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The journal of the Western Australian Herbarium

Astus, a new Western Australian genus of Myrtaceae with heterocarpidic fruits

Astus Trudgen & Rye, a new genus of Myrtaceae with four species endemic to the south-west of Western Australia, is described and its affinities discussed. While the genus is circumscribed on the basis of a range of characteristics that separate it from related genera, all its members are unusual in having a fruit with both dehiscent and indehiscent loculi. In addition, two of the species have a marked heteromorphy in their calyx lobes. Astus is one of a number of genera belonging to the tribe Chamelaucieae that have reniform seeds. While the floral morphology of the new genus does not readily indicate which of the other reniform-seeded genera it is closest to, DNA evidence indicates affinities to the Eastern Australian genus Triplarina Raf. The type species, Astus tetragonus (F. Muell. ex Benth.) Trudgen & Rye, is based on Baeckea tetragona F. Muell. ex Benth. Astus duomilius Trudgen & Rye, A. subroseus Trudgen & Rye and A. wittweri Trudgen & Rye are new species. A key to the species, descriptions, illustrations and distribution maps are provided.