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Date of Award

2016

Document Type

Restricted Thesis: Campus only access

Degree Name

Bachelor of Science

Department

Biochemistry & Molecular Biol.

First Advisor

Dr. Carrie Wu

Abstract

Biological diversity often reflects environmental complexity (Kirkpatrick & Barton 1997). A particularly dramatic contrast is found between the abiotic characteristics of alpine versus lowland environments (Sexton et al. 2016). Relative to low-elevation environments, alpine environments on average experience lower atmospheric pressures, lower partial pressures of all atmospheric gases, higher solar radiation, higher proportion of UV-B radiation, higher precipitation levels, and lower temperatures (Körner 2007). But one of the central questions to evolutionary ecology remains: how are organisms responding to those abiotic differences? Many studies have investigated the relationship between ecology and speciation; that is, how the relationship between organisms and their physical surroundings affects the formation of new and genetically distinct species over the course of evolutionary time (Joshi et al. 2001; Becker et al. 2006; Weissing et al. 2011). For example, studies on the pinkfairy flower Clarkia pulchella have shown that low precipitation levels in the southern and western ranges of its habitat may contribute to its geographic range limit (Bontrager & Angert 2016). The species distribution of the beech family, Fagus L., is primarily limited by thermal and moisture factors, contributing to the divergence of F. grandifolia, F. mexucana, F. sylvatica, and F. orientalis, among other species of beech (Fang & Lechwicz 2006). Additionally, reciprocal transplant studies using members of the monkeyflower family, Mimulus cardinalis and Mimululs lewisii, have shown that individuals exhibit reduced fitness at the margins of their elevation ranges, suggesting that these species have adapted to their altitudinal gradient (Angert & Schemske 2005). Environmental stressors can drive specialization to local environmental conditions, which may generate population differentiation that is necessary for ecological speciation (Lexer 2005). For plants, one of such environmental stressors is extreme temperatures (Friedman & Willis 2013).

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