Functional Trait Evolution and Diversity Patterns

Abstract

Functional traits -- measurable characteristics of organisms that influence their fitness, ecological interactions, and ecosystem function -- provide a mechanistic bridge between evolutionary processes and diversity patterns at community and global scales. The leaf economics spectrum (LES), the global spectrum of plant form and function, and analogous trait spectra in animals (pace-of-life syndrome; fast-slow continuum) organise most of the functional trait variation in terrestrial organisms along a small number of major axes -- yet how these trait spectra evolved, diversified, and relate to contemporary diversity patterns across biomes and clades remains incompletely understood. This study presents a comprehensive phylogenetic comparative analysis of functional trait evolution across 8,470 plant species from 247 families and 2,847 animal species from 84 orders, quantifying trait evolutionary rates (Brownian motion sigma2), trait-environment correlations (PGLS), functional diversity metrics (FRic; FEve; FDiv) and their relationships to species richness across 247 biome-level assemblages. Trait evolutionary rates were highest in leaf traits (LMA; SLA; N content) and lowest in whole-plant architecture traits (height; growth form) -- consistent with leaf traits being more directly responsive to local climate selection than architectural constraints. Functional diversity was positively correlated with species richness (r = 0.74; p < 0.001) but the relationship saturated above 200 species -- trait space filling was near-complete at intermediate richness. Trait-environment correlations confirmed temperature as the strongest abiotic driver of plant LES traits (partial R2 = 0.54) and precipitation as the strongest driver of water-use strategy traits (R2 = 0.47).