Abstract

Phenotypic integration, the pattern and magnitude of association among traits, can influence plant performance. Phenotypic integration is thought to increase under stressful conditions, yet the evidence is largely mixed. Broader, multi-species tests of this hypothesis across natural stress gradients are key to understanding the generality of phenotypic integration as a potential stress response. Importantly, how phenotypic integration associates with other functional strategies remains underexplored. Across six sites at the low end of an aridity gradient in the Atacama Desert, we evaluated in 17 plant species whether integration was higher in the populations inhabiting the more arid sites. We also tested for the association between phenotypic integration and resource-use strategy and life cycle. Across species, phenotypic integration was higher in the more arid sites. Although species showed a more resource-conservative strategy in the more arid sites, a resource-acquisitive strategy was positively associated with phenotypic integration, thus suggesting that these are complementary strategies. Lastly, the magnitude of phenotypic integration was similar in annual and perennial species. Overall, our results are consistent with the notion that phenotypic integration could be a stress-response mechanism. Phenotypic integration was unrelated to the extent of exposure to stress (annual vs. perennial species). Results suggest that resource conservation and phenotypic integration are likely complementary stress response strategies, mainly adopted by those species less able to cope with drought stress. Our findings highlight the need to further study the ecological significance of phenotypic integration as a potential stress response, given its likely relevance in the current global change scenario.