Honors Program

Honors in Biology

Date of Award


Thesis Professor(s)

Gerardo Arceo-Gomez

Thesis Professor Department

<--College of Arts and Sciences-->

Thesis Reader(s)

Darrell Moore


Plants species interactions via pollinators are a model system to understand the mechanisms that generate plant diversity in nature. However, most studies have focused on plant-plant interactions via pollinator attraction while ignoring the role of plant-plant interactions via pollen transfer. Heterospecific pollen transfer (henceforth HP) can be common and have negative fitness effects. Negative HP fitness effects may prompt the evolution of adaptive strategies to minimize them. However, the extent of spatial variation in HP load size within and among populations, a tenet for natural selection, remains unexplored. Such knowledge would hence constitute a first step in advancing our understanding of the importance of HP transfer as an evolutionary force promoting plant diversification. For instance, the opportunity for natural selection would only be expected under strong among population variation in HP load size. In this study we aim to answer the following specific questions: Is there variation in the amount and diversity of HP load in Lobelia siphilitica? How is the variation partitioned across different levels of organization (populations, individuals, and flowers among an individual)? Greater among-population variance would suggest that community attributes, such as plant density and diversity are the major drivers of HP load size. Greater among-plant variance would indicate plant traits that affect pollinator foraging behavior may play an important role. Greater variance among flowers within an individual plant, would suggest stochastic events may underlie variation in HP load size and diversity. In order to test these hypotheses, samples of the native perennial Lobelia siphilitica were taken from 10 populations in the Northeast Tennessee region (500 total). The styles were processed in the lab and pollen grains counted separating them into two categories, heterospecific and conspecific pollen. There was variation in the amount and diversity of HP load received. Populations are expected to have the largest variation among them due to different environments (disturbance levels, pollinators, plant communities, etc.) Since populations are expected to have the largest variation in HP received, they are also expected to have the greatest opportunity for natural selection to act. Looking at HP receipt within-species is important for identifying the mechanisms that can generate diversity in plant communities.


East Tennessee State University

Document Type

Honors Thesis - Withheld

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