Phylogenetic Signal in Ecosystem Functions

Abstract

Phylogenetic signal -- the tendency for closely related species to resemble each other more than distantly related species, reflecting the conservation of traits through evolutionary lineages -- is one of the foundational concepts linking evolutionary history to ecological function. When ecosystem functions (nutrient cycling; productivity; decomposition; pollination) are mediated by specific functional traits that show strong phylogenetic signal, the phylogenetic composition of a community predicts its functional contributions -- making phylogenetic diversity (PD) a proxy for functional diversity and a basis for ecosystem function prediction. Conversely, when traits mediating functions show weak phylogenetic signal (convergent evolution producing similar functional traits in distant lineages), phylogenetic composition provides little predictive power for ecosystem functions. This study quantifies phylogenetic signal (Blomberg's K and Pagel's lambda) for 247 functional traits across 84 plant and animal taxonomic groups, and tests whether phylogenetic diversity predicts 18 ecosystem functions across 247 study sites after controlling for species richness and functional diversity. Phylogenetic signal was strong (K > 1.0) for 67.4% of morphological traits but weak (K < 0.5) for 74.7% of behavioural and physiological traits -- consistent with convergent evolution repeatedly producing similar physiological solutions across distantly related lineages. PD predicted 12 of 18 ecosystem functions significantly after controlling for richness and FRic, with the strongest PD effects for carbon sequestration (partial R2 = 0.38; p < 0.001) and decomposition (R2 = 0.34; p < 0.001) -- functions mediated by root architecture and litter chemistry traits with high phylogenetic signal.