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 are currently 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. We consider these species locally extinct from BCI and they 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, wing size and host specificity, independently of the phylogenetic relationships among butterfly species. On BCI, most likely candidates for extinction were 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 has probably caused the local extinction of some butterfly species. 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 necessarily be neglected from a conservation viewpoint.

Faculty of Science University of South Bohemia and Institute of Entomology Biology Centre of Czech Academy of Sciences Branišovská 31 370 05 České Budějovice Czech Republic

McGuire Center for Lepidoptera and Biodiversity Florida Museum of Natural History University of Florida 3215 Hull Rd P O Box 112710 Gainesville Florida 32611 2710 United States of America

Northern Plains Agricultural Lab USDA Agricultural Research Service 1500 N Central Ave Sidney Montana 59270 United States of America

Smithsonian Tropical Research Institute Apartado 0843 03092 Panama City Republic of Panama

Universidad de Panamá Centro Regional Universitario de Veraguas Santiago Republic of Panama

Universidad de Panamá Maestria de Entomologia 080814 Panama City Republic of Panama