An integrative framework for dark taxa biodiversity assessment at scale: A case study using Megaselia (Diptera, Phoridae)

1. Species extinctions increase at a global scale; therefore, rapid inventorying of our planet's biodiversity is becoming more and more important. As insects represent the highest portion of the fauna and play key ecological roles, it is a pressing need to investigate their biodiversity and accelerate species discovery, especially for understudied insect groups, also known as "dark taxa." Phoridae (Diptera) are a great example of a "dark taxon," in particular the genus Megaselia Rondani. 2. The use of integrative methodologies is the best approach to face up to the task of describing hyperdiverse and dark taxa, as morphology alone can be imprecise and slow, and molecular methods alone are often insufficient and lead to errors. 3. Here, we used the Large-Scale Integrative Taxonomy (LIT) approach to sort 9000 Megaselia into 277 putative species based on DNA barcodes. Each cluster passed through an evaluation of the predictors for incongruence indices between clusters and morphology (maximum p-distance, stability index), and a subset of specimens were morphologically examined. 4. We provided species estimates with Chao1, and our results suggest a 15% increase in species richness on our dataset. As this estimate was mostly based on samples from southern Germany, the species count will likely increase with expanded geographic sampling. This is a step forward in the study of this taxon, despite the fact that the German insect fauna is one of the best known in Europe and boasts more than one hundred years of study on phorids.