d. Neutral evolution
We found that MHC diversity was significantly associated with
genome-wide genetic diversity that should mostly reflect neutral
processes. First, the average MHC allelic richness covaried positively
with population mean heterozygosity (coefficient=25.4, F=6.57, df = 24,
p = 0.02, Fig. 6A). Second, there was a strong positive correlation
between MHC divergence between populations, and genome-wide divergence
(Mantel test: r = 0.51, p=0.002, Fig. 6B). That is, more closely related
populations tended to be more similar at their MHC loci as well.