Research Programs
My research interests center on evolution and ecology. I am finishing two funded projects on the evolution of mating systems and behavioral ecology. I am also just beginning two collaborative projects on paleoecology and the bio-control of invasive species.
I have long been interested in the evolution mating systems, working with both branchiopod crustaceans and livebearing fish. Currently, my research has focused on delineating the factors allowing the coexistence of male and hermaphrodite (termed "androdioecy") freshwater shrimp in ponds across the world. Over the years of studying this question, my research has evolved into an interdisciplinary (or "integrative") set of projects that combine to approach the complex question of how mating systems have evolved in these shrimp. Several graduate students and I are studying a variety of ecological and genetic aspects of the unique mating system found in one of these shrimp (Eulimnadia texana), seeking to discern the costs and benefits of selfing vs. outcrossing in this interesting system. Since this early work on this one species, we have expanded to study mating system evolution across the family Limnadiidae using phylogeographic, ecological, behavioral, and genetic approaches. We recently published a paper establishing that shrimp in the genus Eulimnadia have reproduced via androdioecy for 24-180 million years, which is orders of magnitude longer than predicted by models of this mating system and the only system in which androdioecy is known to be this long-lived. We also published a recent review outlining the various androdioecious animals described to date, and noted that our clam shrimp are the most specious taxon known that is entirely androdioecious. We are now pursuing another dimension to this research which will add a paleontological aspect to our comparisons. We have teamed up with Dr. Lisa Park (UA Geology Dept.) to begin to explore our ability to assess mating system type using only fossilized carapaces of Limnadiidae. If we can reliably ascertain mating system from the fossil record, we will then open up a broad range of research possiblities that would allow us to explore associations of mating system with habitat characteristics over broad time spans. Additional previous research on mating system evolution in Eulimnadia has focused on inbreeding depression, relative survival of males and hermaphrodites, and the effectiveness of males in fertilizing hermaphrodites (including the competitiveness of their sperm).
Our behavioral work centers on the mating behavior of clam shrimp. We are particularly interested in a type of behavior termed "mate guarding" in which males hold ("clasp") onto hermaphrodites for up to two hours before mating. This type of mating sets up an intersexual conflict in that the optimal timing of such mate guarding is often longer for males than it is for hermaphrodites. My PhD student (Chiara Benvenuto) is currently exploring the effects of various social environments on the timing of mate guarding to test how such environments might influence such intersexual conflict.
Along with our evolutionary questions involving E. texana, we are additionally interested in understanding its basic biology. We are currently working on understanding the reproductive system of these crustaceans, using both genetic and histological methods to understand whether these shrimp can store sperm, how hermaprhoditism may have evolved, the ultrastructure of the male gonad, and where and when fertilization takes place. The evolutionary research on mating systems has logically led us to reconstruct the phylogeny of the Limnadiidae, which we are further pursuing and expanding in collaboration with Dr. Randy Hoeh of Kent State University and Christopher Rogers of EcoAnalsysts, Inc. We are also exploring the population genetics of these shrimp by genetically typing individuals from a number of natural populations and comparing these genetic metrics to those of a closely related congener (E. diversa). Additionally, we are documenting the extent of inbreeding in these natural populations using genetic techniques.
New Research Directions
I am starting two new research directions as a result of interactions in our new Integrated Bioscience PhD program. The first is a collaboration with Dr. Lisa Park, a paleontologist in the University of Akron's Geology Department. Dr. Park is an expert in ostracod evolution and thus has background in inferring evolutionary relationships among species on the basis of carapace shape and ornamentation. We are teaming up to use the broad array of clam shrimp samples that we have accumulated across the planet to refine our understanding of the fossil records of conchostracans. We then plan to use this new understanding of these fossil clam shrimp to test ideas on long-term breeding system evolution in these crustaceans.
The second collaboration involves a North-east Ohio bio-monitoring company (Enviroscience, Inc.) that has developed an intriguing bio-control process to control the Eurasian watermilfoil, an invasive water-dwelling plant that has become a major scourge throughout much of the U.S. Our collaborative effort is aimed at further understanding the life history of the control organism, the weevil, Euhrychiopsis lecontei. We seek a better understanding of this weevil so that we can better culture these animals in the laboratory.
NSF-Funded Research
We (Joel Duff and I) are finalizing a project funded from the National Science Foundation that broadened our lab estimates of inbreeding depression, relative survival and male mating effectiveness in E. texana by measuring these parameters under field conditions. In this project, we used a combination of molecular, behavioral, and field-based projects to address the maintenance of androdioecy in this species. We have two Ph.D. students (Chiara Benvenuto and Sadie Reed) working on these projects, overseeing both the molecular project (using microsatellites to determine natural rates of outcrossing in the field studies) and the field-based projects in Las Cruces, New Mexico. Chiara is also involved with two laboratory-based mating behavior projects. The data generated from these projects will be used to corroborate/reevaluate our laboratory estimates of these parameters.
A second NSF-funded project is also in its final phase. In this project, we examined the extent of androdioecy in the clam shrimp family Limnadiidae to note the evolutionary history of this mating system among the five genera in this family. I am collaborating with Randy Hoeh from Kent State University and Christopher Rogers of Ecoanalysts, Inc. We have discovered androdioecy in 13 total species in the genus Eulimnadia, and phylogenetic evidence suggests that androdioecy is the predominant mode of reproduction in this genus. We have published a preliminary analysis of the family, but are also working on a larger DNA and morphologically-based phylogeny of the Limnadiidae. We are finalizing our comparison of these reproductive findings to our best estimate of this family’s evolutionary history to gauge the age of androdioecy in these shrimp.
Three of my students recently returned from an extended research trip to Perth, Australia studying an intriguing rock pool system in which a related androdioecious clam shrimp (Eulimnadia feriensis) coexists with a closely related dioecious (separate males and females) clam shrimp (Limnadia badia). Their projects include genetic, behavioral, and community studies to better understand this interesting mating system dichotomy. We are collaborating with Dr. Brenton Knott of the University of Western Australia for this project. Our first publication about this system is scheduled to come out shortly.
If any of the above research topics interests you, please link to my bibliography page for access to the abstracts of this work and requests for reprints. If you are a student interested in possibly working on these or related topics, please e-mail me at the following address: SCWeeks@uakron.edu.
Interested PhD students should note that we are offering 8 fully-funded PhD positions in our new Integrated Bioscience PhD program, which include a generous stipend plus tuition remission for 5 years.
E-mail address : SCWeeks@uakron.edu.