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.

Introduction: Herbivores specialized in consuming ant-defended plants evolve strategies to prevent the attack of ant workers. When the plant can associate with more than one ant species, the herbivore evasion strategies may either be species-specific, or flexible enough to successfully deter workers of different ant-plant species. Objectives: We studied the behavior of an herbivore bug (Piezogaster reclusus) on ant-defended acacia trees (Vachellia collinsii), which associates with one of three mutualistic Pseudomyrmex ant species, and report the geographical distribution of the acacia bug species of Costa Rica and Panama. Methods: We tested whether herbivore bugs (1) associate with a particular ant species; (2) use chemical or behavioral strategies to evade the ant workers; (3) adjust the evasion strategy to the ant species living on the acacia tree. We also compared collected acacia bugs with Museum specimens to clarify the identification from Costa Rica and Panama. Results: We found bugs more often on trees with ants, particularly Ps. spinicola, and never on trees with Ps. nigrocinctus. To avoid ant attacks, bugs use evasive behaviors to prevent encounters with the ant workers, that depended on the ant species. Also, indirect evidence of intra and interspecific transfer experiments suggest species-specific chemical camouflage or repellence. We also report an expansion of the Southern limit of Pi. reclusus distribution in Central Panama, and reduced the distribution of Pi. chontalesis to the Chiriquí region. Conclusions: Similar to herbivores specialized on chemically defended plants, herbivores on ant-defended trees could evolve specific mechanisms to deal with the plant defenses. However, plants associated with multiple partners are a challenge to herbivore specialization, and might require behavioral plasticity, as our evidence suggests.

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