Phylogenetic patterns and trait correlations
Fig. 4 shows the phylogenetic tree of the 144 identified species in our dataset, color coded by T50 standardized to sea level using the linear relationship with elevation shown in Fig. 1. There are some distinct clusters of related species with similar trait values, such as the high T50 values of the species ofZamia , the relatively high heat tolerance of the Moraceae (Ficus spp, Castilla elastica, Poulsenia armata , andBrosimum guianense ), and the relative low heat tolerance of the Annonaceae. However, the phylogenetic signal on T50 was not statistically significant with α of 0.05 (Blomdahl’s K= 0.11,P =0.06; Pagel’s λ=0.51, P =0.08), suggesting that across the phylogenetic tree related pairs of species were not significantly more similar to each other than random pairs. TCritlikewise did not show a significant phylogenetic signal (K=0.11,P =0.05; λ =0.17, P =0.99. Fig. S7). In fact, the species with the highest and lowest TCrit values among native lowland trees both belong to the Urticaceae: 44.0°C for Pourouma bicolor , and 50.8°C for Cecropia longipes .
The leaf functional traits all had phylogenetic signals, with the exception of Blomdahl’s K for leaf length. τ was also phylogenetically structured (K=0.18, P =0.022; λ=0.90, P <0.001).