Dr. Stephen Weeks

Dr. Stephen Weeks

Title: Professor/Interim Chair of Biology/Interim Director of the Integrated Biosciences Program
Dept/Program: Biology
Office: ASEC D401
Phone: 330-972-6954
Fax: 330-972-8445
Email: scw@uakron.edu
Website: http://www3.uakron.edu/biology/hmpg1.html


I earned a B.A. in Aquatic Biology from the University of California, Santa Barbara in 1983.

I then earned an M.A. in Biology from the University of California, Riverside in 1986, conducting research on the ecological ramifications of different breeding systems in branchiopod crustaceans.

I then went to Rutgers University in New Jersey for my Ph.D., working with Dr. Robert Vrijenhoek, again researching the ecological effects of sexual relative to asexual reproduction, this time in live-bearing fish (Poecillidae). I earned my PhD in 1991.

From there, I did a short-term post-doc (1991) at Pennsylvania State University, in the Anthropology Department, studying the evolution of aging.

I did a second post-doc at the Savannah River Ecology lab (run through the University of Georgia, Athens) from 1992-1994, working with Dr. Gary Meffe on life history evolution in another live-bearing fish (Gambusia affinis).

I started at the University of Akron in 1994.


2010 | Research on sex chromosomes featured in F1000 Biology

2007 | Research Award, Buchtel College of Arts and Sciences, The University of Akron

2005-06 | Research on mating systems featured in Nature (2005, 438:893), Science (2006, 313:1381) and Current Biology (2006, 16:R36-R37).

2005 | “Top Researcher” in College of Arts & Sciences, University of Akron        

2000 | Early Career Research Award, Buchtel College of Arts and Sciences, The University of Akron

1986-91 | PhD - Ecology, Rutgers University

1983-86 | MA - Biology, University of California, Riverside

1979-83 | BA - Aquatic Biology, University of California, Santa Barbara

Research Accomplishments

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 favoring the evolution of hermaphroditism from dioecy (separate males and females) in animals. 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 crustaceans. Several graduate students and I are studying a variety of ecological and genetic aspects of the unique mating system found in one genus of Crustacea (Eulimnadia), seeking to discern the costs and benefits of selfing vs. outcrossing in this interesting set of species. Since this early work on this one genus, we have expanded to study mating system evolution across the family Limnadiidae using phylogeographic, ecological, behavioral, and genetic approaches. We 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 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 (University of Connecticut, Storrs) to explore our ability to assess mating system type using only fossilized carapaces of Limnadiidae. A previous graduate student (Dr. Tim Astrop) developed a method to reliably ascertain mating systems from the fossil record, which has opened up a broad range of research possibilities that allow us to explore associations of mating system with habitat characteristics over broad time spans.

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. A former PhD student (Dr. Chiara Benvenuto) explored 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 hermaphroditism 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.


Reed, SK, RJ Duff, and SC Weeks. 2015. A systematic study of the genus Eulimnadia. Journal of Crustacean Biology 35:379-391.

Weeks, SC, C. Benvenuto, SK Reed, RJ Duff, and ZH Duan. 2014. A field test of a model for the stability of androdioecy in the freshwater shrimp, Eulimnadia texana. Journal of Evolutionary Biology 41:251-261.

Brown, B.P., T.I. Astrop, and S.C. Weeks. 2014. Post-larval developmental dynamics of the Spinicaudatan (Crustacea: Branchiopoda) carapace. Journal of Crustacean Biology 34:611-617.

Weeks, SC, JS Brantner, TI Astrop, DW Ott and N Rabet. 2014. The evolution of hermaphroditism from dioecy in crustaceans: Selfing hermaphroditism described in a fourth Spinicaudatan genus. Evolutionary Biology 41:251-261.

Brantner, J. S., D. W. Ott, R. J. Duff, J.I. Orridge, J. R. Waldman and S.C. Weeks. 2013. Evidence of selfing hermaphroditism in the clam shrimp Cyzicus gynecia (Branchiopoda, Spinicaudata). J. Crust. Biol. 33:184-190.

Brantner, J. S., D. W. Ott, R. J. Duff, L-O Sanoamuang, GP Simhachalam, KK Subhash Babu, and SC Weeks. 2013. Androdioecy and Hermaphroditism in Five Species of Clam shrimp (Crustacea: Branchiopoda: Spinicaudata) From India and Thailand. Invertebrate Biology 132:27-37.

Weeks, S.C. 2012. The role of androdioecy and gynodioecy in mediating evolutionary transitions between dioecy and hermaphroditism in the Animalia. Evolution 66:3670-3686.

Astrop, TI, LE Park, B Brown and SC Weeks. 2012. Sexual discrimination at work: Spinicaudatan ‘Clam Shrimp’ (Crustacea: Branchiopoda) as a model organism for the study of sexual system evolution. Palaeontologia Electronica 15.2.20A.

Rogers, DC, N Rabet, and SC Weeks. 2012. A revision of the extant genera of the Limnadiidae (Branchiopoda, Spinicaudata). Journal of Crustacean Biology 32:827-842

Benvenuto, C, and SC Weeks. 2012. Intersexual conflict during mate guarding in an androdioecious crustacean. Behav. Ecol. 23:218–224.

Benvenuto C,and SC Weeks. 2011. Mate guarding behavior in clam shrimp: The influence of mating system on intersexual conflict. Behav. Ecol. Sociobiol. 65:1899-1907.

Weeks SC, TF Sanderson , BF Wallace, and B Bagatto. 2011. Behavioral cost of reproduction in a freshwater crustacean (Eulimnadia texana). Ethology 117:880-886.

Weeks SC, C Benvenuto , TF Sanderson, and RJ Duff. 2010. Sex Chromosome Evolution in the Clam Shrimp, Eulimnadia texana. J. Evol. Biol. 23:1100-1106.

Rogers DC, SC Weeks, and WR Hoeh. 2010. A new species of Eulimnadia (Crustacea; Branchiopoda; Diplostraca; Spinicaudata) from North America. Zootaxa 2413:61-68.

Weeks SC, EG Chapman , DC Rogers, DM Senyo, and WR Hoeh. 2009. Evolutionary transitions among dioecy, androdioecy and hermaphroditism in limnadiid clam shrimp (Branchiopoda: Spinicaudata). J. Evol. Biol. 22:1781-1799.