Community phylogenetics and invertebrate herbivory in managed grasslands
Land-use change and intensification poses one of the major threats to biodiversity in terrestrial ecosystems now and for the next decades (Sala et al. 2000). To assess the consequences of ongoing and future biodiversity loss, it is crucial to understand the complex interactions between biodiversity...
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|Land-use change and intensification poses one of the major threats to biodiversity in terrestrial ecosystems now and for the next decades (Sala et al. 2000). To assess the consequences of ongoing and future biodiversity loss, it is crucial to understand the complex interactions between biodiversity and ecosystem functions. Biodiversity, however, is a fuzzy term that comprises different aspects of natural communities. So far, community species richness and functional diversity are two aspects of biodiversity that have received most attention in community ecology. Although these biodiversity measures have provided the predominant part of our knowledge on biodiversity – ecosystem relationships, advances in ecological theory and methods have revealed several shortcomings related to these approaches. In the past 20 years community phylogenetics has been proposed as an additional measure of biodiversity to enhance our understanding of the biodiversity – ecosystem functioning relationships (Webb et al. 2002a; Cavender-Bares et al. 2009; Srivastava et al. 2012). For example, phylogenetic diversity of plant communities has been shown to be a better predictor of productivity than species richness or functional diversity (Flynn et al. 2011). It has also been shown that phylogenetic diversity affects ecosystem processes. Herbivory in forests and grasslands was altered by phylogenetic diversity of plant communities (Parker et al. 2012; Dinnage 2013). Community phylogenetics also provide additional insights into community assembly processes compared to species richness or functional diversity. For example, Pellissier et al. (2014) showed that application of nitrogen and herbicides lead to a decrease in plant species richness, but promoted different responses in plant traits (specific leaf area and canopy height). Plant phylogenetic diversity increased when nitrogen and herbicides were applied together, most likely because traits that facilitate plant success under the applied conditions were not phylogenetically conserved. Dinnage (Dinnage 2009) showed that plant communities contain species that are closer related than expected by chance in plots that experienced higher disturbance, a pattern called phylogenetic under-dispersion or clustering (Webb et al. 2002a). Although most studies focus on primary producers in community phylogenetic analyses, these patterns apply also to animal communities as shown by Helmus et al. (Helmus et al. 2010). He analyzed zooplankton communities in disturbed lakes and found that communities in disturbed lakes contained more closely related species than in undisturbed lakes. Arthropod communities in general and in particular herbivorous arthropods, play a major role in ecosystem processes (Weisser and Siemann 2007). To date, however, our knowledge about the effects of land-use intensification on invertebrate herbivore communities, phylogenetic diversity of communities in particular, is still limited. Trophic interactions also play a major role in structuring insect communities. Dinnage et al. (2012) showed that increasing plant species richness and phylogenetic diversity increased arthropod diversity, insect herbivore diversity in particular. The relationships between plant and insect phylogenetic diversity yet remain largely unknown. Hence, understanding the effects of land use on phylogenetic diversity of plant and herbivore communities, as well as the relationships between plant and insect phylogenetic diversities, is crucial to predict the consequences of biodiversity loss on ecosystems.
To study the relationships mentioned above, an appropriate study system is of importance. This study was conducted within the Biodiversity Exploratories, a large-scale and long-term research project to study the relationships between land use, biodiversity and ecosystem functioning (Fischer et al. 2010). The Biodiversity Exploratories are situated in three regions in Germany (Schwäbische Alb in SW Germany; Hainich-Dün in Central Germany and Schorfheide-Chorin in NE Germany). Each of the regions comprises 300 experimental plots (150 in grasslands and 150 in forests) under constant land use. This study focuses on the grasslands which experience different levels and types of land use.