Figueroa-Castro, Dulce , Valverde, Pedro , Aguilar-García, Sandra .
Is reproductive success in Pachycereus weberi (Cactaceae) constrained by pollination success or resource availability?
Numerous studies have shown that floral traits such as size, shape, color and floral display have a significant effect on flower attractiveness towards pollinators and thus, affect reproductive success. Recently, it has been shown that flower angle and flower direction (components of flower orientation) are also important traits affecting reproductive success. It has been suggested that in columnar plants within the Cactaceae family, flower reproductive success is constrained by the amount of resources on each rib, since photosynthetic active radiation (PAR) is heterogeneous around the stem and there is not carbohydrate translocation among ribs within the stem. Therefore, reproductive success might be constrained by resource availability and floral attractiveness. In this study we attempt to determine if flower orientation has an effect on floral attractiveness and on reproductive success using Pachycereus weberi as the study system. We collected flowers and fruits with different orientations (Northeast vs. Southeast). We tested if flower length, corolla diameter, ovary diameter, flower volume, ovule and pollen production and pollen:ovule ratio were different among flowers with different orientations. Seed set, seed weight and percentage of germination were used as estimators of reproductive success. Among all the floral traits that we measured, only ovule production was significantly different between flowers with contrasting orientations. Flowers oriented towards the Southeast produced significantly more ovules than flowers oriented towards the northeast. Seed set was not significantly different among flowers with different orientations, but seed weight and percentage of germination were significantly greater for flowers oriented towards the southeast. Our results indicate that flower orientation does not have an effect on flower attractiveness and seed set; thus, similar rates of visitation and similar reproductive success would be expected. Contrastingly, seed quality (an estimator of reproductive success) was different, suggesting that resource availability is the main factor affecting reproductive success in Pachycereus weberi.
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1 - Universidad Autónoma de Puebla, , Escuela de Biología, , Blvd. Valsequillo y Av. San Claudio, Edif. 112A,, Ciudad Universitaria, Col. San Manuel, Puebla, Puebla, 72570, México
2 - Universidad Autónoma Metropolitana-Iztapalapa, Biología, México, D.F., México
photosynthetic active radiation
Presentation Type: Oral Paper:Papers for Topics
Location: Forsyth Room/Chase Park Plaza
Date: Tuesday, July 12th, 2011
Time: 9:00 AM