These are quail thrushes, really gorgeous little birds that run around on the ground and live in Australia. You can see that they're different to one degree or another. All the quail-thrushes have different shapes of patches, presence of patches, streaking and so forth, and the question is, how many species are there?

Well, over the last, say, 50 years there's been many different opinions. In 1926 one person recognized all the different kinds of quail thrushes as separate species. So did another in 1962. But you can see that one scientist recognized three biological species - species with two of the other forms as subspecies of them. You can see that yet another scientist recognized four species with one subspecies. There's five species with one subspecies and four species according to another scientist. As you can see, they're all across the board. These people were all applying the biological species concept and they had different ideas about what would interbreed and what could be considered a species. Now some of these forms do in fact interbreed along very narrow hybrid zones. I will come back to this group in a minute and show you why the biological species concept has made people misrepresent and misunderstand the evolution of the group.

These are areas of endemism. One of the important things that we do in systematics is we look at the biogeographic range, we look at how organisms are distributed. And we find what are called areas of endemism. Areas of endemism are simply areas that house a number of species that are found there and nowhere else. So, in Australia, there are a series of areas of endemism for birds. For example Tasmania has a group of species of birds that are found nowhere else but in Tasmania, and the same is true for the Atherton Plateau, Cape York, Arnhemland, Kimberley Plateau and on and on. In general, areas around the periphery of the continent have more moist habitats than the areas in the central desert regions.

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