Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Biology and Biomedical Sciences: Evolution, Ecology and Population Biology

Language

English (en)

Date of Award

Winter 1-1-2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Barbara A. Schaal

Abstract

Plant domestication is the process by which people take wild plants into cultivation and shape them over time into reliable food sources enhanced for consumption and propagation via agriculture. It causes genetic, phenotypic, and ecological changes in cultivated populations. This process is frequently studied in domesticated crops. And yet incipiently domesticated taxa, intermediate to wild and domesticated plants, offer unique opportunities to study domestication as it occurs.

In this dissertation, I use the incipiently domesticated Neotropical fruit tree, Byrsonima crassifolia: Malpighiaceae), to study the timing and extent of genetic and ecological changes in a plant with a varied cultivation history throughout its broad geographic range.

I first use ecological modeling with field- and herbarium-collected localities to compare the distributions of non-cultivated and cultivated plants in ecological space. This study detected no appreciable difference in the environmental characteristics of the predicted localities of these plant types, suggesting that the ecological needs of cultivated plants may not change significantly early in the domestication process.

I next used rapidly evolving microsatellite markers to analyze levels and structuring of genetic diversity in non-cultivated and cultivated populations. Little differentiation was observed in most regions. However, the reduced variation typically associated with domestication was detected in southeastern Mexico, which has the longest cultivation history and strongest phenotypic differentiation. A distinct structuring of genetic diversity was observed in southwestern Mexico, where commercial cultivation has recently developed.

Finally, I used DNA sequence data to explore domestication within a phylogeographic context. These findings complement the microsatellite analyses. They additionally reveal high genetic diversity in Panama, situated at the juncture of North and South America, where B. crassifolia is commonly cultivated, but shows few effects of selective pressures.

These studies illustrate the complexity of early domestication processes. The early impact of domestication on genetic, phenotypic, and ecological change varies by region with the intensity and duration of cultivation. The strong maintenance of genetic variation in cultivated populations indicates that people can be powerful stewards of plant genetic resources. The onset of modern agricultural practices, including sharing plants across large distances, may alter traditional patterns of change associated with plant domestication.

Comments

This work is not available online per the author’s request. For access information, please contact digital@wumail.wustl.edu or visit http://digital.wustl.edu/publish/etd-search.html.

Permanent URL: http://dx.doi.org/10.7936/K7NV9G73

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