Loss of dominant caterpillar genera in a protected tropical forest

ABSTRACT

Insects are the most species rich terrestrial taxa and their interactions with plants together comprise the majority of Earth’s biodiversity. Recent reports provide evidence for large climate driven declines in the abundance and diversity of insects- some suggest up to 40% of temperate species will go extinct in the next two decades. However, it has been less clear if substantive losses are occurring in intact low-latitude forests, where insect diversity is the highest. Further, the implications of reported declines on ecosystem services provided by these insects are speculated but not quantified. Using 22 years of plant-caterpillar-parasitoid data, we document the loss of entire genera of Lepidoptera and declines in parasitism in a protected tropical forest. Forty-percent of Lepidoptera genera studied are declining in frequency and reductions in parasitism events suggest a 30% drop over the next 100 years. These declines in parasitism represent a reduction in an important ecosystem service: enemy control of primary consumers. Reported reductions in diversity, density and parasitism appear to be partly driven by a changing climate and weather anomalies. Our results demonstrate the ecological costs of climate driven insect declines in intact tropical forests and support predictions that specialized parasitoids are likely to suffer. The consequences of these changes are in many cases irreversible, and declines in parasitism will likely negatively impact surrounding agriculture. The loss of important tropical taxa and erosion of associated ecosystem function underlines the apparent threat to global insect diversity and provides additional impetus for research on tropical diversity.