Annual temperature range
We use the annual temperature range (ATR) as the independent variable for the climate variability hypothesis. To catch the precise characteristics of climate, we set seven mini weather stations in Lebu Valley (2,440, 2,822, 2,914, 3,311, 3,499, 4,219, 4,504 m a.s.l.). Each mini weather station concluded two data loggers (HoBo Pro‐ RH/Temp and HoBo Pro‐Precipitation/Temp) (Half a meter above the ground) and was surrounded by fences to keep interference from wild animals. Annual temperature maximum and annual temperature minimum were recorded from 2018 to August 2019. ATR was calculated as the annual temperature maximum minus annual temperature minimum and then extrapolated to 26 elevational bands using the simple ordinary least square (OLS) regression.