TITLE:
A Geometric Morphometrics Study of Stigma-Anther Polymorphism in the Tropical Distylous Palicourea padifolia (Rubiaceae)
AUTHORS:
Angélica María Hernández-Ramírez, José A. Aké-Castillo
KEYWORDS:
Ancillary Traits, Flower Shape and Entire Flower Design, Heterostyly, Landmark, Procrustes
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.5 No.10,
May
7,
2014
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.