The magnitude of cryptic insect diversity in one tropical rainforest

Abstract

1. Cryptic species represent significant entities in conservation planning and are common among tropical insects. Many studies focusing on cryptic species have been restricted to a narrow taxon and it is not clear whether some insect clades or assemblages may have a greater propensity for cryptic speciation than others. Here, we contrast cryptic diversity among 22 insect assemblages surveyed on Barro Colorado Island (BCI), a tropical rainforest in Panama.

2. Cryptic species were defined as externally indistinguishable from their sister species but with a different barcode index number. We detected 214 cryptic species out of a total of 2,006 species studied (10.6%). The percentage of cryptic species varied greatly among assemblages (0-19%), with half of assemblages devoid of cryptic species, and the highest proportions of cryptics in Pieridae and Formicidae.

3. The percentage of cryptic species was weakly influenced by phylogeny, and it was best explained by the local number of species and an index of taxonomic knowledge. Cryptic species were distinguished by an average distance divergence in sequence of 9%, but their ecological characteristics remain unclear.

4. Asymptotic estimates indicated that 11.4% of species studied on BCI may be cryptic. Since many of the species-rich insect assemblages occurring on BCI were not considered in this study, this estimate probably represents a lower bound to the true cryptic insect richness on BCI.

5. This significant contribution to biodiversity should not be ignored and, because of apparent low population levels, may be particularly vulnerable to habitat loss and climate change.