The evolutionary response to hunting-induced selection on horn characteristics in Yukon thinhorn sheep (Ovis dalli)
Abstract
When harvest criteria are based on phenotype, trophy hunting may select against the size of secondary sexual characteristics, including horns. Here I investigated the effects of trophy hunting on horn growth and morphology in thinhorn sheep (Ovis dalli). Trophy rams, harvested between 1996-2021 in the Yukon (n = 247), were genotyped from dried flesh or horn core specimens using a custom-designed 6050 SNP genotype-by-sequencing panel. With this panel, I calculated a genomic relationship matrix to estimate trait heritability, temporal changes in breeding values and the predicted response to selection based on age at harvest. Among measured horn characteristics, only growth was under negative directional selection because of harvesting; however, observed trends did not vary over this period, due to changes in the environment or bias in the sampling design. My study illustrates the potential and challenges of genotyping historical specimens to reveal the impacts of harvesting selection on trait variation.