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Floral variation and environmental heterogeneity in a tristylous clonal aquatic of the Pantanal wetlands of Brazil.

Abstract

BACKGROUND AND AIMS

The balance between stochastic forces and frequency-dependent mating largely governs style morph frequencies in heterostylous populations. In clonal species, deviations from equal morph ratios often result from founder events and unfavourable conditions for sexual reproduction. The aim of this study was to investigate whether different flooding regimes, because of their influence on sexual vs. clonal reproduction, are associated with regional variation in morph frequencies and floral trait differentiation in populations of the clonal, tristylous, aquatic Eichhornia azurea (Pontederiaceae) in the Pantanal wetlands of Brazil.

METHODS

Style morph frequencies were sampled from 73 populations distributed across four flooding regimes differing in depth and duration. Measurements of flower size, sex-organ dimension, pollen size and pollen production were made in selected populations, and pollinator assemblages and their functional traits were recorded.

KEY RESULTS

Most populations of E. azurea were tristylous (78 %), but the majority exhibited uneven morph ratios. The frequency of the mid-styled morph was significantly lower than that of the long- and short-styled morphs. Morph evenness was positively associated with population size but not with flooding regime. There were significant phenotypic differences among flooding regimes for all floral traits, including populations with reduced flower size, sex-organ length and smaller pollen. Pollinator assemblages varied with flood duration.

CONCLUSIONS

The similar morph structure and evenness of populations, regardless of flooding regime, suggest that sexual reproduction and clonal dispersal are sufficiently common to prevent the signature of founder events from dominating in a region. However, the pervasive occurrence of biased morph ratios in most populations suggests that many are in a non-equilibrium state. The reduced frequency of the mid-styled morph in trimorphic and dimorphic populations may be associated with the weak self-incompatibility of this morph resulting in selfing and inbreeding depression. Clonality in E. azurea and the weak self-incompatibility of the mid-styled morph may make it more vulnerable to geitonogamous selfing.

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  • Authors+Show Affiliations

    ,

    Programa de Pós-Graduação em Ecologia e Conservação, Universidade Federal de Mato Grosso do Sul, 79070-900 Campo Grande, Mato Grosso do Sul, Brazil nicolaycunha@gmail.com.

    ,

    Centro de Ciências Biológicas e da Saúde, Universidade Federal de Mato Grosso do Sul, 79070-900 Campo Grande, Mato Grosso do Sul, Brazil.

    ,

    Centro de Ciências Biológicas e da Saúde, Universidade Federal de Mato Grosso do Sul, 79070-900 Campo Grande, Mato Grosso do Sul, Brazil.

    Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, M5S 3B2, Canada.

    Source

    Annals of botany 114:8 2014 Dec pg 1637-49

    MeSH

    Animals
    Aquatic Organisms
    Brazil
    Eichhornia
    Environment
    Floods
    Flowers
    Geography
    Organ Size
    Pollen
    Pollination
    Population Density
    Quantitative Trait, Heritable
    Wetlands

    Pub Type(s)

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

    Language

    eng

    PubMed ID

    25180289