Isham, Samuel T. , de Vos, Jurriaan M. , Conti, Elena , Kelso, Sylvia .
Stigmatic receptivity, pollen viability and outcrossing potential in the herkogamous homostylous species Primula halleri.
The genus Primula (primrose) has been exemplary for the study of breeding system transitions, especially in sect. Aleuritia where shifts from predominant outcrossing in distyly to homostyly with presumptive selfing are thought to have spurred diversification through speciation via secondary contact. From distyly, a dimorphic breeding system characterized by reciprocal herkogamy and self- and intra-morph incompatibility, homostyly evolved. Homostylous species are monomorphic and self-compatible, and occur frequently in marginal habitats such as high alpine environments where pollinator density and reliability decreases. The actual amount of selfing in such species is a matter of longstanding controversy evident in the literature, but never tested experimentally. Studies in Primula halleri, a European high Alpine homostyle, show dramatic variation in anther-stigma separation (herkogamy) that decreases significantly during the life of a single flower. Herkogamy is known to enhance outcrossing in unrelated systems. The observation of a significant period of herkogamy in P. halleri coupled with unusually long period of anthesis, (up to 12 days for an individual flower and up to ~20 days for an entire inflorescence), suggests that this reproductive system, though nominally homostylous, may enhance outcrossing. As part of a larger study of reproductive complexity in a homostylous system, we investigated aspects of flower function throughout anthesis. In the study reported here, we examined pollen viability and stigmatic receptivity over the blooming period, using artificial pollination and pollen germination techniques. Stigmatic tissues were receptive over the entire period of flowering and pollen remains viable from dehiscence throughout anthesis. The combination of unusually long anthesis and an extended period of herkogamy with full stigmatic receptivity and pollen viability supports the hypothesis that, despite the ability of P. halleri to self, its potential for outcrossing is maximized.
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1 - Colorado College, Department of Biology, 14 E. Cache la Poudre, Colorado Springs, CO, 80903, USA
2 - University of Zurich, Institute of Systematic Botany, Zollikerstrasse 107, Zurich, CH-8008, Switzerland
3 - Institute of Systematic Botany, University of Zürich, Zollikerstrasse 107, Zürich, CH-8008, Switzerland
4 - Colorado College, Biology Department, 14 E. Cache La Poudre, Colorado Springs, Colorado, 80903, USA
Presentation Type: Poster:Posters for Topics
Location: Hall A/Convention Center
Date: Monday, August 2nd, 2010
Time: 5:30 PM