1Department of Psychology, University of Washington, 2Department of Anthropology, Washington University, 3Department of Anthropology, Pennsylvania State University, 4Department of Biology, Pennsylvania State University, 5Department of Anthropology, New York University, 6New York Consortium in Evolutionary Primatology, 7Human Genome Sequencing Center, Baylor College of Medicine, 8Department of Neuroscience, Washington University School of Medicine
April 12, 2018 9:15, Foothills Ballroom II
Hybridization in the wild offers valuable insights into mechanisms of natural selection. By creating novel genetic combinations from distinct populations or species, hybridization provides a natural experiment for evaluating selection on alleles in new genomic backgrounds. In this study, we examine a baboon hybrid zone in the Kafue river valley of Zambia, where Kinda baboons (P. kindae) and gray-footed chacma baboons (P. ursinus griseipes) coexist and hybridize despite unusually large body size differences between them. Using FecalSeq and double-digest RADseq, we genotype hundreds of baboons at >10,000 autosomal SNPs. Comparing our data to previously reported mitochondrial DNA and Y chromosome results, we find significantly directional Kinda>chacma introgression of Y-DNA relative to both mtDNA and autosomal DNA. Using a Bayesian genomic cline model, we find evidence for significantly restricted introgression of genes in the JAK/STAT signaling pathway, which plays an important role in growth hormone signaling, providing a possible mechanism for selection against body size differences in the hybrid zone. We also find evidence for significantly directional chacma>Kinda introgression in genes from immune pathways, such as toll-like-receptor and interferon-gamma signaling, as well as ODF2, a gene playing an important role in sperm tail function. The directional penetration of the species boundary of Kinda Y-DNA despite their small size remains an unexplained pattern, but may be explained by selection on Y-linked traits. One possible mechanism is epistatic selection on Y-DNA in the context of sperm-related hybrid dysgenesis, a pattern that has been reported in European house mouse hybrids.
This study was supported by the National Science Foundation (BCS 1341018, BCS 1029302, SMA 1338524), the Leakey Foundation, and the National Geographic Society.