Bernd Sturmfels wrote a book called Algebraic Statistics for Computational Biology.
A variety (no pun intended) of mathematical topics occur. Phylogenetic trees are studied by means of "tropical" algebraic geometry. It's been long enough since I've looked at it that I'm not going to trust myself to give more examples yet. Here's the amazon.com page: http://www.amazon.com/Algebraic-Statistics-Computational-Biology-Pachter/dp/0521857007