x1 = species_1 x2 = species_2 x3 = species_3 x4 = species_4 x5 = species_5 x6 = species_6 x7 = species_7 x8 = species_8 x9 = species_9 x10 = species_10 x11 = species_11 x12 = species_12 x13 = species_13 x14 = species_14 x15 = species_15 x16 = species_16 x17 = species_17 x18 = species_18 x19 = species_19 x20 = species_20 x21 = species_21 x22 = species_22 x23 = species_23 x24 = species_24 x25 = species_25 x26 = species_26 x27 = species_27 x28 = species_28 x29 = species_29 x30 = species_30 x31 = species_31 x32 = species_32 x33 = species_33 x34 = species_34