Histerid beetles are conspicuous members of the arthropod microfauna. As predators of numerous insect pests, especially flies and bark beetles, they have forensic and economic significance. Some are specialist predators of social insects, and have evolved remarkable ecological integrating mechanisms. Despite their ecological and economic importance, our knowledge of their diversity is poor. This project will clarify the taxonomy of approximately 400 Neotropical species in the Exosternini, resolving their evolutionary relationships using DNA and anatomical characteristics, describing hundreds of new species, providing illustrated identification guides, and developing species pages for the Encyclopedia of Life.
This project will strengthen international scientific collaborations. Our fieldwork will be done in collaboration with Latin American research institutes, who will serve as specimen repositories, provide local expertise and support, and benefit through project workshops. This research will open up an important component of beetle biodiversity to further study, provide greater understanding of the evolution of the most diverse group of animals on the planet, and will help develop human resources in biodiversity science.
This project funded a detailed study of the evolutionary relationships, taxonomy, and natural history of a poorly known group of histerid beetles (also known as 'clown beetles'), in the tribe Exosternini, revising all the members of the tribe occurring in North, Central, and South America. In these regions the tribe previously contained 188 named species. By visiting or borrowing specimens from over 30 other museums, and through 9 weeks of fieldwork in the Neotropics, the number of known species more than doubled. Beetles in this group are quite small, no more than about 5mm. However, they can be extremely abundant, appearing by the hundreds in suitable microhabitats. The species are all suspected to be predators of other insects, particularly larval flies and wood-destroying beetles. Therefore they are of particular interest as natural enemies of various pest insects. However, prior to this study there had never been a comprehensive study of their taxonomy and distributions, and their identification was virtually impossible, even by specialists. The project's first task was to visit historic European collections to study the original (or 'type') specimens for all the previously described species. Most of these were described in the mid- to late-1800s, by English, French, and German experts. We visited three of the most significant collections, in London, Paris, and Berlin, in 2010. By carefully photographing these type specimens, and comparing their characteristics with modern specimens, we were able to confidently associate these names with more recently collected material. Then it became possible to distinguish new species from those previously known. Although we borrowed over 10,000 specimens of Exosternini from other museums, there were still major gaps in sampling. In addition there were extremely few specimens collected and preserved in such a manner as to preserve DNA, which would be essential to confidently inferring evolutionary relationships. Finally, very little was known about the ecological relationships of most of the species. Therefore we planned field trips to areas we felt most likely to produce new species, unusual species, and field observations of natural history. In 2011 we mounted three separate expeditions, to northern Argentina, to Coastal, Andean, and Amazonian Ecuador, and to southeastern Brazil. During each of these trips we studied other existing in-country collections, and presented our research to several groups of students and local scientists. In turn our work was greatly facilitated by their assistance. With identities established, and large collections at hand, we were ultimately able to sort available specimens into nearly 700 species. We successfully sequenced DNA from nearly 150 of these, and created a database of over 250 morphological characteristics. Together these formed the basis for one of the largest phylogenetic datasets ever analyzed in entomology. The evolutionary tree obtained served as the foundation for a reclassification of most of the species and placement of several hundred new species in meaningful genera. By the end of the funded project we had published numerous peer-reviewed papers, totalling nearly 1000 pages, describing over 250 species as new, redescribing 100 others, and providing thousands of images of all the known species in publications and public databases (such as Morphbank). Although the enormous number of new species precluded describing all of them during the period of funding, the groundwork is set, and the remaining descriptions will be completed over the coming years. Not only did this project substantially advance our knowledge of Neotropical beetle biodiversity and evolution, but it set a strong example for modern revisionary systematics, proving that large-scale revisions are feasible. Furthermore the project helped build a strong international network of scientific collaborators, across several countries and continents, establishing a foundation for future research. The project also provided an entry point for a number of high school and undergraduate students into systematic entomology, through workshops and employment at the Santa Barbara Museum of Natural History.
