Current Research

Stephen M. Shuster


My research and scholarship efforts at Northern Arizona University have developed in several directions, all of which are extensions of my fundamental research goals. These goals are to understand: (1) the processes by which genetic variation in maintained in natural populations, (2) the genetic and environmental bases for phenotypic expression at all levels of biological organization, (3) how selection can be measured in nature at all levels of biological organization, and (4) how mating systems and alternative mating strategies evolve.


The first project involves investigation of expression of adult phenotype and population sex ratio in marine isopods, Paracerceis sculpta (NSF grants OCE 84-01067, BSR 87-00112, BSR-9106644, DEB-9726504, DBI-0243914, IBN-0400867, DBI-0552644). This project is an extension of my dissertation research beginning in 1984. The goal of this project is to understand the genetic and environmental mechanisms that maintain phenotypic variability in natural populations, and that allow alternative male mating strategies to persist in nature. All of my publications on P. sculpta (see CV) are part of this research. Current projects involve investigating the effect of variation in food availability, light, temperature and density on the expression of known male and female genotypes, and identifying single nucleotide polymorphisms in 16S rDNA sequences that identify invasive and noninvasive populations (see Mungia and Shuster 2013).


The second project involves my ongoing collaboration with Michael J. Wade at Indiana University. We extend the theoretical principles developed in our book entitled "Mating Systems and Strategies" published by Princeton University Press in 2003. This book outlines a novel statistical approach for measuring the intensities of natural and sexual selection in nature. This approach provides new insight, even after nearly a decade, into why sexual selection is such a powerful evolutionary force, and it provides unique explanations for observed variation in mating systems and alternative mating strategies for all sexually reproducing organisms. Recent contributions include Shuster et al. 2013, Shuster 2011, 2010 and 2009, Krakauer et al. 2011 and Wade and Shuster 2010.


The third project involves a theoretical framework and empirical applications for community genetics, the study of how genetic varation in one species can influence fitness variation in another species. This work is an extention of a $5M Frontiers in Integrative Biological Research (FIBR; Foundations in Integrative Biological Research) grant at NAU (National Science Foundation, DEB-0425908). As coinvestigator of the Cottonwood Ecology Group directed by Tom Whitham. This group has been the focus of the PBS Documentary, "A Thousand Invisible Cords: Connecting Genes to Ecosystems," aired in 2012 at over 250 public television stations in the USA and translated for distribution in French and Spanish.   I am exploring methods for estimating the intensity and form of genetic interactions among species within communities, as well as methods for estimating community heritability, a statistical approach for demonstrating the degree to which communities are genetically and phenotypically distinct. Current developments of this project include methods for calculating community heritability in the broad and in the narrow sense as well as multivariate methods for summarizing community-level phenotypes. Recent contributions include Smith et al. 2012, 2011, and Allan et al. 2010. A spreadsheet for calculating broad sense community heritability (H2C) is available at Calculating H2C


The fourth project involves investigation of genetic differences in natural and captive populations of the endangered Socorro Isopod in Socorro, New Mexico (NMGF grant 97042), This project uses biochemical and molecular markers to compare genetic variation in this and other isopods in the genus Thermosphaeroma. A former postdoc, Bronwyn H. Bleakley, now an Assistant Professor at Stonehill College has shown that cannibalistic behavior in T. thermophilum varies in predictable ways with social environment, as is expected for traits evolving via indirect genetic effects (IGEs; Bleakley et al. 2013). This experimental system provides an ideal model for understanding the genetics of social interactions, particularly in endangered species (see Lang et al. 2012). In future years I plan to extend these investigations to include the 7 other known species in the Thermosphaeroma complex. An understanding of these isolated species could provide useful information toward understanding how species with limited habitat ranges persist over evolutionary time. Part of this project is an investigation into the evolution of genitalic morphology within this genus with Veijo Jormalainen of the University of Turku, Finland. (see Recent Presentations).

The fifth project involves investigation of parental care in Glossiphoniid leeches with current Ph.D. student Becky Beresic-Perrins and my former postdoctoral associate, Fred Govedich. This project will compare the predictions of the 3 dominant theoretical frameworks for understanding the evolution of mating systems, sex allocation and parental care: Parental Investment/Sex Allocation Theory, Opportunity for Selection Theory and Indirect Genetic Effects Theory. Information gained from this research will enhance current understanding of these fields and will add to the overall knowledge of a poorly known annelid group. Former IGERT and current GK-12 STEM Fellow Becky Beresic-Perrins also co-directs the research of several undergraduate students investigating various aspects of parental and aggregation behavior in Helobdella leeches. Among these researchers are Shayla Mulhern, an NAU Interns-To-Scholars fellowship recipient, and a 2014 Hooper Undergraduate Research Fellow, and Kelsey Banister, also a 2014 Hooper Undergraduate Research Fellow. (see Recent Presentations).

Additional projects involving graduate students in my laboratory include research efforts by Ken Sterling, a former undergraduate student investigating asexual reproduction in sea stars (Sterling and Shuster 2011) and presently a Ph.D. student at Utah State University. Ben Jaffe, a Science Foundation Arizona Fellow and Ph.D. Candidate who is investagating the elemental allelopathy, via bioaccumulation of arsenic in ferms, Dana Ikeda, a Ph.D. Candidate who, in collaboration with the CEG and Greg O'Neill of the University of British Columbia is investigating the effects of climate change on the expression of foundation tree phenotypes, Bill Briggs, a Ph.D. student who is exploring next-gen sequencing of the Paracerceis sculpta genome, Dannielle Jensen, a M.S. student who is investigating genetic population structure in Physalia, the Portuguese Man-O-War, as well as collaborating with former Hooper Fellow Amber Shows to understand the reproductive life history and systematics of Leucetta losangelensis and other calcareous sponges in the Gulf of California. Patricia Dennis, a M.S. student is investigating landscape variation in referential communication in prarie dogs, and Kim Whitley, a M.S. student is investigating the life history of Pemphigus aphids on their herbaceous hosts.