Closely related native and non-native urban trees have similar leaf chemistries

Previous studies found that non-native plants have different stoichiometries than natives, suggesting broad impacts on food webs and nutrient cycling. These studies focused on questions relating to sets of problematic invasives, but did not focus on the trait of nativeness itself. In urban settings, where closely-related native and non-native ornamental trees are often grown in close proximity, understanding how stoichiometry varies with nativeness or relatedness would be useful for urban planners trying to preserve ecosystem function. Here, we use leaves and needles from pairs of close relatives grown within a single urban arboretum to determine how stoichiometry varies between native and non-native trees within the same genus (congeneric species), representing a broad phylogenetic diversity that includes angiosperms and gymnosperms spread across four orders, five genera, and ten species. Additionally, we examined associated soil chemistries as a control. We find that stoichiometry is principally dictated by relatedness, and not by nativeness. Accordingly, prior observations that non-natives have fewer consumers and food web connections is likely not due to nativeness, but other traits. We suggest urban planners should increase phylogenetic diversity of native tree species to maximize the chemical composition of the trees that form the base of many urban food webs.