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Selection and Floral Evolution in <em>Platanthera bifolia</em> and <em>P. chlorantha</em> (Orchidaceae) [Elektronisk resurs]

Maad, Johanne, 1970- (författare)
Fenster, Charles B. (opponent)
Publicerad: Uppsala : Acta Universitatis Upsaliensis, 2002
Engelska 26
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  • E-bokAvhandling(Diss. (sammanfattning), 2002)
Sammanfattning Ämnesord
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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. 

Ämnesord

Natural Sciences  (hsv)
Biological Sciences  (hsv)
Developmental Biology  (hsv)
Naturvetenskap  (hsv)
Biologiska vetenskaper  (hsv)
Utvecklingsbiologi  (hsv)
NATURAL SCIENCES  (svep)
Biology  (svep)
Organism biology  (svep)
Developmental biology  (svep)
NATURVETENSKAP  (svep)
Biologi  (svep)
Organismbiologi  (svep)
Utvecklingsbiologi  (svep)

Indexterm och SAB-rubrik

Developmental biology
Evolution
phenotypic selection
male function hypothesis
mating systems
floral shifts
orchids
pollination
moth pollinators
Platanthera.
Utvecklingsbiologi
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