species_0 -> species_1
species_2 -> species_3
species_3 -> species_4
species_5 -> species_6
species_6 -> species_7
species_1 -> species_0
species_4 -> species_3
species_3 -> species_2
species_7 -> species_6
species_6 -> species_5
species_7 -> species_11
species_11 -> species_7
0 -> species_12
species_12 -> species_13
species_13 -> 0
0 -> species_14
species_14 -> species_15
species_15 -> species_14
species_14 -> 0
species_15 -> 0
species_5 -> species_16
species_16 -> species_5
species_6 -> species_17
species_17 -> species_6
species_11 -> species_17
species_17 -> species_16