LMAM, School of Mathematical Sciences and Center for Theoretical Biology, Peking University, Beijing 100871, PR China. porcupine.hao@gmail.com|LMAM, School of Mathematical Sciences and Center for Theoretical Biology, Peking University, Beijing 100871, PR China. porcupine.hao@gmail.com|LMAM, School of Mathematical Sciences and Center for Theoretical Biology, Peking University, Beijing 100871, PR China. porcupine.hao@gmail.com|LMAM, School of Mathematical Sciences and Center for Theoretical Biology, Peking University, Beijing 100871, PR China. porcupine.hao@gmail.com|LMAM, School of Mathematical Sciences and Center for Theoretical Biology, Peking University, Beijing 100871, PR China. porcupine.hao@gmail.com|LMAM, School of Mathematical Sciences and Center for Theoretical Biology, Peking University, Beijing 100871, PR China. porcupine.hao@gmail.com|LMAM, School of Mathematical Sciences and Center for Theoretical Biology, Peking University, Beijing 100871, PR China. porcupine.hao@gmail.com