Contrasting patterns of genetic structure in the South African species Androcymbium bellum, A-guttatum and A-pulchrum (Colchicaceae)

Spatial autocorrelation analyses on genetic variability from three isozymic loci was used to explore the presence of possible patterns of genetic structure in four populations representing the South African species Androcymbium bellum, A. guttatum and A. pulchrum. Consistent profiles of short-distance genetic structure are only detected in patchy populations (A. bellum and A. guttatum), regardless of the sharp ecological differences between them. In the absence of microhabitat heterogeneity, our result strongly suggests that the predominant action of assortive mating (in A. bellum) and of vegetative reproduction (in A. guttatum) fostered the creation and enhancement of physical clumps that correspond to genetically related plants. A much lower incidence of both clonal propagation and outcrossing in the two continuous populations of A. pulchrum examined explains why isozymic variability is not spatially structured in this species. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.