Aridity drives coordinated trait shifts but not decreased trait variance across the geographic range of eight Australian trees

Abstract

Context Large intraspecific functional trait variation strongly impacts many aspects of natural communities and ecosystems, yet is inconsistent across traits and species. Approach We measured within-species variation in leaf mass per area (LMA), leaf dry matter content (LDMC), branch wood density (WD), and allocation to stem area vs. leaf area in branches (branch Huber value, HV) across the aridity range of seven Australian eucalypts and an Acacia species to explore how traits and their variances change with aridity. Results and Conclusions Within-species, we found consistent increases in LMA, LDMC and WD, and HV with increasing aridity, resulting in consistent trait coordination across tissues. However, this coordination only emerged across sites with large climate differences. Unlike trait means, patterns of trait variance with aridity were mixed across populations and species and showed limited support for constrained trait variation in dryer populations or more xeric species. Synthesis Our results highlight that climate can drive consistent within-species trait patterns, but that these patterns might often be obscured by the complex nature of morphological traits and sampling incomplete species ranges or sampling confounded stress gradients.