Where are the biggest gaps in phylogenetic coverage of insect diversity?

Abstract

Gaps in phylogenetic knowledge are unlikely to be filled in an optimal manner in the absence of a quantitative descriptive framework of phylogenetic coverage to date and a strategy for addressing the remainder (the Darwinian Shortfall). One strategy would be modelling phylogenetic progress on a framework of insect diversity, such as a taxonomic database. I herein sampled existing phylogenetic coverage by collating a machine-readable tree from each of 1000 insect publications. Processing comprised primarily taxonomic harmonization, the standardization of terminal labels and pruning of uninformative terminal sets such as taxon duplicates. The phylogeny database contained 94,173 unique species IDs over 154,938 terminals in total, with a respective mean and median number of species per phylogeny of 155 and 44. Omics phylogenies contained the most species on average, though not the most novel species, and mitogenome phylogenies contributed the fewest novel species. Synthesis phylogenies were very few in number, but nonetheless predicted to contribute most to increasing phylogenetic coverage of insect diversity. 6.2% of the 970,000 species of the Catalogue of Life were contained amongst the terminals of the database of phylogenies. Phylogenetic coverage of insect families was often disproportionate to species-richness; those most undersampled were beetles and included families Curculionidae, Staphylinidae, Cerambycidae, and Scarabaeidae, and those with disproportionately high phylogenetic coverage included families of the dragonflies, bees, butterflies and ants. The work herein provides a foundation for quantification of the Darwinian Shortfall, and for shifting to an objective strategy for completing the insect Tree of Life.