LAUSR

BACKGROUND AND AIMS Non-native plant species are not restricted to lowlands, but increasingly invade high elevations. While we expected for both native and non-native species variability of plant functional traits due to the changing environmental conditions along elevational gradients, we additionally assumed that non-native species are characterized by a more acquisitive growth strategy, since traits reflecting such a strategy have been found to correlate with invasion success. Further, the typical lowland introduction of non-native species coming from multiple origins should lead to higher trait variability within populations of non-native species specifically at low elevations, and they might therefore occupy a larger total trait space. METHODS Along an elevational gradient ranging from 55 to 1925 m a.s.l. on Tenerife, we collected leaves from eight replicate individuals in eight evenly distributed populations of five native and six non-native forb species. In each population, we measured ten eco-morphological and leaf biochemical traits and calculated trait variability within each population and the total trait space occupied by native and non-native species. KEY RESULTS We found both positive (e.g. LDMC) and negative (e.g. leaf N) correlations with elevation for native species, but only few responses for non-native species. For non-native species, within-population variability of LDMC and SLA decreased with elevation, but increased for native species. The total trait space occupied by all non-native species was smaller than and a subset of that of native species. CONCLUSIONS We found little evidence that intra-specific trait variability is associated with the success of non-native species to spread towards higher elevations. Instead, for non-native species, our results indicate that intermediate trait values that meet the requirements of various conditions are favourable across the changing environmental conditions along elevational gradients. As a consequence, it might prevent non-native species from overcoming abruptly changing environmental conditions, e.g. when crossing the treeline.