Figueroa-Castro, Dulce , Holtsford, Timothy P. .
Floral traits in two Nicotiana species: interpopulational variability and correlations with pollen limitation and self-pollination.
Floral characteristics are strongly associated with plant mating systems, for example, short flowers, small anther-stigma distance and small pollen:ovule ratio are common in self-pollinated species, whereas the opposite is more frequent in outcrossers. Mating systems may vary depending not only on the genetics of floral traits but also on ecological conditions which populations are exposed to, such as interactions between species sharing pollinators. Nicotiana plumbaginifolia and N. longiflora are sister species that grow sympatrically in Northwest Argentina. They have contrasting floral characteristics and are assumed to also have contrasting mating systems. The main goal of this study was to determine if floral traits in these Nicotiana species are associated with mating systems (estimated as pollen limitation, % selfing). We estimated: i) interpopulational variability of floral traits (corolla length, anther-stigma distance, and pollen:ovule ratio) in 12 natural populations, ii) the effect that the presence/absence of the sister species has on the floral traits and, iii) the correlation between floral traits with selfing and pollen limitation as indicators of mating systems. All floral traits showed significant variability among populations, although in all cases, floral variability was greater in N. longiflora. Pollen:ovule ratio increased in sympatric populations, whereas all the other traits did not change significantly. Corolla length was significantly correlated with pollen limitation. Larger flowers were more pollen limited than small flowers. Corolla length and anther-stigma distance were significantly correlated with percentage of selfing, indicating that larger flowers with greater anther-stigma distance tend towards outcrossing. Surprisingly, pollen:ovule ratio was not significantly correlated with pollen limitation, and had only marginal significance with percentage of selfing, showing the same pattern as the other floral traits. Pollen:ovule ratio varied between allopatric and sympatric populations, suggesting a possible interaction between the two Nicotiana species.
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Dulce's dissertation project with N. longiflora and N. plumbaginifolia
Holtsford's lab- Nicotiana floral evolution
1 - University of Missouri-Columbia, Biological Sciences, 202 Tucker Hall, Columbia, Missouri, 65211-7400, USA
2 - University of Missouri-Columbia, Biological Sciences, 105 Tucker Hall, Columbia, Missouri, 65211, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Lake Ontario/Hilton
Date: Tuesday, July 10th, 2007
Time: 8:30 AM