Social foraging by honeybees: how colonies allocate foragers among patches of flowers

Summary To understand how a colony of honeybees keeps its forager force focussed on rich sources of food, and analysis was made of how the individual foragers within a colony decide to abandon or continue working (and perhaps even recruit to) patches of flowers. A nectar forager grades her behavior toward a patch in response to both the nectar intake rate of her colony and the quality of her patch. This results in the threshold in patch quality for acceptance of a patch being higher when the colonial intake rate of nectar is high than when it is low. Thus colonies can adjust their patch selectivity so that they focus on rich sources when forage is abundant, but spread their workers among a wider range of sources when forage is scarce. Foragers assess their colony's rate of nectar intake while in the nest, unloading nectar to receiver bees. The ease of unloading varies inversely with the colonial intake rate of nectar. Foragers assess patch quality while in the field, collecting nectar. By grading their behavior steeply in relation to such patch variables as distance from the nest and nectar sweetness, foragers give their colony high sensitivity to differences in profitability among patches. When a patch's quality declines, its foragers reduce their rate of visits to the patch. This diminishes the flow of nectar from the poor patch which in turn stimulates recruitment to rich patches. Thus a colony can swiftly redistribute its forager force following changes in the spatial distribution of rich food sources. The fundamental currency of nectar patch quality is not net rate of energy intake, (Gain-Cost)/Time, but may be net energy efficiency, (Gain-Cost)/Cost.     

The use of waggle dance information by honey bees throughout their foraging careers

We studied the extent to which worker honey bees acquire information from waggle dances throughout their careers as foragers. Small groups of foragers were monitored from time of orientation flights to time of death and all in-hive behaviors relating to foraging were recorded. In the context of a novice forager finding her first food source, 60% of the bees relied, at least in part, on acquiring information from waggle dances (being recruited) rather than searching independently (scouting). In the context of an experienced forager whose foraging has been interrupted, 37% of the time the bees resumed foraging by following waggle dances (being reactivated) rather than examining the food source on their own (inspecting). And in the context of an experienced forager engaged in foraging, 17% of the time the bees initiated a foraging trip by following a waggle dance. Such dance following was observed much more often after an unsuccessful than after a successful foraging trip. Successful foragers often followed dances just briefly, perhaps to confirm that the kind of flowers they had been visiting were still yielding forage. Overall, waggle dance following for food discovery accounted for 12–25% of all interactions with dancers (9% by novice foragers and 3–16% by experienced foragers) whereas dance following for reactivation and confirmation accounted for the other 75–88% (26% for reactivation and 49–62% for confirmation). We conclude that foragers make extensive use of the waggle dance not only to start work at new, unfamiliar food sources but also to resume work at old, familiar food sources.     

Potential effects of forest policies on terrestrial biodiversity in a multi-ownership province.

We used spatial simulation models to evaluate how current and two alternative policies might affect potential biodiversity over 100 years in the Coast Ranges Physiographic Province of Oregon. This 2.3-million-ha province is characterized by a diversity of public and private forest owners, and a wide range of forest policy and management objectives. We evaluated habitat availability for seven focal species representing different life histories. We also examined how policies affected old-growth stand structure, age distributions relative to the historical range of variability, and landscape patterns of forest types. Under the current policy scenario, the area of habitat for old-growth forest structure and associated species increased over time, the habitat for some early-successional associates remained stable, and the area of hardwood vegetation and diverse early-successional stages declined. The province is projected to move toward but not reach the historical range of variation of forest age classes that may have occurred under the wildfire regimes of the pre-Euroamerican settlement period. Ownership explained much of the pattern of biodiversity in the province, and under the current policy scenario, its effect increased over time as the landscape diverged into highly contrasting forest structures and ages. Patch type diversity declined slightly overall but declined strongly within ownerships. Most of the modeled change in biodiversity over time resulted from policies on public forest lands that were intended to increase the area of late-successional forests and species. One of the alternative policies, increased retention of wildlife trees on private lands, reduced the contrast between ownerships and increased habitat availability over time for both early- and late-successional species. Analysis of another alternative, stopping thinning of plantations on federal lands, indicated that current thinning regimes improve habitat for the Olive-sided Flycatcher, but the no-thinning alternative had no effect on the habitat scores for the late-successional species in the 100-year simulation. A comparison of indicators of biological diversity suggests that using focal species and forest structural measures can provide complementary information on biodiversity. The multi-ownership perspective provided a more complete synthesis of province-wide biodiversity patterns than assessments based on single ownerships.     

Influence of environment, disturbance, and ownership on forest vegetation of coastal Oregon.

Information about how vegetation composition and structure vary quantitatively and spatially with physical environment, disturbance history, and land ownership is fundamental to regional conservation planning. However, current knowledge about patterns of vegetation variability across large regions that is spatially explicit (i.e., mapped) tends to be general and qualitative. We used spatial predictions from gradient models to examine the influence of environment, disturbance, and ownership on patterns of forest vegetation biodiversity across a large forested region, the 3-million-ha Oregon Coast Range (USA). Gradients in tree species composition were strongly associated with environment, especially climate, and insensitive to disturbance, probably because many dominant tree species are long-lived and persist throughout forest succession. In contrast, forest structure was strongly correlated with disturbance and only weakly with environmental gradients. Although forest structure differed among ownerships, differences were blurred by the presence of legacy trees that originated prior to current forest management regimes. Our multi-ownership perspective revealed biodiversity concerns and benefits not readily visible in single-ownership analyses, and all ownerships contributed to regional biodiversity values. Federal lands provided most of the late-successional and old-growth forest. State lands contained a range of forest ages and structures, including diverse young forest, abundant legacy dead wood, and much of the high-elevation true fir forest. Nonindustrial private lands provided diverse young forest and the greatest abundance of hardwood trees, including almost all of the foothill oak woodlands. Forest industry lands encompassed much early-successional forest, most of the mixed hardwood-conifer forest, and large amounts of legacy down wood. The detailed tree- and species-level data in the maps revealed regional trends that would be masked in traditional coarse-filter assessment. Although abundant, most early-successional forests originated after timber harvest and lacked legacy live and dead trees important as habitat and for other ecological functions. Many large-conifer forests that might be classified as old growth using a generalized forest cover map lacked structural features of old growth such as multilayered canopies or dead wood. Our findings suggest that regional conservation planning include all ownerships and land allocations, as well as fine-scale elements of vegetation composition and structure.     

Rapid assessment of postfire plant invasions in coniferous forests of the western United States.

Fire is a natural part of most forest ecosystems in the western United States, but its effects on nonnative plant invasion have only recently been studied. Also, forest managers are engaging in fuel reduction projects to lessen fire severity, often without considering potential negative ecological consequences such as nonnative plant species introductions. Increased availability of light, nutrients, and bare ground have all been associated with high-severity fires and fuel treatments and are known to aid in the establishment of nonnative plant species. We use vegetation and environmental data collected after wildfires at seven sites in coniferous forests in the western United States to study responses of nonnative plants to wildfire. We compared burned vs. unburned plots and plots treated with mechanical thinning and/or prescribed burning vs. untreated plots for nonnative plant species richness and cover and used correlation analyses to infer the effect of abiotic site conditions on invasibility. Wildfire was responsible for significant increases in nonnative species richness and cover, and a significant decrease in native cover. Mechanical thinning and prescribed fire fuel treatments were associated with significant changes in plant species composition at some sites. Treatment effects across sites were minimal and inconclusive due to significant site and site x treatment interaction effects caused by variation between sites including differences in treatment and fire severities and initial conditions (e.g., nonnative species sources). We used canonical correspondence analysis (CCA) to determine what combinations of environmental variables best explained patterns of nonnative plant species richness and cover. Variables related to fire severity, soil nutrients, and elevation explained most of the variation in species composition. Nonnative species were generally associated with sites with higher fire severity, elevation, percentage of bare ground, and lower soil nutrient levels and lower canopy cover. Early assessments of postfire stand conditions can guide rapid responses to nonnative plant invasions.     

Inhibition of diatom photosynthesis by germanic acid: Separation of diatom productivity from total marine primary productivity

Germanic acid was shown to inhibit photosynthetic ¹⁴CO₂ uptake in marine diatoms. Inhibition was not complete even at concentrations of 20 mg Ge/1 nor in cultures incubated for extended periods of time (up to 24 h). The decrease in photosynthesis due to Ge(OH)₄ was independent of the stage of growth of the diatom culture. At 0.5 and 1.0 mg Ge/1, the degree of inhibition was dependent on the concentration of Si(OH)₄ in the medium. At 5 and 10 mg Ge/1, inhibition was not affected by Si(OH)₄ concentrations as high as those found in the sea-120 g-at Si/1. The effect of Ge(OH)₄ on photosynthesis is specific for diatoms; other marine phytoplankton were not inhibited. In mixed cultures of diatoms and marine flagellates, the reduction in ¹⁴CO₂ fixation upon addition of Ge(OH)₄ was used to calculated the proportion of diatom photosynthesis to total photosynthesis, and calculated proportions agreed well with actual proportions. Inhibition by Ge(OH)₄ was also used to estimate the percent of diatom photosynthesis in a natural marine community, and this was compared with the diatom portion of the crop. Diatom photosynthesis was higher than one might expect from crop figures, although both diatom photosynthesis and diatom numbers in the crop were low.     

How <Emphasis Type="Italic">Doratomyces stemonitis</Emphasis> copes with Benzoxazolin-2(3<Emphasis Type="Italic">H</Emphasis>)-one (BOA), its derivatives and detoxification products

Summary. Doratomyces stemonitis (Hyphomycetales, Dematiaceae) is a saprotrophic fungus belonging to the mycobiota of the cereal rhizosphere. The fungus is able to metabolize benzoxazolin-2-(3H)-one and a variety of its derivatives including higher plant detoxification products, microbial degradation products and the chemically rather stable 2-amino-(3H)-phenoxazin-3-one. D. stemonitis can use all of these compounds as sole C-sources but their utilization, especially that of microbial degradation products and 2-amino-(3H)-phenoxazin-3-one, seems to be highly energy consuming, resulting in slow mycelium growth and a change of colony morphology. Benzoxazolin-2-(3H)-one derived compounds induce the synthesis of different isoforms of a glycosylated protein with sequence homologies to the endo-1,3-β-glucanase Asp f2, an allergen from Aspergillus fumigatus and other Asp f2-like proteins e.g., from Verticillium dahliae or PRA1 antigen from Candida albicans. The induction of the protein is regarded as a stress response.     

Cumulative ecological and socioeconomic effects of forest policies in coastal Oregon.

Forest biodiversity policies in multi-ownership landscapes are typically developed in an uncoordinated fashion with little consideration of their interactions or possible unintended cumulative effects. We conducted an assessment of some of the ecological and socioeconomic effects of recently enacted forest management policies in the 2.3-million-ha Coast Range Physiographic Province of Oregon. This mountainous area of conifer and hardwood forests includes a mosaic of landowners with a wide range of goals, from wilderness protection to high-yield timber production. We projected forest changes over 100 years in response to logging and development using models that integrate land use change and forest stand and landscape processes. We then assessed responses to those management activities using GIS models of stand structure and composition, landscape structure, habitat models for focal terrestrial and aquatic species, timber production, employment, and willingness to pay for biodiversity protection. Many of the potential outcomes of recently enacted policies are consistent with intended goals. For example, we project the area of structurally diverse older conifer forest and habitat for late successional wildlife species to strongly increase. 'Other outcomes might not be consistent with current policies: for example, hardwoods and vegetation diversity strongly decline within and across owners. Some elements of biodiversity, including streams with high potential habitat for coho salmon (Oncorhynchus kisutch) and sites of potential oak woodland, occur predominately outside federal lands and thus were not affected by the strongest biodiversity policies. Except for federal lands, biodiversity policies were not generally characterized in sufficient detail to provide clear benchmarks against which to measure the progress or success. We conclude that land management institutions and policies are not well configured to deal effectively with ecological issues that span broad spatial and temporal scales and that alternative policies could be constructed that more effectively provide for a mix of forest values from this region.     

The value of small size: loss of forest patches and ecological thresholds in southern Madagascar.

Many services generated by forest ecosystems provide essential support for human well-being. However, the vulnerability of these services to environmental change such as forest fragmentation are still poorly understood. We present spatial modeling of the generation of ecosystem services in a human-dominated landscape where forest habitat patches, protected by local taboos, are located in a matrix of cultivated land in southern Madagascar. Two ecosystem services dependent on the forest habitats were addressed: (1) crop pollination services by wild and semidomesticated bees (Apoidea), essential for local crop production of, for example, beans, and (2) seed dispersal services based on the presence of ring-tailed lemurs (Lemur catta). We studied the vulnerability of these ecosystem services to a plausible scenario of successive destruction of the smallest habitat patches. Our results indicate that, in spite of the fragmented nature of the landscape, the fraction of the landscape presently covered by both crop pollination and seed dispersal services is surprisingly high. It seems that the taboo system, though indirectly and unintentionally, contributes to upholding the generation of these services by protecting the forest patches. Both services are, however, predicted to be very vulnerable to the successive removal of small patches. For crop pollination, the rate of decrease in cover was significant even when only the smallest habitat patches were removed. The capacity for seed dispersal across the landscape displayed several thresholds with habitat patch removal. Our results suggest that, in order to maintain capacity for seed dispersal across the landscape and crop pollination cover in southern Androy, the geographical location of the remaining forest patches is more crucial than their size. We argue that in heavily fragmented production landscapes, small forest patches should increasingly be viewed as essential for maintaining ecosystem services, such as agricultural production, and also should be considered in the ongoing process of tripling the area of protected habitats in Madagascar.     

渔民的利益和合作:瑞典沿岸渔业共同管理的前提

本文在"共同管理"、"参与性管理"或"地方管理"等概念下用不同的理念探讨了渔民参与渔业管理的问题.瑞典渔业范围内的经验研究阐明了关于渔民参与渔业管理先决条件的新观点.在影响成败的重要因素中,我们这里着重探讨了其中两个:渔民利益的明确表达、组织及代表问题和通常参与资源管理合作的各群体即:渔民、政府管理人员以及研究人员之间的信任.本文所概述的研究论及了渔民在资源管理、地方渔业管理方面的利益以及渔民的参与.连接这三个主题的问题是:在渔业管理中如何更好地反映渔民的利益?利益与信任,即"软事实",对于渔业管理和参与的成败而言,可以犹如所有权、资源的数量和质量或资源的货币价值之类的"硬事实"一样的重要.