118 In Darwin’s Footsteps: A Shared Genetic Control for Toe and Beak Length in Colombia Livia

Domestic rock pigeons (Columba livia) display an incredible amount of variation among different breeds. Even though they can look and act differently, these breeds all belong to the same species. We are therefore able to breed individuals with very different traits and perform genetic mapping. In The Variation of Animals and Plants Under Domestication, Darwin observed that the data he collected “indicate pretty plainly some kind of correlation between the length of the beak and the size of the feet” (Darwin, 1868). The goal of my research is to determine whether there is a shared genetic control of foot size and beak size in domestic rock pigeons. First, I collected limb length measurements from the F2 generation of a cross between a Homer (medium beaked) and an Old German Owl (small beaked) pigeon. This cross segregates different beak lengths and variation at a locus on Chromosome Z, ROR2, is linked to beak shortening (Boer et al., 2021); therefore, this cross presents an ideal opportunity to test for anatomical and genetic associations between beak and toe lengths. My anatomical data confirmed that foot and beak size are indeed associated. Next, I used quantitative trait locus (QTL) mapping and found that toe size is controlled by at least two genetic loci on linkage group Z and 8, one of which maps to the same genomic region that controls beak length. Therefore, it is likely that toe size and beak length are controlled by the same or closely linked genes. Thus, variation in one genomic region – and possibly one gene – can lead to coordinated changes in seemingly unrelated anatomical structures.

Bibliography

Boer, E. F., Van Hollebeke, H. F., Maclary, E. T., Holt, C., Yandell, M., & Shapiro, M. D. (2021). A ROR2 coding variant is associated with craniofacial variation in domestic pigeons. Current Biology, 31(22), 5069-5076.e5. https://doi.org/10.1016/j.cub.2021.08.068

Darwin, C. (1868). The Variation of Animals and Plants Under Domestication (Vol. 1). John Murray.