Reproductive Biology of Oxalis corniculata (Oxalidaceae): Style Length Polymorphisms and Breeding Systems of Japanese Populations

Abstract

Abstract Style length polymorphisms and breeding systems of Oxalis corniculata populations in Japan were investigated. In Japan this species is composed of two floral morphs, a homostyled morph in which the level of the stigma and the anther of longer stamens are more or less the same, and a long‐styled morph in which the stigmas conspicuously protrude from the level of anthers of the longer stamens. Homostyled plants are common in artificially disturbed urban and ruderal habitats, whereas long‐styled plants occur mainly in less disturbed habitats of maritime Pinus thunbergii forests. Each of five populations examined in this study was exclusively composed of one or the other of the two floral morphs, with no mixed populations observed. Measurements of floral traits and reproductive parameters indicated that plants of homostyled populations exhibited characteristics of a typical autogamous breeding system, whereas those of long‐styled populations exhibited characteristics of predominant outcrossing. Crossing experiments revealed that the length of the stigmas and anthers of longer stamens, which characterizes the two floral morphs, is quantitatively inherited. The results obtained suggest that disassortative pollination among different floral morphs, which is commonly observed in some other heterostylous species, does not occur in O. corniculata populations in Japan. The origin of homostyled and long‐styled morphs in O. corniculata is also discussed.