Temporal distribution in a tri-trophic system associated with Piper amalago L. in a tropical seasonal forest

Abstract

Insect seasonality is a known pattern that has intrigued ecologists for over 30 years. However, despite being well understood in general, for several taxa such as Lepidopteran caterpillars its underlying causes and mechanisms are still not fully understood. This is especially critical for Brazilian tropical forests where caterpillars have previously been shown to have a puzzling pattern of peaking in abundance only in the first months of the dry season; however, this pattern still lacks an explanation. Here, to advance our understanding of the factors underlying seasonal changes in caterpillar abundance in tropical forests, we addressed how the lepidopteran caterpillar community that feeds on Piper amalago L. plants, their host plants leaf numbers, the herbivory levels, and the parasitoid pressure all change throughout the dry and wet seasons in a Brazilian tropical semideciduous forest. We found that immature abundance and herbivory peak in the first 2 months of the dry season and then rapidly decrease and remain low throughout the remaining of the dry season and the entire wet season at the study site. However, although the proportion of parasitized immatures increased alongside caterpillar abundance, it peaked in the month that followed a drastic decrease in caterpillar abundance. These results suggest that parasitoids play a major role in the observed caterpillar abundance pattern and thus, we propose the hypothesis that high parasitoid predation pressure causes early eclosion and emergence of caterpillars and primarily drives caterpillar abundance seasonality in Brazilian tropical forests.