Fig. 5

Genome-wide F_ROH vs F_IS. Values are plotted for all individuals of (a) 33 domestic horse breeds and Sable Island feral horses and (b) Sable Island horses only. Corresponding linear trendlines with 95% confidence intervals are shown for all horse populations, and the trendline equation is presented for Sable Island horses. F_ROH is the summed length of all ROH divided by total genome length whereas F_IS is a measure of expected vs observed homozygosity and provides a measure of non-random mating in the most recent generation (F_IS = 0 indicates random mating, F_IS > 0 indicates consanguinity and F_IS < 0 indicates inbreeding avoidance). The dashed line on both plots indicates where F_ROH = F_IS, along which all excess homozygosity is accounted for by ROH. Points along the Y axis would indicate ROH caused primarily by small N_e while those along the X axis would indicate elevated admixture