A Report of Hybridisation in Hymenachne (poaceae, Panicoideae) with Description of Hymenachne X Calamitosa, a New Species of Hybrid Origin from Tropical Australia

Naturally occurring hybridisation between the introduced species Hymenachne amplexicaulis, a Weed of National Significance, and the Australian native species H. acutigluma is reported from two widely separated locations in tropical Australia. Molecular studies including RAPD analysis and DNA sequencing of the ITS region of each parent species and the putative cross confirm initial evidence for hybridisation based on gross morphology. The legislative implications of this are discussed and the species of hybrid origin is described as Hymenachne × calamitosa J.R. Clarkson.