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FACULTY

Randall Hughes, Ph. D.

Assistant Scholar Scientist
Ph.D., University of California, Davis
B.A., University of North Carolina, Chapel Hill

Office: 850-697-4093
Fax: 850-697-3822

RESEARCH AND PROFESSIONAL INTERESTS

My research goal is to understand the causes and consequences of diversity at multiple levels of biological organization. Many ecosystems are dependent on one or a few key species (e.g., kelps, redwoods, pelagic phytoplankton) that perform numerous ecosystem functions associated with multiple species in other systems. What factors shape diversity in these 'foundation' species? Does genetic diversity in these key species perform a comparable role to species diversity in speciose systems? If so, do similar processes contribute to this effect? How do reciprocal relationships between diversity and factors such as disturbance alter predictions based solely on unidirectional effects?

I focus on marine and estuarine systems because of the strong experimental tradition in these systems and their importance both to ecological and human communities. The incredible productivity of these systems and our increasing impact and reliance on them makes marine ecology an ideal field for addressing questions of concern to basic and applied science.

Does genetic diversity within key species affect ecosystem function?
The relationship between species diversity and ecosystem function has stimulated a large body of research in the last 20 years. However, less attention has focused on the ecological importance of genetic diversity within a species. Genetic variation in dominant estuarine and marine primary producers may have important effects on the overall productivity of these systems. My previous research concentrates primarily on genotypic (i.e., clonal) diversity in eelgrass (Zostera marina), a habitat-forming seagrass species that is found in shallow coastal systems throughout the northern hemisphere. Eelgrass can reproduce clonally as well as sexually, generating variation in clonal diversity within and among beds. Such variation in clonal diversity can have large and lasting effects on eelgrass productivity and response to disturbance in experimental systems (Hughes and Stachowicz 2004). In addition, a positive relationship between eelgrass clonal diversity and shoot density in natural eelgrass beds suggests that the positive effect of diversity is sufficiently strong to impact patterns of primary production in the field, despite the presence of many confounding factors (Hughes and Stachowicz 2009). I am currently investigating similar questions in salt marsh (Spartina alterniflora) communities along the Panhandle of Florida.

How do biodiversity and habitat structure interact to shape food webs and trophic structure?
As a complement to my empirical research on eelgrass genotypic diversity and ecosystem function, I have worked on several projects to examine the role of herbivore and/or predator diversity on food web dynamics. For example, interactions among multiple predator species and their herbivore prey in a kelp food web can strengthen the effects of a trophic cascade in this system, leading to increased primary production (Byrnes et al. 2006). In seagrass systems, a diverse suite of grazer species can have contrasting effects on seagrass productivity due to their opposing impacts on epiphyte biomass, often resulting in no net effect (Hughes et al. 2004). In addition to examining the effects diversity at higher trophic levels, I am interested in how habitat complexity mediates these effects. My research with Dr. Jonathan Grabowski (Gulf of Maine Research Institute) suggests that an understanding of how habitat characteristics like physical complexity influence predator interactions may be critical to predicting the effects of predator diversity on resource capture (Hughes and Grabowski 2006, Grabowski et al. 2008).

What are the causes and impacts of seagrass declines?
Seagrasses are highly productive coastal ecosystems, providing critical habitat for a wide variety of commercially and ecologically important species. Because of their close proximity to shore, seagrasses are also highly impacted by coastal development and human influences. I recently participated in a working group at the National Center for Ecological Analysis and Synthesis focused on quantifying the population status of seagrasses around the globe. Our analyses revealed that seagrasses are declining in areal extent overall, and the rates of decline have increased in recent years (Waycott et al. 2009). As a consequence, species that depend on seagrasses for food and/or habitat are also of conservation concern (Hughes et al. 2009). Various factors can contribute to seagrass declines, including increases in water column nutrients and reductions in epiphyte grazers (Hughes et al. 2004). Currently, awareness of seagrass loss and its potentially dramatic effects on marine ecosystems lags behind that of other coastal habitats such as coral reefs and mangroves (Orth et al. 2006).

Information for prospective graduate students

SELECTED PUBLICATIONS
Hughes, A.R. and J.J. Stachowicz. 2009. Ecological impacts of genotypic diversity in the clonal seagrass Zostera marina. Ecology 90: 1412-1419.

Hughes, A.R., S.L. Williams, C.M. Duarte, K.L. Heck, Jr., and M. Waycott. 2009. Associations of concern: declining seagrasses and threatened dependent species. Frontiers in Ecology and the Environment 7: 242-246.

Hughes, A.R., J.J. Stachowicz, and S.L. Williams. 2009. Morphological and physiological variation among seagrass (Zostera marina) genotypes. Oecologia 159:725-733.

Hughes, A.R., B. Inouye, M.T.J. Johnson, N. Underwood, and M. Vellend. 2008. Ecological consequences of genetic diversity. Ecology Letters 11: 609-623.

Hughes, A.R., J.E. Byrnes, D.L. Kimbro, and J.J. Stachowicz. 2007. Bi-directional feedbacks between biodiversity and disturbance. Ecology Letters 10: 849-864.

Byrnes, J.E., J.J. Stachowicz, K.M. Hultgren, A.R. Hughes, S.V. Olyarnik, and C.S. Thornber. 2006. Predator diversity strengthens trophic cascades in kelp forests by modifying herbivore behavior. Ecology Letters 9: 61-71..

Harley, C.D.G., A.R. Hughes, K.M. Hultgren, B.G. Miner, C.J.B. Sorte, C.S. Thornber, L.F. Rodriguez, L. Tomanek, and S.L. Williams. 2006. The impacts of climate change in coastal marine systems. Ecology Letters 9: 228-241.

Hughes, A.R. and J.H. Grabowski. 2006. Habitat context influences predator interference interactions and the strength of resource partitioning. Oecologia 149: 256-264.

Hughes, A.R. and J.J. Stachowicz. 2004. Genetic diversity enhances the resistance of a seagrass
ecosystem to disturbance. Proceedings of the National Academy of Sciences 101: 8998-9002.

Hughes, A.R., K.J. Bando, L.F. Rodriguez, and S.L. Williams. 2004. Relative effects of grazers
and nutrients on seagrasses: a meta-analysis approach. Marine Ecology Progress Series 282: 87-99.

GRADUATE STUDENTS:

Emily Field (Biological Science)

UNDERGRADUATE STUDENTS:

Nicholas Coria - FSU DIS - Environmental Studies
Justis Freeley - FSU DIS - Biology
Liz Hibner - FSU certificate program - Biology