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Ph.D. University of Maine
My research interests lie in two areas. One is the different levels of integration exhibited among individual organisms aggregated in a group, clone or colony and how this variation impacts both, their population ecology, and the evolution of their life histories. The second is the scale- and context-dependence of ecological processes in community development. I study both benthic marine invertebrates and seaweeds for three reasons: first, both taxa are easily manipulated in field and laboratory experiments, second interactions between these taxa are often central features of community organization and third, a great diversity of unitary and clonal lifestyles (often in a single lineage) coexist in one ecosystem.
Life history evolution in clonal taxa
In many clonal eukaryotes variation in morphology and life history traits often are correlated and show concordant plasticity during development, but relatively little is known about the underlying physiology. Here, we seek to determine from laboratory experiments, primarily, whether the correlation between morphology and life history traits in clonal organisms is causal. This research employs colonial hydrozoans (Phylum Cnidaria). Colonies consist of individuals (polyps) connected to one another by a network of circulatory tubes (stolons) that define a colonyís morphology. The transport of fluid through the colonyís stolons emerges from the collective behavior of oscillating polyps. Variation in colony form and polyp behavior generates variation in flow patterns within this gastrovascular system that underlies different developmental patterns and demographic schedules, implying that colony morphology is self-maintaining through the differential expression of pattern-forming genes in response to internal fluid transport. Research to date suggests that patterns of vascular connections codetermine life history and morphology,and that the evolution of life history traits is constrained by physiological and developmental mechanisms before selection can eliminate unfit variants.
Scale- and context-dependence of ecological processes
The ecological processes that generate pattern in communities are well known. How these processes vary in importance across different spatial and temporal scales and, thereby, contribute added variation to patterns in space and time is less well known. For instance, the signatures left by historical events may affect interactions between species in present-day communities. Current research employs field and laboratory experiments to address two related questions: (1) under what spatial and temporal scales and environmental conditions do historical events mediate processes that influence species distribution and abundance?, (2) how do the strengths, or nature, of interactions between species differ in different environmental backgrounds?
My research in the Gulf of Maine suggests that large scale historical events, such as may occur from severe ice scour, can initiate the origin of either rockweed or mussel bed communities at a given site. Alternative communities may arise because disturbances over large areas affects subsequent rates of recruitment and predation during succession. If alternative states do exist, it implies that community transitions are threshold-dependent and that small scale perturbations that cross a threshold may cause large, irreversible changes in ecosystems. Non-linear responses by communities to environmental changes demand that our plans for managing ecosystems be sensitive to these phenomena.
Like the signatures left by historical events, the present environmental context affects interactions between species. My work on intertidal seaweeds has shown that species may compete in favorable environments, but not interact in more stressful environments. This interaction is mediated by physiological responses of each species to varying environments. Continued research will determine variations in the strength, or nature, of species interactions for taxa living together in different environments and how such variation within a target species pair affects other indirectly associated species. The goal is to better predict the dynamics of populations and the structure of communities by casting predictions of species interactions in an environment-dependent context.
Ecological significance of genet fusion among algal holdfasts.
Considerable evidence indicates that among clonal eukaryotic organisms large size is favored by selection. Often genets of a taxon can fuse to rapidly increase their size. In animals fusion is confined to kin, but in plants selection to develop historecognition systems during their evolution may have been weak relative to animals. Consequently, in red seaweeds (at least) cellular fusions are common, but its ecological significance is unknown. I plan to study the adaptive significance of holdfast fusion in suitable red algal species (e.g., on the Pacific coast, Gracilariopsis lemaeniformis). By acquiring suitable genetic markers for different genotypes and outplanting to the field different combinations of fused products (i.e., single clones, chimeras, etc.) of known identity, the demographic performance of each genet can be assessed. Fusions of holdfasts within and among clones may be adaptive for red algae, particularly those that inhabit space-limited, wave-swept shores. A long term goal is to determine if red algal species of different clades in similar habitats show convergence for this trait.
Recent and Seminal Publications (†students as coauthors)
Dudgeon, S. R. and J. Kübler. 2011. Hydrozoans and the shape of things to come. Advances in Marine Biology 59: 107-144
Kordas, R. L.† and S. R. Dudgeon. 2011. Dynamics of species interaction strength in space, time and with developmental stage. Proceedings of the Royal Society of London B 278: 1804-1813
Dudgeon, S.R., R. B. Aronson, J. F. Bruno, W. F. Precht. 2010. Phase shifts and stable states on coral reefs. Marine Ecology Progress Series 413: 201-216
Fierst, J. L. †, J. E. Kübler and S. R. Dudgeon. 2010. Spatial distribution and reproductive phenology of sexual and asexual Mastocarpus papillatus (Rhodophyta). Phycologia 49: 274-282
Dudgeon, S.R., K. M. Benes†, S. A. Krueger†, J. E. Kübler, P. Mroz†, and C. T. Slaughter†. 2009. On the use of experimental diets for physiological studies of hydrozoans. Journal of the Marine Biological Association of the U. K. 89: 83-88
Kordas, R†. and S. R. Dudgeon. 2009. Modeling variation in interaction strength between barnacles and fucoids. Oecologia 158: 717-731.
terHorst, C. P†. and S. R. Dudgeon. 2009. Beyond the patch: Disturbance affects species abundances in the surrounding community. Journal of Experimental Marine Biology and Ecology 370: 120-126.
Petraitis, P. S., E. T. Methratta, E. C. Rhile, N. A. Vidargas and S. R. Dudgeon. 2009. Experimental confirmation of multiple stable states in a marine ecosystem. Oecologia 161: 139-148
Petraitis, P. S., J. A. D. Fisher and S. R. Dudgeon. 2008. Rocky Intertidal Zone. In: Sven Erik Jorgensen and Brian D. Faith (Editor-in-Chief), Ecosystems. Vol.  of Encyclopedia of Ecology, 5 vols. Pp. 3107-3113. Elsevier Press, Oxford
Dudgeon, S. R. and P. S. Petraitis. 2005. Early life demography of a foundation species and the community-level implications. Oikos 109: 405-415.
Petraitis, P. S. and S. R. Dudgeon. 2005. Divergent succession and implications for alternative states on rocky intertidal shores. Journal of Experimental Marine Biology and Ecology 326: 14-26.
Fierst, J. L.†, C. Terhorst†, J. E. Kübler and S. R. Dudgeon. 2005. Fertilization success can drive patterns of phase dominance in complex life cycles. Journal of Phycology 41: 238-249.
Petraitis, P. S. and S. R. Dudgeon. 2004. Detection of alternative stable states in marine communities. Journal of Experimental Marine Biology and Ecology 300: 343-371
Petraitis, P. S., and S. R. Dudgeon. 2004. Do alternative stable states exist in the Gulf of Maine rocky intertidal zone? A comment. Ecology 85: 1160-1165
Dudgeon, S. R., A. Wagner, J. R. Vaisnys, and L. W. Buss. 1999. Dynamics of gastrovascular circulation in the hydrozoan Podocoryne carnea: the one polyp case. The Biological Bulletin 196: 1-17.
Dudgeon, S. R., R. S. Steneck, I. R. Davison, and R. L. Vadas. 1999. Coexistence of similar species in a space-limited intertidal zone. Ecological Monographs 69: 331-352.
Dudgeon, S. R. and L. W. Buss. 1996. Growing with the flow: On the maintenance and malleability of colony from in the hydroid, Hydractinia. The American Naturalist 147: 667-691.
Petraitis, P. S. and S. R. Dudgeon. 1999. Experimental evidence for the origin of alternative communities on rocky intertidal shores. Oikos 84: 239-245.
Wagner, A., Dudgeon, S. R., J. R. Vaisnys, and L. W. Buss. 1998. Non-linear oscillations in polyps of the colonial hydroid Podocoryne carnea. Naturwissenschaften 85: 1-5.