Mathematical Sciences Institute, Australian National University, Canberra, ACT 2601, Australia. paul.lin@unsw.edu.au.|Research School of Biology, Australian National University, Canberra, ACT 2601, Australia. Sylvain.Foret@anu.edu.au.|Mathematical Sciences Institute, Australian National University, Canberra, ACT 2601, Australia. Sue.Wilson@anu.edu.au.|Mathematical Sciences Institute, Australian National University, Canberra, ACT 2601, Australia. Conrad.Burden@anu.edu.au.