Figure 2:

The sequence alignment depth along each chromosome. To determine the sex chromosome, the alignment depth was calculated along the genome. Chromosome 1 (Chr1) is the longest, and the alignment depth was twofold higher in female than male beetles, suggesting that this is the X chromosome. Chromosome 8 (Chr8) is the shortest chromosome, explicitly associated with male beetles as the Y chromosome. This pattern was highly congruent in 3 independent beetle families, F8 (A), F17 (B), and F31 (C). Collectively, the data suggest an XY sex determination mechanism in small hive beetles. Red indicates female beetles; blue indicates male beetles; the error bar indicates standard error.