Journal Article

Unusual heterostyly: style dimorphism and self-incompatibility are not tightly associated in <i>Lithodora</i> and <i>Glandora</i> (Boraginaceae)

V. Ferrero, J. Arroyo, S. Castro and L. Navarro

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 109, issue 3, pages 655-665
Published in print February 2012 | ISSN: 0305-7364
Published online October 2011 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcr222
Unusual heterostyly: style dimorphism and self-incompatibility are not tightly associated in Lithodora and Glandora (Boraginaceae)

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  • Ecology and Conservation
  • Evolutionary Biology
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Background and Aims

Heterostyly is a floral polymorphism characterized by the reciprocal position of stamens and stigmas in different flower morphs in a population. This reciprocal herkogamy is usually associated with an incompatibility system that prevents selfing and intra-morph fertilization, termed a heteromorphic incompatibility system. In different evolutionary models explaining heterostyly, it has been alternately argued that heteromorphic incompatibility either preceded or followed the evolution of reciprocal herkogamy. In some models, reciprocal herkogamy and incompatibility have been hypothesized to be linked together during the evolution of the heterostylous system.

Methods

We examine the incompatibility systems in species with different stylar polymorphisms from the genera Lithodora and Glandora (Boraginaceae). We then test whether evolution towards reciprocal herkogamy is associated with the acquisition of incompatibility. To this end, a phylogeny of these genera and related species is reconstructed and the morphological and reproductive changes that occurred during the course of evolution are assessed.

Key Results

Both self-compatibility and self-incompatibility are found within the studied genera, along with different degrees of intra-morph compatibility. We report for the first time extensive variability among members of the genus Glandora and related species in terms of the presence or absence of intraspecies polymorphism and heteromorphic incompatibility. Overall, our results do not support a tight link between floral polymorphism and incompatibility systems.

Conclusions

The independent evolution of stylar polymorphism and incompatibility appears to have occurred in this group of plants. This refutes the canonical view that there is strong linkage between these reproductive traits.

Keywords: Character transitions; Lithodora; Glandora; Boragineae; evolution; heterostyly; incompatibility system; ITS; Lithospermeae; phylogenetic reconstruction; trnLUAA intron

Journal Article.  6977 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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