Following on from last week, this plant follows the theme of bird pollinated flowers from arid Western Australia. It is also a little controversial, and I have a conflict of interests. Until recently, the plant pictured above was generally considered to belong to the genus Calothamnus, closely related to another genus of shrubby plants, Melaleuca (below, right). For some time there was disagreement as to whether there was sufficient visible differences between these two groups to justify this separation. However using molecular sequence data for my honors project, I showed that as far as relationships go, these two groups of plants are mixed in together, and should be considered one and the same. Essentially Calothamnus are just slightly odd Melaleucas. Specifically, they have single flowers, rather than clusters, and these have squeezed their stamens together to form an elongated tube, the entrance to which is covered by a fringe of anthers (yellow capsules) holding the pollen. This is classic evolution toward specialized bird pollination, where the deep curved flower forces the bird to push it's bill well down into the nectaries, receiving a face-full of pollen for it's trouble. Compare this to the classical Melaleuca flower (below right) which has multiple flowers arranged in a cluster, each holding it's stamens much more openly, allowing access not only to birds but to insects and other animals as well. The whole cluster of flowers acting as a pollen brush. It is an interesting hypothesis that the evolution of more specialized bird pollinated flowers in the group-formerly-known-as-Calothamnus may be beneficial in moving pollen between the small, highly fragmented and widely dispersed populations of these plants.
Photos: R.D. Edwards