species_1 + species_2 <-> species_3 species_3 -> species_2 + species_4 species_2 + species_4 <-> species_5 species_5 -> species_2 + species_6 species_13 + species_6 <-> species_21 species_21 -> species_13 + species_4 species_13 + species_4 <-> species_22 species_22 -> species_1 + species_13 species_23 <-> species_1 + species_13 species_7 + species_8 <-> species_9 species_9 -> species_10 + species_8 species_10 + species_8 <-> species_11 species_11 -> species_2 + species_8 species_13 + species_2 <-> species_12 species_12 -> species_10 + species_13 species_10 + species_13 <-> species_14 species_14 -> species_13 + species_7 species_15 <-> species_13 + species_7 species_16 + species_18 <-> species_17 species_17 -> species_18 + species_8 species_20 + species_8 <-> species_19 species_19 -> species_16 + species_20 species_2 + species_20 <-> species_24 species_24 -> species_10 + species_20 species_10 + species_20 <-> species_25 species_25 -> species_20 + species_7 species_26 <-> species_20 + species_7 species_27 <-> species_16 + species_20