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Pollen Performance in Clarkia Taxa with Contrasting Mating Systems: Implications for Male Gametophytic Evolution in Selfers and Outcrossers
Biology Department, Warren Wilson College, P.O. Box 9000, Asheville, NC 28815, USA
Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA
* Author to whom correspondence should be addressed.
Received: 15 February 2013; in revised form: 13 March 2013 / Accepted: 3 April 2013 / Published: 24 April 2013
Abstract: We tested three predictions regarding the joint evolution of pollen performance and mating system. First, due to the potential for intense intrasexual competition in outcrossing populations, we predicted that outcrossers would produce faster-growing pollen than their selfing relatives. Second, if elevated competition promotes stronger selection on traits that improve pollen performance, then, among-plant variation in pollen performance would be lower in outcrossers than in selfers. Third, given successive generations of adaptation to the same maternal genotype in selfers, we predicted that, in selfing populations (but not in outcrossing ones), pollen would perform better following self- than cross-pollinations. We tested these predictions in field populations of two pairs of Clarkia (Onagraceae) sister taxa. Consistent with our predictions, one outcrosser (C. unguiculata) exhibited faster pollen germination and less variation in pollen tube growth rate (PTGR) among pollen donors than its selfing sister species, C. exilis. Contrary to our predictions, the selfing C. xantiana ssp. parviflora exhibited faster PTGR than the outcrossing ssp. xantiana, and these taxa showed similar levels of variation in this trait. Pollen performance following self- vs. cross-pollinations did not differ within either selfing or outcrossing taxa. While these findings suggest that mating system and pollen performance may jointly evolve in Clarkia, other factors clearly contribute to pollen performance in natural populations.
Keywords: Clarkia exilis; Clarkia unguiculata; Clarkia xantiana ssp. parviflora; Clarkia xantiana ssp. xantiana; sexual selection; mating system evolution; pollen performance; pollen tube growth
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MDPI and ACS Style
Hove, A.A.; Mazer, S.J. Pollen Performance in Clarkia Taxa with Contrasting Mating Systems: Implications for Male Gametophytic Evolution in Selfers and Outcrossers. Plants 2013, 2, 248-278.
Hove AA, Mazer SJ. Pollen Performance in Clarkia Taxa with Contrasting Mating Systems: Implications for Male Gametophytic Evolution in Selfers and Outcrossers. Plants. 2013; 2(2):248-278.
Hove, Alisa A.; Mazer, Susan J. 2013. "Pollen Performance in Clarkia Taxa with Contrasting Mating Systems: Implications for Male Gametophytic Evolution in Selfers and Outcrossers." Plants 2, no. 2: 248-278.