Document Detail

Temporal variation in the pollen:ovule ratios of Clarkia (Onagraceae) taxa with contrasting mating systems: field populations.
MedLine Citation:
PMID:  18005114     Owner:  NLM     Status:  MEDLINE    
Among plants, pairs of selfing vs. outcrossing sister taxa provide interesting systems in which to test predictions concerning the magnitude and direction of temporal changes in sex allocation. Although resource availability typically declines towards the end of the growing season for annual taxa, temporal changes in mating opportunities depend on mating system and should change less in selfing taxa. Consequently, given that the pollen:ovule (P:O) ratio of flowers reflects the investment in (and potential fitness pay-off due to) male vs. female function, we predicted that the P:O ratio should also be less variable among and within selfers than in closely related outcrossers. To test these predictions, we measured temporal changes in sex allocation in multiple field populations of two pairs of sister taxa in the annual flowering plant genus Clarkia (Onagraceae). In the outcrossing Clarkia unguiculata and the selfing Clarkia exilis, ovule production declined similarly from early to late buds, whereas pollen production remained constant or increased in the outcrosser but remained constant or decreased in the selfer. Consequently, the P:O ratio increased within unguiculata populations but marginally increased or stayed constant in exilis populations. In all populations of the selfing Clarkia xantiana spp. parviflora and the outcrossing C. x. spp. xantiana, both ovule and pollen production per flower declined over time. The effects of these declines on the P:O ratio, however, differed between subspecies. In each xantiana population, the mean P:O ratio did not differ between early and late flowers, although individuals varied greatly in the direction and magnitude of phenotypic change. By contrast, parviflora populations differed in the mean direction of temporal change in the P:O ratio. We found little evidence to support our initial predictions that the P:O ratio of the selfing taxa will consistently vary less than in outcrossing taxa.
V A Delesalle; S J Mazer; H Paz
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2007-11-12
Journal Detail:
Title:  Journal of evolutionary biology     Volume:  21     ISSN:  1420-9101     ISO Abbreviation:  J. Evol. Biol.     Publication Date:  2008 Jan 
Date Detail:
Created Date:  2008-01-03     Completed Date:  2008-04-17     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  8809954     Medline TA:  J Evol Biol     Country:  Switzerland    
Other Details:
Languages:  eng     Pagination:  310-23     Citation Subset:  IM    
Department of Biology, Gettysburg College, Gettysburg, PA 17325, USA.
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MeSH Terms
Clarkia / genetics,  physiology*
Flowers / physiology*
Genetic Variation
Reproduction / physiology
Time Factors
Erratum In:
J Evol Biol. 2008 Jul;21(4):1173

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