Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

Bees provide essential pollination services that are potentially affected both by local farm management and the surrounding landscape. To better understand these different factors, we modelled the relative effects of landscape composition (nesting and floral resources within foraging distances), landscape configuration (patch shape, interpatch connectivity and habitat aggregation) and farm management (organic vs. conventional and local-scale field diversity), and their interactions, on wild bee abundance and richness for 39 crop systems globally. Bee abundance and richness were higher in diversified and organic fields and in landscapes comprising more high-quality habitats; bee richness on conventional fields with low diversity benefited most from high-quality surrounding land cover. Landscape configuration effects were weak. Bee responses varied slightly by biome. Our synthesis reveals that pollinator persistence will depend on both the maintenance of high-quality habitats around farms and on local management practices that may offset impacts of intensive monoculture agriculture.

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A global quantitative synthesis of local and landscape effects on wild bee pollinators in agroecosystems

Landscape Ecology in Theory and Practice

Recent reports of local extinctions of arthropod species1, and of massive declines in arthropod biomass2, point to land-use intensification as a major driver of decreasing biodiversity. However, to our knowledge, there are no multisite time series of arthropod occurrences across gradients of land-use intensity with which to confirm causal relationships. Moreover, it remains unclear which land-use types and arthropod groups are affected, and whether the observed declines in biomass and diversity are linked to one another. Here we analyse data from more than 1 million individual arthropods (about 2,700 species), from standardized inventories taken between 2008 and 2017 at 150 grassland and 140 forest sites in 3 regions of Germany. Overall gamma diversity in grasslands and forests decreased over time, indicating loss of species across sites and regions. In annually sampled grasslands, biomass, abundance and number of species declined by 67%, 78% and 34%, respectively. The decline was consistent across trophic levels and mainly affected rare species; its magnitude was independent of local land-use intensity. However, sites embedded in landscapes with a higher cover of agricultural land showed a stronger temporal decline. In 30 forest sites with annual inventories, biomass and species number—but not abundance—decreased by 41% and 36%, respectively. This was supported by analyses of all forest sites sampled in three-year intervals. The decline affected rare and abundant species, and trends differed across trophic levels. Our results show that there are widespread declines in arthropod biomass, abundance and the number of species across trophic levels. Arthropod declines in forests demonstrate that loss is not restricted to open habitats. Our results suggest that major drivers of arthropod decline act at larger spatial scales, and are (at least for grasslands) associated with agriculture at the landscape level. This implies that policies need to address the landscape scale to mitigate the negative effects of land-use practices. Analyses of a dataset of arthropod biomass, abundance and diversity in grassland and forest habitats in Germany for the period 2008–2017 reveal that drivers of arthropod declines act at the landscape level.

Arthropod decline in grasslands and forests is associated with landscape-level drivers

A growing body of evidence highlights the importance of biodiversity for ecosystem stability and the maintenance of optimal ecosystem functionality Conservation measures are thus essential to safeguard the ecosystem services that biodiversity provides and human society needs Current anthropogenic threats may lead to detrimental (and perhaps irreversible) ecosystem degradation, providing strong motivation to evaluate the response of ecological communities to various anthropogenic pressures In particular, ecosystem functions that sustain key ecosystem services should be identified and prioritized for conservation action Traditional diversity measures (eg ‘species richness’) may not adequately capture the aspects of biodiversity most relevant to ecosystem stability and functionality, but several new concepts may be more appropriate These include ‘response diversity’, describing the variation of responses to environmental change among species of a particular community Response diversity may also be a key determinant of ecosystem resilience in the face of anthropogenic pressures and environmental uncertainty However, current understanding of response diversity is poor, and we see an urgent need to disentangle the conceptual strands that pervade studies of the relationship between biodiversity and ecosystem functioning Our review clarifies the links between response diversity and the maintenance of ecosystem functionality by focusing on the insurance hypothesis of biodiversity and the concept of functional redundancy We provide a conceptual model to describe how loss of response diversity may cause ecosystem degradation through decreased ecosystem resilience We explicitly explain how response diversity contributes to functional compensation and to spatio-temporal complementarity among species, leading to long-term maintenance of ecosystem multifunctionality Recent quantitative studies suggest that traditional diversity measures may often be uncoupled from measures (such as response diversity) that may be more effective proxies for ecosystem stability and resilience Certain conclusions and recommendations of earlier studies using these traditional measures as indicators of ecosystem resilience thus may be suspect We believe that functional ecology perspectives incorporating the effects and responses of diversity are essential for development of management strategies to safeguard (and restore) optimal ecosystem functionality (especially multifunctionality) Our review highlights these issues and we envision our work generating debate around the relationship between biodiversity and ecosystem functionality, and leading to improved conservation priorities and biodiversity management practices that maximize ecosystem resilience in the face of uncertain environmental change

Response diversity determines the resilience of ecosystems to environmental change.

Understanding how landscape characteristics affect biodiversity patterns and ecological processes at local and landscape scales is critical for mitigating effects of global environmental change. In this review, we use knowledge gained from human-modified landscapes to suggest eight hypotheses, which we hope will encourage more systematic research on

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Doug A. Landis

Papers

Landscape moderation of biodiversity patterns and processes - eight hypotheses