Hybridization in Tradescantia. III. The Evidence for Introgressive Hybridization

Abstract

Introgressive hybridization is described and defined. Analyses of intraspecific variation in herbarium material indicate a strong introgression of Tradescantia canaliculata into T. occidentalis and of T. canaliculata into T. bracteata. There is no evidence for an introgression of T. subaspera into T. canaliculata, although these species are known to hybridize. The above conclusions are supported by an analysis of variation in natural populations of T. occidentalis. This analysis further demonstrates that introgression is roughly proportional to the frequency of the introgressive species and that it is greater when plants are growing as weeds than when they occupy more natural habitats.