Land-Use and Climate Impacts on Plant-Pollinator Interactions and Pollination Services

Most flowering plants rely on animals for pollination and most animal pollinators rely on flowering plants for food resources. However, there is an ongoing concern that anthropogenic-induced global change threatens the mutualistic association between plants and pollinators. Two of the most important factors of global change are land-use and climate change. Land-use and climate change may affect species distributions and species phenologies, leading to spatial and temporal mismatches between mutualistic partners. Land-use and climate change may also influence species abundances, nesting habitats, floral resources and the behaviors of pollinators. Thus, mutualistic plant–pollinator interactions should be more susceptible to global change than simple measures of biodiversity, such as species richness and species composition. The potential negative impacts of land-use and climate change on plant–pollinator interactions may have large consequences for the conservation of threatened plants and pollinators and economically by diminishing crop productivity. Here I highlight ‘fruitful avenues’ for research into better understanding the influence of land-use and climate change on plant–pollinator interactions

Specialization in Plant-Hummingbird Networks Is Associated with Species Richness, Contemporary Precipitation and Quaternary Climate-Change Velocity

Bo Dalsgaard et al...Large-scale geographical patterns of biotic specialization and the underlying drivers are poorly understood, but it is widely believed that climate plays an important role in determining specialization. As climate-driven range dynamics should diminish local adaptations and favor generalization, one hypothesis is that contemporary biotic specialization is determined by the degree of past climatic instability, primarily Quaternary climate-change velocity. Other prominent hypotheses predict that either contemporary climate or species richness affect biotic specialization. To gain insight into geographical patterns of contemporary biotic specialization and its drivers, we use network analysis to determine the degree of specialization in plant-hummingbird mutualistic networks sampled at 31 localities, spanning a wide range of climate regimes across the Americas. We found greater biotic specialization at lower latitudes, with latitude explaining 20–22% of the spatial variation in plant-hummingbird specialization. Potential drivers of specialization - contemporary climate, Quaternary climate-change velocity, and species richness - had superior explanatory power, together explaining 53–64% of the variation in specialization. Notably, our data provides empirical evidence for the hypothesized roles of species richness, contemporary precipitation and Quaternary climate-change velocity as key predictors of biotic specialization, whereas contemporary temperature and seasonality seem unimportant in determining specialization. These results suggest that both ecological and evolutionary processes at Quaternary time scales can be important in driving large-scale geographical patterns of contemporary biotic specialization, at least for co-evolved systems such as plant-hummingbird networks.Funding for BD was supported by Frimodt-Heineke Foundation, Augustinus Foundation, Knud Højgaard Foundation, a PhD fellowship by Aarhus University, Weis-Fogh Fund at Department of Zoology, University of Cambridge, and The Danish Council for Independent Research | Natural Sciences. EM was supported by the Center for Massive Data Algorithmics, a Danish National Research Foundation Center of Excellence. JF and CR thank the Danish National Research Foundation for its support of the Center for Macroecology, Evolution and Climate. AMG was supported by Svend Fiedler & Wife Foundation, J.Olesen by the Danish Council for Independent Research - Natural Sciences and Novozymes/World Wildlife Foundation-Denmark, J.Ollerton and SW by the British Ecological Society, Idea Wild, The Biodiversity Trust, The Anglo Peruvian Society and The Leslie Church Bursary Fund, RA by The United States National Science Foundation's Predoctoral Fellowship Program and The California Alliance for Minority Participation, ACA by The Fundação de Amparo à Pesquisa do Estado da Bahia (FAEP) and The National Council for Scientific and Technological Development (CNPq), PC by the British Ornithologists' Union, CL by the Consejo Nacional de Ciencia y Tecnología, CM by FAPESB and CNPq, IS and MS by FAPESP and CNPq, AT by Aarhus University, and J-CS by the Danish Council for Independent Research - Natural Sciences (grant 272-07-0242). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewe

Redesign af kursus i Biogeography of Species Interaction Networks

Et intensivt 1-uge kursus (Biogeography of species interaction networks) for kandidat og PhD studerende udbudt på Brasilianske universiteter. Jeg er hovedansvarlig for kurset, hvor der også er en dansk og en brasiliansk postdoc der underviser. Formålet med kurset er, at give de studerende et indblik i de basale koncepter der ligger bag en ”netværks tankegang” og hvordan det kan bruges til, at forstå biogeografiske principper. Desuden lære de studerende rent praktisk at lave nogle udvalgte netværks udregningerne, og de skal under kurset udtænke og arbejde med egne projekt ideer. Et af vores håb er, at nogle af dem bliver inspirerede til, at bruge netværks analyser i deres egne kandidat eller PhD afhandlinger

Nitrogen removal in marine environments: recent findings and future research challenges

Respiratory reduction of nitrate (denitrification) is recognized as the most important process converting biologically available (fixed) nitrogen to N2. In current N cycle models, a major proportion of global marine denitrification (50–70%) is assumed to take place on the sea floor, particularly in organic rich continental margin sediments. Recent observations indicate that present conceptual views of denitrification and pathways of nitrate reduction and N2 formation are incomplete. Alternative N cycle pathways, particularly in sediments, include anaerobic ammonium oxidation to nitrite, nitrate and N2 by Mn-oxides, and anaerobic ammonium oxidation coupled to nitrite reduction and subsequent N2 mobilization. The discovery of new links and feedback mechanisms between the redox cycles of, e.g., C, N, S, Mn and Fe casts doubt on the present general understanding of the global N cycle. Recent models of the oceanic N budget indicate that total inputs are significantly smaller than estimated fixed N removal. The occurrence of alternative N reaction pathways further exacerbates the apparent imbalance as they introduce additional routes of N removal. In this contribution, we give a brief historical background of the conceptual understanding of N cycling in marine ecosystems, emphasizing pathways of aerobic and anaerobic N mineralization in marine sediments, and the implications of recently recognized metabolic pathways for N removal in marine environments

Landscape-level effects of forest on pollinators and fruit set of guava (<i>Psidium guajava</i> L.) in orchards across Southern Thailand

Pollination by wild pollinators is a key ecosystem service threatened by anthropogenic-induced land-use change. The proximity to natural habitat has previously been shown to positively affect pollinator communities and improve crop yield and quality but empirical evidence is limited from most parts of the World. Here, across six farms in Southern Thailand, we investigated the significance of landscape-level effects of natural habitat (proportion of and distance to evergreen forest) on both visitation rate and richness of pollinators as well as fruit set of guava (Psidium guajava L.), a local economically-important crop in the tropics. Overall, the most abundant pollinator was the Asian honey bee Apis cerana (39% of all visits) and different species of stingless bees (37%). We found that pollinator richness was unrelated to the proportion and distance to evergreen forest, however, the proportion of forest within a 1, 5 and 10 km radius had a significant positive impact on visitation rate of wild pollinators. Still, neither the various forest parameters nor pollinator visitation rate showed a significant impact on fruit set of guava, perhaps because guava self-pollinates. This illustrates that landscape-level degradation of natural habitat may negatively impact pollinator communities without diminishing the crop yield of the farmers

The Inflationary Gravity Waves in light of recent Cosmic Microwave Background Anisotropies data

One of the major predictions of inflation is the existence of a stochastic background of cosmological gravitational waves (GW). These gravitational waves can induce significant temperature anisotropies in the Cosmic Microwave Background (CMB) on the angular scales recently probed by the Archeops experiment. Here, we perform a combined analysis of Archeops together with information from other CMB experiments and/or cosmological datasets, in order to constrain the amplitude of the GW background. We find that, for a scale-invariant GW background, the ratio of tensor/scalar perturbations at the CMB quadrupole is now constrained to be $r \leq 0.43$ at 95% c.l., while the bound on the spectral index of primordial density fluctuations is $n_S=0.97_{-0.12}^{+0.10}$. We discuss the implications for future GW detections through CMB polarization measurements.Comment: 5 pages, 3 figures. Replaced with final updated proof versio

Oxygen at Nanomolar Levels Reversibly Suppresses Process Rates and Gene Expression in Anammox and Denitrification in the Oxygen Minimum Zone off Northern Chile

A major percentage (20 to 40%) of global marine fixed-nitrogen loss occurs in oxygen minimum zones (OMZs). Concentrations of O[subscript 2] and the sensitivity of the anaerobic N[subscript 2]-producing processes of anammox and denitrification determine where this loss occurs. We studied experimentally how O[subscript 2] at nanomolar levels affects anammox and denitrification rates and the transcription of nitrogen cycle genes in the anoxic OMZ off Chile. Rates of anammox and denitrification were reversibly suppressed, most likely at the enzyme level. Fifty percent inhibition of N[subscript 2] and N[subscript 2]O production by denitrification was achieved at 205 and 297 nM O[subscript 2], respectively, whereas anammox was 50% inhibited at 886 nM O2. Coupled metatranscriptomic analysis revealed that transcripts encoding nitrous oxide reductase (nosZ), nitrite reductase (nirS), and nitric oxide reductase (norB) decreased in relative abundance above 200 nM O[subscript 2]. This O[subscript 2] concentration did not suppress the transcription of other dissimilatory nitrogen cycle genes, including nitrate reductase (narG), hydrazine oxidoreductase (hzo), and nitrite reductase (nirK). However, taxonomic characterization of transcripts suggested inhibition of narG transcription in gammaproteobacteria, whereas the transcription of anammox narG, whose gene product is likely used to oxidatively replenish electrons for carbon fixation, was not inhibited. The taxonomic composition of transcripts differed among denitrification enzymes, suggesting that distinct groups of microorganisms mediate different steps of denitrification. Sulfide addition (1 µM) did not affect anammox or O[subscript 2] inhibition kinetics but strongly stimulated N[subscript 2]O production by denitrification. These results identify new O[subscript 2] thresholds for delimiting marine nitrogen loss and highlight the utility of integrating biogeochemical and metatranscriptomic analyses.Gordon and Betty Moore FoundationAgouron InstituteDanish National Research Foundation (Grant DNRF53

The macroecology of animal versus wind pollination: ecological factors are more important than historical climate stability

Background: The relative frequency of wind and animal pollinated plants is non-randomly distributed across the globe and numerous hypotheses have been raised for the greater occurrence of wind pollination in some habitats and towards higher latitudes. To date, however, there has been no comprehensive global investigation of these hypotheses. Aims: Investigating a range of hypotheses for the role of biotic and abiotic factors as determinants of the global variation in animal versus wind pollination. Methods: We analysed 67 plant communities ranging from 70º North to 34º South. For these we determined habitat type, species richness, insularity, topographic heterogeneity, current climate and Late-Quaternary climate change. The predictive effects of these factors on the proportion of wind- and animal-pollinated plants were tested using correlations, ordinary least squares (OLS) and logistic regression analyses with information-theoretic model selection. Results: The proportion of animal-pollinated plant species was positively associated with plant species richness and current temperature. Furthermore, in forest, animal pollination was positively related to precipitation. Historical climate was only weakly and idiosyncratically correlated with animal pollination. Conclusion: Results were consistent with the hypothesised reduced chance for wind-transported pollen reaching conspecific flowers in species-rich communities, fewer constraints on nectar production in warm and wet habitats, and reduced relative effectiveness of wind dispersal in humid areas. There was little evidence of a legacy of historical climate change affecting these patterns