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Selection and Flora...
Selection and Floral Evolution in Platanthera bifolia and P. chlorantha (Orchidaceae)
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- Maad, Johanne, 1970- (author)
- Uppsala universitet,Institutionen för evolutionsbiologi,Uppsala universitet, Institutionen för evolutionsbiologi
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- Fenster, Charles B., Professor (opponent)
- Department of Biology, University of Maryland, Collage Park, MD 20742
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(creator_code:org_t)
- ISBN 9155452264
- Uppsala : Acta Universitatis Upsaliensis, 2002
- English 26 s.
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Series: Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1104-232X ; 685
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Abstract
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- Natural selection mediated by pollinators has influenced the evolution of floral diversity of the flowering plants (angiosperms). The scope of this thesis was to study: 1) phenotypic selection, 2) mating systems, and 3) floral shifts involved in plant speciation. Model plant species were Platanthera bifolia and P. chlorantha (Orchidaceae). These orchids are moth-pollinated, strictly co-sexual (bisexual flowers), and produce a spike that displays 10-20 white flowers.I explored the influence of characters on plant fitness by using multiple linear regressions. Pollen removal (male fitness) and fruit set (female fitness) increased with more flowers per plant in three P. bifolia populations. There was selection towards longer spurs in a dry year when average spur length was shorter than in normal-wet years. Female function was sensitive to drought, which enabled an application of the male function hypothesis of floral evolution (Bateman's principle). The results show that selection may vary between populations, years, and sex-functions.I examined inbreeding by estimating levels of geitonogamy (self-pollination between flowers of an individual) with an emasculation method in two P. bifolia populations. Geitonogamy did not vary with inflorescence size. Levels of geitonogamy was 20-40% in the smaller, but non-significant in the larger population. This may relate to lower number of possible mates and pollinator activity in the smaller population.Platanthera bifolia exhibits the ancestral character state of tongue-attachment of pollinia on the pollinator. Its close relative P. chlorantha attaches its pollinia onto the pollinator's eyes. To explore the mechanism of a floral shift, pollination efficiency and speed was compared between the two species. The results showed no differences in pollination efficiency, but P. chlorantha had faster pollen export and import. Efficiency of pollination in terms of speed may cause floral shifts, and thus speciation.
Subject headings
- NATURVETENSKAP -- Biologi -- Utvecklingsbiologi (hsv//swe)
- NATURAL SCIENCES -- Biological Sciences -- Developmental Biology (hsv//eng)
Keyword
- Developmental biology
- Evolution
- phenotypic selection
- male function hypothesis
- mating systems
- floral shifts
- orchids
- pollination
- moth pollinators
- Platanthera.
- Utvecklingsbiologi
- Developmental biology
- Utvecklingsbiologi
- systematisk botanik
- Systematic Botany
Publication and Content Type
- vet (subject category)
- dok (subject category)
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