1. The diversity of insects in tropical forests remains poorly known, in particular regarding the critical feeding associations of herbivores, which are thought to drive species richness in these ecosystems.
2. Host records remain elusive and traditionally require labour-intensive feeding trials. A recent approach analyses plant DNA ingested by herbivorous insects; direct PCR amplification from DNA extracts from weevils (Curculionoidea) using chloroplast (trnL intron) primers was successful in 41 of 115 cases, resulting in 40 different sequences.
3. The resulting trnL intron sequences were identified against public databases to various hierarchical levels based on their position in phylogenetic trees and shown to be members of 26 plant families from different major groups of angiosperms.
4. Among the trnL intron sequences, seven pairs or triplets of close relatives (0–2 bp difference) were found which may represent intraspecific variation in the respective host plants.
5. Molecular clock calibrations of mitochondrial cox1 sequences of weevils established great distances of lineages obtained (all splits estimated >20 Mya). Distant taxa were found to feed on the same or similar hosts in some cases, showing low evolutionary conservation of host associations among deeper levels.
6. The technique provides a new means of studying species diversity and plant–herbivore interactions in tropical forests, and removes the constraints of the need for actual observations of feeding in ecological and evolutionary studies.