The butterflies of Barro Colorado Island: Local extinction rates since the 1930's

Authors: BASSET, YVES - Smithsonian Tropical Research; BARRIOS, HECTOR - Universidad De Panama; SEGAR, SIMON - University Of South Bohemia; Srygley, Robert; AIELLO, ANNETTE - Smithsonian Tropical Research; WARREN, ANDREW - University Of Florida; DELGADO, FRANCISCO - Universidad De Panama; CORONADO, JAMES - Smithsonian Tropical Research; LEZCANO, JORGE - Smithsonian Tropical Research; ARIZALA, STEPHANY - Smithsonian Tropical Research; RIVERA, MARLENY - Universidad De Panama; PEREZ, FILONILA - Smithsonian Tropical Research; BOBADILLA, RICARDO - Smithsonian Tropical Research; LOPEZ, YACKSECARI - Smithsonian Tropical Research; RAMIREZ, JOSE' - Smithsonian Tropical Research

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/2015
Publication Date: 8/25/2015
Publication URL: http://handle.nal.usda.gov/10113/61603
Citation: 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.A. 2015. The butterflies of Barro Colorado Island: Local extinction rates since the 1930's. PLoS One. 10(8):e0136623. doi:10.1371/journal.pone.0136623.

Interpretive Summary: In the few studies that have been conducted, local extinction of tropical butterfly species is typically due to loss of their host-plants. Using data sets that cover 90 years, we evaluated changes in butterfly composition on Barro Colorado Island (BCI, Panama). Of the 601 butterfly species recorded from BCI between 1923-2013, we estimate that only 390 are currently breeding on the island, including 34 cryptic species that are currently only known by their DNA Barcode Index Number. Twenty-three butterfly species that were abundant nearly a century ago were not found more recently, despite a much higher sampling effort in recent times, and we conclude that these species are extinct from BCI. These extinct species from several taxonomic families conservatively represent 6% of the estimated local pool of resident species. Growth form of the host growth and butterfly wing size influenced risk of extinction with the most likely candidates for extinction being small skippers (Hesperiidae) feeding on herbs (35% of extinct species). However contrary to our working hypothesis, extinction cannot be attributed to loss of host plants on BCI. In most cases the host plants remain extant, although they probably subsist at lower or more fragmented densities. Coupled with low dispersal power, this reduced availability of host plants probably has caused the local extinction of some of the species that we report. Many more bird than butterfly species have been lost from BCI recently, suggesting that small preserves may be far more effective at conserving invertebrates than vertebrates and, therefore, should not necessarily be neglected from a conservation viewpoint.

Technical Abstract: Few data are available about the regional or local extinction of tropical butterfly species. When confirmed, local extinction was often due to the loss of host-plant species. We used published lists and recent monitoring programs to evaluate changes in butterfly composition on Barro Colorado Island (BCI, Panama) between an old (1923-1943) and a recent (1993-2013) period. Although 601 butterfly species have been recorded from BCI during the 1923-2013 period, we estimate that 390 species currently are breeding on the island, including 34 cryptic species, currently only known by their DNA Barcode Index Number. Twenty-three butterfly species that were considered abundant during the old period could not be collected during the recent period, despite a much higher sampling effort in recent times. These species are considered locally extinct from BCI and conservatively represent 6% of the estimated local pool of resident species. Extinct species represent distant phylogenetic branches and several families. The butterfly traits most likely to influence the probability of extinction were host growth form and wing size, independently of the relationships among butterfly species. On BCI, our most likely candidates for extinction are small hesperiids feeding on herbs (35% of extinct species). However, contrary to our working hypothesis, extinction of these species on BCI cannot be attributed to loss of host plants. In most cases these host plants remain extant, but they probably subsist at lower or more fragmented densities. Coupled with low dispersal power, this reduced availability of host plants probably has caused the local extinction of some of the species that we report. Many more bird than butterfly species have been lost from BCI recently, suggesting that small preserves may be far more effective at conserving invertebrates than vertebrates and, therefore, should not necessarily be neglected from a conservation viewpoint.