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Frequency-dependent variation in reproductive success in Narcissus: implications for the maintenance of stigma-height dimorphism.

Abstract

Negative frequency-dependent selection is a major selective force maintaining sexual polymorphisms. However, empirical demonstrations of frequency-dependent reproductive success are rare, particularly in plants. We investigate this problem by manipulating the frequencies of style morphs in a natural population of Narcissus assoanus, a self-incompatible herb with style-length dimorphism and intra-morph compatibility. We predicted that the reproductive success of morphs would vary negatively with their frequency because of the effects of morph-specific differences in sex-organ position on patterns of pollen transfer. This prediction was generally supported. The fruit and seed set of the two morphs did not differ significantly in plots with 1 : 1 morph ratios. However, short-styled plants produced significantly fewer seeds than long-styled plants in monomorphic plots, and significantly more seeds than long-styled plants in plots with 'long-biased' morph ratios. These patterns indicate that in the absence of physiological barriers to intra-morph mating, negative frequency-dependent selection contributes to the maintenance of stylar polymorphism through inter-morph pollen transfer. Our experimental results also provide insights into the mechanisms governing the biased style-morph ratios in populations of Narcissus species.

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    MeSH

    Biological Evolution
    Genetic Variation
    Narcissus
    Pollen
    Polymorphism, Genetic
    Reproduction
    Selection, Genetic
    Sex Characteristics

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    12803910

    Citation

    TY - JOUR T1 - Frequency-dependent variation in reproductive success in Narcissus: implications for the maintenance of stigma-height dimorphism. AU - Thompson,John D, AU - Barrett,Spencer C H, AU - Baker,Angela M, PY - 2003/6/14/pubmed PY - 2003/11/8/medline PY - 2003/6/14/entrez SP - 949 EP - 53 JF - Proceedings. Biological sciences / The Royal Society JO - Proc. Biol. Sci. VL - 270 IS - 1518 N2 - Negative frequency-dependent selection is a major selective force maintaining sexual polymorphisms. However, empirical demonstrations of frequency-dependent reproductive success are rare, particularly in plants. We investigate this problem by manipulating the frequencies of style morphs in a natural population of Narcissus assoanus, a self-incompatible herb with style-length dimorphism and intra-morph compatibility. We predicted that the reproductive success of morphs would vary negatively with their frequency because of the effects of morph-specific differences in sex-organ position on patterns of pollen transfer. This prediction was generally supported. The fruit and seed set of the two morphs did not differ significantly in plots with 1 : 1 morph ratios. However, short-styled plants produced significantly fewer seeds than long-styled plants in monomorphic plots, and significantly more seeds than long-styled plants in plots with 'long-biased' morph ratios. These patterns indicate that in the absence of physiological barriers to intra-morph mating, negative frequency-dependent selection contributes to the maintenance of stylar polymorphism through inter-morph pollen transfer. Our experimental results also provide insights into the mechanisms governing the biased style-morph ratios in populations of Narcissus species. SN - 0962-8452 UR - https://www.unboundmedicine.com/medline/citation/12803910/Frequency_dependent_variation_in_reproductive_success_in_Narcissus:_implications_for_the_maintenance_of_stigma_height_dimorphism_ L2 - http://rspb.royalsocietypublishing.org/cgi/pmidlookup?view=long&pmid=12803910 ER -