The importance of small-island populations for the long-term survival of endangered large-bodied insular mammals

Island populations of large vertebrates have experienced higher extinction rates than mainland populations over long timescales due to demographic stochasticity, genetic drift, and inbreeding. While being more susceptible to extinction and as such potentially targeted for conservation interventions such as genetic rescue, small-island populations can experience relatively less anthropogenic habitat degradation than those on larger islands. Here, we determine the consequences and conservation implications of long-term isolation and recent human activities on genetic diversity of island populations of two forest-dependent mammals endemic to the Wallacea archipelago: the anoa (<i>Bubalus</i> spp.) and babirusa (<i>Babyrousa</i> spp.). Using genomic analyses and habitat suitability models, we show that, compared to closely related species, populations on mainland Sulawesi exhibit low heterozygosity, high inbreeding, a high proportion of deleterious alleles, and experience a high rate of anthropogenic disturbance. In contrast, populations on smaller islands occupy higher-quality habitats, possess fewer deleterious mutations despite exhibiting lower heterozygosity and higher inbreeding. Site frequency spectra indicate that these patterns reflect stronger, long-term purging in smaller-island populations. Our results thus suggest that conservation efforts should focus on protecting small-island high-quality habitats and avoiding translocations from mainland populations. This study highlights the crucial role of small offshore islands for the long-term survival of Wallacea's iconic and indigenous mammals in the face of development on the mainland.

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Publication Details

Journal
Proceedings of the National Academy of Sciences
Published
2025-06-24
DOI
https://doi.org/10.1073/pnas.2422690122
Citations
2
Primary Topic
Animal Ecology and Behavior Studies
Type
article
Field-Weighted Citation Impact
3.43

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article

The importance of small-island populations for the long-term survival of endangered large-bodied insular mammals

David J. I. Seaman, Jatna Supriatna, Wahono Esthi Prasetyaningtyas, Rosie Drinkwater et al.
2 citations
Proceedings of the National Academy of Sciences
Animal Ecology and Behavior Studies
3.43
article

The importance of small-island populations for the long-term survival of endangered large-bodied insular mammals

David J. I. Seaman, Jatna Supriatna, Wahono Esthi Prasetyaningtyas, Rosie Drinkwater, James O. Burton, Greger Larson, Gono Semiadi, Matthew J. Struebig, Nurul L. Winarni, Selina Brace, Maria Voigt, Laurent Frantz, Nicolas J. Deere, Abdul Haris Mustari, Kusdiantoro Mohamad, Ross Barnett, J. L. Williams, Sabhrina Gita Aninta, Peter Galbusera, Dwi Sendi Priyono, Noviar Andayani, Matteo Fumagalli, Stephen J. Rossiter, Darren J. Shaw, Alberto Carmagnini, Alastair Macdonald, Deborah Greer
article en
2 citations

Abstract

Island populations of large vertebrates have experienced higher extinction rates than mainland populations over long timescales due to demographic stochasticity, genetic drift, and inbreeding. While being more susceptible to extinction and as such potentially targeted for conservation interventions such as genetic rescue, small-island populations can experience relatively less anthropogenic habitat degradation than those on larger islands. Here, we determine the consequences and conservation implications of long-term isolation and recent human activities on genetic diversity of island populations of two forest-dependent mammals endemic to the Wallacea archipelago: the anoa (<i>Bubalus</i> spp.) and babirusa (<i>Babyrousa</i> spp.). Using genomic analyses and habitat suitability models, we show that, compared to closely related species, populations on mainland Sulawesi exhibit low heterozygosity, high inbreeding, a high proportion of deleterious alleles, and experience a high rate of anthropogenic disturbance. In contrast, populations on smaller islands occupy higher-quality habitats, possess fewer deleterious mutations despite exhibiting lower heterozygosity and higher inbreeding. Site frequency spectra indicate that these patterns reflect stronger, long-term purging in smaller-island populations. Our results thus suggest that conservation efforts should focus on protecting small-island high-quality habitats and avoiding translocations from mainland populations. This study highlights the crucial role of small offshore islands for the long-term survival of Wallacea's iconic and indigenous mammals in the face of development on the mainland.

Proceedings of the National Academy of SciencesVol. 122(26)
Università Cattolica del Sacro Cuore (IT), Natural History Museum (GB), Universitas Gadjah Mada (ID), Queen Mary University of London (GB), University of Kent (GB), IPB University (ID), University of Indonesia (ID), Royal Zoological Society of Antwerp (BE), Research Network (United States) (US), University of Edinburgh (GB)
Natural Environment Research Council
Openalex Percentile: Top 9%
Animal Ecology and Behavior Studies
3.43
DOIOpen Access PDFOpenAlex
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