Undergraduate Honors Theses

Thesis Defended

Spring 2012

Document Type

Thesis

Department

Ecology and Evolutionary Biology

First Advisor

Dr. Cesar Nufio

Abstract

Reproduction in flowering plants is thought to be most heavily influenced by patch level display. In the present study, patch level display was measured as both the display size (number of flowers) of a focal plant and the density of conspecific (of the same species) neighbors around a focal plant. Conspecific neighbors may facilitate reproduction when they increase the number of visits by suitable pollinators to a focal plant. In contrast, competition may result when the presence of neighbors decreases visits to individual plants by limited pollinators, or when resources such as soil nutrients and water are limiting. In this study, the effects of flower density at the individual level, and conspecific neighbor density at the patch level, on the reproductive success of focal individuals in a sub-alpine population of Thermopsis divaricarpa (Golden Banner) were measured. In addition, the flowering phenology (temporal flowering period), the distribution of individuals throughout the population, and the self-compatibility of these plants were measured to better understand the flowering biology of this system. The flowering phenology in this population of T. divaricarpa showed high synchrony, and plants demonstrated an aggregated distribution. Both measures indicate that the presence of co-flowering neighbors, and their potential effects, is common in this system. In addition, this population of T. divaricarpa is self-compatible, but my results indicate that pollination is important for maximizing seed set. The results of the density experiments indicate higher fecundity, but not facilitation per say in individuals with larger display sizes, as indicated by total seed output, but not by the number of seeds per fruit. In contrast, an increase in conspecific neighbor density resulted in a trend towards competition as plants experienced a decrease in fruit set with an increase in the number of conspecific neighbors in a patch. This study provides a foundation for continued research into the mechanisms driving reproduction in sub-alpine flowering plant populations. Understanding these mechanisms is important for species conservation, specifically in fragmented and degraded habitats, and for potentially threatened or endangered plant species.

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