| Research
Interests
As an ecologist, I am interested in the evolution and maintenance of biodiversity (the variety of life), and in particular, what determines species diversity at different spatial scales. At the local scale, the number and type of species found in a community depends on biotic and abiotic interactions, species sorting, and dispersal of colonists from a regional species pool. At broad spatial scales (regions, continents), we need to consider the factors that drive rates of diversification (speciation and extinction), as well as the dispersal of species between regions. Studying biodiversity at these different spatial scales requires different tools and different approaches. Local communities often lend themselves to experimental manipulation and my current research in this area includes experimental studies in freshwater communities (working with fish and aquatic invertebrates), and a long-term, collaborative study on the effects of resource heterogeneity on species diversity in a terrestrial grassland. To study the causes of biodiversity patterns at broad spatial scales, I work collaboratively with a group of ecologists, evolutionary biologists, and paleontologists, focusing particularly on the evolution of the latitudinal gradient in biodiversity. Below are brief sketchs of these research areas and references to recently published papers.
Biodiversity and ecosystem functioning in aquatic communities (Most of this research is done in collaboration with my graduate students, who work with a variety of organisms in different aquatic habitats).
Garcia, E.A. and G. G. Mittelbach (2008). Regional coexistence and local dominance in Chaoborus: species sorting along a predation gradient. Ecology (in press). By experimentally manipulating fish density in small ponds, we were able to show that variation in predation pressure, in combination with species traits, determines the distribution and local dominance of Chaoborus (phantom midge) species across a landscape of lakes and ponds.
Mittelbach, G.G., E. A. Garcia, and Y. Taniguchi. 2006. Fish reintroductions reveal smooth transitions between lake community states. Ecology 87:312-318. Whether communities respond smoothly or discontinuously to changing environmental conditions has important consequences for the preservation and restoration of ecosystems. In this seventeen year study of a Michigan lake, we show that manipulating the fish community from high plantivore density to low planktivore density back to high planktivore density results in dramatic, but smooth transitions between ecosystem states.
Wojdak, J.M. and G. G. Mittelbach (2007). Consequences of niche overlap for ecosystem functioning: an experimental test of pond grazers. Ecology 88:2072-2083. We outline an experimental approach for testing how niche complimentarity contributes to positive biodiversity effects on ecosystem functioning and apply this approach in an experimental study with pond grazers (gastropods).
Consequences of resource heterogeneity, productivity, and clonality to species diversity in a low-productivity grassland (in collaboration by Drs. Katherine Gross and Heather Reynolds, plus students and postdocs).
Coexistence theory predicts that greater heterogeneity of resources or other fitness-constraining environmental factors will promote species diversity, yet this classic mechanism of coexistence has rarely been tested in manipulative field experiments. We are manipulating soil resource heterogeneity, in combination with species introductions (by seed), and the presence/absence of clonal species, to test this hypothesis in a low productivity grassland in Michigan. Our results show that the large foraging area of clonal plants limits the positive impact of resource heterogeneity on species coexistence.
Gross, K.L., G.G. Mittelbach, and H.L. Reynolds. 2005. Grassland invasibility and diversity: responses to nutrients, seed input, and disturbance. Ecology 86:476-486.
Reynolds, H.L., G.G. Mittelbach, T.L. Darcy-Hall, G.R. Houseman, and K.L. Gross. 2007. No effect of varying soil resource heterogeneity on plant species richness in a low fertility grassland. Journal of Ecology 95:723-733.
Houseman, G.R., G.G. Mittelbach, H.L. Reynolds, and K.L. Gross. 2008. Perturbations alter community convergence, divergence, and formation of multiple community states. Ecology (in press).
Biodiversity at broad spatial scales: evolution and the latitudinal diversity gradient The dramatic increase in biodiversity as one moves from the poles to the tropics “..is the major, unexplained pattern in natural history…. it mocks our ignorance” (Ricklefs 1989). My interest in the latitudinal diversity gradient stems from a general interest in understanding how climate and history affect broad scale patterns in biodiversity, and most of my work in this area is the result of collaborations developed from three working groups supported by the National Center for Ecological Analysis and Synthesis in Santa Barbara, CA. Listed below are some representative publications.
Mittelbach, G.G., D.W. Schemske, H.V. Cornell, et al. 2007. Evolution and the latitudinal diversity gradient: speciation, extinction and biogeography. Ecology Letters 10:315-331.
Schemske, D.W., G.G. Mittelbach, H.V. Cornell, J.M. Sobel, and K. Roy. Latitudinal variation in the strength of biotic interactions: evidence and consequences for the biodiversity gradient. (in prep. for the 2009 issue of Annual Review of Ecology, Evolution, and Systematics).
Currie, D.J., G.G. Mittelbach, H.V. Cornell, et al. 2004. Predictions and tests of climate-based hypotheses of broad-scale variation in taxonomic richness. Ecology Letters 7:1121-1134.
Hawkins, B.A., R. Field, H.V. Cornell, et al. 2003. Energy, water, and broad-scale geographic patterns of species richness. Ecology 84:3105-3117.
|
SOME RECENT PUBLICATIONS:
Garcia, E.A. and G. G. Mittelbach. 2008. Regional coexistence and local dominance in Chaoborus: species sorting along a predation gradient. Ecology (in press).
Houseman, G.R., G.G. Mittelbach, H.L. Reynolds, and K.L. Gross. 2008.Perturbations alter community convergence, divergence, and formation of multiple community states. Ecology (in press).
Reynolds, H. L., G. G. Mittelbach, T. L. Darcy-Hall, G. R. Houseman, and K. L. Gross. 2007. No effect of varying soil resource heterogeneity on plant species richness in a low fertility grassland. J. of Ecology 95:723-733.
Mittelbach, G. G., D. Schemske, H. V. Cornell, et al. 2007. Evolution and the latitudinal diversity gradient: speciation, extinction, and biogeography. Ecology Letters 10:315-335..
Wojdak, J. M. and G. G. Mittelbach. 2007. Consequences of niche overlap for ecosystem functioning: an experimental test with pond grazers. Ecology 88:2072-2083.
Mittelbach, G. G., E. A. Garcia, and Y. Taniguchi. 2006. Fish reintroductions reveal smooth transitions between lake community states. Ecology 87:312-318. [pdf]
McGill, B. and G. G. Mittelbach. 2006. An allometric vision and motion model to predict predator-prey encounter rates. 2006. Evolutionary Ecology Research 8:1-11.
C. F. Steiner, T. L. Darcy-Hall, N. J. Dorn, E. A. Garcia, G. G. Mittelbach and J. M. Wojdak. 2005. The influence of consumer diversity and indirect facilitation on trophic-level biomass and stability. Oikos 110:556-566.
Gross, K. L., G. G. Mittelbach, and H. L. Reynolds. 2005. Grassland invasibility and diversity: responses to nutrients, seed input, and disturbance. Ecology 86:476-486.
Mittelbach, G. G. Parasites, communities, and ecosystems: conclusions and perspectives. 2005. pp 171-176 In: F. Thomas, F. Renaud, and J. F. Guégan (eds). Parasites and Ecosystems. Oxford University Press.
Dorn, N. J. and G. G. Mittelbach. 2004. Effects of native crayfish on the reproductive success and nesting behavior of freshwater sunfish (Lepomis spp.). Canadian Journal Fisheries and Aquatic Sciences 61:2135-2143.
Currie, D. J., G. G. Mittelbach, H. V. Cornell, R. Field, J-F. Guégan, B. A. Hawkins, D. M. Kaufman, J. T. Kerr, T. Oberdorff, E. O’Brien, and J. R. G. Turner. 2004. Predictions and tests of climate-based hypotheses of broad-scale variation in taxonomic richness. Ecology Letters 7:1121-1134.
Mittelbach, G. G., T. L. Darcy-Hall, N. J. Dorn, E. A. Garcia, C. F. Steiner, and J. M.Wojdak. 2004. The impact of density-independent mortality on species coexistence: an experimental test with zooplankton Oikos 107:415-421.
Petchey, O. L., A. L. Downing, G. G. Mittelbach, L. Persson, C. F. Steiner, P. H. Warren, and G. Woodward. 2004. Species loss and the structure and functioning of multitrophic aquatic systems. Oikos 104:467-478.
Hawkins, B. A., R. Field, H. V. Cornell, D. J. Currie, J. Guegan, D. M Kaufman, J. T. Kerr, G. G. Mittelbach, T. Oberdorff, , E. M. O’Brien, E. E. Porter, and J. R. G. Turner. 2003. Energy, water, and broad-scale geographic patterns of species richness. Ecology 84:3105-3117.
Wilson, W. G., P. Lundberg, D. P Vázquez, J. B. Surin, M. D. Smith, W. Langford, K. L. Gross, and G. G. Mittelbach.2003. Biodiversity and species interactions: extending Lotka-Volterra community theory. Ecology Letters 6:944-952.
Symstad, A. J., F. S. Chapin III, D. H. Wall, K .L. Gross, L. F. Huenneke, G. G. Mittelbach, D. P C. Peters, G. D. Tilman. 2003. Long-term and large-scale perspectives on the relationship between biodiversity and ecosystem functioning. BioScience 53:89-98.
DeRoos, A., K. Leonardsson, L. Persson, and G. G. Mittelbach. 2002. Ontogenetic niche shifts and flexible behavior in size-structured populations. Ecological Monographs 72:271-292.
Mittelbach, G. G., C. F. Steiner, S. M. Scheiner, K. L. Gross, H. L. Reynolds, R. B. Waide, M. R. Willig, S. I. Dodson, and L. Gough. 2001. What is the observed relationship between species richness and productivity? Ecology 82:2381-2396. |
