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Abstract Detail


Pollination Biology

Arceo-Gomez, Gerardo [1], Martinez, Maria Luisa [1], Parra-Tabla, Victor [2], Garcia-Franco, José G. [1].

Reproductive biology of enantiostylous Chamaecrista chamaecristoides (Leguminosae): a mixed mating system?

Enantiostyly is a polymorphism in plants in which the style is deflected away from the main axis of the flower, either to the left or right side. This sexual polymorphism is usually interpreted as a floral design that promotes outcrossing. However interpretation of its functional significance has been complicated by the occurrence of monomorphic and dimorphic enantiostyly. We examined the breeding system and pollination of the enantiostylous species Chamaecrista chamaecristoides, and its relationship with floral architecture. We analyzed style morph-ratios, floral morphology, pollen production, reproductive system and visitation patterns. Style morph proportions were significantly different between individuals along the flowering period, condition that promotes outcrossing. Flowers are truly mirror-image flowers as they don’t differ in style, stamens and petal size. Position, size and pollen production was different between stamen groups within flowers suggesting functional differentiation; the eight short feeding anthers produce more pollen than the two pollinating anthers in order to supply for the high pollen requirements of the large bees that pollinates this species. The two pollinating anthers, one at the opposite and one at the same side of the style (this stamen also correlates with style size), produce the same amount of pollen suggesting that one could function as an outcrossing and the other as a selfing anther to ensure fertilization, all types of pollen were viable. These functional differences can prevent pollen loss (pollen assigned to fertilization) via grooming by the bees since pollen is the only reward, and pollen discounting via self-fertilization. C. chamaecristoides is self-compatible but no differences were found in fruit-set between the pollinations performed (e.g. self and outcross), although geitogamous pollination had significantly fewer seed-set. Pollinators moved randomly between floral types. The results of this study suggests that enantiostyly promotes outcrossing and selfing in this species resulting in a mixed mating system.


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1 - Instituto de Ecologia, A.C., Ecologia Funcional, Km 2.5 Ant Carr a Coatepec No 351 Congregacion El Haya, Xalapa, Veracruz, 91070, Mexico
2 - Campus de Ciencias Biologicas y Agropecuarias, Univ. Aut. de Yucatan, Ecologia Tropical, Km. 15.5 Carretera Mérida Xtmakuil, Merida, Yucatan, 97000, Mexico

Keywords:
Chamaecrista chamaecristiodes
enantiostyly
mixed mating system
pollen discounting
floral polymorphism
self-fertilization.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM
Number: PPL001
Abstract ID:226


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