Data processing
To extract parameters from the photosynthesis-temperature response curves (Figure S2), we fitted an equation after June et al.(2004), yielding two parameters: optimal temperature for photosynthesis (TOpt) and the temperature range for photosynthesis (Ω ; at which photosynthesis falls to e-1 of its value at Topt, Eq. S1). To estimate respiration sensitivity to temperature (Figure S3), we fitted an exponential equation, estimating the change in respiration rate with a temperature increase of 10°C (“Q10, Eq. S2-S3, Tjoelker et al. 2001; Atkinet al. 2005).
We calculated a measure of plasticity for all the traits that had been collected from more than one site (Table 2). For traits measured at all the four sites we calculated a simplified relative distance plasticity index (“RDPIS”) after Valladares et al. (2006). The index ranges from 0 (no plasticity) to 1 (maximal plasticity) and is calculated as the sum of absolute trait differences divided by the sum of the traits (Eq. S4), and is recommended for ranking species according to their plasticity (Valladares et al. 2006). For traits that were measured in only two treatments, we used the same approach (i.e. (mean at lower elevation – mean at origin) / sum), but with a signed (+/-) rather than absolute value of the trait differences, so that we could measure the direction of change between the two sites (Eq. S5).