c. Fluctuating selection
Despite spatial heterogeneity in the distribution of parasite species (Bolnick et al., 2019), we did not detect parasite-mediated spatially fluctuating selection. The Mantel test between the distance matrix of parasite community and the distance matrix of MHC alleles across all populations suggested that the two matrices were not correlated (r = 0.089, p=0.22, Fig. 5). Thus, although MHC alleles and parasite communities both differ strongly between lakes, there is no detectable relationship between them.