Low heterozygosity at microsatellite markers in Iberian red deer with small antlers

Deer antlers are costly structures subjected to directional sexual selection that may be sensitive to heterozygosity. However, a relationship between heterozygosity and antler development has only been found for select protein-coding loci and MHC genes in one deer species (the white-tailed deer Odocoileus virginianus). Here, we study the relationship between multilocus heterozygosity at 11 microsatellite markers and antler size (AS) in a sample of 367 Iberian red deer males (Cervus elaphus hispanicus) from two study areas with different ecological and genetic conditions. We found that males with very small antlers (10% of the sampled individuals with the lowest values of AS) had lower levels of heterozygosity than those with bigger antlers (significant effect in an analysis of variance, P = 0.011). This relationship was noticeable mainly in situations of low genetic diversity, where the differences in heterozygosity between groups of males were greater. Finally, we conducted analyses to address the hypotheses proposed by the heterozygosity-fitness correlation, and we found the local effect as the most likely hypothesis. Our findings reveal an expected but not previously detected association between low heterozygosity and reduced AS, with implications for red deer evolution and management.