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Reproductive character displacement shapes a spatially structured petal color polymorphism in Leavenworthia stylosa
Author(s) -
Norton Nicholas A.,
Fernando M. Thilina R.,
Herlihy Christopher R.,
Busch Jeremiah W.
Publication year - 2015
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/evo.12659
Subject(s) - biology , character displacement , petal , pollinator , pollination , pollen , reproductive isolation , reciprocal cross , zoology , sympatry , hybrid , botany , ecology , evolutionary biology , sympatric speciation , population , demography , sociology
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 .