Is mate choice based on relatedness or heterozygosity?
We found no evidence for relatedness- or heterozygosity-based assortative mating. There was no difference between relatedness of real mating pairs and randomly generated mating pairs (n = 10 pairs, breeding pool of 12 females and 12 males, p = 0.565). Likewise, homozygosity by loci (HL) was not significantly correlated between pair mates (r = -0.527, n = 10 pairs, p = 0.118).
Despite the lack of evidence for active inbreeding avoidance during mate choice, relatedness (Wang’s r ) between mating partners was generally low, averaging -0.033 (for comparison, mean r for simulated unrelated individuals was 0.012), and none of the pair mates shared the same mtDNA haplotype (Supplementary Table 1, Fig. 1). Only in one pair were the partners found to be second-degree kin (Group 6,r = 0.285). The mtDNA haplotype network (Fig. 2) showed no clear pattern of haplotype similarity between pair mates: some had closely related haplotypes (e.g., Groups 4, 5, 9), while others had only distantly related haplotypes (e.g., Groups 1, 11).