What can an analysis of Australian tropical rainforest bark beetles suggest about the missing millions of Earth's insect species?

Abstract

Abstract Only 20% of the estimated 5 million species of insects on Earth are named and yet insects are poorly represented in protected area assessments, and insect declines are of concern globally. Here, we explore how to increase the discovery of new species and understanding of this group through analysis of 10,097 tropical rainforest bark beetles (Scolytinae) from eight different ecological studies between 2000 and 2018 in the Australian Wet Tropics. Of the 107 species identified, 58 are undescribed: an increase of 37% on the 156 species known from Australia. Rarefaction indicates doubling sampling would increase the number of species by 17. As hypothesised, new species are significantly smaller, less abundant and less widespread than described species making them more extinction‐prone than named species. Flight interception traps collected 84% of individuals and 98% of species confirming the effectiveness of a single sampling method for some beetles. Increased locations and collection from the canopy may sample further species rather than additional collecting methods. Scolytines are relatively well studied with taxonomists at the forefront of using modern methods to resolve formerly intractable groups. Hence, these new species are more likely to be named than others in many other beetle groups where taxonomy has largely stalled. To increase species description rates and to avoid most species becoming extinct before being named, we call on taxonomists to use new character systems provided by DNA methods and advances in the rapidly developing field of artificial intelligence.