2 1 0 a b c d 7 6 4 1 0 a1_a a2_a a3_a 3 2 b1_b b2_b b3_b 5 c1_c c2_c 13_speciation 13 12 10 9 8 c2_c 06_speciation 18_speciation a4_a a5_a d1_d 11 d2_d 19_speciation 25_speciation 5 4 c1_c 04_speciation 16_speciation b3_b b4_b 17_speciation 1 b1_b a3_a 03_speciation a1_a a2_a