A simple function for plotting phylogenies in ggplot2

UPDATE: Greg jordan has a much more elegant way of plotting trees with ggplot2. See his links in the comments below.

I wrote a simple function for plotting a phylogeny in ggplot2. However, it only handles a 3 species tree right now, as I haven’t figured out how to generalize the approach to N species. It’s at https://gist.github.com/977207

Any ideas on how to improve this?