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Assess the Evolutionary Potential in Natural Plant Populations by Estimating the Additive Genetic Variation or Performance in Populations in a Longitudinal Transect Across the Species RangeEPA Grant Number: U914758
Title: Assess the Evolutionary Potential in Natural Plant Populations by Estimating the Additive Genetic Variation or Performance in Populations in a Longitudinal Transect Across the Species Range
Investigators: Etterson, Julie R.
Institution: University of Minnesota
EPA Project Officer: Broadway, Virginia
Project Period: January 1, 1995 through January 1, 1998
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1995) Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology
The objective of this research project is to assess the evolutionary potential in natural plant populations to evolve heat and drought tolerance necessary to survive global warming.
I selected species as potential subjects on the basis of their range. I will narrow the possibilities this winter, but will likely collect seed from at least two species in the summer of 1995. This winter, I plan to grow 20 plants of each to determine growth rate, time to flowering, and amenability for genetic crosses in the greenhouse. I plan to produce out-crossed and self-seed to determine viability and germination characteristics of each. It is necessary that my focal species be self-incompatible or be easy to emasculate to be certain of seed paternity. Through literature and herbarium searches and contact with conservation organizations and universities, I will locate four source populations for each species to be sampled. I plan to collect seeds and tissue samples from at least 200 individuals per population during the summer of 1995. At each site, I will measure a rectangular area including the maximum number of individuals. I will generate 200 random x,y coordinates, and will collect seed and tissue samples from the plant closest to each point.
I will plant 50 seeds and seedlings at Cedar Creek Natural History Area and on campus. This experiment also will indicate whether these perennial species are likely to flower during their first year. I also plan to investigate alternative methods of establishing a heat gradient in the field. I plan to monitor temperature, humidity, and light intensity inside small, portable greenhouses designed to protect tomatoes from frost. Ideally, I would like to test plants under a temperature gradient to avoid surpassing the critical temperature that the plants can withstand and to get a finer scale picture of plant performance across a range of conditions. Other heat transducing devices will be tested. During the summer of 1996, I will reciprocally plant seeds from each greenhouse across in a randomized block design at naturally occurring densities in each of the locations where plants originated. Plants will be monitored midsummer and at the end of the growing season for 3 years. Survival and fecundity data will be collected each year. Survivorship and fecundity are direct measures of fitness, and they reflect the evolutionary relevant response of plants to aspects of their environment.
Representatives from each cross will be planted into a common garden subjected to two temperature treatments in an experimental plot chosen on the basis of studies in the summer of 1995. This experiment will indicate whether temperature is a causal basis for differences among populations. The ambient temperature will serve as the lowest temperature treatment. Pending the outcome of the summer 1995 preliminary experiments, I plan to use plastic greenhouses such as those used to study the effects of temperature on tussock tundra species to create warmer conditions (Chapin & Shaver, 1985). Chapin and Shaver report that greenhouses had no significant effects on other environmental variables that they measured.
Artificial selection experiments in growth chambers will be conducted during each winter to measure the potential for increased temperature tolerance. This experiment will allow plants to be selected for more generations and under more extreme conditions than will be feasible in the field. I plan to select on two replicate lines from one central and one southern population for six generations. Each replicate line will be composed of 100 plants, 20 percent of which will be sampled for the next generation. An unselected control line will be carried on for the same number of generations. Following the experiment, selected and control plants will be grown in a common environment for one generation to avoid confounding nongenetic effects. A comparison of progeny from the selected lines grown under selective conditions and the progeny of the control lines grown under nonselective conditions will determine the potential of plants to adapt to increased temperature. Quantitative genetic studies of natural plant populations often assume that the sampled population has historically mated at random and is not inbred. However, if this is not the case, calculated components of variance may be inflated. Variance components may be corrected if the inbreeding coefficient of the population is determined (Cockerham, 1963). I plan to estimate Wright's Coefficient of Inbreeding from electrophoretic or restriction fragment length polymorphism data.