Patterns and consequences of stigma height variation in a natural population of a distylous plant, Primula sieboldii

Abstract

Summary 1.In order to reveal the direction and magnitude of phenotypic selection on the stigma height of heterostylous morphs in a natural population of Primula sieboldii E. Morren (Primulaceae), morphological traits including stigma and anther heights, flowering phenology, local density of potential mating partners, size of ramet, number of pollen grains deposited from the opposite morph and seed set were measured in two flowering seasons. 2. Both components of female reproductive success, pollen receipt and seed set, were significantly larger in the long-styled than in the short-styled morph in both years. 3. Selection analyses based on bivariate correlation and path-analysis models revealed positive relationships between stigma height and pollination or seed set in the short-styled morph only, although the effect was statistically significant only in one year. In contrast, seed set in the long-styled morph was correlated with ramet size. 4. Morph difference in reproductive success and the natural selection revealed for higher stigmas in the short-styled morph should be ascribed to the narrow corolla tube of the species that strictly restrict the path of the proboscis of the pollinators.

Correlations among traits associated with herbivore resistance and pollination: implications for pollination and nectar robbing in a distylous plant

“…However, floral morphs of distylous plants often vary systematically in a number of other floral characters related to pollination (Ganders, 1979), including flower and anther color (Wolfe, 2001), pollen and stigma size and morphology (Ornduff, 1970a), flower size (Pailler and Thompson, 1997), and the timing or amount of nectar reward (Arroyo and Dafni, 1995;Contreras and Ornelas, 1999). Such differences in floral characters between distylous (and tristylous) morphs may promote differential pollinator visitation or efficiency, pollen donation and receipt, and male and female plant reproduction (Wolfe andBarrett, 1987, 1989;Nishihiro et al, 2000). Interestingly, distylous morphs have also been shown to vary in the amount and pattern of damage received by herbivores, florivores, and seed predators (Olesen, 1979;Contreras and Ornelas, 1999;Leege and Wolfe, 2002).…”

Toward predicting gene flow in plant populations

“…In some natural populations of P. sieboldii, a strong effect of opposite-morph density within a 5 m radius on the seed set was found (Nishihiro et al 2000;Watanabe et al 2003), implicating relatively short pollen-dispersal distance and the possible importance of the local arrangement of genetically compatible mates for successful seed reproduction.…”

“…Most remaining populations of the species are more or less isolated due to habitat fragmentation (Environment Agency of Japan 2000), but variously sized populations differing greatly with regarding to extinction probability and genetic diversity still remain. A relatively sufficient amount of data on the demographic, eco-physiological, and genetic traits of the species is available, most of which has been obtained from wild populations in Southern Hokkaido or central Honshu (Washitani et al 1991(Washitani et al , 1994a(Washitani et al , 1994bKakishima et al 1995;Washitani 1996;Nishihiro et al 2000;Washitani 2000, 2002;Okayama et al 2003;Ishihama et al 2003Ishihama et al , 2005Watanabe et al 2003;Noda et al 2004;Honjo et al 2004;Kitamoto et al 2005).…”

Floral morphology affects seed productivity through pollination efficiency in radish (Raphanus sativus L.)

“…Self pollen grains landing on the stigma can lead to seed set, because self-incompatibility in radish is incomplete (Niikura and Matsuura 1999). Therefore, pollination efficiency of both self and cross pollen grains should be assessed.…”