Figure Legends:
Figure 1 A): Illustrates carbon assimilation as a function of leaf temperature for a single exemplar species, Cynophalla flexuosa . The black and gray colours indicate Eq. 1 and Eq. 2 model fits to the diamond-shaped data points, respectively. Eq. 1 was used to calculate Topt, Popt, and Ω; Eq. 2 was used to calculate Topt, Popt, and Tmax; B) Illustrates the quantum yield (FV/FM) as a function of temperature treatment used to calculate the Tcrit, T50, and T95 heat tolerance (represented as shaded vertical lines) using Eq.’s 3 and 4 for Cynophalla flexuosa . The curved shaded lines show 1 of 100 bootstrapped iterations
Figure 2: We address the assumption that PSII heat tolerance can promote greater carbon assimilation at higher temperature. Figure the change in a given trait between a species with a low heat tolerance (solid line) and high heat tolerance (dashed line). Hypothesis 1 (H1) proposes Tmax is constrained by PSII heat tolerance, which could be associated with an increase in Ω (short dashed line), an increase in Tmax (long dashed line), or a combination of the two; H2 is that high PSII heat tolerance promotes greater Ω indicative of a thermal generalist strategy of carbon assimilation; H3 that high PSII heat tolerance promotes higher Popt characteristic of species with “fast” carbon acquisition strategies; and 4) PSII heat tolerance promotes higher Topt
Figure 3: (top) The mean Topt (circles), Tcrit (left edge of the box), Tmax(triangles), T50 (vertical line in center of box), and T95 (right edge of box) for our dataset. The coloured boxes depict the thermal safety margins of PSII heat damage. Dotted lines connect the carbon assimilation traits; (middle) Box plots of temperatures that correspond to the heat tolerance and carbon assimilation parameters of each species; (bottom) The relative temperatures of Topt, Tcrit, Tmax, T50, and T95 for each species arranged from highest to lowest Tmax
Figure 4: Here we illustrate the significant correlations among A) Ω and Tmax, and B) Ω and Topt photosynthetic traits after correcting for phylogenetic independence. Each figure shows the phylogenetically independent contrasts for each trait with the phylogenetically corrected Pearson’s correlation coefficient and significant in the bottom left corner. Solid lines within plots indicate significant correlations
Figure 5: Here we illustrate the correlations among PSII heat tolerances and photosynthetic traits after correcting for phylogenetic independence. The top rows panels A-C correspond to hypothesis 1, panels D-F correspond to hypothesis 2; panels G-I correspond to hypothesis 3; and panels J-L correspond to hypothesis 4. Each figure shows the phylogenetically independent contrasts for each trait with the phylogenetically corrected Pearson’s correlation coefficient and p-value in the bottom left corner. No line within a plot indicates no significant correlation, solid lines indicate significant correlations, and the dashed line indicates a marginally insignificant correlation