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Birds, Bats, Fungus, and Plants: Modeling Population Dynamics of Tropical Forest Pioneers

Principal Investigator: Drs. K. Greg Murray and Brian Yurk (Mathematics)

Tropical rainforests are legendary for their biological diversity and for the complexity of interactions among their species. The interactions between animals and plants are especially prominent – animals are important as pollinators, seed dispersers and seed predators, and plants are under strong selection pressure to reinforce the positive interactions with animals and to weaken the negative ones. “Pioneer” plants – those that specialize on colonizing recently disturbed patches of forest but which cannot compete in the shaded understory – constitute a model system in which to study tropical plant-animal and plant-microbe interactions. Our research group seeks to understand how seed dispersers, seed predators, microbial pathogens, and physical disturbance interact to influence the demography of tropical pioneer plants and thus the maintenance of forest structure and species composition. We are especially interested in questions that encompass several levels of biological organization or that combine the approaches of other disciplines (e.g., mathematics, computational science, and organic chemistry) with those of ecology. The focus of this particular project is to combine data on pioneer demography and forest disturbance rates with mathematical models that address the evolution of life history traits (“how to be a pioneer plant”) and the potential consequences of climate change for forest composition. Students involved in this research will employ tools from mathematics (e.g., linear algebra) and computational science (e.g., MATLAB), and those participating during the summer may have the opportunity to collect field data in Costa Rica. All students will participate in hypothesis formation, experimental design, data acquisition and analysis. They will routinely read and discuss scientific literature, and they will have ample opportunity to develop skills for writing scientific papers and delivering scientific presentations.

Using Ecological Processes to Guide Bioprospecting for Medicinally Useful Compounds

Drs. K. Greg Murray, Aaron Best and Michael Short

Tropical rainforests are legendary for their biological diversity and for the complexity of interactions among their species. The interactions between plants and their mutualists and enemies are especially prominent – animals are important as pollinators, seed dispersers, herbivores and seed predators, and pathogenic fungi attack plants at all stages of development. Plants have responded to their enemies with a wide variety of morphological and chemical defenses, and in fact most pharmaceuticals originated with the compounds that plants use to protect themselves from herbivores and pathogens. Yet despite the wide array of pharmaceuticals already in use, the need for new treatments against chronic and emerging human pathogens is more pressing than ever, ranging from tropical parasitical diseases like malaria and Leishmaniasis to the opportunistic fungal infections that plague HIV and other immunocompromised patients. The traditional approach to finding medicinally useful compounds depends on screening various tissues from large numbers of randomly chosen plant species – a highly inefficient process. Our group is using a particular ecological pattern – the “dormant seed strategy” of tropical pioneer plants, whose seeds survive for tens to hundreds of years in tropical rainforest soils – to focus on the plant species and tissues most likely to contain antimicrobial compounds. Students involved in this research will employ a variety of chemical separation and analysis techniques, as well as toxicity bioassays against fungi and arthropods, to isolate and identify the toxic compounds. In addition, they will screen seed extracts against tropical parasites such as Leishmania. Students working during the summer may have the opportunity to collect plant materials and field data in Costa Rica, and all students will participate in hypothesis formation, experimental design, data acquisition and analysis. Students will also develop their ability to analyze the scientific literature critically and to present their research results in written and oral formats

Representative Publications:

  • Murray, K.G., K. Winnett-Murray, J. Roberts*, K. Horjus*, W.A. Haber, W. Zuchowski, M. Kuhlmann*, and T.M. Long-Robinson*. In press. The roles of disperser behavior and physical habitat structure in regeneration of post-agricultural fields. Chapter 8, in: R. Myster [ed.]. Post-Agricultural Succession in the Neotropics. Springer U.S., New York.
  • Veldman, J.W.*, K.G. Murray, A.L. Hull*, J.M. Garcia-C., W.S. Mungall, G.B. Rotman*, M.P. Plosz*, and L.K. McNamara*. 2006. Chemical Defense and the Persistence of Pioneer Plant Seeds in the Soil of a Tropical Cloud Forest. Biotropica. 39: 87-93.
  • Murray, K. G., S. Kinsman, and J. Bronstein. 2000. Plant-animal interactions. In Monteverde: Ecology and Conservation of a Tropical Cloud Forest. Oxford University Press, New York. Edited by N. M. Nadkarni and N. T. Wheelright. Pp. 245-302
  • Murray, K.G., and J. Mauricio Garcia-C. 2002. Contributions of seed dispersal and demography to recruitment limitation in a Costa Rican cloud forest. Pp. 323-338, in: Levey, D. J., W. R. Silva, and M. Galetti. (eds) Seed dispersal and frugivory: Ecology, evolution, and conservation. CABI Publishing, Wallingford, UK
  • Murray, K.G. 1988. Avian seed dispersal of three neotropical gap-dependent plants. Ecological Monographs 58: 271-298.
  • Murray, K.G., S. Russell*, C.M. Picone*, K. Winnett-Murray, W. Sherwood*, and M.L. Kuhlmann*. 1994. Fruit laxatives and seed passage rates in frugivores: consequences for plant reproductive success. Ecology 75: 989-994.
  • Murray, K.G. 2000. The importance of different bird species as seed dispersers. Pp. 294-295, in: N.M. Nadkarni and N.T. Wheelwright [eds]. Monteverde: Ecology and Conservation of a Tropical Cloud Forest. Oxford University Press, New York.

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