Jack Sytsma¹ , Keoni Akamu² , Ian Heimburge²

1 Kansas State University, Manhattan, KS, USA
2 US Fish and Wildlife Service, Hana, HI, USA
Author    Correspondence author
International Journal of Molecular Ecology and Conservation, 2026, Vol. 16, No. 2   doi: 10.5376/ijmec.2026.16.0006
Received: 05 Apr., 2026    Accepted: 20 Apr., 2026    Published: 27 Apr., 2026

This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Sytsma J., Akamu K., and Heimburge I., 2026, Occurrence trends and genomic diversity reveal population decline and genomic erosion in Hawaiian birds, International Journal of Molecular Ecology and Conservation, 16(2): 52-67 (doi: 10.5376/ijmec.2026.16.0006)

Understanding how contemporary population declines translate into genomic consequences is critical for conservation, particularly in island ecosystems where species are highly vulnerable to environmental change. Here, we integrate long-term occurrence data with genome-wide diversity metrics to assess population status across four Hawaiian bird species representing a gradient of conservation concern: Hawaiʻi ʻamakihi (Chlorodrepanis virens), Maui parrotbill (Pseudonestor xanthophrys), ʻalalā (Corvus hawaiiensis), and Christmas shearwater (Puffinus nativitatis). Occurrence trends were quantified using reporting rates from 2000-2025 and genomic diversity was assessed using nucleotide diversity, heterozygosity, runs of homozygosity, and inbreeding coefficients from shotgun sequencing data. Results indicate that species exhibiting stronger declines in occurrence showed significantly reduced genomic diversity and elevated inbreeding. The ʻalalā and Maui parrotbill, which displayed the steepest declines in reporting rate, also exhibited the low Atkinson est nucleotide diversity and highest inbreeding coefficients. In contrast, the Hawaiʻi ʻamakihi and Christmas shearwater showed relatively stable occurrence and retained higher genetic diversity. Elevational analyses further indicated upward shifts in detection for declining forest species, consistent with restriction to high elevation refugia. Across species, occurrence trends were strongly associated with genomic metrics, suggesting that recent demographic changes reflect patterns of genetic variation. Our findings demonstrate that integrating occurrence data with genomic analyses provides a powerful framework for assessing population health. Such approaches are particularly valuable for conservation in island systems, where rapid environmental change and disease pressure continue to threaten endemic biodiversity.

Conservation genomics; Hawaiian birds; Nucleotide diversity; Inbreeding; Runs of Homozygosity; Island ecosystems