Alignment across taxonomic levels in strategies rather than in traits along elevational gradients.

Trait variation along environmental gradients can indicate the different strategies that organisms have evolved in response to environmental heterogeneity. So far, many inferences on trait-environment associations come from global studies performed at high taxonomic levels, and their transferability to lower evolutionary and spatial scales is unclear. Here, we tested for alignment in trait-environment relationships in 13 life-history and physiological traits among and within 7 Brassicaceae species over elevational gradients. Species and source populations originated from different elevations in the central Alps, and plants were raised under benign and warm conditions in greenhouse chambers. Some traits showed alignment in both within- and among-species trait clines, with even higher alignment on the level of trait complexes. There was high parallelism in resource allocation to leaves, particularly of carbon, with allocation decreasing with elevation. Size and biomass also decreased with elevation at the species and within-species level, respectively. Overall, the concordance in resource investment strategies when coping with lower as compared to higher elevations across evolutionary and spatial scales highlights their general role in adaptation to elevation.