The Ecology of Sexual and Apomictic Reproduction in Antennaria Parlinii Gaertner (Apomixis, Plant Breeding Systems, Evolution)
Michaels, Helen Judith
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https://hdl.handle.net/2142/71282
Description
Title
The Ecology of Sexual and Apomictic Reproduction in Antennaria Parlinii Gaertner (Apomixis, Plant Breeding Systems, Evolution)
Author(s)
Michaels, Helen Judith
Issue Date
1986
Department of Study
Plant Biology
Discipline
Plant Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, General
Biology, Ecology
Abstract
Differences in habitat and geographic distributions of sexually and asexually reproducing species are often attributed to differences in relative colonizing and competitive abilities. In this thesis, fitness components that influence colonizing and competitive ability are compared in an herbaceous perennial, Antennaria parlinii, in which seed production occurs in plants that are either sexual and dioecious or apomictic. Studies of seedlings and ramet production by adult plants in natural populations documented differences in survivorship and allocation between sexual and apomictic plants. Populations of sexual and apomictic plants also differed in overall growth and reproduction in response to greenhouse gradients of light and nutrients, as well as in the breadths and magnitudes of the niche responses. The populations also differed in the diversity of internal responses shown among their component individual genotypes. Competition experiments compared the growth and reproduction of sexual and apomictic plants in monocultural and mixed pairwise treatments in the field and under greenhouse conditions of high and low light.
These studies indicate that apomictic A. parlinii possess many characteristics that enhance colonizing ability: (1) a high potential for dispersal provided by large numbers of light seeds, (2) preferential allocation to seed production over vegetative growth and future reproduction, and (3) highly plastic and opportunistic responses to resource variation. In contrast, sexual A. parlinii produce fewer seeds, while seedlings and adult plants are more likely to survive, resulting in a solid mat of long-lived, wandering stolons. Sexual populations show a stable pattern of allocation to offspring production as resource levels increase, and consist of individuals with diverse responses to resouce gradients. In the field and under low light in the greenhouse sexual plants were more competitive than apomictic plants. The results imply that sexual Antennaria parlinii are capable of competitively excluding apomicitic plants from resource-limited environments and that the long-term success of apomicitic A. parlinii is dependent upon the availability of competition-free sites for colonization.
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