Branches on the enormous Beetle Tree of Life
KRISTIN KALITA
Sophomore Biology major at Loyola University
REU Mentor: Dr. Margaret Thayer (Associate Curator, Zoology/Insects)
Symposium Presentation Title: One species, or more? Is Stenomalium helmsireally a widespread austral species? (Arthropoda: Hexapoda: Insecta: Coleoptera: Polyphaga: Staphylinidae: Omaliinae)
Symposium Presentation Abstract: Currently, the beetle family Staphylinidae (rove beetles) includes more than three percent of all described animal species and occupies virtually all terrestrial habitats. Among those inhabiting lands of the southern hemisphere, most are endemic to a single area. Stenomalium helmsi appears to be an exception to that pattern, having been collected in Australia, New Zealand, and southern Chile and Argentina. Typically, divergent evolution after the breakup of Pangaea resulted in various austral lands having similar yet distinct species, so the existence of a widespread species would demand other distributional explanations.
A specimen from the middle of the range of distribution in New Zealand was chosen as a reference specimen of S. helmsi. Through the study of 69 morphological characters, including detailed genitalia and macrosetae analyses, the supposed S. helmsi specimens were compared to the reference specimen. Ten other species of Stenomalium and related genera of Omaliini were also coded in order to generate a phylogenetic tree using TNT and to examine character distribution in WinClada.
The examination of 28 S.helmsi specimens provided no significant evidence of more than one species being involved. Furthermore, the tree search produced two most parsimonious trees, each of length 136. Each tree placed S. helmsi two nodes up from the group of other Stenomalium,a well-supported group with a Bootstrap value of 92. Thus, Stenomalium does not include S. helmsi. Possibly, S. helmsi represents an undescribed genus that is characterized by three synapomorphies. Because S. helmsi has been more widely and more abundantly collected in New Zealand than in other austral locations, the species may have originally dispersed from New Zealand. Regardless of the cause of dispersal, the fact that S. helmsi defies the area-endemic pattern reveals that the distribution of all austral Staphylinids is not the result of a single set of causes.
Original Project Description: Part of the NSF-funded project Assembling the Beetle Tree of Life is based at the Field Museum: the TWiG (Taxonomic Working Group) dealing with the huge family Staphylinidae (rove beetles) and related smaller families that make up the series Staphyliniformia. The project as a whole is analyzing the phylogenetic relationships among the 4 suborders, nearly 200 families, and over 500 subfamilies of the order Coleoptera, using both morphological data from adults and larvae and DNA sequence data. The aim of the project is constructing a robust evolutionary framework as a basis for studies of the phylogeny and evolution of this enormous group of insects. It is also – for the first time in most cases – contributing content on the Tree of Life web project (tolweb.org) for the branch pages of all families and subfamilies.
Research methods and techniques: The REU intern will focus on one (or more if small) family or subfamily of Staphylinoidea from among the 5 families and 48 subfamilies whose pages are currently only skeletal (see http://tolweb.org/Staphylinoidea/9076; Silphidae is a good example of a largely complete page). The intern will gain insights into beetle diversity, morphology, phylogenetics, evolution, and biology, synthesize (with guidance) relevant research literature, and learn specimen imaging techniques (possibly including SEM) to provide illustrations for the page(s). The result will be one or more completed tolweb branch pages. The intern will gain a thorough understanding of the wealth of information – accumulated over decades or centuries – that goes into creating clear and informative summaries for non-specialists. Depending on the group chosen, the intern may also have the opportunity to interact (probably via email) with specialist(s) elsewhere, to seek their input and/or feedback on the page content.
