Although similar challenges are experienced by individuals inhabiting high-elevation páramo environments, the more arid conditions of the puna ecosystem ([ 36, 41]) and the average higher and more southern location of puna populations, may exacerbate the cold-desertification and hypoxia effects of high elevation environments.
Therefore, in a cold high-elevation environment with a subzero annual mean temperature, as in the Mongolian Altai Mountains, an increase in temperature could theoretically promote the growth and productivity of larch trees (Dulamsuren et al. 2014).
Therefore, although under positive selection, these genes may not be related to adaptation to a high-elevation environment.
We identified a set of candidate genes that may have promoted adaptation of R. kukunoris to its high-elevation environment.
Detailed functional research is also needed to illustrate how the positively selected genes promote the fitness of poikilothermic species under the high-elevation environment.
They may have experienced accelerated evolutionary rates in mitochondrial genes that were driven by positive selection to better adapt to the high-elevation environment of the Tibetan Plateau.
Detailed molecular, physiological, and phenotypic studies are required to better understand the roles of these genes in improving the performance of R. kukunoris in a high-elevation environment.
Adaptation to the high-elevation environment apparently did not result in reduced performance of Mt. Hood beetles at low elevation (Fig. 3).
Our results suggest that Italian ancestry beetles from lowland Oregon introduced to the high-elevation environment of Mt. Hood underwent rapid evolution in <30 generations.
The Glyptosternoids may have experienced accelerated evolutionary rates in mitochondrial genes that were driven by positive selection to better adapt to the high-elevation environment of the Tibetan Plateau.
In particular, the specialized Glyptosternoid fishes have higher nonsynonymous to synonymous substitutions than the basal species, suggesting the specialized species developed accelerated evolutionary rates in order to adapt to the high-elevation environment.
