s10 -> s11 s2 -> s9 s9 -> species_12 s10 -> species_12 s11 -> species_12 s13 -> s10 species_2 -> species_1 s11 + species_3 -> species_4 species_1 -> species_3 species_1 -> species_12 species_4 -> species_12 species_3 -> species_1 species_3 -> species_12