High-altitude adaptation in birds: From phenomics to genomics

Abstract

In the field of evolutionary biology and population genetics, the revealing of the genetic basis of adaptation in birds in response to extreme environmental conditions in highlands (e.g., hypothermia, hypoxia, and high UV radiation) is an interesting study topic. Previous studies based on comparative morphological and physiological analyses have revealed that body size, flight ability, and hematology are significantly altered in high-altitude birds. Some genes associated with oxygen transport and utilization (e.g., hemoglobin and cytochrome coxidase) are reportedly involved in hypoxic responses and could facilitate adaptive hypoxic evolution. Next-generation sequencing techniques applied in highland adaptation research, comparative genome analyses, and transcriptome analyses are revealing the genetic mechanisms underlying numerous complex traits. However, systematic studies based on adaptive phenotypes and molecular methods are unreliable, particularly in investigating bird metabolism under hypoxic cold stress, which remains largely unclear to date. In addition, the influence of phenotypic plasticity on some geographical variations in complex traits poses a challenge in highland adaptation studies. Therefore, the integration of traditional methods and sequencing techniques, in combination with functional and common garden experiments is essential for a comprehensive understanding of the genetic basis of such complex traits, which are interesting key topics of study on avian highland adaptation.