Figueroa-Castro, Dulce M. , Holtsford, Timothy P. .
Post-pollination mechanisms in Nicotiana longiflora and N. plumbaginifolia: pollen tube growth rate, offspring paternity and hybridization.
In natural populations where interfertile species coexist, conspecific and heterospecific pollen grains can be delivered on the stigmas. Post-pollination mechanisms might determine the paternity success of different pollen donors within species as well as the chances for hybridization between species. Nicotiana longiflora and N. plumbaginifolia co-occur in sympatry in Northwest Argentina, where they have overlapping flowering seasons and share floral visitors. We explored i) pollen tube growth rates (PTGR) for outcross vs. self pollen in single-donor pollinations; ii) siring success of self vs. outcross pollen donor in competitive pollinations, and iii) possibilities for hybridization by performing two- (outcross conspecific vs. heterospecific) and three-pollen donor (self vs. outcross vs. heterospecific) crosses. We found that in N. longiflora, both PTGR and siring success favored outcross pollen over self pollen. In two- and three-donor crosses with heterospecific pollen, N. longiflora outcross pollen was also more successful at siring seeds. These results suggest that N. longiflora experiences incompatibility reactions that prevent both self-fertilization and hybridization. In N. plumbaginifolia, PTGR was similar for self and outcross pollen. It seems that N. plumbaginifolia experiences strong post-pollination mechanisms when conspecific and heterospecific pollen mixtures grow in the style. Interspecific pollen was more successful at siring seeds when competing with conspecific outcross pollen. In three-donor crosses, self and interspecific pollen sired similar number of seeds, thus having a greater reproductive success than conspecific outcross pollen. Our results suggest that in natural sympatric populations, interspecific crosses would likely lead to unidirectional hybridization with N. plumbaginifolia as the seed parent. The post-pollination selection detected in both species seems to be acting at different times and through different mechanisms in each species, i.e., through greater pollen tube growth rate of outcross over self pollen within N. longiflora and seemingly through selective abortion of conspecific seeds in N. plumbaginifolia.
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1 - Universidad Autónoma Metropolitana, Unidad Iztapalapa, Biología, Av. San Rafael Atlixco #186, Col. Vicentina, Del. Iztapalapa, Mexico , DF, 09340, Mexico
2 - University of Missouri-Columbia, Biological Sciences, 105 Tucker Hall, Columbia, Missouri, 65211, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Wasatch A/Cliff Lodge - Level C
Date: Monday, July 27th, 2009
Time: 4:30 PM