A highly resolved food web for insect seed predators in a species-rich tropical forest.

The top-down and indirect effects of insects on plant communities depend on patterns of host use, which are often poorly documented, particularly in species-rich tropical forests. At Barro Colorado Island, Panama, we compiled the first food web quantifying trophic interactions between the majority of co-occurring woody plant species and their internally feeding insect seed predators. Our study is based on more than 200 000 fruits representing 478 plant species, associated with 369 insect species. Insect host-specificity was remarkably high: only 20% of seed predator species were associated with more than one plant species, while each tree species experienced seed predation from a median of two insect species. Phylogeny, but not plant traits, explained patterns of seed predator attack. These data suggest that seed predators are unlikely to mediate indirect interactions such as apparent competition between plant species, but are consistent with their proposed contribution to maintaining plant diversity via the Janzen-Connell mechanism.

DNA-based taxonomy of larval stages reveals huge unknown species diversity in neotropical seed weevils (genus Conotrachelus): relevance to evolutionary ecology.

High diversity in tropical phytophagous insects may be linked to narrow host specificity and host shifts, but tests are complicated by incomplete taxonomy and difficulties in food source identification. Specimens of the highly diverse New World genus Conotrachelus (Coleoptera: Curculionoidea) were reared from >17,500 fruits (seeds) at six Central American rain forests. Interception traps were used for comparison with assemblages flying in the forest. Mitochondrial cox1 and the nuclear 28S genes were sequenced for 483 larval and adult specimens. A Yule-Coalescent technique was used to group cox1 sequences into putative species (17 from traps, 48 from rearing). Cox1 sequences of 24 species from museum collections provided matches for three species from traps and no match for the reared species. Inga (Fabaceae) was the predominant host among 15 other genera and 67% of the weevils were monophagous. A three gene tree (cox1, rrnL, 28S) recovered four well-supported clades feeding on Inga confirmed by phylogenetic community analyzes that showed phylogenetic conservation of host plant utilization. This suggests that host shifts are not directly involved in speciation, while the broad taxonomic host range and the evolutionary repeated shifts still contribute to the high species richness in Conotrachelus. The DNA-based approach combining species delimitation and phylogenetic analysis elucidated the evolutionary diversification of this lineage, despite insufficient taxonomic knowledge. Conotrachelus is an example of the diverse tropical groups that require DNA-based taxonomy to study their evolutionary ecology.