A new species of Vallisneria L. for Western Australia and recircumscription of V. triptera S.W.L.Jacobs & K.Frank

Vallisneria kristinae R.W.Jobson & Dunning (Hydrocharitaceae) is described as a new species endemic to North Kimberley, Western Australia. It was previously included within the Northern Territory species V. triptera S.W.L.Jacobs & K.A.Frank. Here it is distinguished from that species based on its overall smaller size and weakly-winged fruit capsules. We also find strong genetic differentiation with accessions sampled from across the entire distribution of both taxa. We present a phylogeny based on nuclear ITS and plastid trnK 5′ intron data that also includes all Australian species of Vallisneria. Along with a redescription of V. triptera s. str., diagnostic features are illustrated, a taxonomic key containing all Australian species is provided, and distribution, habitat, and conservation status are discussed.