title: Reproductive character displacement shapes a spatially structured petal color polymorphism in Leavenworthia stylosa.
abstract: Character displacement is a potentially important process driving trait evolution and species diversification. Floral traits may experience character displacement in response to pollinator-mediated competition (ecological character displacement) or the risk of forming hybrids with reduced fitness (reproductive character displacement). We test these and alternative hypotheses to explain a yellow-white petal color polymorphism in Leavenworthia stylosa, where yellow morphs are spatially associated with a white-petaled congener (Leavenworthia exigua) that produces hybrids with complete pollen sterility. A reciprocal transplant experiment found limited evidence of local adaptation of yellow color morphs via increased survival and seed set. Pollinator observations revealed that Leavenworthia attract various pollinators that generally favor white petals and exhibit color constancy. Pollen limitation experiments showed that yellow petals do not alleviate competition for pollination. Interspecific pollinator movements were infrequent and low hybridization rates (∼0.40-0.85%) were found in each morph, with natural rates likely being lower. Regardless, hybridization rates were significantly higher in white morphs of L. stylosa, yielding a small selection coefficient of s = 0.0042 against this phenotype in sympatry with L. exigua. These results provide support for RCD as a mechanism contributing to the pattern of petal color polymorphism in L. stylosa.
authors: School of Biological Sciences, Washington State University, PO Box 644236, Pullman, Washington, 99164.
authors: Nicholas A
authors: NA
authors: Norton
authors: Department of Biology, Evolution and Ecology Group, Middle Tennessee State University, PO Box 60, Murfreesboro,Tennessee, 37132.
authors: M Thilina R
authors: MT
authors: Fernando
authors: Department of Biology, Evolution and Ecology Group, Middle Tennessee State University, PO Box 60, Murfreesboro,Tennessee, 37132.
authors: Christopher R
authors: CR
authors: Herlihy
authors: School of Biological Sciences, Washington State University, PO Box 644236, Pullman, Washington, 99164. jwbusch@wsu.edu.
authors: Jeremiah W
authors: JW
authors: Busch
mesh_terms: D019607:Brassicaceae / Q000235:genetics*; D019143:Evolution, Molecular; D035264:Flowers / Q000235:genetics*; D049810:Genetic Speciation; D010858:Pigmentation / Q000235:genetics*; D051479:Plant Infertility / Q000235:genetics; D054817:Pollination; D011110:Polymorphism, Genetic; D012641:Selection, Genetic; D061350:Sympatry
keywords: Carotenoids; competition; hybridization; pollination; sympatry