Gehring, J. L. .
Aspects of the mating system of Gentiana puberulenta.
Gentiana puberulenta is a widespread species of the North American tallgrass prairie. Most of this ecosystem has been destroyed and what remains is highly fragmented. Populations of G. puberulenta are now restricted, with a few exceptions, to small remnant prairies. Fragmented populations are expected to have low genetic variability because they are small and isolated and, as a result, are susceptible to the loss of alleles via genetic drift. Unexpectedly, even large populations (> 1500 plants in 2002) of G. puberulenta in central Illinois have low polymorphism (based on allozymes, RAPDs and ISSRs). There are several possible reasons for low allelic diversity in large populations, including previous population bottleneck(s) or inbreeding. I conducted this study to determine if selfing occurs in this species despite flowers that exhibit both protandry and herkogamy. The results indicate both autogamy and geitonogamy are possible. Bagged and unmanipulated flowers set an average of 44.4 seeds (Range 0-245) whereas control flowers (bagged and emasculated) produced only 1.1 seeds (Range 0-11). At least one anther was touching the edge of the stigma in 101 of 895 flowers (11.3%), even though mean distance between the stigma and closest anther was 1.9 mm on the first day of female function. These data indicate that herkogamy is incomplete and protandry cannot prevent autogamy if pollen is not removed during the male phase of the flower. Furthermore, during four weeks of peak flowering, more than 30% of plants had flowers in both male and female phase so geitonogamy is also likely. Although the flowers of G. puberulenta probably promote outcrossing, both autogamy and geitonogamy are possible under some ecological circumstances. Thus, inbreeding may contribute to low within-population genetic diversity.
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1 - Bradley University, Department of Biology, 1501 W. Bradley Avenue, Peoria, Illinois, 61625, USA
Presentation Type: Poster
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM