Browsing by Author "Kopp, Jason"

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    Effects of White-tailed Deer (Odocoileus virginianus) Browsing and Prescribed Burns on Seedlings and Saplings in Itasca State Park, Minnesota
    (2010-04-12) Cosgrove, Angela; Kopp, Jason; Wallace, Courtney
    The purpose of the study was to determine if white-tailed deer browsing or prescribed burning had an effect on seedlings and saplings in Itasca State Park. There were four study sites located in the park: Mary Lake Unburned Exclosure, Wildness Drive Burned Exclosure, Wildness Drive Burned Area and Wildness Drive Unburned Area. It was hypothesized that the highest abundance of seedlings and saplings would be at the Wilderness Drive Burned Exclosure and the lowest abundance at Wilderness Drive Unburned Area. The data showed no correlation between abundance of deer scat and abundance of seedlings but there is a positive correlation between deer scat and abundance of saplings. This could be due in part to the fact that the deer exclosures did not completely exclude deer. The data showed no correlation between seedlings and saplings between burned sites and between unburned sites. Pine regeneration was not significant in the study transects but it was noted that there were white pine seedlings present at each site.
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    Post-Mating Reproductive Isolation and Hybrid Pollen Inviability Between Two Subspecies of Clarkia xantiana (Onagraceae)
    (2011-04-13) Kopp, Jason
    The origin of new species of organisms (speciation) is a source of continual debate in the realm of evolutionary biology. When two diverging populations of the same species become reproductively isolated from each other speciation can occur because of phenotypic or genetic changes. Phenotypic changes prevent mating from happening (pre-mating changes) and genetic changes render hybrids, or the product of the two populations, sterile (post-mating changes). For my study, I examined the post-mating isolation between two subspecies of Clarkia xantiana, an endemic, native herb of California. The species is currently divided into two subspecies Clarkia xantiana ssp. xantiana and Clarkia xantiana ssp. parviflora. These two subspecies overlap in distribution in a narrow contact zone (sympatric zone). In sympatry, these subspecies rarely form hybrids in nature but can be forced to produce hybrids in the lab. My study focused on the fertility of pollen grains (male fertility) in the parents and hybrids of these two subspecies to assess post-mating isolation. Answering these questions provides insight into the mechanisms behind speciation due to post-mating changes, an understudied but fundamental process of evolutionary biology.