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  • 1
    ISSN: 1432-2145
    Keywords: Hydrophyllum appendiculatum ; Mating system ; Outcrossing rates ; Protandry ; Floral display ; Biparental inbreeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mating system of Hydrophyllum appendiculatum (Hydrophyllaceae), a protandrous, self-compatible, monocarpic plant was examined using progeny arrays assayed at three polymorphic allozyme loci. We were particularly interested in the effect of ecological factors on spatial and temporal variation in outcrossing rates. Multilocus estimates of outcrossing rates in three populations ranged from 0.62–0.81 indicating that the majority of seeds are produced via outcrossing. The population estimates did not differ significantly from each other indicating that there is little or no spatial variation in the mating system of this species. The estimates were, however, significantly less than unity, which demonstrates that although mainly outcrossing, a significant fraction of seeds are produced by selfing. Estimates suggested that biparental inbreeding occurred, although it was statistically significant in only one population. Individuals of H. appendiculatum may remain in anthesis 3–4 weeks and produce up to 30 inflorescences. As a result, the possibility exists for the mating system to vary through the flowering season. Although the mean outcrossing rate was highest in the middle of the flowering phenology than at the beginning or end, there was no evidence for statistically significant temporal heterogeneity. We were also interested in determining if the size of the floral display (number of inflorescences produced by a plant) influenced the outcrossing rate. The results obtained by two different statistical analyses were contradictory; there was a significant positive correlation between size of floral display and outcrossing rate, but the outcrossing rates of large plants (\s〉 8 inflorescences) did not differ significantly from small plants (〉 8 inflorescences).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Keywords: Pontederia cordata ; Bombus ; Tristyly ; Pollination ; Behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The foraging behavior of the pollinators of tristylous Pontederia cordata was studied to determine if differences in floral morphology would lead to preferential visitation of the floral morphs. Although nectar production is not different in the three floral morphs, differences in the production and size of pollen grains produced by the three anther levels results in the morphs offering variable amounts of resources to pollen-collecting insects. Bumblebees (Bombus spp.) and the solitary bee Melissodes apicata used P. cordata primarily as a nectar source and therefore did not seem to exhibit any morph preference. In contrast, honeybees visited flowers mainly for pollen and preferred to forage on long-level anthers of the short-and mid-styled morphs. An analysis of the composition of corbicular pollen loads indicated that, relative to the frequency of production in the population: 1) honeybees collected an excess of pollen from long-level anthers; 2) bumblebees collected the three types of pollen without any apparent preference; and 3) M. apicata preferentially collected pollen from the short-level anthers — presumably because their proboscides are modified by the presence of tiny hairs. The results suggest that P. cordata in Ontario is serviced by a diverse, unspecialized pollinator fauna which is not co-adapted to the tristylous floral polymorphism.
    Type of Medium: Electronic Resource
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