The allometry of flower size dimorphism in dioecious Dombeya species on La Réunion

Authors

  • Laurence Humeau,

    1. Centre d’Ecologie Fonctionnelle et Evolutive, CNRS 1919 route de Mende, 34293 Montpellier cedex 5, and, Laboratoire de Biologie et Physiologie Végétales, Université de La Réunion, 15 avenue René Cassin, BP 7151, 97715 Saint Denis Messag. cedex 9, Ile de La Réunion, France.
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  • John D. Thompson

    1. Centre d’Ecologie Fonctionnelle et Evolutive, CNRS 1919 route de Mende, 34293 Montpellier cedex 5, France.
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John D. Thompson E-mail: thompson@cefe.cnrs-mop.fr

Abstract

In this paper we examine whether variation in male and female flower size follows an allometric relation for 10 dioecious species in the genus Dombeya endemic to La Réunion. Male flowers are significantly larger than female flowers and the degree of dimorphism varies significantly across species. There is a significant allometric relationship between male and female flower size: as mean flower size decreases the degree of flower size dimorphism increases. This is the first study to document an allometric relationship between male and female flower size in unisexual plants. We discuss this allometric relationship in relation to two characteristics frequently observed in dioecious flowers: flower size dimorphism is common in unisexual plants and dioecious species often have smaller flowers than hermaphrodites.

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