Polymorphic Floral Traits in Linaria canadensis (Scrophulariaceae)

Abstract

-This study examined several aspects of a previously unreported flower color polymorphism in the annual plant Linaria canadensis. Natural populations in southeastern Georgia contained mainly two petal color morphs: the 'dark' purple morph and the 'light' blue morph (two individuals of a completely 'white' albino morph were also found). The frequency of the color morphs varied dramatically among six natural populations. The color morphs were equally common in two populations, in two more populations the dark morph was significantly more abundant than the light morph, and the light morph was more common than the dark morph in two other populations. The two flower color morphs did not differ significantly in number of stems, stem length and number of flowers and fruit. Also, the probability of germination under greenhouse conditions was the same for seeds produced by both flower types. However, flower size was an extremely variable trait (range 624 mm in length) and differed significantly between the morphs; flowers of the light morph were approximately 40% larger than those of the dark morph. Perhaps due to the developmental continuity between flowers and fruits, fruit derived from light-colored flowers were significantly larger than fruit produced by dark-colored flowers. Since fruit size will be correlated with either the size or number of seeds produced, there are likely to be fitness consequences of the flower color polymorphism for the population biology of L. candensis.