Dodonaea, commonly known as hop-bushes, is a genus of approximately 70 species of flowering shrubs and small trees in the soapberry family Sapindaceae (order Sapindales). The genus has a broad cosmopolitan distribution across tropical, subtropical, and warm-temperate regions of Africa, the Americas, southern Asia, and Australasia, but around 59 of its species are endemic to Australia, making it one of the most species-rich shrub genera on that continent.
Plants in the genus typically grow between 0.1 and 4 metres in height. The foliage is often notably sticky (hence the genus's traditional association with "hop-bush" — the dried capsules were historically used as a hop substitute in brewing). Leaves are arranged alternately along the stems and may be simple or pinnate. The flowers are unusual among flowering plants in lacking petals entirely; instead they bear three to seven deciduous sepals, six to sixteen stamens, and a slender threadlike style. Individual plants may be dioecious, monoecious, or polygamous. The fruit is a distinctive two- to six-angled or winged capsule that facilitates wind dispersal.
The genus was first formally described in 1754 by the Scottish-English botanist Philip Miller in The Gardeners Dictionary, with Dodonaea viscosa as the founding species. That species is now regarded as one of the world's most widely dispersed transoceanic plants. Within Sapindaceae, Dodonaea is placed in the tribe Dodonaeeae alongside Diplopeltis and Distichostemon; recent molecular phylogenetic work supports the monophyly of the genus and indicates that Distichostemon is in fact nested within Dodonaea.
Etymology
The genus name Dodonaea was coined by Philip Miller in 1754 to honour Dodonaeus — the Latinised form of Rembert Dodoens — a sixteenth-century Flemish physician and botanist renowned for his influential herbal writings.
Distribution
Dodonaea has a cosmopolitan distribution across tropical, subtropical, and warm-temperate zones of Africa, the Americas, southern Asia, and Australasia. Of its roughly 70 species, approximately 59 are endemic to Australia. Dodonaea viscosa, the most widespread member, is considered one of the world's most broadly dispersed transoceanic plant species.
Ecology
Seeds of at least some species, notably Dodonaea viscosa, bear small funicular elaiosomes and are collected by Pheidole ants, which deposit them in middens after consuming the elaiosome — a form of myrmecochory. The winged capsule fruits of most species are adapted for wind dispersal.
Taxonomy Notes
Dodonaea was first formally described by Philip Miller in 1754 (Gard. Dict. Abridg. Ed. 4), with D. viscosa as the type species. Early infrageneric classifications divided the genus by leaf form (simple vs pinnate) and capsule-appendage morphology into sections and series. Later revisions by Radlkofer and West reorganised species into tribes and species groups. Modern molecular (Bayesian MCMC) phylogenetics confirms the monophyly of Dodonaea and shows that Distichostemon is nested within it; the most closely related genera are Diplopeltis and Cossinia. GBIF (backbone) recognises 136 descendants under the genus.
