Graduate Thesis Or Dissertation

 

Life-history and physiological trade-offs to reproduction of invasive and noninvasive Rubus Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/ft848t480

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  • The goal of this dissertation was to improve our understanding of the physiology and life-history of invasive plants and of the mechanisms underlying life-history trade-offs. I compared invasive and noninvasive species of Rubus (blackberry) that grow together in the Pacific Northwest. Three hypotheses were investigated: (1) Invasive Rubus have higher photosynthetic capacity and lower leaf-level resource costs of photosynthesis than native, noninvasive species; (2) The physiological effects of reproduction on foliage result in higher reproductive effort for noninvasive Rubus than for an invasive species, in spite of the greater number and size of fruit produced by the invasive species; and (3) Reproduction produces greater trade-offs to growth for noninvasive Rubus because of its higher reproductive effort, and these trade-offs affect the population demographics of these species. I found that two invasive species, R. discolor and R. laciniatus, had higher photosynthetic capacities and maintained these rates for a longer portion of the year than two noninvasive species, R. ursinus and R. leucodermis. Furthermore, the two invasive species had higher rates of photosynthesis per unit resource investment, such as carbon, nitrogen, and water, than the noninvasive Rubus. I found that these photosynthetic characteristics could be used to distinguish between the noninvasive and invasive species using discriminant analysis. I compared reproductive effort for one of the invasive, R. discolor, and one of the noninvasive, R. ursinus, species. I found that, although the invasive Rubus allocated more resources directly to reproduction than the noninvasive species, it had lower reproductive effort because it did not have the significant decline in leaf nitrogen and photosynthetic capacity and significant increase in mid-day water stress that were associated with reproduction in the noninvasive species. I also observed that sexual reproduction in the noninvasive species was associated with trade-offs to growth both within and between generations, but these were not observed in the invasive species. These trade-offs in the noninvasive species resulted in an almost complete dependence on clonal growth rather than sexual reproduction for population growth. The invasive Rubus relied on sexual reproduction for population growth relatively more than the noninvasive species and, therefore, reproductive effort influenced the demographics of these species.
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