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Butterfly Extinctions on Barro Colorado Island

September 14, 2015

Butterfly Extinctions on Barro Colorado Island

During 90 years of note-taking and net-swinging, scientists identified 601 butterfly species on Panama’s Barro Colorado Island, the most intensively studied piece of tropical real-estate in the world

During 90 years of note-taking and net-swinging, scientists identified 601 butterfly species on Panama’s Barro Colorado Island, the most intensively studied piece of tropical real-estate in the world. Currently, 390 butterfly species breed on the 6 square mile island, one-seventh the size of Orlando’s Disney World, according to a team lead by Yves Basset at the Smithsonian Tropical Research Institute. Since the 1930’s, 23 species disappeared from the island, compared to 50-60 species of birds lost during the same period.

The team compared the richest sets of records: from 1923-1943, when lepidopterists scrutinized the newly-founded field station to discover what inhabited America’s tropical forests with records from 1993-2013. Most of the records from the recent period come from the butterfly-monitoring component added to the Smithsonian’s large-scale, long-term global forest monitoring project, ForestGEO, in 2008.

In the early period, researchers identified butterflies based on their shape, size and color. Now collectors also use gene sequences (genetic barcodes) to distinguish one species from another. Overall, the butterfly families on the island with the most species were the skippers in the Hesperiidae family—with 33 percent--and the colorful Nymphalidae—also known as brush-footed butterflies--with 31 percent.

Six percent of the species identified in early studies were not found in recent studies. Butterfly extinctions are usually caused by habitat loss or by extinction of the host plants eaten by butterfly larvae. Local extinction of the host plants probably only accounted for the disappearance of four species from Barro Colorado.

Many of the butterfly species that disappeared were small-winged species Hesperiids, which feed on herbaceous plants. They may have disappeared because the island continues to lose open areas as the forest ages. Their host plants are still there, but are scattered and may be harder for the butterflies to locate.

Many more bird than butterfly species have been lost from BCI recently, confirming that small preserves may be far more effective at conserving invertebrates than vertebrates, and therefore, should not be neglected by conservationists.

The team of lepidopterists who collaborated on this study work at the University of South Bohemia and Biology Centre of the Czech Academy of Sciences, the Universidad de Panama, the Northern Plains Agricultural Lab of the USDA-Agricultural Research Service, the Florida Museum of Natural History McGuire Center for Lepidoptera and Biodiversity and at the Smithsonian.

Reference: Basset, Y., Barrios, H., Segar, S., Srygley, R.B., Aiello, A., Warren, A.D., Delgado, F., Coronado, J., Lezcano, J., Arizala, S., Rivera, M., Perez, F., Bobadilla, R., Lopez, Y., Ramirez, J. 2015. The butterflies of Barro Colorado Island, Panama: local extinction since the 1930’s. Plos 1, DOI:10.1371/journal.pone.0136623

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