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Insect pollination plays a vital role for the yield of many crops, such as apples, strawberries and coffee, which are economically significant commodities on the global market. Yet, knowledge about the role of insect pollination is lacking for many cash crops that support the livelihoods of small-scale farmers in developing countries. To assess if yields of watermelon are pollen limited, we conducted a supplemental hand-pollinated experiment (using a pollen mixture of cross and self-pollen) in 13 small-scale farms in an agricultural landscape in the Kilimanjaro and Arusha regions in northern Tanzania. We assessed fruit set, fruit abortion and weight of the mature fruits stemming from hand pollinated and control flowers. To check if differences in yield responses between hand-pollinated and control treatments depended on resource availability, we also accounted for local soil conditions. We found that hand pollination (i) increased the probability of fruit initiation by 30%, (ii) reduced the probability of fruit abortion by 13%, (iii) increased the probability of flowers developing into mature fruits by 42% and (iv) increased average fruit weight by 1.3 kg (±0.15 SE). Our results indicate that our system is pollen limited, due to insufficient visitor frequency and/or inefficient pollinator species. Fruit initiation and fruit weight were positively related to soil carbon, irrespective of treatment. The influence of soil moisture was not consistent across the measured responses, and differed between hand-pollinated and the control treatments. We suggest that farmers in our focal area should focus on improving the quality of the landscape to sustain and enhance healthy pollinator communities ultimately improving yields. We also suggest that farmers should continue current practices with respect to fertilization. The role of soil moisture on fruit initiation and maturation should be investigated to ensure that the positive effects of pollen is not hindered by soil moisture conditions.

Advancing phenology is one of the most visible effects of climate change on plant communities, and has been especially pronounced in temperature-limited tundra ecosystems. However, phenological responses have been shown to differ greatly between species, with some species shifting phenology more than others. We analysed a database of 42,689 tundra plant phenological observations to show that warmer temperatures are leading to a contraction of community-level flowering seasons in tundra ecosystems due to a greater advancement in the flowering times of late-flowering species than early-flowering species. Shorter flowering seasons with a changing climate have the potential to alter trophic interactions in tundra ecosystems. Interestingly, these findings differ from those of warmer ecosystems, where early-flowering species have been found to be more sensitive to temperature change, suggesting that community-level phenological responses to warming can vary greatly between biomes.

Understanding the responses of different ontogenetic stages to environmental and human disturbance factors is essential for developing efficient conservation strategies for endangered plant species. We examined how three ontogenetic stages of a locally endangered tree species, Olea europaea subsp. cuspidata, responded to environmental factors and human disturbance in Hugumburda dry Afromontane forest in Ethiopia. We counted individual seedlings, saplings and adults of O. europaea in 70 20 × 20 m quadrats over ca. 2.8 ha, and measured biotic (woody species richness, canopy cover, aboveground tree biomass, herbaceous cover), abiotic (soil and topographic variables), and human disturbance factors (logging and tracks). To detect ontogenetic niche shifts, we compared observed vs. simulated locations of trees in the three life stages and how they related to the environmental and human disturbance factors. We found that the population structure of O. europaea showed generally low recruitment, with few seedlings per hectare compared with the abundance of saplings and adults. The probability of finding O. europaea individuals was influenced by biotic (woody species richness) and abiotic (soil depth, slope) environmental conditions and human disturbance (logging intensity), but the direction, strength and shape of the relationships differed between seedling, sapling and adult life stages, indicating ontogenetic niche shifts. All life stages showed a positive relationship with elevation. The observed environmental niches of the different lifestages of O. europaea, and their association with human disturbance levels, should be considered when conservation strategies are developed for this species. Human disturbance in terms of logging decreases the abundance of saplings, but may facilitate emerging seedlings through creation of gaps with improved light conditions. Recruitment is, however, very low in the study area, and seedlings should be protected from browsing to enhance survival. Woody species richness in general should be conserved to optimize conditions also for O. europaea saplings.

Rapid climate warming is altering Arctic and alpine tundra ecosystem structure and function, including shifts in plant phenology. While the advancement of green up and flowering are well-documented, it remains unclear whether all phenophases, particularly those later in the season, will shift in unison or respond divergently to warming. Here, we present the largest synthesis to our knowledge of experimental warming effects on tundra plant phenology from the International Tundra Experiment. We examine the effect of warming on a suite of season-wide plant phenophases. Results challenge the expectation that all phenophases will advance in unison to warming. Instead, we find that experimental warming caused: (1) larger phenological shifts in reproductive versus vegetative phenophases and (2) advanced reproductive phenophases and green up but delayed leaf senescence which translated to a lengthening of the growing season by approximately 3%. Patterns were consistent across sites, plant species and over time. The advancement of reproductive seasons and lengthening of growing seasons may have significant consequences for trophic interactions and ecosystem function across the tundra., Nature Communications, 12 (1), ISSN:2041-1723

Understanding the effects of landscape fragmentation on global bumblebee declines requires going beyond estimates of abundance and richness and evaluating changes in community composition and trophic and competitive interactions. We studied the effects of forest fragmentation in a Scandinavian landscape that combines temperate forests and croplands. For that, we evaluated how forest fragmentation features (patch size, isolation and shape complexity, percentage of forest in the surroundings) as well as local flowering communities influenced bumblebee abundance, richness and community composition in 24 forest patches along a fragmentation gradient. In addition, we assessed the effect of fragmentation on bumblebee–plant network specialization (H2′), and potential inter- and intraspecific competition via shared plants. Patch isolation was associated with lower bumblebee abundance, whereas flower density was positively related to both bumblebee abundance and richness. Overall, forest fragmentation reduced the abundance of forest-specialists while increasing the abundance of open-habitat species. Patches with complex shapes and few flowers showed more generalized bumblebee–plant networks (i.e., fewer specific interactions). Patch shape complexity and the percentage of forest also modified inter- and intraspecific competitive interactions, with habitat generalists outcompeting forest specialists in fragmented areas. Understanding these mechanisms is necessary to anticipate to the impact of forest fragmentation on bumblebee decline., This study was supported by the projects 170532/V40 and 11551017, financed by the Norwegian Research Council and the Norwegian University of Life Sciences, respectively. During the writing of this manuscript AL was supported by a Ramón y Cajal (RYC-2015-19034) contract from the Spanish Ministry of Science, Innovation and Universities, the Spanish State Research Agency, European Social Funds (ESF invests in your future) and the University of the Balearic Islands. CGM was supported by project CGL2017-89254-R supported by Feder founds, the Spanish Ministry of Economy and Competitiveness and the Spanish Research Agency (FPI PRE2018-083185, Call 2018). JRP was supported by BIOINTFOREST funded by “Obra Social la Caixa” and “Fundación Caja Navarra” in the framework of UPNA's “Captación de Talento” program.

Habitat fragmentation threatens plant and pollinator communities, as well as their interactions. However, the effects of landscape fragmentation on the pollination of wild plant species are not well understood yet, partly because there are many correlated features in fragmented landscapes (e.g., decreased patch size, increased isolation, and patch complexity) whose influences are difficult to disentangle. Using a structural equation modeling approach, we assessed the direct and indirect effects of landscape fragmentation (patch size, isolation and complexity, percentage of surrounding land in forest) on the abundance, functional‐group richness, and evenness of pollinators of 24 habitat fragments within an agricultural landscape in Southern Norway. In addition, we studied how these variables affected visitation rates (visits per flower) and seed production (seed set, seed mass) in the four most abundant plant species in the area. Flower abundance was higher in larger and complex patches and decreased with the percentage of forest in the surroundings, while flower richness increased with patch complexity. We found a direct negative relationship between patch complexity and the overall number of pollinator visits that the habitat fragments received. Apart from this direct landscape effect, pollinator visits were mostly affected by the floral communities, with overall flower abundance and richness increasing both total number of pollinator visits and pollinator‐group richness, and flower richness having an additional negative influence on pollinator‐group evenness. Interestingly, we did not find any direct link between visitation rates and reproductive success for any of the study plant species. Instead, several landscape variables directly affected species seed production, although the effects of landscape on seed production were highly species specific. Patch complexity had a negative effect on seed production in two of the four focal species, while other components of the landscape had species‐specific effects. Increasing fragmentation of agricultural landscapes affects pollination interactions at the community level and the reproduction of wild plants. However, understanding the effects of fragmentation on seed production requires going beyond estimating visitation rates, since landscape effects on plant reproduction are not always related to overall interaction frequencies., This study was supported by the projects 170532/V40 and 11551017, financed by the Norwegian Research Council and the Norwegian University of Life Sciences, respectively. During the writing of this manuscript AL was supported by a Ramón y Cajal (RYC‐2015‐19034) contract from the Spanish Ministry of Science, Innovation and Universities, the Spanish State Research Agency, European Social Funds (ESF invests in your future) and the University of the Balearic Islands, and by project CGL2017‐89254‐R, financed by the Spanish Ministry of Economy and Competitiveness, Feder funds and the Spanish Research Agency.

Agricultural practices to improve yields in small‐scale farms in Africa usually focus on improving growing conditions for the crops by applying fertilizers, irrigation, and/or pesticides. This may, however, have limited effect on yield if the availability of effective pollinators is too low. In this study, we established an experiment to test whether soil fertility, soil moisture, and/or pollination was limiting watermelon (Citrullus lanatus) yields in Northern Tanzania. We subjected the experimental field to common farming practices while we treated selected plants with extrafertilizer applications, increased irrigation and/or extra pollination in a three‐way factorial experiment. One week before harvest, we assessed yield from each plant, quantified as the number of mature fruits and their weights. We also assessed fruit shape since this may affect the market price. For the first fruit ripening on each plant, we also assessed sugar content (brix) and flesh color as measures of fruit quality for human consumption. Extra pollination significantly increased the probability of a plant producing a second fruit of a size the farmer could sell at the market, and also the fruit sugar content, whereas additional fertilizer applications or increased irrigation did not improve yields. In addition, we did not find significant effects of increased fertilizer or watering on fruit sugar, weight, or color. We concluded that, insufficient pollination is limiting watermelon yields in our experiment and we suggest that this may be a common situation in sub‐Saharan Africa. It is therefore critically important that small‐scale farmers understand the role of pollinators and understand their importance for agricultural production. Agricultural policies to improve yields in developing countries should therefore also include measures to improve pollination services by giving education and advisory services to farmers on how to develop pollinator‐friendly habitats in agricultural landscapes., Extra pollination increased the probability of a watermelon plant producing a second sellable fruit as well as fruit sugar content. Moreover, we learnt that, increased number of pollinators does not necessarily increase fruit set. Finally, we learnt that, increased fertilizer and watering/irrigation did not influence yield quality or quantity.

Understanding the relationship between biotic, abiotic and disturbance factors in dry degraded forests is crucial for effective conservation of endangered plant species. We studied the relationship between two locally endangered tree species, Olea europaea subsp. cuspidata and Juniperus procera, and environmental conditions in the Hugumburda dry Afromontane forest in Northern Ethiopia. We surveyed species richness of woody plants, herbaceous plant cover, soil and human disturbance factors from 70 plots (20 m × 20 m). The abundance of both species was positively correlated with each other, and with woody species richness and elevation. Moreover, the biomass of both species correlated positively with total tree biomass and number of O. europaea cut stumps. The positive relationship between O. europaea trees and cut stumps suggests that illegal selective logging is taking place in O. europaea-dominated areas. Based on the observed relationships we predict that conserving woody species may result in an increase in the abundance of both O. europaea and J. procera in the forest.

Aim Because the ecological similarity between species is expected to increase with relatedness and that speciation is a local process, phylogeny may provide a common measure for the influence of ecological and biogeographic processes on community assembly. We tested if similarities in floral visitation patterns within communities and the phylogenetic beta-diversity among communities were related to the position of bees within the bee phylogeny. Location Global. Methods We combined a genus level phylogeny with within-genera phylogenies for the bee species occurring within 18 globally distributed bee-flower networks. Networks consisted of a matrix of bee and plant species and information on whether or not a bee species had been observed visiting flowers of a given plant species. For each network, we used Abouheif's Cmean to test if the similarity in floral associations (niche similarity) between bees and the number of plant species visited displayed a significant phylogenetic signal. To test if biogeography influenced the relatedness among species within networks we tested if the phylogenetic beta-diversity increased with geographical distance and dissimilarity in climatic conditions among networks. Results We found a phylogenetic signal for niche similarity in only 50% of the bee-flower networks. However, network size influenced the likelihood of observing a phylogenetic signal and for seven of the eight bee-flower networks with >20 species it was statistically significant. On a global scale, the phylogenetic beta-diversity increased with geographical distances and with climatic dissimilarity between sites. Main conclusions Bee communities are structured by processes of speciation and migration so that regional species pools are dominated by a subset of the global phylogenetic clades, resulting in increasing phylogenetic beta-diversity with geographical distance. Moreover, ecological filtering processes operating at both local (floral resource use) and continental (climatic constraints) scale determine the distribution of species among resources and geographical regions. The assembly of bee communities should therefore be understood as a product of both biogeographic and community ecological processes.

Protected areas generally occur within a matrix of intensively human-modified landscapes. As a way to maintain the biodiversity in these areas, enclosure by fencing is often preferred. This strategy, however, is costly and little is known about the effectiveness of the alternative of unfenced borders on the vegetation and fauna. The objectives of this study are to assess whether there is a distinct difference in biodiversity and composition of plants and mammals between the protected Lake Mburo National Park and the adjacent ranchlands across an unfenced border and to determine the associations between vegetation and faunal species over the same border. We recorded herbaceous vegetation, woody vegetation, and mammal species composition in plots 300 to 500 m away from the border both inside the protected area and in the adjacent ranchlands. The species composition of herbs and mammals in the protected area differ from the adjacent ranchlands, but there is no difference for trees and shrubs. After accounting for land-use type, distance from the border did not significantly account for any additional variation. We also find a correlation between the species composition of vegetation and fauna. Our results suggest that unfenced borders around protected areas create a clear effect.

In the version of this Article originally published, the following sentence was missing from the Acknowledgements: “This work was supported by the Norwegian Research Council SnoEco project, grant number 230970”. This text has now been added.

Understanding how biotic interactions and abiotic conditions affect plant performance is important for predicting changes in ecosystem function and services in variable environments. We tested how performances of Astragalus rigidulus and Potentilla fruticosa change along gradients of biotic interactions (represented by plant species richness, abundance of the dominant plant species Kobresia pygmaea, and herbivory intensity) and abiotic conditions (represented by elevation, aspect, and slope steepness) across a semi-arid landscape in central Tibet. Redundancy analyses showed that the biotic variables explained 30 and 39 % of the variation in overall performance of A. rigidulus (P = 0.03) and P. fruticosa (P = 0.01), respectively. Abiotic variables did not contribute significantly to variation among A. rigidulus populations. Plant size decreased with species richness in both species and was larger on south- rather than north-facing slopes. Reproductive effort for both species was significantly negatively related to the abundance of K. pygmaea and both species had larger reproductive effort on south- rather than north- and west-facing slopes. The proportion of biomass allocated to sexual reproduction in P. fruticosa was negatively correlated with K. pygmaea abundance and herbivory intensity. The population density of P. fruticosa was positively related to elevation, species richness, and K. pygmaea abundance. We conclude that plant performance at a local scale was more strongly related to biotic than abiotic conditions, but different components of plant performance responded differently to predictor variables and the responses were species-specific. These findings have important implications for rangeland management under changing environmental conditions.

Motivation The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene. Main types of variables included The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record. Spatial location and grain BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km2 (158 cm2) to 100 km2 (1,000,000,000,000 cm2). Time period and grain BioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year. Major taxa and level of measurement BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates. Software format .csv and .SQL., Global Ecology and Biogeography, 27 (7), ISSN:1466-822X, ISSN:1466-8238

Dominant woody species can determine the structure and composition of a plant community by affecting environmental conditions experienced by other species. We explored how dominant tree species affect the tree species richness, diversity, evenness and vertical structural heterogeneity of non-dominant species in wet and dry miombo woodlands of Tanzania. We sampled 146 plots from eight districts with miombo woodlands, covering a wide range of topographic and climatic conditions. We recorded 217 woody plant species belonging to 48 families and 122 genera. Regression analysis showed significant negative linear associations between tree species richness, relative species profile index of the non-dominant and the relative abundance of the dominant tree species (Brachystegia spiciformisandBrachystegia microphyllain wet, andBrachystegia spiciformisandJulbernardia globiflorain dry miombo woodlands). Shannon diversity and evenness had strong non-linear negative relationships with relative abundance of dominant tree species. A large number of small individual stems from dominant and non-dominant tree species suggesting good regeneration conditions, and intensive competition affecting survival. We suggest that dominant miombo tree species are suppressing the non-dominant miombo tree species, especially in areas with high recruitments, perhaps because of their important adaptive features (extensive root systems and ectomycorrhizal associations), which enhance their ability to access limited nutrients.

Summary Power line clearings are edge-creating disturbances in landscapes world-wide, but there have been few studies on their bordering vegetation. Our aim was to quantify edge effects on plant communities along such clearings in Norway and to identify factors that influence these edge effects. We surveyed understorey plant communities on either side of the power line clearing–forest edge at 51 sites, along four parallel transects at each site. Each transect had four plots located, respectively, in the clearing centre, clearing edge, forest edge and forest. We quantified the magnitude of edge effects (MEE) on either side by comparing edges with their corresponding ‘non-edge’ reference habitats. We also measured differences in species composition across the edge (clearing edge vs. forest edge). Habitat characteristics were sampled at plot and site level and from digital maps. Differences in species composition were greater between clearing centres and clearing edges than between forests and forest edges. Differences in species composition across the edge increased with edge contrast and forest productivity. Edge effects on species composition into the forest were smallest along north-facing edges, whereas those in the clearings increased with power line age. Species richness increased slightly towards the edge in forests but decreased considerably towards the edge in clearings. The direction and MEE on either side differed among functional groups. Edge contrast and edge aspect were the prime factors influencing the MEE into forests, whereas in clearings, these were influenced principally by tree regrowth in the clearings and by forest productivity. Synthesis and applications. Edge effects on plant communities bordering power line clearings were determined by factors that can be influenced by planners and managers. For existing power lines, management plans should differentiate between the following: (i) clearings through high conservation value forests, where edge effects into the adjacent forest should be limited; (ii) clearings that can act as replacement habitat for cultural landscape species, where maintaining open-canopy habitats should be prioritized; and (iii) ‘business-as-usual’ clearings, where continuing the current practice of cutting every 5–10 years is recommended.

Understanding how carbon storage and tree diversity are related in forests and woodlands is crucial for a sustainable flow of ecosystem goods and services. The goal of this study was to determine how tree species richness, evenness and environmental factors influence aboveground live tree carbon stocks (AGC) in two tropical vegetation types in Tanzania. We surveyed trees and sampled soil from 222 vegetation plots (20 m × 40 m) in montane forests (n = 60) and miombo woodlands (n = 162). We used a multimodel inference approach to determine how AGC related to tree species richness, evenness and environmental factors, and linear mixed effect models to test the role of tree sizes on the AGC-richness and evenness associations. AGC were related unimodally to tree species richness and evenness in the montane forest. Likewise, AGC in the miombo woodlands was positively related to tree species richness. AGC from small trees were related unimodally to tree species richness in both vegetation types. Apparently the AGC had both monotonically increasing and decreasing associations with all abiotic environmental factors in both vegetation types. We emphasize that both tree size, number of multi-stemed trees and environmental factors have an important role in determining how AGC are related to richness and evenness. Finally, management of montane forests and miombo woodlands of Tanzania to enhance ecosystem benefit, such as AGC, will require strategies that consider tree sizes, tree species richness, evenness and underlying environmental and disturbance factors.

Human influences affect plant species diversity and composition in many tropical forest ecosystems. We assess the effects of human use of woody plants on plant species composition and diversity in an intensively used open-access forest in Northern Ethiopia, and compare these community attributes with those of relatively intact forest patches. In each of 90 20 × 20 m plots in the open-access forest, we counted the number of woody plant species in different growth stages, and compared with those of 48 same-sized plots in nearby intact forest patches. Forest utilisation resulted in major shifts in dominance, with the dominant species in relatively intact forests being absent in open-access forest, whereas those species dominant in the open-access forest were absent from intact forests. Open-access forest had a lower total number of species, individuals and beta diversity than relatively intact forests. Intensive forest utilization has resulted in the dominance of disturbance-tolerant native and invasive species. Opuntia ficus-indica, regarded as a problem weed in Ethiopia, was abundant in the open-access forest. Dominance of a few species in the open-access forest could cause local and landscape-scale species loss. Relatively intact forest patches are therefore important for biodiversity conservation and ecological restoration in northern Ethiopia.

Summary1. Pollinator decline causes great concern because reduced pollinator availability may negativelyaffect plants’ seed production and in turn influence seedling recruitment and densities of plant popu-lations.2. We used a novel experimental approach that simulates pollinator decline to assess the effects of a4-year reduction in pollinator availability on reproduction and recruitment in two common Europeanherbs, Centaurea jacea and Leucanthemum vulgare.3. The experiment strongly reduced visitation rates (by 59%) and seed set (by 23%) in Leucanthe-mum, but this did not cause reduced seedling recruitment, suggesting that other factors, such aswater availability or the existence of a seed bank, are important for recruitment in this population ofLeucanthemum.4. The experiment also significantly reduced visitation rates to Centaurea (by 33%), but did notaffect seed set or seedling recruitment. In this species, however, seed set increased with visitationrates and local recruitment increased with seed production, indicating that a consistent pollinatordecline may negatively affect Centaurea population densities.5. Synthesis. Our experiment reduced pollinator availability without artificially affecting qualitycomponents of the pollination process. Therefore, this approach may represent a realistic simulationof a pollinator decline. To our knowledge, this is the first study that uses an experimental reductionin pollinator visitation to assess its effects on population recruitment in plants. This study shows thata large pollinator decline may affect population densities, but only in populations where seedlingrecruitment is limited by seed production. Our results also highlight the importance of going beyondvisitation rates and seed production to study the impact of pollinator decline on plant populations.Key-words: Centaurea jacea, Leucanthemum vulgare, pollinator loss, reproductive ecology, seedset, seed weight, seedling density, visitation rateIntroduction

Discovering temperature effects on the performance of tundra plants is important in the light of expected climate change. In this 4-year study on alpine Ranunculus acris, I test the hypothesis that temperature influences flowering phenology, reproductive success, growth, population dynamics, and phenotypic selection on quantitative traits, by experimental warming using open-top chambers (OTCs). Warming significantly advanced flowering phenology in only one season. Seed number and weight were significantly increased by warming during the first three seasons, but not in the fourth. Plants inside OTCs produced bigger leaves than control plants in the fourth season, but leaf number was unaffected by the OTC treatment. Despite increased seed number and weight, the density of flowering plants decreased inside OTCs compared to control plots, possibly because of a higher graminoid cover inside OTCs. Phenotypic-selection regression showed a significant selection differential and gradient in the direction of larger leaf sizes in control plants, whereas no selection on leaf size was detected on warmed plants. The direction and strength of selection on flowering time, flower number, and leaf number did not differ between control and warmed plants. The results suggest that increased reproductive output of R. acris may not be sufficient to maintain current population density under a denser vegetation cover.

The species composition within communities is highly dependent on the rate of species immigration and whether immigrating species possess the functional traits required by the prevailing environmental conditions. Once established, random fluctuations in birth and death rates may reduce the diversity of ecologically equivalent species if local populations are not replenished by immigrating individuals. Consequently, three key processes drive community assembly: dispersal limitation, ecological filtering, and ecological drift. However, disentangling the relative contribution of these processes remains a challenge in community ecology. We used a binomial generalized linear mixed model to test whether the occurrences of solitary bees within 46 communities in southeast Norway were driven by (1) dispersal limitation, that is, the geographic distance to the nearest site where conspecifics occurred; (2) ecological filtering, that is, if forb species richness selected for non-Ericaceae-affiliated species; and (3) ecological drift, that is, if small, isolated communities were dominated by regionally common species. The regression slopes from the model for each potential driver of community composition were compared with those expected under a null model, in which species were treated as ecologically equivalent. Both dispersal limitation and ecological filtering influenced the probability of species occurring within communities. The occurrence of species decreased with elevation, and this relationship depended on the relative commonness of species and their floral preferences. For non-Ericaceae-affiliated species, the patterns of occurrence mirrored that expected under the null (neutral) model, resulting in the same patterns as would be expected under ecological drift. In contrast, the response of Ericaceae-affiliated species differed from what would be expected from the null model. Our results also indicate that processes leading to neutral dynamics in species compositions drive a large part of the gradient in species richness in Norwegian bee communities. These processes seem related to sampling effects so that large and interconnected communities have a higher probability of including regionally rare species than small, isolated communities. Our results suggest that targeting habitats—where the influence of ecological filtering is expected to be greater than that of neutral dynamics—can increase the success of habitat management plans aimed at promoting rare species.

Human disturbance, natural environmental conditions and seed dispersal are often inferred as important drivers of plant community richness and diversity in wetland ecosystems. However, plant functional groups within a plant community have different environmental requirements and may respond differently to human disturbance. Therefore, the understanding of the relative importance of these variables in determining community and functional groups richness and diversity is important for improved management and wise use of wetland resources. We collected data on vegetation and environmental conditions, human disturbance and seed dispersal from 60 plots of 20 × 50 m, to identify variables that potentially affect total species richness and Shannon-Wiener diversity of the grassland plant community at the Kilombero Valley wetland, Tanzania. We further tested whether important predictor variables for species richness and Shannon-Wiener diversity differ among graminoid, forb and shrub functional groups. Overall, our results suggest that environmental conditions, human disturbance and seed dispersal determine spatial variation in species richness and Shannon-Wiener diversity of the grassland vegetation. The total richness and Shannon-Wiener diversity and the richness of shrubs decreased with distance from the Kilombero River, whereas the total Shannon-Wiener diversity and the Shannon-Wiener diversity of graminoids decreased with the increase in grazing intensity. Shrub species richness was related to the spatial position of plots and decreased with total organic carbon of soil. Current increase in human disturbances through cattle husbandry and changes in natural environmental conditions (e.g. through water diversion and drainage) should be discouraged in order to restore and sustain biodiversity of the Kilombero wetland.

The negative effects of alien plant species on ecosystem structure and functions are increasingly recognised, and efforts to control these species are vital to restore degraded ecosystems and preserve biodiversity. However, we lack a full understanding of factors that determine alien species invasions along spatial gradients in herbaceous vegetation of tropical systems. We therefore examined the effects of community properties, environmental variables and human-related disturbance factors on the invasion of the alien grass Echinochloa colona (L.) Link at small- and large scales in the Kilombero Valley wetland, Tanzania. Generalized additive mixed models showed that E. colona abundance on a small scale was negatively related to above-ground biomass and evenness of resident species, whereas E. colona abundance was positively related to grazing intensity. On a large scale, biomass (negatively related to E. colona abundance) and distance to river (positive) were important in explaining E. colona abundance. These findings support the assertion that different factors may contribute to the invasion of alien plant species at different spatial scales, as also reported in many temperate systems. Overall, our results show that successful invasion of alien species is a function of plant community properties, human-related disturbance and favourable environmental conditions. Effective management strategies should consider mitigations that can increase the biomass and evenness of native species and a reduction of grazing pressure to restore the wetland and conserve biodiversity.

A central goal in ecology is to develop theories that explain the diversity and distribution of species. The evolutionary history of species and their functional traits may provide mechanistic links between community assembly and the environment. Such links may be hierarchically structured such that the strength of environmental filtering decreases in a step-wise manner from regional conditions through landscape heterogeneity to local habitat conditions. We sampled the wild bee species assemblages in power-line strips transecting forests in south-eastern Norway. We used altitude, landscape diversity surrounding sites and plant species composition, together with total plant cover as proxies for regional, landscape and local environmental filters, respectively. The species richness and abundance of wild bees decreased with altitude. The reduction in species richness and abundance was accompanied by a phylogenetic clustering of wild bee individuals. Furthermore, regional filters followed by local filters best explained the structure of the functional species composition. Sites at high altitudes and sites with Ericaceae-dominated plant communities tended to have larger bees and a higher proportion of social and spring-emerging bees. When Bombus species were excluded from the analysis, the proportion of pollen specialists increased with the dominance of Ericaceae. Furthermore, we also found that the taxonomic, phylogenetic and functional compositional turnover between sites was higher in the northern region than in the southern part of the study region. Altogether, these results suggest that regional filters drive the species richness and abundance in trait-groups whereas local filters have more descrete sorting effects. We conclude that the model of multi-level environmental filters provides a good conceptual model for community ecology. We suggest that future studies should focus on the relationship between the biogeographical history of species and their current distribution, and on the assumption that closely related species do indeed compete more intensely than distantly related species.

Failures in the process of pollen transfer among conspecifi c plants can severely impact female reproductive success. Th us, pollen limitation can cause selection on plant mating systems and fl oral traits. Th e relationships between pollen limitation and fl oral traits might be partly mediated by the quantity and identity of pollinator visits. However, very little is known about the relationship between pollinator visits and pollen limitation. We examined the relationships between pollen limitation and fl oral traits at the community level to connect them to community ecology processes. We used 48 plant species from two contrasting communities: one species-rich lowland community and one species-poor alpine community. In addition, we calculated visitation rates and ecological pollination generalization for 38 of the species to examine the relationship between pollinator visitation and pollen limitation at the community level. We found low overall levels of pollen limitation that did not diff er signifi cantly between the alpine and the lowland community. In both communities, species with evolutionary specialized fl owers were more pollen limited than species with unspecialized fl owers. Species ’ visitation rates and selfi ng capability were negatively related to pollen limitation in the alpine community, where pollinators are scarcer. However, fl ower size/number, ecological generalization of plants and fl owering onset had greater eff ects on pollen limitation levels at the lowland community, indicating that the identity of the visitors and plant-plant competitive interactions are more decisive for plant reproduction in this species-rich community. Th ere, pollen limitation increased with fl ower size and fl owering onset, and decreased with ecological generalization, but only in species with evolutionary specialized fl owers. Our study suggests that selection on plant mating system and fl oral traits may be idiosyncratic to each particular community and highlights the benefi ts of conducting community-level studies for a better understanding of the processes underlying evolutionary responses to pollen limitation.

The bees (Hymenoptera: Apiformes) are important pollinators in many ecosystems, but their diversity has declined in Europe during the past century, mainly due to habitat loss. However, some of the habitat requirements of wild bees are met in anthropogenic landscape elements, such as road sides, power-line strips and field edges. Moreover, as the bee species assemblages change throughout the season the habitat requirements of the bee fauna may change accordingly. Understanding such seasonally distinct responses of solitary bees with different phenologies may be of high value for local conservation planning. The purpose of this study was to examine if the habitat quality of field edges for solitary bees change throughout the season, and how this temporal variation relates to local habitat and landscape conditions. By sampling solitary bees in 18 field edges in southeast Norway throughout the season we found that the species richness and abundance of bees was highest in sun exposed field edges, independently of the season. However, we found phenologically distinct responses to the landscape context. Moreover, field edges situated in landscapes with a high proportion of forests and semi-natural landscape elements hosted the most phenologically diverse bee species assemblages. We conclude that in order to fulfil the habitat requirements of bee species assemblages throughout the season, one should conserve and direct habitat restoration schemes towards increasing sun exposure at field edges with a diverse flora and a high proportion of semi-natural areas in the vicinity.

Plant community properties such as species richness, evenness, and composition vary along environmental gradients. Arid and semi-arid ecosystems, such as the central Tibetan Plateau, are thought to be sensitive to changes in temperature and water availability, and also influenced by a long history of herbivore grazing. We used linear mixed effect models and Canonical Correspondence Analysis to explore how plant community properties varied along gradients of elevation, soil moisture, grazing intensity, solar radiation, ground surface roughness (ground concavity), and pika abundance in an alpine meadow ecosystem in central Tibet. We found that species richness increased with elevation. Species evenness increased with soil moisture at lower elevation, but decreased with soil moisture at higher elevation. Species composition was significantly associated with all environmental variables except solar radiation. The abundance of the dominant plant species, K. pygmaea, which is driven primarily by soil m...

Whether invasion of introduced plant species may be aided by certain community properties is poorly understood for species-rich ecosystems, such as tropical montane forests. In Kenya, the non-native tree Fraxinus pennsylvanica has invaded degraded montane forests. We used generalized linear mixed models to examine the relative importance of different community properties to Fraxinus invasion after agricultural abandonment and in the secondary forest. Fraxinus invasion was positively related to plant community species diversity and the abundance of tree saplings, shrubs, ferns, and herbs in the abandoned fallows, but negatively related to the same community properties in the secondary forest. The number of Fraxinus recruits declined with declining propagule pressure in the fallows, but not in the secondary forest. Although adult and saplings of Fraxinus were positively related to community diversity in the fallows, Fraxinus appeared to decrease diversity in the secondary forest. These results show that the success of non-native species invasion and the effects of an invader on the resident community may depend both on properties and degree of disturbance of the community. Plant community diversity and evenness appeared to determine the invasion success by increasing invasibility of the abandoned fallows, but decreasing invasibility of the secondary forest. Our results from a tropical degraded forest emphasize the importance of including habitat characteristics when predicting both the potential of non-native plant invasion and effects of invasives on the particular community.

Petals of the alpine, arctic perennial herb Ranunculus glacialis are retained also during seed maturation, as opposed to most species where the petals wither after they have contributed to insect attraction during anthesis. To assess the adaptive significance of perianth retention after anthesis for annual reproduction, we experimentally removed perianths of R. glacialis and explored its impact on achene surface temperature, the growth rate of achenes, carbon allocation, and seed production. Perianth removal immediately after anthesis decreased achene surface temperature, decelerated the growth of achenes and reduced seed set, compared to plants with intact perianth. Measurement of mass allocation showed no further perianth growth during seed maturation, and a 13C labelling experiment demonstrated that photosynthate allocation to perianths during seed maturation was much smaller than developing achenes. Thus, annual seed production of R. glacialis might be accelerated by perianth retention during seed maturation, while the cost of perianth retention is small compared to that of seed development. In alpine and arctic environments, cold temperatures limit the growth rate of achenes. Hence, the heating of developing achenes by perianth retention might be an adaptive trait that enhances female reproductive success in this arctic, alpine species.

There is growing concern that current pollinator decline will affect the reproduction of plant species, potentially driving a decline in plant population densities. We experimentally tested whether a reduction in flower visitation caused a reduction in fertilization rate in several species, and whether any reduction in fecundity of species depends on their degree of reproductive dependence on pollinators and their attractiveness for pollinators. We recorded visitation rate, fertilization rate, seed weight, flower size and density of nineteen insect-pollinated perennial herbs inside thirty 2 x 2 m dome-shaped cages covered with fishnet (experimental plots) and in thirty control plots in a Norwegian hay meadow. We used a bagging experiment to estimate the ability of the study species to produce seeds in the absence of pollinators. The visitation rate for fifteen of nineteen study species was lower inside cages than outside and only three of the fifteen species showed significantly reduced fertilization rates in the experimental plots. The magnitude of reduction in fertilization rate was positively related to the degree of pollinator dependence, but not to their attractiveness for pollinators or to the reduction in visitation rate. Seed weight was not affected by the experiment. The lack of an overall effect of reduced pollinator visitation on fertilization rate suggests that some species may be robust to a pollinator decline that could increase pollen limitation on plant reproduction. Our results suggest that species with greater pollinator dependence are more vulnerable to pollinator loss, This work was supported by the project 170532/V40, financed by the Norwegian Research Council

Species diversity and interactions vary on a landscape scale and are sensitive to landscape alterations, such as landscape fragmentation and habitat degradation. At the same time, the species position within food webs or mutualistic networks (e.g. generalist or specialist, network hub or peripheral vertex) may affect their ability to persist after perturbations. This study was conducted in a heavily managed boreal forest landscape in southeastern Norway, using study plots situated in forest stands with contrasting disturbance history: old growth forest (least disturbed), young forest (intermediate) and clear cuts (most disturbed). By studying 12 pollination networks with contrasting disturbance history we found that important network descriptors were conserved after perturbation. Link-diversity was higher, both overall and per site, in the more disturbed communities while link-turnover was highest in the least disturbed community. We conclude that despite an increase in diversity in the more degraded habitat, the higher link-turnover in the least degraded, old growth forest, community indicates a homogenization of the plant–pollinator networks as a result of habitat degradation. Finally, we found that the degree (number of interacting partners) and network functional role for particular species changed along the disturbance gradient, though not in any systematic way. We conclude that structural properties of the pollination network are conserved after perturbations, but that particular species’ network functional roles may change.

Woody plant encroachment alters the structure and function of rangeland ecosystems. The objective of this study was to explore the association between woody plant encroachment and various ecosystem properties (i.e. vascular plant species diversity, richness, evenness, soil organic matter, herbaceous biomass, leaf litter and bare ground cover) in a semiarid savanna rangeland, and also to test whether the relationships were influenced by woody species composition, elevation and site. We carried out a vegetation survey in four rangeland sites in the lower Omo region of southwestern Ethiopia, and regressed each one of the ecosystem properties, separately, against woody plant density, elevation and site using multiple linear regressions. We found that vascular plant species diversity, richness and evenness increased with woody plant density, most likely due to increased spatial heterogeneity and soil microclimate improvement. Bare ground cover increased significantly, whereas herbaceous biomass and soil organic matter did not respond to woody encroachment. In a subsequent investigation, we used a redundancy analysis to assess whether ecosystem properties were influenced by the identity of encroaching woody plant species. Species diversity and richness responded positively to Lannea triphylla, whereas leaf litter responded positively to Grewia tenax and G. villosa. Our findings suggest that woody plant encroachment in a semiarid rangeland does alter ecosystem properties. However, its impact is highly variable, influenced by a set of factors including the level of encroachment and identity of encroaching woody species.

Low nitrogen (N) supply is a limiting factor for plant growth in most terrestrial ecosystems. N-fixing legumes therefore have the potential to facilitate surrounding vegetation by increasing soil N levels. This effect should be especially pronounced in low-productivity habitats where ambient soil N levels are low, such as in alpine areas. We examined whether plant species composition, community diversity measures, and soil N levels differed with and without the presence of two alpine legumes, Oxytropis lapponica (Wahlenb.) Gay and Astragalus alpinus L., in a Dryas octopetala heath at Finse, Norway. Species composition and richness differed between plots with and without Oxytropis in one of two study sites, as other plant species were positively associated with the legume. None of the measured community properties differed between plots with and without the presence of Astragalus. The contrasting influence of the two legume species corresponds to our findings of higher soil N levels below Oxytropi...

Spatial and temporal isolation and environmental variability are important factors explaining variation in plant species composition. The effect of fragmentation and disturbance on woody plant species composition was studied using data from 32 remnant church forest patches in northern Ethiopia. The church forests are remnants of dry Afromontane forest, embedded in a matrix of intensively used crop and grazing lands. We used canonical correspondence analysis and partial canonical correspondence analysis to analyze the effects of fragmented and isolated forest-patch identity, environmental and spatial variables on woody plant species composition in different growth stages. The dominance of late successional species was higher at the adult growth stage than seedlings and saplings growth stages. In the adult stages, late successional species like Olea europaea subsp. cuspidate had high frequency of occurrence. Forest patch identity was more important in explaining woody plant assemblages than environmental and spatial variables. For all growth stages combined, environmental variables explained more of the explained total fraction of variation in species composition than spatial variables. Topographic variables best explained variations in species composition for saplings, adults and all growth stages combined, whereas the management regime was most important for seedlings species composition. Our results show that in a matrix of cultivated and grazing land, fragmented and isolated forest patches differ in woody plant species assemblages. Some species are widely distributed and occurred in many patches while other occurred only in one or a few forest patches. Thus, our results indicate that remnant forest patches are important for preserving rare plant species and therefore management practices should focus on minimizing disturbance to the church forests and if possible increase church forest patch size.

Woody encroachment is one of the several factors aggravating rangeland degradation in arid and semiarid areas. The goal of this study is to improve our understanding about the relationship between woody encroachment and its potential drivers by analyzing the temporal and spatial pattern of land-cover changes in the lower Omo region of southern Ethiopia. We used a combination of multi-temporal images, as well as climatic and demographic data for the analysis. Between 1985 and 2010 woody vegetation cover increased by 30.6% in the pastoral landuse type, while declining by 4.4% in the semipastoral areas. The increment was negatively associated with altitude and browser livestock density. However, contrary to the traditional presumption, it was not associated with grazer livestock density. Moreover, woody encroachment was higher in remote sites, farther from rivers and towns, where there is relatively lower human activities and livestock disturbance. The finding suggests the ecological significance of landuse type and livestock browsing to regulate the dynamics of woody vegetation in disturbance-adapted rangelands. Thus, a careful introduction of native larger browsers into woody encroached pastoral areas may help to facilitate rapid ecosystem recovery.

Grazing is regarded as one of the most important factors influencing rangeland ecosystems. Many previous studies have used indirect measures (proxies) of grazing intensity, such as the distance from congregation areas and the number of herbivore excreta, to estimate effects of grazing on vegetation parameters in rangeland ecosystems. However, little is known about how such proxies reflect the true grazing intensity, and if their suitability is consistent across landscape conditions. We measured grazing intensity based on the amount of plant ramets being grazed in 75 plots positioned across a rangeland landscape in central Tibet. Several grazing intensity proxies (distance from pastoral camp sites, number of yak dung patches (old and fresh), sheep and goat dropping piles, and pika (Ochotona curzoniae) burrows (active and abandoned)) were also measured in each plot. Regression models were used to examine the suitability of these proxies in predicting our measure of real grazing intensity. None of t...

Pollinator decline can disrupt the mutualistic interactions between plants and pollinators and potentially affect the maintenance of plant populations. However, there is still little knowledge on how changes in pollinator abundance can affect seedling recruitment, which is essential for population persistence. We experimentally simulated a community-wide reduction in pollinator availability during four years to examine its effects on seedling recruitment in 10 perennial herbs in a Norwegian hay meadow. Our experimental reduction in pollinator availability significantly reduced community-wide seedling diversity. Overall seedling abundance was also consistently lower under reduced pollinator availability, although this effect was only significant when the most abundant plant species in the community was excluded from the analysis. Despite an overall negative effect on seedling abundance, the experimental reduction in pollinator availability had contrasting effects on individual plant species. This tended to cause a larger change in seedling species composition in the experimental than in the control plots after the four study years. Our study demonstrates for the first time a direct causal link between reduced pollinator availability and reduced plant diversity and abundance.

Global climate change is predicted to have large impacts on the phenology and reproduction of alpine plants, which will have important implications for plant demography and community interactions, trophic dynamics, ecosystem energy balance, and human livelihoods. In this article we report results of a 3-year, fully factorial experimental study exploring how warming, snow addition, and their combination affect reproductive phenology, effort, and success of four alpine plant species belonging to three different life forms in a semiarid, alpine meadow ecosystem on the central Tibetan Plateau. Our results indicate that warming and snow addition change reproductive phenology and success, but responses are not uniform across species. Moreover, traits associated with resource acquisition, such as rooting depth and life history (early vs. late flowering), mediate plant phenology, and reproductive responses to changing climatic conditions. Specifically, we found that warming delayed the reproductive phenology and decreased number of inflorescences of Kobresia pygmaea C. B. Clarke, a shallow-rooted, early-flowering plant, which may be mainly constrained by upper-soil moisture availability. Because K. pygmaea is the dominant species in the alpine meadow ecosystem, these results may have important implications for ecosystem dynamics and for pastoralists and wildlife in the region.

Competition and facilitation in species interactions attract much attention in ecology, but their relative importance has seldom been evaluated in a community context. We assessed competitive and facilitative interactions for pollinator visitation among co-flowering species in a plant community, investigated the subsequent consequences for plant reproduction, and investigated whether effects could be trait-based. We removed the flowers of two species attractive to pollinators, in two separate experiments and assessed the effects on pollinator visitation rates and components of reproductive success in 11 co-flowering focal herb species. Overall, most focal species appear not to interact with the removal species with respect to pollinator visitation and subsequent reproduction (neutral interactions). Three focal species in the community had significantly higher reproductive responses (fruit production and seed weight) in the presence of the attractive removal species (facilitative interactions), but species interaction effects were less pronounced in species' flower visitation rates. A community-wide meta-analysis demonstrated that the two experiments did not have a significant effect on either facilitation or competition, and that there was no overall correlation between effect sizes for visitation and reproduction. Based on species-specific responses, it seems likely that floral traits such as similar flower colors contribute to interspecific facilitation of pollinator visitation and, in particular, that high pollinator dependence for plant reproduction, and associated pollen limitation, may contribute to subsequent interaction effects on reproduction in the focal species.

Understanding driving factors of spatial heterogeneity in plant species composition and functional structure is a key step towards wetland ecosystems restoration and biodiversity conservation. We surveyed 60 randomly selected plots of 20 × 50 m each and collected 12 explanatory variables to understand potential impacts of natural environmental conditions, human disturbance and spatial position of plots variables on plant functional groups (PFGs) and species composition within grasslands of the Kilombero Valley Floodplain wetland, Tanzania. Ordination analyses were used to identify important vegetation gradients and establish significant natural environmental conditions, human disturbance and spatial position of plots correlates. Partial redundancy analysis (RDA) and partial canonical correspondence analysis (CCA) were used to determine the individual and shared effects of these three sets of explanatory variables on the PFGs and species composition, respectively. In total, 115 plant species, including 22 weed and 3 invasive species, and five PFGs were registered. Annual graminoid was the most abundant, whereas perennial forb the least abundant PFG with 50 and 1 % relative covers, respectively. Overall, spatial position, altitude, total organic carbon, cow dung, distance to the river and distance to kraal (cattle enclosure near human settlement commonly made of wood materials for animal protection) were important descriptors of both PFGs and overall species composition. Separate CCA of only weed and invasive plant species showed that some species, particularly the invasive Polygala paniculata were strongly associated with cow dung, indicating that present increase in cattle numbers may result in future problems associated with this species. Intensification of human activities and alteration of natural environmental conditions associated with these factors should be discouraged to maintain plant species composition and functional structure for wetland restoration and sustainable biodiversity conservation.

35 Abstract Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation - and associated ecosystem consequences - have the potential to be much greater than we have observed to date.

Cultivation of annual crops in the initial stage of reforestation has been commonly practiced in the tropics. In recent decades, however, cultivation of such areas has been discontinued, resulting in widespread abandoned settlements. In this article we used a former forest village settlement in Kenya, which had been cleared, cultivated and then abandoned, to study how natural vegetation recovers after such disturbances. Species richness, abundance, and composition of tree seedlings, saplings, adult trees, shrubs, and herbs were recorded in different zones, from a heavily degraded zone in the center of the settlement, through less disturbed transition zones (TZs), and in the surrounding secondary forest (SF). Species richness and abundance of tree seedlings, saplings, and adult trees increased gradually from the heavily degraded zone to the SF, whereas shrub and herb richness were the same for TZs and SF and abundance was lowest in the SF. Total species richness was highest in the SF. Some pioneer tree species were highly associated with the TZs, whereas sub-canopy tree species were associated with the SF. A group of tree species were not particularly associated with any of the four zones. Thus, these species might have good potential as restoration species. The results of our study contribute to the knowledge of natural regeneration in general, and of individual species characterizing the different stages of recovery of abandoned settlements in particular. Such information is urgently needed in designing ecologically sound management strategies for restoring abandoned forest settlements in tropical areas.

1. Understanding how foraging decisions take place at the local scale is relevant because they may directly affect the fitness of individual plants. However, little is known about how local diversity and density affect the foraging behaviour of most pollinator groups. 2. By introducing two potted plant species (Salvia farinacae and Tagetes bonanza) into two populations of Taraxacum officinale, we investigated how plant identity, the mixtures of these plant species, and total plant density affected the attraction to and the foraging within a patch for six pollinator groups. 3. The foraging behaviour was mainly driven by the availability of the preferred plant species, and secondly by patch diversity and density. In general, dense patches and those containing the three-species mixture were preferred by all insect groups for arrival, although muscoid and hover flies responded less to local floral composition than bees. Local diversity and density had, however, a weaker effect on foraging behaviour within patches. Site dependence in response to floral treatments could be attributable to differences between sites in pollinator assemblage and Taraxacum density. 4. Studies like ours will help to understand how foraging decisions occur at the local scale and how foraging patterns may differ between pollinators and sites.

PREMISE OF THE STUDY. The fitness of plants depends on their immediate biotic and abiotic environmental surroundings. The floral neighborhood of individual plants is part of this immediate environment and affects the frequency and behavior of their pollinators. However, the interactions among plants for pollination might differ among populations because populations differ in floral densities and pollinator assemblages. Despite that, manipulative experiments of the floral neighborhood in different populations with a specific focus on pollinator behavior are still rare. METHODS. We introduced mixtures of two species (Salvia farinacae and Tagetes bonanza) in two populations of Taraxacum officinale and examined their effect on pollinators' foraging behavior on Taraxacum. KEY RESULTS. The effects of the heterospecific neighborhood differed among pollinator groups and between the two populations. Only honeybees consistently preferred both the most diverse (containing three species) and completely pure patches of Taraxacum in both populations. We found a strong and positive effect of patch diversity on visitation to Taraxacum in one population, whereas in the other population either no effect or a negative effect of plant diversity occurred, which we attribute to differences between populations in the ratio of pollinators to inflorescences. Pollinator visitation consistently increased with local Taraxacum density in both populations. CONCLUSIONS. Our study shows that a similar local neighborhood can differentially affect the frequency and foraging behavior of pollinators, even in closely situated populations. Experimental studies conducted in several populations would contribute to determine which factors drive the variation in pollination interactions among populations.

The number of pollinators of a plant species is considered a measure of its ecological generalization and may have important evolutionary and ecological implications. Many pollination studies report inter-annual fluctuations in the composition of pollinators to particular species. However, the factors causing such variation are still poorly understood. Here we investigate how flowering duration and plant and pollinator assemblages influenced the inter-annual changes in the functional gener alization level of the 20 most common plant species of a semi-natural meadow in southern Norway. We also studied the extent to which changes in generalization levels were controlled by flower-shape and flowering time. Large inter-annual changes in generalization levels were common and there was no relationship between the generalization level one year and the following. Generalization level of particular plant species increased with flowering duration, sampling effort, and the abundance of managed honeybees in the community. Generalization level decreased with the flowering synchrony between the focal plant species and the rest of the plant community and with the focal species’ own abundance, which we attribute to inter-specific competition for pollinator attraction and foraging decisions made by pollinators. Plants with different flower-shapes and flowering times did not differ in the extent of inter-annual variation in generalization levels. Most studies do not consider the effect of the plant community on the generalization level of particular plant species. We show here that both pollinator and plant assemblages can affect the inter-annual variation in generalization levels of plant species. Studies like ours will help to understand how pollination interactions are structured at the community level, and the ecological and evolutionary consequences that these inter-annual changes in generalization levels may have.

Slash-and-burn agriculture is an important driver of deforestation and ecosystem degradation, with large effects on biodiversity and carbon sequestration. This study was conducted in a forest in Madagascar, which consists of fragments of slash-and-burn patches, within a matrix of secondary and primary forest. By recording species richness, abundance, and composition of trees, shrubs, and herbs in fallows of various age and slash-and-burn history, and in the secondary and primary forest, we show how slash-and-burn intensity (number of cycles, duration of abandonment), years since last abandonment, and environmental factors (distance to primary forest and topography) affect the natural succession and recovery of the forest ecosystem. We used ordination analyses to examine how the species composition varied between the different successions stages, and to examine tree recruitment. Our results show shrub dominance the first years after abandonment. Thereafter, a subsequent increase in species richness and abundance of tree seedlings and saplings suggests a succession towards the diversity and composition of the secondary and primary forest, although a big gap between the oldest fallows and the secondary forest shows that this will take much more than 30 years. A high number and frequency of slash-and-burn cycles decreased tree seedling and sapling richness and abundance, suggesting that reducing slash-and-burn intensity will increase the speed of tree recruitment and fallow recovery. Trees can be planted into fallows to speed up vegetation and soil recovery, such that fallows can be usable within needed time and thus the extension of cultivated areas reduced. We recommend further testing of six potential species for restoration based on their early colonization of the fallows and their survival through vegetation succession.