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Susan Mazer >
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The Detection of the Long-term Outcome of Natural Selection and the Ecological Sorting of Species Among Habitats
Current Research: 5) The Detection of the Long-term Outcome of Natural Selection and the Ecological Sorting of Species Among Habitats: Comparative Studies of Plant Reproductive CharactersOne way to examine the long-term role of natural selection in molding plant reproductive characters is to use a comparative approach. That is, one examines the joint distribution, across an array of species, of character states (for the trait[s] of interest) and an environmental attribute. A related method is to make explicit use of phylogenetic relationships among species in order to evaluate:
These methods are non-experimental in nature, but they have been extremely successful in elucidating the ecological importance of life history and reproductive characters in plants and animals. I am currently pursuing two long-term comparative research projects: Project I. Ecological associations among life history and physiological traits in a tropical rain forest.Dr. Horacio Paz is a postdoctoral fellow in my lab, funded by the Centro de Ecologia of the Universidad Nacional Autonoma de Mexico. In collaboration with Dr. Miguel Martinez-Ramos of the Instituto de Ecologia (UNAM) and Dr. David Ackerly (Stanford University), we are using a comparative approach to detect ecological associations among morphological, life history, and physiological characteristics of several hundred rainforest species that have been monitored over the last seven years in Las Tuxtlas, Mexico. This project addresses two major questions in the comparative ecology and evolution of plants in tropical forests. First, what combinations of seed and seedling attributes are associated with high seedling emergence, survival and growth under the light-limited conditions of the rain forest understory? And, second, do these trait combinations represent evolutionary adaptations to the shaded environment? We will address these questions by using comparative statistical methods and long-term demographic data for over 200 species represented by thousands of seeds and seedlings in Dr. Martinez-Ramos' data set. Over the next two years, we will construct a flexible relational data base that will allow us to explore a variety of ecological and evolutionary phenomena (e.g., phenological patterns, evolutionary convergence, and evolutionary divergence in life history traits). This data set will allow us to evaluate the ecological and adaptive significance of alternative trait combinations associated with the demographic success of seeds and seedlings. In addition, we will seek evidence for "trade-offs" between species attributes and seedling demography that have been proposed in the theoretical literature to account for the maintenance of life history variation among species (e.g., proposed trade-offs between seed mass and growth rate, and between resistance to herbivores and growth rate). We will seek evidence for the adaptive significance of seed and seedling traits by using two methods: cross-species comparisons (treating species as independent data points) and comparative analyses that take into account the phylogenetic relationships among species. This study represents an extension of my previous comparative work (Mazer, 1989; Mazer, 1990; Mazer and Hultgard, 1993; Mazer and Wheelwright, 1993; Tiffney and Mazer, 1995; Paz, Mazer, and Martinez-Ramos, 1999). Finally, Dr. David Ackerly (Stanford University), Dr. Miguel Martinez-Ramos, Dr. Horacio Paz and I are organizing a group of investigators with complementary New World tropical rain forest data sets in order to develop a common quantitative approach to the analysis of this kind of data and to synthesize our data to detect common ecological and evolutionary patterns throughout the neotropics. This collaboration will be the focus of a working group supported and facilitated by the National Center for Ecological Analysis and Synthesis during 2001 - 2002. Project II. Adaptations of Fruits, Seeds, and Taxa to Lowland Tropical Rainforest HabitatsPrevious work that I conducted in Manu National Park, Peru, (Mazer, 1996) motivated me to seek evidence for adaptations of fruits and seeds to terra firma vs. floodplain habitats. I am now working on a comprehensive field guide (to be co-authored by Ing. Fernando Cornejo, a Peruvian forester and ecologist) to the fruits and seeds of Peruvian lowland neotropical rainforest habitats. This book will be the only field guide to the fruits of lowland tropical rain forest communities in the western Amazonian basin, the only field guide to seeds of any South American flora. To date, we have completed a one-year period of fruit and seed collecting and photography at a research site on the Tambopata River, near Manu National Park. This field work was followed by a year of herbarium and lab work. We have collected, identified, described, photographed, and prepared voucher specimens of over 1000 species (including more than 100 families and 500 genera) that will be included in the Field Guide. Click here for a small selection of the photographic images. My long-term goal is to evaluate adaptations of fruits and seeds (involving modes of dispersal, germination behavior, environmental tolerances, secondary chemistry, and morphology) that belong to species restricted to particular rainforest habitats. Current Research Projects
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| Department of Ecology, Evolution and Marine Biology • University of California, Santa Barbara |
