Reproductive biology of a mycoheterotrophic species, Burmannia wallichii (Burmanniaceae)

The breeding system of a mycoheterotrophic species, Burmannia waliichii (Mi ers) Hook. f (Burmanniaceae), is assessed using field observations, floral anatomy, pollen histochemistry and isozyme electrophoresis. The structure o f the flower effectively prevents pollinators from accessing the stamens, a nd no pollinators were observed visiting natural populations in Hong Kong. The pollen is starch-rich but lipid-poor. Analysis of isozyme variation rev ealed a small proportion of polymorphic loci, a low level of total heterozy gosity (H-T = 0.1972), and a very high overall fixation index of population s (F-IT = 0.6602). These results strongly suggest that B, wallichii is pred ominantly self-pollinated. The coefficient of gene differentiation (GST) is low (0.05), although it is suggested that this is due to genetic homogeniz ation of populations consonant with the formation of numerous tiny 'diaspor a' seeds that are wind dispersed. (C) 2000 The Linnean Society of London.