In a paper just out in Biological Conservation, we estimate that 46% of Singapore’s butterfly species have been extirpated since 1854. Our study, one of the most comprehensive of its kind for tropical insects, gives a window on to how insect biodiversity may suffer as habitat destruction and degradation continues across the tropics. The paper was led by Meryl Theng, who was a research assistant in our lab and has recently started a PhD at the University of Adelaide.
To make our estimate of Singapore butterfly extirpations, we first put together an extensive database of butterfly records in Singapore going back to the first major collections in 1854. This included records from the Natural History Museum London, to which we sent two staff members to search for Singapore butterfly records. We then applied statistical models, recently developed in our lab, that estimate the total extirpation rate accounting for both observed and unobserved species.
We also looked at traits associated with early detection and early extirpation among Singapore’s butterflies. We found that species with rare larval host plants tended to be discovered later and extirpated earlier. Additionally, species with small wingspans tended to be discovered later, and species that were forest-dependent tended to be extirpated earlier.
Our paper provides an informative and timely case study of tropical insect extirpations. The estimated 46% extirpation rate of butterflies in Singapore (95% confidence interval [41%, 51%]) is greater than that previously estimated for birds in Singapore (33% [31%, 36%]), and suggests that tropical insects may be suffering more than other groups from human impacts.
Theng M., W. F. A. Jusoh, A. Jain, B. Huertas, D. J. X. Tan, H. Z. Tan, N. P. Kristensen, R. Meier, R. A. Chisholm. A comprehensive assessment of diversity loss in a well-documented tropical insect fauna: Almost half of Singapore’s butterfly species extirpated in 160 years. Biological Conservation 242:108401
Update: Our work has been reported on in the Straits Times (paywall) and in the Star online.
Ancistroides gemmifer, a species of skipper butterfly last recorded in Singapore 1926 and presumed extirpated there. The species persists in other parts of the region, including Penang, Malaysia, where this photo was taken. Image Credit: Gan Cheong Weei