Study sites
We used five sites that differed in elevation (100, 700, 1280, 1800, 2400 m) along the Saddle Road on the east slope of Mauna Loa on the island of Hawai’i, which were the same sites used in previous studies (Kitayama, Pattison, Cordell, Webb, & Mueller‐Dombois, 1997; Tsujiiet al ., 2015). Climate data for these sites are shown in Table 1 (Giambelluca et al ., 2014). Among the study sites, the 2400 m site has the coldest and driest environments because this site is above the base height of trade-wind inversion zone (2255 ± 497 m; Cao, Giambelluca, Stevens, & Schroeder, 2007) and therefore exposed to cold dry descending air of the Hadley cell circulation. On the other hand, the 700 m site has the least dry stress. We established one additional site at 2000 m asl to determine the temperature dependence of photosynthesis in M. polymorpha . We measured air temperature and relative humidity at each site (TR‐72WF‐H, T&D Co., Japan), and photosynthetic photon flux density (PPFD) at the 2400 m sites (DEFI2‐L, JFE Advantec Co. Ltd., Japan) every ten minutes in September 2017.