The taxonomy of bracken (Pteridium: Dennstaedtiaceae) in Australia

Abstract

Investigation of Australian bracken ferns in the genus Pteridium (Dennstaedtiaceae) shows that there is one common and widespread species, P. esculentum, found in all States, and a second species, P. revolutum, confined to north-eastern Queensland and the Northern Territory. Plants first described as P. aquilinum var. yarrabense and more recently referred to P. semihastatum are intermediate in morphology between the other two species and have aborted spores. They are now believed to be sterile hybrids between P. esculentum and P. revolutum. This is the first record of wild hybrids in Pteridium and provides strong evidence that the concept of a monotypic genus is incorrect. Other evidence for speciation within the genus is reviewed.