Research Interests

My current research interests include speciation, genetics, reproductive isolation, and mating system evolution. My research can be divided into several broad areas. I work with several collaborators, and undergraduate, M.Sc., and Ph.D. students have participated in all aspects of this research.

Distribution of periodical cicadas. Understanding the distributions of periodical cicada species and broods (year-classes) is key to formulating hypotheses for their formation and understanding their ecological importance. Although crude maps of periodical cicadas have existed for over a century, many current maps of these insects are only modernizations of older maps. I am currently a principal member of a project to refine data collection methods and create entirely new, highly detailed maps of periodical cicada broods. My involvement in the mapping project began when I was a graduate student; when I became a postdoctoral associate in Chris Simon's lab at the University of Connecticut, I supervised the involvement of at least four undergraduates in this project.

Molecular markers in periodical cicadas. Two species of periodical cicada (M. neotredecim and M. tredecim) exhibit a striking pattern of reproductive character displacement associated with their contact zone (In 1998, I was the co-discoverer of this pattern). The incompatible sexual signals of these species appear to reduce opportunities for gene flow and provide a rare example of insect premating isolation mediated by song pitch. I intend to evaluate the evidence for gene flow between these species (and between other species or brood pairs) by searching for new species-specific genetic markers (AFLPs, satellites, or preferable nuclear genes). Understanding the relationships of periodical cicada species and populations is key to evaluating ecological hypotheses for their formation. Phylogeographic analyses are projects in which undergraduates can participate and learn techniques for DNA isolation and amplification.

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 be relatively easy to explain. While the unusual biology of these animals makes experimental manipulation difficult, a significant research project could be designed in which teams of researchers collected samples of developing cicada nymphs and then surveyed samples of different ages for differences in the expression of "diapause genes" such as period or timeless, or for differences in ecdysteroid levels.

Mating system evolution in periodical cicadas. Male Magicicada form dense, loud acoustical choruses that females visit in order to mate. In 1995, I was the co-discoverer of a previously unknown female receptivity signal in Magicicada; this signal has a species-typical timing in relation to the male call. Before this discovery, functional explanations for the complex and conspicuous behaviors of male Magicicada were lacking, and little was known about the role of females in pair formation. Knowledge of these signals has allowed new experimental approaches to these animals' unusually complex courtship behaviors, and it has revealed a number of surprises, such as a complex form of mate competition in which a courting male acoustically jams the calls of potential rivals. Many of the unresolved questions concerning cicada mating behaviors are easily approached with simple, straightforward experiments that are ideal for student involvement.

Other studies of North American cicadas. In addition to my research on periodical cicadas, I have several ongoing projects concerning the life cycles, behaviors, and distributions of other (non-periodical) cicada species in North America. In particular, I have been making detailed, annual maps of the semiperiodical cicada Okanagana rimosa and its close relative, Okanagana canadensis.

Systematics and revision of Australian and New Zealand cicadas. I have an ongoing collaboration with several Australian colleagues, and as our collections progress, I will be spending more time describing species and constructing molecular phylogenies. The laboratory work involved includes many of the same techniques as the periodical cicada research, and it can provide students an opportunity to learn and use DNA technology.

Significance.

My research has general relevance for understanding processes of speciation, the maintenance of species differences, and mating system evolution. In addition, my research provides information about the postglacial formation of the Eastern Deciduous Forest.


© 2007 John R. Cooley