I study speciation and species distributions, using cicada species as model organisms. I’m particularly interested in the consequences of secondary contact and the ecological correlates of species boundaries and have worked extensively on mating signals and their exploitation by predators and parasites. I also lead a crowdsourcing project to track periodical cicada emergences in the eastern United States.
Current research projects:
My current research includes closely related projects concerning the 13- and 17-year periodical cicadas of eastern North America. Periodical cicadas are divided into species, life cycles, broods (or year-classes), and populations. Almost every year, periodical cicadas emerge somewhere in eastern North America, making them excellent research organisms. I was the co-discoverer of a cryptic periodical cicada species, Magicicada neotredecim, that exhibits a striking pattern of reproductive character displacement where it is sympatric and synchronic with the species M. tredecim. The incompatible sexual signals of these species reduce opportunities for gene flow and provide a rare example of insect premating isolation mediated by song pitch.
During my term as a Visiting Professor at Shizuoka University, my Japanese colleagues and I combined my behavioral, genetic and niche modeling research and their own phylogeographic research into one research program, concentrating on three areas:
Distribution and abundance of Magicicada. Understanding the distributions of periodical cicada species and broods is key to formulating and testing hypotheses for their formation and evolutionary histories. Although crude maps of periodical cicadas have existed for over a century, many current maps of these insects are only modernizations of relatively inaccurate 19th century maps. I am currently leading a project to refine data collection methods, create entirely new, highly detailed georeferenced maps based on both original and crowdsourced data.
Responses of Magicicada to climate change. The distributional data collected for the Magicicada project are the basis of Species Distribution Models (SDM) and SDM-based tests of hypotheses for brood range changes. In a series of manuscripts in preparation, these models will be used to develop hypotheses concerning glacial refugia and to explore predictions about how these insects will respond to climate change.
Population structure and life cycle evolution in periodical cicadas. In collaboration with Teiji Sota of Kyoto University and Jin Yoshimura of Shizuoka University, Hamamatsu Japan, I am working to develop phylogeographic hypotheses for relationships among periodical cicada broods and species, to be compared to the Species Distribution Models under development. Our collaboration also involves developing mathematical models of life cycle evolution in periodical cicadas. Periodical cicada species have either 13- or 17-year life cycles, and each species appears most closely related to one with the other life cycle, a pattern best explained by multiple allochronic speciation events. The life-cycle architecture of 17-year periodical cicadas appears to differ from that of 13-year periodical cicadas by the addition of a 4-year period of dormancy or delayed growth. Thus, life cycle switching and some speciation events in periodical cicadas may have relatively simple underlying explanations. While the long life cycles of these animals makes experimental manipulation difficult, theoretical treatment of minority life cycles as Allee effects has been a productive avenue of research for us.
Future research directions:
The methods and approaches I use are generally applicable to any singing insects, and many interesting questions await investigation. For example, some authors consider the genus Okanagana Distant 1905 to be the most speciose of North American cicada genera. Although they seem to span the North American continent, little natural history or distributional information exists concerning these cicadas. Recent work suggests that the North American genus Okanagana and the European genus Tibicina are synonymic, forming one widespread and speciose genus with a Nearctic distribution. If so, then biogeographic patterns among the members of this species group should reflect Nearctic glacial history, similar to the patterns expected in periodical cicadas and on a larger scale than our research group has found for the New Zealand genera Kikihia and Maoricicada. My preliminary work (mtDNA sequence) with this genus suggests that the Tibicina–Okanagana complex is divided into a European and two North American clades. Moreover, Tibicina may be of North American origin, contrary to conventional wisdom that Okanagana is of European origin. Preliminary work on this project is ongoing.
Examples of student research projects
Undergraduate researchers have participated in all of my projects. Examples of undergraduate research projects include Adrianne Smits’ study of the relationship between female oviposition and underground nymph density and Kathryn Fontaine’s project investigating the surprisingly common occurrence of paternal mitochondrial leakage in F1 hybrid periodical cicadas.