Continuous genetic adaptation to high elevations of alpine bamboos in the Hengduan Mountains, Southwest China

Many examples of phenotypic modifications resulting from high‐elevation adaptation have been documented, however, the underlying processes responsible for these modifications and whether the continuity of the adaptation process remain elusive, particularly in plants. The alpine plants distributed along wide elevational gradients provide an ideal system to address this question. Here, we collected transcriptomes from multiple tissues of three species with different elevations (~1500, ~2500, and ~3600 m in the Hengduan Mountains, Southwest China) in two genera Fargesia and Yushania of alpine bamboos, respectively, and conducted evolutionary and expressional analyses. Results showed that high‐elevation adaptation emerged earlier in the evolutionary history of both genera and evolved continuously as the elevation increased. Moreover, convergence of genetic changes was observed in the two genera, with amounts of candidate genes responsible for high‐elevation adaptation identified under positive selection. Overall, our study provides an empirical example and valuable genetic resource for further investigation of high‐elevation adaptation in plants and sheds new light on how plants adapting to high‐elevation environments in a biodiversity hotspot. This figure displays two points: (i) both genera of alpine bamboo (Fargesia and Yushania) have already experienced selection for genes showing signals of adaptation to the high elevation despite when distributed at relatively low elevations; and (ii) as the elevation increased, a growing number of new elevation‐specific positively selected genes (PSGs) (genes identified to be positively selected exclusively at a certain elevational gradient) associated with high‐elevation adaptation continued to emerge in both genera. Based on the results above, we obtained two significant outcomes: (i) the early appearance of high‐elevation adaptation in bamboo evolutionary history; and (ii) the process of high‐elevation adaptation and their underlying genetic changes were continuous as the elevational gradients increased in both alpine bamboo genera.