Browsing by Author "Holtsford, Timothy P."

Now showing 1 - 2 of 2
  • Artículo
    Floral traits and mating systems in sister species of Nicotiana: interpopulational variability and sympatry effects
    (2010) Figueroa Castro, Dulce María; Holtsford, Timothy P.; Figueroa Castro, Dulce María; 0000-0003-3611-191X
    "Mating systems of Angiosperms are important determinants of population genetic structure and evolutionary potential. Nicotiana longiflora and N. plumbaginifolia are self-compatible, sister species, with contrasting floral morphology and can be found in allopatry and sympatry in North Argentina. In two sympatric and 10 nearby allopatric populations we studied their natural interpopulational variability and sympatry effects on corolla length and anther–stigma distance. We also estimated seed set by selfing and via pollinators using pollination treatments. Both corolla length and anther–stigma distance varied significantly among N. longiflora, but not among N. plumbaginifolia populations. We did not detect an effect of sympatry in either species for any of the floral traits studied. Pollination treatments suggest that N. longiflora is mainly an outcrosser, although selfing occurs at some extent. Seed set attributed to pollinators was significantly higher in N. longiflora whereas most seeds in N. plumbaginifolia were sired through self-pollination. In N. plumbaginifolia, selfing seems to assure reproduction in sympatric populations, where floral visitors have a strong preference for N. longiflora. Corolla length was significantly negatively correlated with an increase in the percentage of self-seeds estimated by pollination treatments. Within N. longiflora, anther–stigma distance showed a positive correlation with selfing".
  • Artículo
    Post-pollination mechanisms in Nicotiana longiflora and N. plumbaginifolia: pollen tube growth rate, offspring paternity and hybridization
    (2009-07-07) Figueroa Castro, Dulce María; Holtsford, Timothy P.; Figueroa Castro, Dulce María; 0000-0003-3611-191X
    "In natural populations where interfertile species coexist, conspecific and heterospecific pollen can be delivered to the stigmas. Post-pollination mechanisms might determine the seed siring success of different pollen donors within species as well as the chances for hybridization between species. Nicotiana longiflora and N. plumbaginifolia occur in sympatry in Northwest Argentina, where they have overlapping flowering seasons and share floral visitors. We explored (1) pollen tube growth rates for outcross versus self pollen in single-donor pollinations; (2) siring success of self versus outcross pollen donors in competitive pollinations, and (3) possibilities for hybridization by performing two- (outcross conspecific vs. heterospecific) and three-pollen donor (self vs. outcross vs. heterospecific) crosses. In N. longiflora, both pollen tube growth rate and siring success favored outcross pollen over self pollen and strong rejection of heterospecific pollen. In N. plumbaginifolia, pollen tube growth rate was similar for self and outcross pollen, self pollen sired similar numbers of offspring than outcross pollen and heterospecific pollen sired roughly the same number of progeny than self pollen. Results suggest that in natural sympatric populations, interspecific crosses would likely lead to unidirectional hybridization with N. plumbaginifolia as the seed parent".