Barrett, Matthew D., de Kock, Pierre-Louis, and Dillon, Steven J. (2023) Four new species of Triodia (Poaceae) from the Pilbara and adjacent bioregions, Western Australia. Nuytsia, 34. pp. 261-294.

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Abstract

The Australian hummock genus Triodia R.Br. is currently undergoing taxonomic revision in light of new collections from surveys of remote Australia and increased resolution provided by molecular methods. This paper describes four new species of Triodia from the Pilbara and adjacent IBRA bioregions: T. avenoides M.D.Barrett, T. degreyensis M.D.Barrett, T. karijini M.D.Barrett & S.J.Dillon, and T. lutiteana M.D.Barrett & P.-L. de Kock. All four species are ‘soft’ spinifexes with elongate glumes and lemma lobes subulate to awned, and are only known from the Pilbara and adjacent Carnarvon and Gascoyne regions of Western Australia. Triodia degreyensis is known from a single range system in the north-eastern Pilbara. The taxon formerly known by the phrase name T. sp. Karijini (S. van Leeuwen 4111) is formally described here as T. karijini, and is restricted to mountains above 900 m altitude in the eastern Hamersley Range. Triodia lutiteana is only known from shale substrates north-west of Tom Price, and may be a polyploid species. The new species T. avenoides is segregated from T. schinzii (Henrard) Lazarides based on morphological and molecular differences and a disjunct distribution on sand sheets and dunes of the Carnarvon basin. The central Australian species T. helmsii (C.E.Hubb.) Lazarides is newly synonymised with T. schinzii, since no clear morphological or genetic differences between the two could be established. An amended description of T. schinzii is provided to accommodate these alterations to the species concept. Diagnostic character combinations for each species are given to allow discrimination from all other Triodia species. Triodia degreyensis, T. karijini and T. lutiteana are known from between one and four localities, and have priority conservation statuses, while T. avenoides and T. schinzii are not considered threatened. With the species described here, a total of 29 species and one hybrid are now known from the Pilbara bioregion and its immediate surrounds.

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