Figure 4. Provenance differences in thermal safety margin (TSM) of four tropical tree species grown under common environmental conditions. TSM calculated using Tcrit as upper threshold in all panels, with operating temperature defined as 32 °C (mean max air temperature of the site) plus ∆Tleaf in (a), ∆Tcan in (b), and ∆Tmod in (c). Ca = Castanospermum australe, Hn = Homalanthus novo-guineensis, Me = Melicope elleryana, and Tm = Terminalia microcarpa . Data is of tree averages (n =6) presented as a box and whisker plots showing median and interquartile range, with the average marked by ×. Results of intraspecific t-test of provenance differences indicated by subscript ns=not significant, * p < 0.05, ** p