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Global change poses increasing threats to ecological communities and ecosystem functioning. To improve our understanding of how arthropod communities, and associated ecosystem functions respond to combined impacts of future climate change and land-use intensification in grassland ecosystems, I used the experimental set-up of the Global Change Experimental Facility (GCEF). In my first chapter, I studied the combined effects of climate change and land-use intensity on arthropod community composition at the whole community level and of four trophic groups (predators, herbivores, detritivores and omnivores). I found that climate change and land-use intensification simultaneously shift species composition across trophic levels, through changes in abundance, species richness, and evenness. In my second chapter, I present a comprehensive set of linear regressions to estimate live body mass using data on body length and width, taxonomy and geographic origin. Furthermore, I quantified prediction discrepancy when using parameters from arthropods of a different geographic region. Incorporating body width into taxon- and region-specific length-mass regressions substantially increased prediction accuracy for live body mass. In my third research chapter, I studied the impacts of future climate change and land-use intensification on ecosystem functioning and the stability of arthropod food-webs. I furthermore studied the response of underlying community characteristics driving these ecosystem processes. Specifically, I tested the response of mean body mass, biomass and community metabolism of the whole community and four trophic groups to climate change and land-use intensification. Despite changes in community characteristics of the trophic groups, community ecosystem processes and food-web stability remained stable under climate change and land-use intensification, while the composition of total ecosystem processes changed.

Bewässerte Reisanbaugebiete gehören zu den biologisch vielfältigsten globalen Agrarökosystemen. Allerdings ist diese Biodiversität gefährdet durch landwirtschaftliche Intensivierung und monokultureller Verarmung von Anbauflächen, welche einen Abbau von Ökosystemleistungen, wie natürliche Schädlingsregulierung, nach sich ziehen. Während Nachweise zeigen, dass unehmende Heterogenität der Landschaft von Agrarökosystemen zur Erhöhung von Feindpopulationen und Verbesserung biologischer Kontrolle führen kann, ist wenig bekannt über Multiskalen-Effekte von Landschaftzusammensetzung und -konfiguration auf Arthropodengemeinschaften in Reis-Agrarökosystemen. In dieser Dissertation untersuchte ich den Einfluss von Landschaftsheterogenität auf die Verteilung von Athropoden in drei philippinischen Reisanbauregionen, um Empfehlungen für den Erhalt von Biodiversität und Verbesserung biologischer Kontrolle in Reis-Agrarökosystemen zu geben. In den verschiedenen Kapiteln der Dissertation, habe ich die Landschaftsheterogenität auf verschiedenen Skalen gemessen und deren Auswirkung auf die Arthropodendiversität (taxonomische und funktionelle Diversität) getestet.

Bewässerte Reisanbaugebiete gehören zu den biologisch vielfältigsten globalen Agrarökosystemen. Allerdings ist diese Biodiversität gefährdet durch landwirtschaftliche Intensivierung und monokultureller Verarmung von Anbauflächen, welche einen Abbau von Ökosystemleistungen, wie natürliche Schädlingsregulierung, nach sich ziehen. Während Nachweise zeigen, dass unehmende Heterogenität der Landschaft von Agrarökosystemen zur Erhöhung von Feindpopulationen und Verbesserung biologischer Kontrolle führen kann, ist wenig bekannt über Multiskalen-Effekte von Landschaftzusammensetzung und -konfiguration auf Arthropodengemeinschaften in Reis-Agrarökosystemen. In dieser Dissertation untersuchte ich den Einfluss von Landschaftsheterogenität auf die Verteilung von Athropoden in drei philippinischen Reisanbauregionen, um Empfehlungen für den Erhalt von Biodiversität und Verbesserung biologischer Kontrolle in Reis-Agrarökosystemen zu geben. In den verschiedenen Kapiteln der Dissertation, habe ich die Landschaftsheterogenität auf verschiedenen Skalen gemessen und deren Auswirkung auf die Arthropodendiversität (taxonomische und funktionelle Diversität) getestet.

Carrion of large animals is an extremely nutrient rich, ephemeral resource that is essential for many species, but is scarce in the anthropogenic Western-European landscape due to legislative restrictions. Rewilding, a novel conservation strategy that aims at restoring natural processes with minimal human intervention, is increasing in popularity and could lead to increased carrion availability in the landscape. It is therefore important to understand the effects of carrion on biodiversity. We investigated the direct and delayed (five months) effects of red deer (Cervus elaphus) carcasses on plants and arthropods in the Oostvaardersplassen, the Netherlands, one of the oldest rewilding sites in Europe. Specifically, we tested whether carrion has a positive direct effect on the abundances and diversity of various arthropod functional groups, as well as a delayed effect on the vegetation and arthropods through the increased nutrient availability. During the active decomposition stage in spring, we, not surprisingly, observed higher abundances of carrion associated species (scavengers and their specialized predators) at the carrion sites than at control sites without carrion, but no higher abundances of predators or detritivores. In late summer, after near-complete decomposition, plant biomass was five times higher, and nutritional plant quality (C:N ratio) was higher at the carrion sites than at the control sites. Arthropod abundance and diversity were also manifold higher, owing to higher numbers of herbivorous and predatory species. Regression analysis showed that abundances of herbivores and detritivores were positively related to plant biomass, and predator abundances were positively related to abundances of herbivores and detritivores, suggesting bottom-up effects propagating through the food chain. Our results show that even in a naturally nutrient-rich ecosystem like the Oostvaardersplassen, carrion can have strong positive effects on local plant biomass and nutritional quality and arthropod abundances, ...

A 4-yr on-farm study was conducted in the Philippines between 2006 and 2009 to determine if there are any long-term impacts of Bt corn on the arthropod community on commercial farms and in adjacent riparian areas. Arthropod counts were gathered by visual inspection of corn plants in three pairs of commercial farms and by sweep sampling in riparian sites close by. Sampling showed that species composition between Bt and non-Bt corn and between riparian areas adjacent to Bt or non-Bt corn were similar. Principal response curves and analysis of variance showed that there were no adverse effects of Bt corn on the abundance of natural enemies either in crops or adjacent riparian sites. The frequently observed natural enemies in Bt corn were the predatory coccinellid beetle, Micraspis discolor (F.) and spiders (Araneae). Arthropod diversity was similar 1) in Bt- and non-Bt corn and 2) the adjacent riparian areas. Taken together, the two parts of this study show that Bt corn does not have any long-term adverse effect on arthropod communities in corn (Zea mays L.) or in adjacent riparian ecosystems. The methods and results described in this study will be useful to Philippine government regulators in making recommendations and policy guidelines related to monitoring for environmental effects of transgenic crops. The current study did not attempt to demonstrate the direct exposure of arthropods in riparian sites to transgenic Cry1Ab protein that might come from adjacent Bt corn fields; that would require different experimental methods but the current study suggests such effects are unlikely. © 2012 Entomological Society of America.

AbstractIn an Afrotropical region experiencing massive deforestation, restoration approaches should provide sustainable solutions for recovering biodiversity. Arthropods are a sensitive taxonomic group for habitat alteration by deforestation and can be good indicators for restoration studies. Ground-dwelling arthropods provide important ecosystem functions, such as predation or organic matter decomposition, thereby contributing to ecosystem functionality. The consequences of post-mining management on arthropods in the Afrotropical region remain understudied. We carried out a comprehensive sampling of ground-dwelling arthropods in the dry and wet seasons across four land-use types in the semi-deciduous forest zone of Ghana. We then analysed whether the specific tree communities, vegetation structure and seasonal differences affected arthropod communities in the restored post-mining forest compared to the dominant alternative land-use type (agroforestry plantation), a natural reference (natural forest) or an unmanaged former mining area (gravel mine). In total, 43,364 arthropods were sampled and assigned to 78 taxonomic groups representing 14 order/sub-order, 28 beetle families, 25 spider families, 5 hunting guilds of spiders and 6 trophic groups of beetles. Overall, Araneae, Coleoptera, Hymenoptera and Orthoptera all had higher activity densities in the wet season. The vegetation structure of the three land-use types with trees supported a greater overall activity density of arthropods and a more diverse functional composition compared to the unmanaged gravel site. Pronounced variation between the dry and wet seasons further influenced the taxonomic and functional composition. The active forest restoration of this post-mining area is a promising approach to drive arthropod communities towards a comparable state observed in the natural forest.

The 'dehesas' are important and vast agro-silvo-pastoral systems typical of the Iberian Peninsula that are undergoing a crisis due to their low economic profitability and environmental degradation. Thus, it is necessary to identify effective tools that provide a reliable idea of the status of these ecosystems as a starting point for future measures of conservation. In this study we analyse the possible role of ants as surrogates for epigeic arthropods, a common biodiversity indicator group. A total of 15 farms were sampled throughout Sierra Morena (Andalusia, Spain) with pitfall traps, both for the 'dehesa' habitats themselves and for different microhabitats within the study sites. First, we achieve a complete list of the species of ants of the area. The results indicate that the 'dehesa' habitats were very homogenous for all farms, while microhabitats showed differences in species richness and ant communities' composition compared to the 'dehesas'. To evaluate the role of ants as surrogates, the number of traps occupied by each order of arthropod and by each ant species was compared. We found a high correlation between them what confirm the surrogate character of ants for the rest of arthropods in these ecosystems.

Abstract: Plant diversity begets diversity at other trophic levels. While species richness is the most commonly used measure for plant diversity, the number of evolutionary lineages (i.e. phylogenetic diversity) could theoretically have a stronger influence on the community structure of co‐occurring organisms. However, this prediction has only rarely been tested in complex real‐world ecosystems.Using a comprehensive multitrophic dataset of arthropods and fungi from a species‐rich subtropical forest, we tested whether tree species richness or tree phylogenetic diversity relates to the diversity and composition of organisms.We show that tree phylogenetic diversity but not tree species richness determines arthropod and fungi community composition across trophic levels and increases the diversity of predatory arthropods but decreases herbivorous arthropod diversity. The effect of tree phylogenetic diversity was not mediated by changed abundances of associated organisms, indicating that evolutionarily more diverse plant communities increase niche opportunities (resource diversity) but not necessarily niche amplitudes (resource amount).Our findings suggest that plant evolutionary relatedness structures multitrophic communities in the studied species‐rich forests and possibly other ecosystems at large. As global change non‐randomly threatens phylogenetically distinct plant species, far‐reaching consequences on associated communities are expected

The mathematical theory describing small assemblages of interacting species (community modules or motifs) has significantly improved our understanding of the emergent properties of ecological communities. It is not clear whether all interactions accounted for in such models will be realized in real communities. Here, we use community modules to experimentally explore whether the number of trophic links among species scales with community complexity (i.e. by adding species known to feed on each other from pairwise trials) in a simple mite community present in avocado orchards (Persea americana). By varying the presence of each of two predators (Euseius stipulatus and Neoseiulus californicus), one herbivore as shared prey (Oligonychus perseae) and pollen of Carpobrotus edulis as an alternative food resource, we mimicked communities with simple trophic chains, intraguild predation and/or apparent competition. We then assessed predation rates and the conversion of food into offspring in those communities. We found that increasing the number of potential interactions did not result in more complex realized community modules. Instead, all species effectively fed upon a single food item, hence all community modules actually corresponded to one or two linear trophic chains. Therefore, trophic links assumed to occur when species are assembled in pairs do not necessarily occur when other components of the community are present. Consequently, food web structure may be much less complex than predicted by theory. A free Plain Language Summary can be found within the Supporting Information of this article. ; This work was conducted as part of the 'Completing the dryland puzzle: creating a predictive framework for biological soil crust function and response to climate change' Working Group supported by the John Wesley Powell Center for Analysis and Synthesis, funded by the U.S. Geological Survey. We thank the University of Colorado Boulder Undergraduate Research Opportunities Program (UROP), which helped support undergraduate researchers who assisted with data entry for this project. Particularly, we thank CU Boulder undergraduate researcher assistants Emma Brokyl, Julius Gayo and Whitney Gabbert for their invaluable work on database compilation and organization for this project. C.A.H. was supported by the Department of Ecology and Evolutionary Biology at the University of Colorado Boulder and a National Science Foundation Graduate Research Fellowship (award DGE‐1144083). V.B.C. was supported by grants from the National Science Foundation (award DEB‐1844531) and the DePaul University College of Science and Health. E.H.S. was supported by Consejo Nacional de Ciencia y Tecnología (project SEP‐CONACYT 251388). J.B. was supported by the USGS Ecosystem and Land Change Sciences program. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Vegetation effects on arthropods are well recognized, but it is unclear how different vegetation attributes might influence arthropod assemblages across mixed-agricultural landscapes. Understanding how plant communities influence arthropods under different habitat and seasonal contexts can identify vegetation management options for arthropod biodiversity. We examined relationships between vegetation structure, plant species richness and plant species composition, and the diversity and composition of beetles in different habitats and time periods. We asked: (1) What is the relative importance of plant species richness, vegetation structure and plant composition in explaining beetle species richness, activity-density and composition? (2) How do plant-beetle relationships vary between different habitats over time? We sampled beetles using pitfall traps and surveyed vegetation in three habitats (woodland, farmland, their edges) during peak crop growth in spring and post-harvest in summer. Plant composition better predicted beetle composition than vegetation structure. Both plant richness and vegetation structure significantly and positively affected beetle activity-density. The influence of all vegetation attributes often varied in strength and direction between habitats and seasons for all trophic groups. The variable nature of plant-beetle relationships suggests that vegetation management could be targeted at specific habitats and time periods to maximize positive outcomes for beetle diversity. In particular, management that promotes plant richness at edges, and promotes herbaceous cover during summer, can support beetle diversity. Conserving ground cover in all habitats may improve activity-density of all beetle trophic groups. The impacts of existing weed control strategies in Australian crop margins on arthropod biodiversity require further study. ; This work was supported by Central Tablelands Local Land Services (through Australian Government funding), Lake Cowal Foundation and Mount Mulga Pastoral Company. KN was supported by an Australian Government Research Training Program (RTP) scholarship.