Defense Date

2010

Document Type

Thesis

Degree Name

Master of Science

Department

Biology

First Advisor

Rodney Dyer

Abstract

This study examined aspects of local reproductive variation in the flowering dogwood (Cornus florida L.) coincident with recent differences in primary canopy architecture. The dogwood trees in this study were impacted by a hurricane that created numerous treefall gaps, which created fine scale heterogeneity in the primary canopy. Fine scale disturbances in a forest can result in changes for multiple members of the forest community, including the reproductive responses of the trees and interspecific pollination mutualisms. Previously determined differences in offspring genetic structure suggested that pollen movement among genetically unstructured maternal individuals was significantly impacted between open, or disturbed, canopy and closed, or undisturbed, types. To further understand mechanisms by which this nonrandom mating occurred, this study examined both intrinsic and extrinsic reproductive factors for C. florida. The first chapter examines several parameters of the reproductive phenology of sample groups of dogwood between the canopy types as intrinsic factors. The parameters observed included initiation, course and termination of flowering, seed set and seed germination ratios. The results showed some significant differences between the sampling areas in flowering intensity, although the majority of the variation was between maternal individuals throughout the entire sample. The second chapter examines insect community composition across areas of differential canopy disturbance. Community analysis showed that the open canopy contained a larger and more diverse assemblage of insects than the closed canopy or the field, which represented an area of complete canopy removal. This shift in insect community composition may have created functional differences in the local pattern of pollen flow by altering the functional composition of local potential pollinator assemblages. The major finding of this study was that the impact of intermediate natural disturbance on the mating systems of understory plant populations may be more indirect than direct. In conclusion, the observed differences in insect community structure within these habitat types in this study were consistent with predetermined patterns of pollen flow; this structure can explain some of the previously observed genetic structure within locally proximate understory tree populations.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

August 2010

Included in

Biology Commons

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