RTE age and piRNA coverage. The median millidivergence from consensus (as a proxy for age) is plotted against the average piRNA coverage (all reads) values. RTE families are coloured according to their type as indicated on the left chart. To allow for easier comparison between RTE types, coverage values are indexed so that the family with the highest average coverage is set to a value of 1. Error bars denote 25 and 75 percentiles for both piRNA coverage and millidivergence.