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The journal of the Western Australian Herbarium

Update to the taxonomy of Hypocalymma sect. Hypocalymma (Myrtaceae: Chamelaucieae), including hybrids and new species

In updating the taxonomy of Hypocalymma (Endl.) Endl. sect. Hypocalymma (Myrtaceae: Chamelaucieae), the section is described, a key is provided to the species and hybrids, full descriptions given for 11 species (three of them new, one reinstated) and three hybrids (one newly named). Taxa needing further study are noted. Five species and two of the hybrids described here have conservation priority. Two new species are described from the H. xanthopetalum F.Muell. complex as H. lateriticola Keighery & Rye and H. quadrangulare Rye & Keighery. The circumscription of H. angustifolium (Endl.) Schauer is reduced with the reinstatement of H. suave Lindl. and the description of the new species H. balbakiae Tauss & Rye. A northern variant of H. balbakiae (previously known as H. angustifolium subsp. Hutt River) is considered to be insufficiently distinct to recognise formally as a subspecies. Evidence is presented that one previously named and two phrase-named taxa are hybrids. Two of the hybrids are known from more than one location and have been recorded in hybrid swarms: one between H. angustifolium and H. tetrapterum Turcz. is named as H. × proliferum Keighery & Rye, while the other, H. × linifolium Turcz., has the parent species H. angustifolium and H. lateriticola. The third hybrid is H. tenuatum × H. xanthopetalum. The description of H. jessicae Strid & Keighery is broadened to include a new variant that has mostly higher ovule and stamen numbers. Amendments are made to the stamen and ovule numbers recorded for H. sylvestre Strid & Keighery; this species has up to 200 stamens, which is the highest stamen number known for the tribe Chamelaucieae DC. A new fruit type that is indehiscent and somewhat winged, is recorded for the genus; it occurs only in H. serrulatum Strid & Keighery, which also has an unusual breeding system.

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