A revision of the species of Hypocalymma (Myrtaceae: Chamelaucieae) with smooth or colliculate seeds

Abstract

Most members of the south-western Australian genus Hypocalymma (Endl.) Endl. have seeds with a shallowly to very deeply pitted testa. Two small groups of species, both revised here, differ in having a smooth or colliculate testa. Both groups occur in humid environments in the extreme south-west of Western Australia and show vegetative adaptations consistent with this habitat preference. The larger group, Hypocalymma sect. Cardiomyrtus Schauer, is reinstated. A new combination, H. minus (Strid & Keighery) Keighery, is made, bringing the total species recognised to five, and lectotypes are selected for two synonyms, H. boroniaceum F.Muell. ex Benth. and H. hypericifolium Benth. The other group is extremely rare, consisting of the possibly extinct species H. connatum Strid & Keighery, and a new species known from a single population, H. verticillare Rye. The latter group, named here as Hypocalymma sect. Verticilla Rye, is readily distinguished by its 3-ridged young stems and consistently whorled leaves, and the new species is unusual in having extreme differences in the sizes of the anthers on different stamens within each flower. Molecular data indicate that sect. Verticilla is sister to sect. Cardiomyrtus. Evidence of taxonomic relationships is also presented from studies of hybridisation and insect associations.

Western Australian plant taxa not collected for more than 50 years

“…spp. by young stems 3-angled, leaves in whorls of 3 with oil glands in 2 or 3 main, irregular rows on each side of the midvein, and flowers solitary; distinguished from the similar H. verticillare Rye by leaf blades c. 7 × 1-1.5 mm, petals 3.5-4 mm long persistent in fruit, and multiple ovules in each loculus (Rye et al 2013).…”

“…Gardner later acquired the specimen for PERTH. While the origin of that collection is unknown, Rye et al (2013) Diagnostic features. Clements (1989) considers that it differs from P. fimbria Rchb.f.…”

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

“…Hypocalymma, such as black scales formed by the larvae of white flies (Hemiptera family Aleyrodidae), but less commonly than in H. sect. Cardiomyrtus (see Rye et al 2013 for details of scale-forming insects in that section).…”

“…Recent publications on Hypocalymma began with a review of the whole genus (Strid & Keighery 2002) in which eleven new taxa were named. Two of these new taxa were originally treated as subspecies but both have subsequently been raised to the species level (Rye 2010;Rye et al 2013).…”

“…Cardiomyrtus Schauer with five species and sect. Verticilla Rye with two species, were described in Rye et al (2013). Another small section of five species, distinguished by having petals much longer than the stamens, has been described as sect.…”