More pea flowers

Different pea flowers are coming into bloom.  These purple ones are hardenbergia and you will see quite different from the purple flowers of Hovea and native indigo even though they are all pea-like.

And in among the grass I found in quite a few places this little vine with yellow/red pea flowers. Again quite different from yellow/red pea flowers shrub.  I wonder why so many of Australia's native plants have pea flowers?  I've answered my own question below.

Sub-family Faboideae - those members of the Fabaceae which have the typical "pea" flowers ...

In Australia, there are about 140 genera and 1,100 species in the sub-family Faboideae. They are found in every state and territory of Australia, from coastal cliffs to alpine areas, from the tropics to the arid inland. Many of Australia's peas are representatives of genera found elsewhere in the world (eg indigo (Indigofera), coral trees (Erythrina) and rattlepods (Crotalaria). However, there are two groups ("tribes") within the family which are almost entirely Australian:

"These are the egg-and-bacon peas, the tribes Bossiaeeae and Mirbelieae. They probably originated from a single common ancestor in Australia millions of years ago. All their ancestors have remained "true blue" except for a single species which has just managed to cross Torres Strait into Papua New Guinea. Together these tribes have 700 species, or more than half of all the peas in this continent. With few exceptions, they can be recognised by their distinctive "egg-and-bacon" flowers, in which the petals are yellow or orange with red markings......"

M D Crisp and J M Taylor, "Australian Plants", June 1993, p102