Functional and phylogenetic diversity of woody plants drive herbivory in a highly diverse forest

Werner Härdtle,David Eichenberg,Wenzel Kröber,Stefan G Michalski,Walter Durka,Andreas Schuldt,Thorsten Assmann,Oliver Purschke,Helge Bruelheide

doi:10.1111/nph.12695

Abstract

Biodiversity loss may alter ecosystem processes, such as herbivory, a key driver of ecological functions in species-rich (sub)tropical forests. However, the mechanisms underlying such biodiversity effects remain poorly explored, as mostly effects of species richness – a very basic biodiversity measure – have been studied. Here, we analyze to what extent the functional and phylogenetic diversity of woody plant communities affect herbivory along a diversity gradient in a subtropical forest.We assessed the relative effects of morphological and chemical leaf traits and of plant phylogenetic diversity on individual-level variation in herbivory of dominant woody plant species across 27 forest stands in south-east China.Individual-level variation in herbivory was best explained by multivariate, community-level diversity of leaf chemical traits, in combination with community-weighted means of single traits and species-specific phylodiversity measures. These findings deviate from those based solely on trait variation within individual species.Our results indicate a strong impact of generalist herbivores and highlight the need to assess food-web specialization to determine the direction of biodiversity effects. With increasing plant species loss, but particularly with the concomitant loss of functional and phylogenetic diversity in these forests, the impact of herbivores will probably decrease – with consequences for the herbivore-mediated regulation of ecosystem functions.

Highlights

The realization that global change alters the biotic composition of ecosystems has spawned a wealth of research showing that biodiversity loss affects significantly ecosystem functions and services (Cardinale et al, 2012; Naeem et al, 2012)
We study the relative effects of morphological and chemical leaf traits commonly considered to affect herbivory and the impact of woody plant phylogenetic diversity on species-specific herbivory levels across 27 forest stands in south-east China
The minimal models based on abiotic characteristics and only phylogenetic or functional plant characteristics had a higher explanatory power than the models including only species richness and abiotic characteristics, or abiotic characteristics alone (Table 1)

Summary

Introduction

The realization that global change alters the biotic composition of ecosystems has spawned a wealth of research showing that biodiversity loss affects significantly ecosystem functions and services (Cardinale et al, 2012; Naeem et al, 2012). The awareness that the functional traits of species (e.g. morphological or physiological features that determine an organism’s performance) play a central role in the determination of many of these diversity effects has led to a stronger focus on the functional dimensions of biodiversity and a more thorough investigation into the role of specific traits for individual functions (Diaz et al, 2007; Reiss et al, 2009). Progress in our understanding of functional diversity effects has been made, for processes within single trophic levels (primarily the producer level), it is increasingly being recognized that, in many cases, trophic interactions are key modifiers of these relationships (Reiss et al., 2009; Cardinale et al, 2012). Phylogenetic diversity incorporates the evolutionary history of species relationships and may capture phylogenetically

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