Plant ecological & evolutionary genetics
Dr. Julie R. Etterson
University of Minnesota Duluth
Department of Biology
153B Swenson Science Building
Duluth, MN 55812-3003
Office Phone: (218) 726-8110
Lab Phone: (218) 726-7408
Fax: (218) 726-8142
2000 PhD, University of Minnesota, Dept. Ecol. Evol. and Behavior
1994 BS, University of Minnesota, Biology
1986 BIS, School for International Training, International Studies
My lab uses the tools of ecological genetics to understand factors that influence the persistence of native plant populations in response to anthropogenic changes in the environment, especially climate change, but also with respect to competition with invasive species, altered disease dynamics, inbreeding due to small population size, introduction of nonnative genotypes during habitat restoration, and increased intensity of deer herbivory. Our goal is to examine how natural plant populations change phenotypically and genetically in response to these agents of selection. We use quantitative genetics to understand the underlying genetic architecture of traits and to attain insight into the potential for ongoing adaptive and the limits of natural selection to molding of populations in response to climate change. To this end, I have: 1) predicted rates of evolutionary change and compared it rates of climate change, 2) I have imposed evolutionary change on flowering time through artificial selection and compared it to observed phenological change in two polyploid species, and 3) am currently leading a collaborative effort to develop a new genome bank to observe evolutionary changes in the future (Project Baseline, Etterson, Franks, Mazer and Shaw). Molecular techniques have been used by lab members to quantify the extent of divergence among populations, the degree of inbreeding within populations, and as tools to distinguish between local and nonlocal genotypes of plants that were introduced for restoration purposes.
Project Baseline is a multi-institutional collaboration that aims to create a unique seed bank specifically designed to facilitate future studies of plant evolution in response to environmental change employing the resurrection approach. Plant species are already responding to climate change, as evidenced by earlier budburst, flowering, and arrival of insect and bird pollinators. However, in only a few cases can we distinguish between phenotypic responses to longer growing seasons and warmer temperatures (plasticity) and genetically based evolutionary change in response to altered patterns of natural selection. In a few cases, direct demonstration of the nature of contemporary change in wild populations has been possible because propagules (e.g., stored seeds, seeds preserved in tundra soils, or eggs in lake sediments) have been fortuitously available in a condition to be revived and grown side-by-side with their contemporary descendants. This "resurrection approach" has permitted phenotypic and genetic comparison of populations representing different time periods. The fundamental goal of Project Baseline is to collect seeds that will be the ancestors in resurrection studies in the future and store them using best practices to preserve their viability and genetic diversity. We are initiating a national effort to systematically collect, preserve and archive seeds to be made available to future biologists for studies of evolutionary responses to anthropogenic and natural changes in the environment over the coming decades. With this valuable resource secured, biologists will be able to grow genetically representative samples of past populations contemporaneously with modern samples, applying both long-established and recently developed genetic approaches, as well as ones yet to be developed, to dissect the architecture of genetic change. Follow this link for more information
Polyploidy and evolutionary potential
It is often assumed that polyploids possess greater evolutionary potential than their diploid progenitors because: 1) organisms with many gene copies harbor greater genetic diversity which is the fundamental substrate of evolutionary change, 2) genetic redundancy creates opportunities for duplicated genes to diverge and acquire new functions without compromising the original function, and 3) gene duplication increases the number of gene interactions, some combinations of which may enhance fitness. Thus, polyploidy may allow organisms to evolve faster or in novel directions compared to their diploid progenitors. Although this is a provocative idea and a compelling hypothesis, it has never been explicitly tested. I am testing this hypothesis in a polyploid goldenrod species. Solidago altissima.
I am examining the role of plant exposure to drought and disease on fitness of offspring in the subsequent generation. In previous work, I collaborated with Dr. Laura Galloway at the University of Virginia to examine the extent to which offspring phenotype is influenced by genetic inheritance and by environmental factors with respect to the parental light environment.
Adaptation Forestry in Minnesota's Northwoods
This new collaborative research project is designed to test whether new combinations of forest management techniques can facilitate the compositional transition of Minnesota's northern forests and bolster resilience as climate changes into the future. Forests gaps and clear cuts will be planted with a range of species with different life history attributes (e.g., tolerance of shade, drought and fire) and that originate from different geographic locations (e.g. from climates anticipated in the future). We used ecological models to select species that are likely to thrive under warmer, drier conditions including bur oak, red oak, white pine, and basswood. These species are native to the region, but are uncommon because of past harvesting, dispersal limitation, and geographical position in the range. Each planting of includes a local provenance and one sampled from more southern regions of Minnesota. This work is a collaborative effort with the Nature Conservancy, the Northern Institute of Applied Climate Science, the Minnesota Forest Resources Council and the Sustainable Forests Education Cooperative and is funded with support from of the Wildlife Conservation Society (WCS) through its Climate Adaptation Fund and the The Nature Conservancy’s Cox Family Fund for Science and Research. Follow this link for more detail.
I am interested in the role that both ecological and evolutionary dynamics play in the persistence of native plant populations that are experiencing invasion. Specifically, I am interested in how evolutionary and ecological dynamics interact to determine the fate of populations. I have recently initiated reserach into an invasive species that only occurs in the Duluth area in North America, Campanula cerviarcia. This species was first collected in this region in 1943 but was not correctly identified until 2003. I have begun to study the demographics and quantitative genetics of the invasive populations in this region. My graduate student, Ada Tse, is also studying genetic variation in Tanectum vulgare in response to simulated insect damage by biocontrol agents.
Campanulastrum americana is an insect-pollinated self-compatible protandrous herb. Thus, inbreeding is most likely to occur as a result of pollinator movement among flowers of the same plant that are in different gender phases. However, Laura Galloway and I found that multilocus outcrossing rate was 94 % and did not differ significantly from unity. This result was unexpected since previous work demonstrated that pollinators frequently move from male- to female-phase flowers on the same plant.C. americana is also an autotetraploid species. Theory predicts that inbreeding depression should be lower in polyploids relative to diploids. In a greenhouse study, we found that inbreeding depression was not significant for most seed and germination characters. However, all later life traits except flowering date differed between inbred and outcrossed individuals resulting in a 26% reduction in cumulative fitness for inbred plants. Limited early- and moderate later-life inbreeding depression suggest it is buffered by the higher levels of heterozygosity found in an autotetraploid. A three-year field study confirmed the strong impact of inbreeding on mortality rates and fecundity.
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©2009 Julie Etterson