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Abstract Detail

The Evolution of Pollen Performance


The population ecology of male gametophytes in stylar habitats and its evolutionary implications.

The fate of male gametophytes after pollen reaches stigmas links pollination to ovule fertilization, thereby governing subsequent siring success and seed production. Although pollen germination and pollen-tube growth fundamentally involve biochemical and physiological processes, an ecological analogy may provide insights into the nature of this linkage.  As independent haploid organisms, male gametophytes of angiosperms complete their lives in localized populations in the complex and dynamic environment provided by the pistils of conspecific sporophytes.  Styles represent a competitive arena for such populations by providing “resources” required for pollen-tube growth, including nutrition and/or space.  Consequently, progamic success likely involves both density-independent processes associated with pollen viability and tube-specific interactions with the style, and density-dependent competition among male gametophytes governed by resource availability and the density and activity of competitors.  If stylar resources are limiting, male gametophytes can compete in manners that depend on their own characteristics and those of the resource supply (i.e., the pistil).  “Contest”, or exploitative, competition should arise if pollen grains differ extensively in the timing of their arrival on a stigma or germination, and/or tube growth rates; whereas “scramble”, or interference, competition could occur when germination time differs little and pollen tubes grow at equal rates, so they compete as an advancing front.  Models based on this ecological analogy demonstrate that the mode of resource competition and the timing and severity of density-independent mortality together create characteristic relations of the mean and among-stigma variation in pollen-tube success to pollen receipt on the stigma.  Observed differences among species in the relation of the number of pollen-tubes entering ovaries or seed production to pollen receipt support the contrasting expectations of contest and scramble competition. Furthermore, consideration of the implications of progamic resource competition reveals explanations for enigmatic aspects of plant reproduction, including limits on the evolution of pollinator attraction, and enriches understanding of the incidence and nature of sexual selection in plant populations.

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1 - University Of Calgary, Department Of Biological Sciences, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada
2 - Inibioma-Conicet, Laboratorio Ecotono, Quintral 1250, Bariloche, Río Negro, 8400, Argentina

Pollen tube
contest competition
scramble competition
siring success.

Presentation Type: Symposium or Colloquium Presentation
Session: SY03
Location: Snake/Boise Centre
Date: Monday, July 28th, 2014
Time: 4:00 PM
Number: SY03006
Abstract ID:307
Candidate for Awards:None

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