Tristaniopsideae Peter G.Wilson, 2022

Wilson, Peter G., Heslewood, Margaret M. & Tarran, Myall A., 2022, Three new tribes in Myrtaceae and reassessment of Kanieae, Australian Systematic Botany 35 (4), pp. 279-295 : 294

Tristaniopsideae Peter G.Wilson , trib. nov.

Type: Tristaniopsis Brongn. & Gris.

Trees or occasionally shrubs. Inflorescences determinate (panicles, metabotryoids, thyrsoids or cymes). Flowers whitish to yellow. Stamens usually in multiple whorls (not in Mitrantia ) and grouped opposite petals, sometimes fused into fascicles. Style-bases not adjacent to placentas, ovules often arranged in circular or semi-circular series. Fruit a capsule, frequently exserted from the fruiting hypanthium (except in Sphaerantia ). Seeds various; hypocotyl straight and cotyledons sometimes foliaceous. Hypanthium vascularisation not reduced to 5 main veins.

A tribe comprising seven genera, Tristaniopsis , Lysicarpus , Barongia , Sphaerantia , Ristantia , Mitrantia , and Basisperma . Tristaniopsis is a genus of ~50 species, with a distribution extending from Myanmar and Thailand in the north, through Malesia and extending to eastern Australia and New Caledonia. The remaining genera are small, comprising between one and three species, and are narrow endemics in Papua New Guinea ( Basisperma ) and Queensland.

Relationships within the tribe

The phylogenies show some well supported groupings of genera within the new tribe. The three genera Sphaerantia , Ristantia and Mitrantia form a strong subclade (>97% jk, 1.00 PP), agreeing with previous analyses ( Wilson et al. 2005) and strongly correlated with pollen morphology ( Thornhill et al. 2012 a) and shared presence of oil glands in the pith ( P. G. Wilson, pers. obs.). Oil glands in the pith are also a feature of Basisperma ( P. G. Wilson, pers. obs.), which was the basis for the comment in Wilson (1982) that Basisperma had no close affinities with the ‘ Kania Alliance’ of Briggs and Johnson (1979). The shared occurrence of oil glands in the pith suggested that the genus was very likely to have affinities with these particular taxa, and this has now been confirmed in genomic analyses ( Maurin et al. 2021).