Graduate Thesis Or Dissertation


Efficacy of Empirical Seed Zones: Pseudoroegneria Spicata Reproductive Phenology & Seedling Stage Traits Public Deposited

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  • Ecological restoration is needed to mitigate losses to biodiversity. Restoration success is enhanced through the use of native plant materials that are genetically diverse and locally adapted. Seed transfer zones have been developed to delineate geographic areas where native seed can be collected and distributed with reduced risk of maladaptation. Pseudoroegneria spicata (Pursh) Á. Löve is a widespread bunchgrass species with recently delineated seed zones, that is used extensively for ecological restoration in the Intermountain West. In this work, I conducted two studies of seed zone efficacy for P. spicata. In the first study, I determined if genetic differences in reproductive timing exist among P. spicata populations, and whether any such differences should be considered to avoid single-harvest stabilizing selection, which would cause inadvertent genetic loss during commercial seed production. In the second study, I determined if seedling traits differ among P. spicata populations, and if seed transfer zones developed using adult traits account for these differences. I utilized linear mixed modeling, intra-class coefficient analysis, nonmetric multi-dimensional scaling, and multi-response permutation procedures to quantify differences in the timing of anthesis, ripening, and dispersal and various seedling stage phenotypic traits for P. spicata. I found that variation in the timing of anthesis is not well explained by seed zones but that there was little difference in the mean values of this trait among populations from the same seed zone. On the other hand, genetic variation in seed ripening is captured by seed zones. For the dispersal stage, a lack of strong evidence for genetic differences among populations suggests a plastic response to environmental cues. Thus, typical single-pass seed harvest techniques are not likely to cause inadvertent selection for reproductive timing when seed transfer guidelines are followed. In the second study, I found that seed zones do not account for variation in seedling traits, meaning the use of current seed zones could risk the transfer of seeds to locations where seedling recruitment and establishment are hindered. This is important, since seedling establishment is often a limiting factor in restoration success. Although I focused these studies on P. spicata, my findings of incongruences between both reproductive timing and seedling stage phenotypic traits with respect to seed transfer zones suggests that such incongruities could be commonplace among other species used in restoration. Inadvertent selection during seed increase does not appear to be a risk in P. spicata when seed transfer guidelines are followed, but more research is needed to ensure that seedling stage traits are accounted for within future native species seed transfer guidelines.
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  • The research reported in this thesis was supported by the Great Basin Native Plant Project.
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