Stamen dimorphism in bird-pollinated flowers – investigating alternative hypotheses on the evolution of heteranthery

Agnes Sophie Dellinger, Silvia Artuso, Diana Margoth Fernández-Fernández, Jürg Schönenberger

Publications: Contribution to journalArticlePeer Reviewed

Abstract

Abstract Heteranthery, the presence of distinct stamen types within a flower, is commonly explained as functional adaptation to alleviate the ‘pollen dilemma’, defined as the dual and conflicting function of pollen as pollinator food resource and male reproductive agent. A single primary hypothesis, ‘division of labour’, has been central in studies on heteranthery. This hypothesis postulates that one stamen type functions in rewarding pollen-collecting pollinators and the other in reproduction, thereby minimizing pollen loss. Only recently, alternative functions (i.e. staggered pollen release), were proposed, but comparative and experimental investigations are lagging behind. Here, we use 63 species of the tribe Merianieae (Melastomataceae) to demonstrate that, against theory, heteranthery occurs in flowers offering rewards other than pollen, such as staminal food bodies or nectar. Although shifts in reward type released species from the ‘pollen dilemma’, heteranthery has evolved repeatedly de novo in food-body-rewarding, passerine-pollinated flowers. We use field investigations to show that foraging passerines discriminated between stamen types and removed large stamens more quickly than small stamens. Passerines removed small stamens on separate visits towards the end of flower anthesis. We propose that the staggered increase in nutritive content of small stamens functions to increase chances for outcross-pollen transfer. This article is protected by copyright. All rights reserved
Original languageEnglish
Pages (from-to)2589-2599
Number of pages11
JournalEvolution
Volume75
Issue number10
Early online date8 May 2021
DOIs
Publication statusPublished - Oct 2021

Austrian Fields of Science 2012

  • 106008 Botany
  • 106012 Evolutionary research
  • 106042 Systematic botany

Keywords

  • cross-fertilization
  • floral trait function
  • male fitness
  • Pollen loss
  • pollen reward
  • stamen dimorphism
  • SYSTEM
  • VISITATION
  • MATTERS
  • fertilization
  • DIVISION-OF-LABOR
  • FLORAL EVOLUTION
  • POLLEN DIVERSITY
  • Cross&#8208
  • ANTHER POSITION
  • PLANTS
  • REPRODUCTIVE SUCCESS
  • FOOD
  • pollen loss
  • Cross-fertilization

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