Tetratheca


Tetratheca is a genus of around 50 to 60 species of shrubs endemic to Australia. It is classified in the botanical family Elaeocarpaceae, now known to encompass the family Tremandraceae, which the genus originally belonged to. It occurs throughout extratropical Australia, and has been recorded in every mainland state except the Northern Territory.

Origin and evolution

The origin of the genus is thought to be southwestern Western Australia, radiating eastward. The distribution of Tetratheca is mainly across the temperate southern part of the continent, most species exist as endemic to local areas and are highly disjunct, very few are widespread across Australia, no species exist across the Nullarbor Plan and only 7 species exist on both the western and the south-eastern side.. The formation of the Nullarbor is thought to have created a barrier to dispersal between the east and west.
It is estimated that the family Elaeocarpaceae is 120 million years old and Tetratheca estimated to be around 37 to 39 million years old, with major diversification over the Miocene and evolving much faster than their relatives, many of which are rainforest species. This coincides with the rapid radiation and diversification of other sclerophyllous groups.

Species

Species include: