreepers. This pathogen invasion, coupled with habitat loss, has led to catastrophic population crashes, especially on the island of Kaua‘i. Unlike other Hawaiian islands with higher elevation sanctuaries, Kaua‘i’s limited topography leaves the two critically endangered species, the ‘akikiki and ‘akeke‘e, virtually defenseless. Both have declined by more than 99% in recent decades, spiraling dangerously toward extinction.
In response to this dire situation, mosquito population control measures are underway, including the strategic release of reproductively incompatible male mosquitoes aimed at suppressing vector numbers. These biocontrol efforts offer a ray of hope, particularly if scaled and maintained effectively. The study’s genomic analyses emphasize that such interventions are essential and urgent if the ‘akeke‘e is to avoid extinction. Without continued and enhanced mosquito suppression, the ‘akeke‘e’s remaining population—estimated at fewer than 100 individuals—is unlikely to survive the rapidly escalating disease pressure.
The extinction narrative of the ‘akikiki is even bleaker. Now extinct in the wild, this species clings to survival only through a conservation breeding program managed by the San Diego Zoo Wildlife Alliance across Maui and Keauhou Bird Conservation Centers. This captive population, roughly 40 birds strong, was established as a last-ditch effort. Genomic analyses of these birds reveal a troubling level of inbreeding depression that could undermine conservation success. Many of the founders reflect mating between closely related individuals, resulting in offspring with diminished survival rates and reproductive success. Such findings provide crucial data to optimize breeding decisions and reinforce genetic health.
This research also took advantage of archived biological material from the extinct po‘ouli, a honeycreeper whose last known individual passed into extinction some years ago. The San Diego Zoo Wildlife Alliance’s Frozen Zoo® biobank, a medical marvel, preserved a cell line from the final po‘ouli in 2004—the first time viable cells from an extinct species were cryopreserved. Recently, researchers successfully thawed one vial to sequence the po‘ouli genome, offering an unparalleled window into the evolutionary and genetic history of this lost species. These genetic blueprints grant invaluable lessons for managing the remaining species facing similar extinction pressures.
The genomic evidence demonstrates that while po‘ouli maintained high genetic variation prior to extinction, this alone could not counteract the combined effects of environmental changes, disease burdens, and human impact. The genetic information derived from extinct species like po‘ouli underscores the untapped potential of biobanking as a conservation tool. Techniques such as assisted reproduction and possibly de-extinction efforts rely heavily on such genetic archives to enrich or restore lost biodiversity, especially for species teetering on the edge.
Critical to this study is the revelation of how inbreeding depression manifests distinctly in small, endangered populations. In ‘akikiki, inbreeding resulted in fewer offspring production and decreased survivorship, phenomena well-documented in conservation genetics but seldom quantified so precisely for Hawaiian honeycreepers. These data enable conservationists to make more informed decisions regarding mate pairings, aiming to maintain heterozygosity and mitigate deleterious genetic effects. As effective captive breeding programs serve as genetic reservoirs, genomic tools facilitate preservation of genetic variation vital for long-term viability.
Moreover, this research sheds light on the complex interplay between demographic collapse and genomic health. While high heterozygosity signals retained genetic diversity, it cannot offset the increased risks posed by small population sizes, where genetic drift rapidly fixes harmful alleles, amplifying extinction risk. This delicate balance between genetic diversity and demographic parameters necessitates integrated conservation approaches that combine habitat protection, disease management, and genetic monitoring.
The genomic insights from this study not only advance fundamental understanding of Hawaiian honeycreeper biology but also serve as a powerful model for other endangered species worldwide confronting similar threats. The findings underscore the urgency of integrative conservation strategies combining proactive disease control, advanced genetic management, and habitat conservation. Without such comprehensive measures, the rapid cascade toward extinction seen in Hawai‘i’s honeycreepers could repeat elsewhere.
In highlighting the fragile fate of these birds amid environmental and pathogenic pressures, the study emphasizes a broader global conservation truth: biodiversity loss is accelerating, but forward-looking science and technological innovations offer pathways to recovery. The marriage of genomic tools with ecological conservation presents unprecedented opportunities to intervene before species vanish completely. For Hawai‘i’s honeycreepers, the battle to save the ‘akeke‘e and ‘akikiki is emblematic of the species survival challenges humanity faces globally.
San Diego Zoo Wildlife Alliance’s Frozen Zoo®, a pioneer in wildlife biobanking, remains critical to these efforts. Housing genetic material from thousands of species, this cryogenic repository preserves the potential for future restorative actions. The successful recovery and sequencing of the po‘ouli genome exemplify the Frozen Zoo’s vital role as a genetic time capsule helping combat extinction. As conservationists strive to protect what remains of Earth’s irreplaceable biodiversity, such technological reservoirs ensure no genetic heritage is lost without record or hope for reprieve.
Ultimately, this landmark genomics study reveals a story of both impending loss and optimism grounded in science. It calls upon the global community to support swift ecological interventions, expand disease mitigation, and leverage cutting-edge genetics. By doing so, there remains a tangible chance that Hawai‘i’s honeycreepers can be brought back from the brink, securing their survival for future generations to appreciate and preserve.
Subject of Research: Population genomics, extinction risk, and recovery potential of critically endangered Hawaiian honeycreeper species
Article Title: Population genomics of recovery and extinction in Hawaiian honeycreepers
News Publication Date: 29-May-2025
Web References:
Image Credits: The image and its data were generated by scientist Elena Ruggeri and the Frozen Zoo team at San Diego Zoo Wildlife Alliance.
Keywords:
- Genomics
- Population genetics
- Genome sequencing
- Conservation genetics
- Endangered species
- Conservation biology
- Genomic analysis
- Inbreeding depression
- Extinction
- Wildlife
- Birds
- Heterozygosity
