Genetic mechanisms of axial patterning in Apeltes quadracus

The genetic mechanisms underlying striking axial patterning changes in wild species are still largely unknown. Previous studies have shown that <i>Apeltes quadracus</i> fish, commonly known as fourspine sticklebacks, have evolved multiple different axial patterns in wild populations. Here, we revisit classic locations in Nova Scotia, Canada, where both high-spined and low-spined morphs are particularly common. Using genetic crosses and quantitative trait loci (QTL) mapping, we examine the genetic architecture of wild differences in several axial patterning traits, including the number and length of prominent dorsal spines, the number of underlying median support bones (pterygiophores), and the number and ratio of abdominal and caudal vertebrae along the anterior-posterior body axis.