Intraspecific variation in the growth–defense trade‐off among deciduous and evergreen broadleaf woody plants

Plants make tradeoffs between growth and defense. However, differences in these tradeoffs interindividual, variation on the axes of trait expression, remain poorly understood. We evaluated six key leaf traits - defense traits (total phenols, condensed tannins, flavonoids, and specific leaf density) and nutrient acquisition traits (nitrogen and phosphorus content)-across 1985 individuals representing 314 species in 18 natural forest communities along a 4000-km latitudinal gradient in China. We found deciduous plants have higher nutrient content, whereas evergreen plants consistently invest more heavily in defense. Moreover, this broad difference in functional type (deciduous vs evergreen) was also a useful lens to examine the influence of intraspecific, interindividual variation on defense-acquisition trait axes. In evergreen plants, intraspecific variation causes a substantial shift in the orientation of trait space, with a 46.75° rotation of the defense-nutrient axis, compared to just 1.11° in deciduous plants. Only one trait-phenology combination (specific leaf density in evergreen plants) changed in a predictable way based on phylogeny. Overall, our results suggest evergreen plants are more constrained in how much they can vary their traits. This advances our understanding of evolution along the conservation/acquisitive axis, at least with regard to leaf traits.