Abstract
Distyly is a floral polymorphism with long-styled flowers and short-styled flowers. Traditionally, floral traits in distylous species have been studied as a variable composed of several linear measurements. We proposed the use of a geometric morphometric approach to studying flower shape and entire flower design variation (including stigma-anther polymorphism) between morphs in Palicourea padifolia. The geometric morphometric approach allowed us to preserve the integrity of the floral form and to project the floral features on the same scale. Moreover, the visualization of a grid deformation allows us to describe shape differences between morphs as well as to estimate the variance-covariance matrix among floral traits. In this study, we demonstrated that flower shape and entire flower design differed between morphs. Intra- and inter-morph variations in the flower size were observed. The flower size has an effect on the anther position between morphs and among individuals. An association between flower shape and flower size was observed in both morphs. A pattern of floral features co-variation between the morphs was demonstrated in the species. In P. padifolia both morphs seemed to be internally coherent with respect to the developmental processes that produce flower shape variation. Changes in floral traits associated with flower size seemed to be more complex than those in the simple uniform expansion of the floral trait positions analogous between morphs. The observed pattern of co-variation of floral features between morphs suggested that flower base shape would be an additionally ancillary trait linked to the stigma-anther polymorphism in the species.
Highlights
Is a genetically controlled floral polymorphism in which plant populations are composed of two or three floral morphs that differ reciprocally in the position of stigmas and anthers in flowers, as well as a suite of ancillary floral traits associated with the polymorphism [1]-[3]
Differences in the Flower Shape and Entire Flower Design between Floral Morphs The principal component analysis (PCA) resulted in a plot in which the floral morphs were not distinguishable based on their flower shape
When we incorporated the entire flower design in the analysis, the PCA resulted in a plot with the two floral morphs were clearly separated
Summary
Is a genetically controlled floral polymorphism in which plant populations are composed of two or three floral morphs that differ reciprocally in the position of stigmas and anthers in flowers, as well as a suite of ancillary floral traits associated with the polymorphism [1]-[3]. Floral polymorphism is often associated with an incompatibility system that prevents self- and intra-morph fertilization [1] [2]. Variations in the precision of reciprocal sexual organs position and the strength of the incompatibility system are not uncommon in heterostylous plants, providing self- and intra-morph mating opportunities [3] [4]. Several developmental pathways produce differences in the stigma and anther position between floral morphs, and these have been documented in distylous species [1] [2]. Differences in growth rates and inhibition times of stigma and anthers heights at different floral bud sizes cause differences in organ positions between floral morphs [6]-[8]
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