DNA Barcoding for Community Ecology- How to Tackle a Hyperdiverse, Mostly Undescribed Melanesian Fauna

Background: Trigonopterus weevils are widely distributed throughout Melanesia and hyperdiverse in New Guinea. They are a dominant feature in natural forests, with narrow altitudinal zonation. Their use in community ecology has been precluded by the ‘‘taxonomic impediment’’. Methodology/Principal Findings: We sampled.6,500 specimens from seven areas across New Guinea; 1,002 specimens assigned to 270 morphospecies were DNA sequenced. Objective clustering of a refined dataset (excluding nine cryptic species) at 3 % threshold revealed 324 genetic clusters (DNA group count relative to number of morphospecies = 20.0% overestimation of species diversity, or 120.0 % agreement) and 85.6 % taxonomic accuracy (the proportion of DNA groups that ‘‘perfectly’ ’ agree with morphology-based species hypotheses). Agreement and accuracy were best at an 8 % threshold. GMYC analysis revealed 328 entities (21.5 % overestimation) with 227 perfect GMYC entities (84.1 % taxonomic accuracy). Both methods outperform the parataxonomist (19 % underestimation; 31.6 % taxonomic accuracy). The number of species found in more than one sampling area was highest in the Eastern Highlands and Huon (Sørensen similarity index 0.07, 4 shared species);M of all areas had no species overlap. Success rates of DNA barcoding methods were lowest when species showed a pronounced geographical structure. In general, Trigonopterus show high a and b-diversity across New Guinea. Conclusions/Significance: DNA barcoding is an excellent tool for biodiversity surveys but success rates might drop whe