Recircumscription of Utricularia leptorhyncha and U. lasiocaulis and three related new species for northern Australia

Abstract

The Utricularia lasiocaulis F.Muell. complex (subg. Polypompholyx; sect. Lasiocaules) is a morphologically and ecologically variable group of closely related taxa with a mostly tropical distribution across northern Australia. A recent molecular phylogenetic study placed the recognised species U. kamienskii F.Muell. sister to a clade of accessions relegated to either U. leptorhyncha O. Schwarz or U. lasiocaulis, with the latter previously circumscribed as an assemblage of highly variable morphological forms. We have expanded the previous study to include populations representing the known distributions of all three species and have attempted to include all morphological variants; 55 ingroup accessions were used in the full phylogenetic analysis based on two non-coding chloroplast regions (rps16, trnD–T) and the nuclear ribosomal internal transcribed spacer (ITS). We found that the pink corolla form of the usually white flowered U. kamienskii is not sufficiently different, and we retain it under that species. We also found strong support for a paraphyletic U. leptorhyncha, with the smaller flowered accessions matching the type material placed sister to all other U. lasiocaulis forms, including a grouping previously assigned as a larger flowered U. leptorhyncha. Within the U. lasiocaulis clade we found that much of the variation sorts into well-supported clades that we find are sufficiently morphologically and genetically differentiated from the type clade for recognition at the specific rank, namely Utricularia brennanii R.W.Jobson & Baleeiro from Northern Territory and Queensland, Utricularia cowiei R.W.Jobson & Baleeiro from the Kimberley region of Western Australia, and U. disjuncta R.W.Jobson & Baleeiro restricted to the Darwin and Gulf region of the Northern Territory.