Consequences of biodiversity shift across phylogenetic scales for aspen and willow growth, survival, and herbivory

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AbstractQuestionIt has been established that community biodiversity has consequences for ecosystem function. Yet research assessing these biodiversity–ecosystem function (BEF) relationships usually occurs at only one phylogenetic scale; as such, the dependence of BEF relationships on phylogenetic scale has not been characterized. We present a novel framework for considering the consequences of biodiversity across phylogenetic scales, allowing us to ask: Do the consequences of intraspecific and interspecific diversity affect the growth, survival, and leaf herbivory of three temperate tree species?Study siteSalicaceous tree plantation, Minnesota, northern USA.MethodsWe established an experimental plantation consisting of trees of three species within the willow (Salicaceae) family. Two aspen (Populus tremuloides, P. alba) and one willow (Salix nigra) species were represented by three unique genotypes such that tree neighborhoods varied both in genotype richness (intraspecific diversity) and species richness (interspecific diversity). We assessed the consequences of tree identity and diversity across these two phylogenetic scales for all trees’ aboveground productivity and survival, and for herbivore damage (on P. tremuloides) at the end of the second full growing season of the experiment.ResultsDiversity at any phylogenetic scale had no effect on the growth and survival of P. alba or S. nigra. However, intraspecific diversity increased the likelihood of P. tremuloides survival while interspecific diversity reduced P. tremuloides survival. Intraspecific diversity also reduced leaf removal and galling herbivory on P. tremuloides, while interspecific diversity had no effect on leaf removal and increased galling herbivory. Neither scale of diversity affected leaf mining.ConclusionsTree diversity within and among populations and species affected plant performance and ecosystem properties differentially, demonstrating that BEF relationships shift across phylogenetic scales in a taxon‐specific manner. We call for further experiments that explicitly span these scales by measuring ecosystem and physiological responses to the manipulation of diversity within and among species.