Provenance level differentiation in leaf and canopy
temperatures
Temperatures of individual leaves recorded with handheld IR sensors
ranged from 18.0 °C to 45.9 °C (Supporting information S6). When
averaged to the plant level, mean Tleaf was 32.3 °C and
ranged from 27.2 to 36.4 °C across all individuals. Mean
∆Tleaf was 4.1 °C and ranged from −0.7 to 8.1 °C (Figure
2a). For most plants mean ∆Tleaf was positive, except
for H. novo-guineensis , which had multiple occurrences of
Tleaf cooler than Tair (Figure 2b).
The mixed effects models found very strong evidence for provenance
differences in ∆Tleaf for both T. microcarpa andC. australe . In T. microcarpa, ∆Tleaf was
higher in the lowland provenance than the upland provenance
(t (124) = 5.87, p < 0.0001),
with a mean of 5.2 °C ± 1.17 and 3.4 °C ± 1.35, respectively (Figure
2b). The opposite was observed for C. australe , in which
∆Tleaf in the lowland provenance was lower than the
upland provenance (t (121) = −3.79, p =
0.0002), with a mean of 4.8 °C ± 1.42 and 6.0 °C ± 1.68 respectively
(Figure 2b). We found no evidence for provenance-differentiation in
∆Tleaf for M. elleryana or H.
novo-guineensis (p > 0.05; Figure 2b).
For ∆Tcan, we found no evidence of provenance effects in
any of the four species (Figure 2c).
Modelled leaf-to-air temperature differences (∆Tmod)
represent the variation in potential leaf temperatures as resulting from
the covariation between leaf width, leaf angle, and stomatal
conductance. Across all individuals, mean Tmod was 29.1
°C and ranged from 27.1 to 31.0 °C. For T. microcarpa, we found
moderate evidence for a provenance effect in ∆Tmod(t (10) = 2.39, p = 0.0381), with
∆Tmod higher in the lowland provenance than the upland
provenance averaging 1.6 °C ± 0.69 and 0.6 °C ± 0.78 respectively. ForH. novo-guineensis , we found (only) weak evidence for provenance
differences (t (10) = 1.81, p = 0.0996),
with the lowland provenance also having a higher average
∆Tmod than the upland provenance, averaging 1.4 °C ± 1.0
and 0.3 °C ± 1.09 respectively. For the other two species, the data
showed no evidence of provenance-differentiation in
∆Tmod.