Biology ETDs

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Populations of invasive species are often characterized as genetically depauperate, an inherent consequence of the colonization process. It has also been suggested that species that are able to avoid these reductions in genetic diversity may be better able to adapt to their introduced range. Evolutionary change can play an important role in the invasion process if novel selective pressures drive adaptive evolution. Species that are able to avoid reductions in genetic diversity associated with colonization may be better able to adapt to their introduced range. To better understand the genetic processes following invasion, introduced populations of the invasive mustard, Isatis tinctoria L. were studied. Given its mating system and introduction history, it may have avoided substantial founder effects. As a consequence, it may maintain high levels of genetic variation in the introduced range. The focus of chapter 1 was to investigate genetically based phenotypic differences in I. tinctoria originating from different source populations by growing plants in a common greenhouse environment. The following questions were addressed: 1) Are there differences in ecologically important traits among introduced populations of I. tinctoria grown in a common greenhouse environment? 2) How is observed variation in traits partitioned among populations and families within populations? 3) Is there a correlation between any traits measured and latitude? 4) Are plants derived from commercial seed sources phenotypically different from plants from invasive populations? The focus of chapter 2 was to measure levels of neutral genetic variation present in introduced populations of I. tinctoria using AFLP markers. The following questions were addressed: 1) What is the level of genetic variation of introduced populations of I. tinctoria? 2) What is the level of genetic variation in commercial populations? 3) How is genetic variation structured across the introduced range of this species? 4) Can populations be separated into distinct clusters or groups and is this grouping related to geography or introduction history? 5) Are populations that are closer together geographically more genetically similar? Lastly, whether there was evidence of adaptive evolution in introduced populations of I. tinctoria was addressed by testing for the presence of phenotypic clines. The development of phenotypic clines is often thought to be an indicator of adaptive evolution. If present, adaptive evolution may contribute to invasion success if it leads to the colonization of environmentally diverse areas. However, not all population differentiation can be considered adaptive; processes that occur during introduction that are selectively neutral can resemble local adaptation. A more reliable indicator of local adaptation can be derived by comparing differences in quantitative trait variation to neutral genetic variation - the primary focus of Chapter 3. In this chapter the following specific questions were addressed: 1) Is geographic location or climate a better predictor of phenotypic variation? 2) Is phenotypic variation best explained by neutral genetic variation and/or environmental conditions? 3) If neutral genetic variation is not the best predictor of phenotypic variation then which variables (if any) contribute to phenotypic clines? Finally, values of QST and FST were compared.




Isatis tinctoria, Invasive, Local differentiation, Adaptive evolution, AFLP

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Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Hanson, David T.

Second Committee Member

Lowrey, Timothy K.

Third Committee Member

Sher, Anna A.