Question 79% of Fijian Insect Species in Decline

Article: Genomic signatures indicate biodiversity loss in an endemic island ant fauna
Published: 11th September, 2025
By:Liu, C., Sarnat, E., Tan, J. A., Janicki, J., Deyrup, J., Ogasawara, M., Grau, M. L., Qiu, L., Hita Garcia, F., Fischer, G., Caginitoba, A., Narula, N., Darwell, C. T., Kubota, Y., Pierce, N. E., Mikheyev, A. S., & Economo, E. P.

Abstract:
'Insect populations have declined worldwide, but the extent and drivers of these declines are debated. Most studies rely on field surveys performed in the past century, leaving gaps in our understanding of longer-term trends. Using a “community genomics” approach, we estimated community assembly over millions of years and more recent demographic trends of ant species in the Fijian archipelago. We found that 79% of endemic species are in decline, starting after the arrival of humans approximately 3000 years ago and accelerating in the past 300 years, whereas recent arrivals are expanding. The primary correlate of population decline among endemic species was found to be sensitivity to habitat disturbance. This study demonstrates the value of contemporary collections for estimating long-term community trends and highlights the vulnerability of endemic island species to anthropogenic change.'

From the Article:
'Recent advances in genomic techniques offer a deeper time window into historical population and community trends (23). These developments can provide insights into insects’ demographic responses to historical human activities and other phenomena without collections or observations that span the time frame of interest.'

'Here, we used the ant community of the Fijian archipelago as a model system with which to evaluate long-term population and community trends and their biogeographic, ecological, and historical context. To do this, we used a community genomics approach (i.e., inferring patterns and processes using genomic data across a community of species) applied to contemporary collections.'

'Moreover, the consequences of human impacts on islands often unfold rapidly and have caused many documented extinctions during settlement history (35). Therefore, island systems provide a good model for evaluating long-term trends and the impacts of human activities to shed light on present-day insect declines.'

'We sequenced 4132 specimens from 144 ant species and 40 genera.'

'Our phylogenomic analysis revealed that the Fijian ant community was assembled through at least 65 colonization events. First, 26 lineages colonized Fiji naturally and led to the evolution of 88 endemic species. The high level of endemism was the result of colonizations that occurred millions of years ago followed by both in situ radiation (cladogenesis) and divergence from mainland relatives (anagenesis).'

'econd, a further 23 colonizations occurred by widespread species native to the Pacific region. This group is likely a mixture of species that colonized Fiji naturally and others that were brought more recently by human movements within the region. Finally, at least 16 non-native species were brought by humans from outside of the Pacific region (Fig. 1A and figs. S1 and S2) after Fiji was connected to global commerce networks.'

'To examine the population trends of these species, we used demographic modeling (44) to characterize changes in effective population size (Ne) for each of the 240 geographic ant populations belonging to 72 species. We found that 79% of endemic species are in decline.'

'y contrast, we detected substantial population expansions in both widespread Pacific species and non-native species that occurred rapidly over the past four centuries, with no declines detected in these groups.'

'e also found that the reductions in endemic species begin after the arrival of humans ~3000 years ago in Fiji and continued until the present, with most declines concentrated in the previous few hundred years.'

'Overall, endemic species are mostly limited to higher elevation, where more intact habitats are still found.'

'Population trends are strongly correlated with habitat disturbance, because species found in more disturbed lowland habitats typically show population expansion, whereas those now found in more intact upland habitats are declining.'

'Our results suggest that most endemic ant species of the Fijian archipelago have declined since the arrival of humans, whereas species that are tolerant of or adapted to human-dominant habitats, including all widely distributed and alien species, are expanding.'

Source:

Liu, C., Sarnat, E., Tan, J. A., Janicki, J., Deyrup, J., Ogasawara, M., Grau, M. L., Qiu, L., Hita Garcia, F., Fischer, G., Caginitoba, A., Narula, N., Darwell, C. T., Kubota, Y., Pierce, N. E., Mikheyev, A. S., & Economo, E. P. (2025). Genomic signatures indicate biodiversity loss in an endemic island ant fauna. Science (American Association for the Advancement of Science), 389(6765), 1133–1136. doi.org/10.1126/science.ads3004