The Role of Introgressive Hybridization in Hypoxia Adaptation of the Tibetan Mastiff

Abstract

The role of introgressive hybridization as a source of adaptive genetic variation in animal populations is generally unclear, although recent findings suggest it may be more important than previously anticipated. While there are a number of tools to detect introgression, a major challenge is to experimentally confirm that it has played a role in adaptation by documenting the phenotypic effects of introgressed alleles. Animals native to high‐altitude are excellent models for such experimental studies, as it is often possible to formulate clear a priori hypotheses about the adaptive significance of particular changes in phenotype (for example, increases or decreases in the oxygen affinity of hemoglobin [Hb]). There is evidence to suggest that the high‐altitude adaptation of the Tibetan mastiff is, in part, the result of adaptive introgresssion with the Tibetan wolf. One of the introgressed regions between the Tibetan wolf and mastiff spans the entire β‐Hb gene cluster and the upstream cis‐regulatory elements. This has resulted in two non‐synonymous amino acid substitutions in the Tibetan mastiff, with respect to domestic dogs, in each of the adult expressed β‐type globin genes. To assess the functional effects of these mutations, we have measured the Hb‐O2 affinity of Tibetan wolves, Tibetan mastiffs and domestic dogs. These analyses revealed that the high‐altitude canids have Hb‐O2 affinity that is increased relative to domestic dogs (Figure 1). Thus, introgressive hybridization with the Tibetan wolf has resulted in a phenotypic change to the Tibetan mastiff that increases blood‐O2 saturation under hypoxia.Support or Funding InformationThis work is supported by the National Institutes of Health, the National Science foundation, and the Chinese Academy of Sciences.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.