羌塘高原人与野生动物冲突的成因

随着自然保护事业的发展,人与野生动物冲突加剧成为自然保护与地区发展面临的新问题。但人与野生动物冲突研究具有多主体性、复杂性和跨学科性,研究难度大。本文以羌塘高原为例,采用人与野生动物相互作用社会生态系统的概念,梳理了人与野生动物冲突主体的规模、分布,识别了食草野生动物与家畜争食牧草、人类聚落与野生动物竞争生存空间、草场围栏分隔栖息地及阻断迁徙通道等三种主要冲突类型。考虑草畜兽平衡核算了草地承载状况,模拟了家畜与野生动物生存空间重叠,刻画了草场围栏对栖息地及迁徙通道的影响。从重叠空间的资源竞争及人类活动扰动等方面剖析了人与野生动物冲突成因。可为厘清冲突机制,提高干预效果提供新认知。     

Prey vulnerability in relation to sexual coloration of prey

Sexual selection that results in the evolution of exaggerated secondary sexual characters has been hypothesized to impose production and maintenance costs of such traits on their bearers. Costs arising from sexual selection could increase the intensity of predator-mediated natural selection, leading to the prediction that species with exaggerated secondary sexual characters should be particularly susceptible to predation. We tested this prediction in a comparative analysis based on 31,745 prey individuals belonging to 66 species of birds collected from a total of 937 breeding events by 33 to 66 different pairs of European sparrowhawks Accipiter nisus annually during a period of 21 years. To assess vulnerability of different species we estimated a prey vulnerability index based on the difference in the logarithmically transformed absolute abundance of prey minus the logarithmically transformed expected abundance as determined by population density of breeding birds. The prey vulnerability index was predicted by sexual dichromatism, accounting for 23% of the variance in risk of predation among species, even when considering similarity in phenotype among species due to common descent (in the latter case explaining 12% of the variance). This finding suggests that sexual selection is an important evolutionary force-affecting predator–prey interactions.Electronic Supplementary Material Supplementary material is available for this article at     

The iridoid glycoside,catalpol, as a deterrent to the predatorCamponotus floridanus (Formicidae)

Summary We investigated the role of the iridoid glycoside, catalpol, as a deterrent to the predator,Camponotus floridanus. Four laboratory colonies of this ant were offered buckeye caterpillars (Junonia coenia: Nymphalidae) raised on diets with and without catalpol. The same colonies were offered sugar-water solutions containing varying concentrations of catalpol, in both no-choice and choice tests. Regardless of diet, buckeye caterpillars appeared to be morphologically protected from predation by the ants, possibly because of their large spines or tough cuticle. However, buckeyes raised on diets with catalpol had high concentrations of catalpol in their hemolymph; extracts of this high-catalpol hemolymph proved to be an effective deterrent to the ants. When starved ants were not given the choice of food items, they were more likely to consume sucrose solutions that contained 5 mg catalpol/ml or 10 mg catalpol/ml than they were to consume solutions with 20 mg catalpol/ml. When they were given a choice of sugar solution or a sugar solution containing catalpol, the ants avoided solutions with catalpol at any of these concentrations. Ant colony responses to catalpol in sucrose solutions varied considerably over time and among colonies.     

Two herbivore-deterrent iridoid glycosides reduce the in-vitro growth of a specialist but not of a generalist pathogenic fungus of Plantago lanceolata L

Summary. Many secondary plant compounds are involved in defense against both insect herbivores and pathogens. Two secondary plant compounds of Plantago lanceolata, the iridoid glycosides catalpol and its precursor aucubin, are well known for their deterrent effects on generalist and non-adapted specialist insect herbivores. We tested the effects of these compounds on the in-vitro growth of a specialist and generalist fungal pathogen of this host species. Two chemical forms of these iridoids were tested. The glycosides and their aglycones, the products of enzymatic conversion by specific $/Beta$-glucosidase enzymes. The glycosides enhanced growth of both the specialist fungus Diaporthe adunca and the generalist fungus Fusarium moniliforme var. subglutinans. The positive effect of these glycosides on the generalist fungus is in sharp contrast with the generally negative effects of these glysosides on generalist insect herbivores. The aglycones of aucubin and catalpol reduced the growth of the specialist fungus D. adunca, but, contrary to expectation, enhanced the growth of the generalist fungus F. moniliforme var. subglutinans. Effects of aucubin on D. adunca were stronger than effects of catalpol. This was true both for the growth stimulating effects of the glycosides and for the fungitoxic effects of the aglycones. We therefore expect that the effects of these iridoids in P. lanceolata on the specialist fungus will strongly depend on the ratio between catalpol and its precursor aucubin and the chemical form (glycoside or aglycone) in which these compounds are encountered by the fungus during growth. Our results suggest that iridoid glycosides in P. lanceolata can be used as defense against both herbivores and pathogens, but that their effects are highly specific with respect to the natural enemy species that is encountered. Received 11 April 2002; accepted 9 August 2002     

Effect of queen quality on interactions between workers and dueling queens in honeybee (Apis mellifera L.) colonies

The fitness of a social insect colony depends greatly on the quality (i.e., mating ability, fecundity, and offspring viability) of its queen(s). In honeybees, there is marked variation in the quality of young queens that compete in a series of lethal duels to replace a colonys previous queen. Workers interact with queens during these duels and could increase their inclusive fitness by biasing the outcomes of the duels in favor of high-quality queens. We predicted that workers will have more antagonistic interactions (chasing, grabbing, clamping) and fewer beneficent interactions (feeding, grooming) with low-quality than high-quality queens. To test this prediction, we reared queens from 0-day-old, 2-day-old, and 3-day-old worker larvae in observation colonies undergoing queen replacement, thus producing high-quality, low-quality, and very low-quality queens, respectively. Immediately after each queen emerged, we observed her for 1 h to record her interactions with the workers. Subsequent morphological measurement of the queens confirmed that initial larval age had a significant effect on queen quality. However, there was no consistent effect of queen quality on the rates of worker–queen interactions, thus falsifying our hypothesis. The mean power of our tests was high (0.599), therefore the probability of a type II error (a false negative) is low. We conclude that if workers actively select high-quality queens, then they do so prior to queen duels, during queen development. We suggest that each worker–queen interaction has a distinct adaptive significance rather than forming a suite of behavior that favors particular queens (e.g., chasing repels any queen that approaches a queen cell, thus protecting all queen cells from destruction).Communicated by M. Giurfa     

Why do plants ‘talk’?

Summary Plant defence can be induced by herbivory. This is true for both direct and indirect plant defence. Induced direct defence has been the most studied of the two. However, in most cases induced direct defence does not appear to be a water-tight defence option. In contrast, induced indirect defence through the production of herbivore-induced carnivore attractants can be a decisive factor in the extermination of herbivore populations. In this paper the main characteristics of induced attraction of carnivores by plants are reviewed. This includes the similarities and dissimilarities among tritrophic systems. There are two main patterns of induced carnivore attraction. (1) Through the emission of the same bouquet as that emitted by mechanically damaged plants, but in larger quantities and for a longer period of time after damage. (2) Through emission of large amounts of new volatiles that are synthesizedde novo in response to herbivore feeding andnot in response to mechanical wounding.Herbivore populations may be decimated by carnivores. Therefore it should be realized that herbivoreinduced carnivore attractants are essential in an important step in carnivore foraging,i.e. long-distance herbivore location. Once herbivores have started feeding on a plant and direct defence is not effective, induced indirect defence may be decisive for plant survival. Therefore, it is concluded that indirect defence is an essential aspect of induced plant defence directed at herbivorous arthropods.     

Variation in composition of predator-attracting allelochemicals emitted by herbivore-infested plants: Relative influence of plant and herbivore

Summary During foraging, natural enemies of herbivores may employ volatile allelochemicals that originate from an interaction of the herbivore and its host plant. The composition of allelochemical blends emitted by herbivore-infested plants is known to be affected by both the herbivore and the plant. Our chemical data add new evidence to the recent notion that the plants are more important than the herbivore in affecting the composition of the volatile blends. Blends emitted by apple leaves infested with spider mites of 2 different species,T. urticae andP. ulmi, differed less in composition (principally quantitative differences for some compounds) than blends emitted by leaves of two apple cultivars infested by the same spider-mite species,T. urticae (many quantitative and a few qualitative differences). Comparison between three plant species — apple, cucumber and Lima bean — reveals even larger differences between volatile blends emitted upon spider-mite damage (many quantitative differences and several qualitative differences).     

Estimating Effects of Tidal Power Projects and Climate Change on Threatened and Endangered Marine Species and Their Food Web

Marine hydrokinetic power projects will operate as marine environments change in response to increased atmospheric carbon dioxide concentrations. We considered how tidal power development and stressors resulting from climate change may affect Puget Sound species listed under the U.S. Endangered Species Act (ESA) and their food web. We used risk tables to assess the singular and combined effects of tidal power development and climate change. Tidal power development and climate change posed risks to ESA‐listed species, and risk increased with incorporation of the effects of these stressors on predators and prey of ESA‐listed species. In contrast, results of a model of strikes on ESA‐listed species from turbine blades suggested that few ESA‐listed species are likely to be killed by a commercial‐scale tidal turbine array. We applied scenarios to a food web model of Puget Sound to explore the effects of tidal power and climate change on ESA‐listed species using more quantitative analytical techniques. To simulate development of tidal power, we applied results of the blade strike model. To simulate environmental changes over the next 50 years, we applied scenarios of change in primary production, plankton community structure, dissolved oxygen, ocean acidification, and freshwater flooding events. No effects of tidal power development on ESA‐listed species were detected from the food web model output, but the effects of climate change on them and other members of the food web were large. Our analyses exemplify how natural resource managers might assess environmental effects of marine technologies in ways that explicitly incorporate climate change and consider multiple ESA‐listed species in the context of their ecological community. Estimación de los Efectos de Proyectos de Energía de las Mareas y el Cambio Climático sobre Especies Marinas Amenazadas y en Peligro y su Red Alimentaria     

Do the elongated eye stalks of Diopsid flies facilitate rival assessment?

The elongated eye span of male Diopsid flies is a sexually selected character that scales positively with body size. Previously, the duration of agonistic contests was found to increase as rival body size and eye span disparities decreased. Hence, along with its role in mate choice, eye span seems to facilitate mutual assessment of rival size. However, such results are also expected in the absence of rival assessment, when each individual persists according to its own size-dependent internal threshold. Here, we reanalyze these contests to distinguish between these two hypotheses using two measures of size: body length and eye span. Mutual assessment predicts that contest duration should increase with loser size and decrease with winner size. In contrast, our results were more consistent with self-assessment: We found a positive relationship between loser size and contest duration, whereas winner size did not affect contest duration. Thus, flies did not appear to assess the size of their rivals, indicating that the mutual assessment function of eye span elongation may be less important than previously suspected. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Parasitoid learning during interactions with ants: how to deal with an aggressive antagonist

Pauesia picta, P. pinicollis and P. silvestris (Hymenoptera: Aphidiidae) are common parasitoids of the conifer aphid Cinara pinea, which is regularly attended by red wood ants (Formica spp.). In this study, I tested whether females of these parasitoid species learned during interactions with honeydew-collecting Formica polyctena workers that caution is not necessary if searching behaviour is adapted, and whether parasitoids benefit from being able to learn. When searching on Scots pines, naive females of P. picta and P. pinicollis generally retreated to a pine needle when making contact with a honeydew-collecting ant, did not approach ants from the side or from the front and kept a ”safe distance” from ants when sitting on needles. After some non- aggressive ant encounters, experienced female parasitoids changed their behaviour: they reduced their searching speed, approached ants from the side and even from the front, retreated less often in response to an approaching ant and reduced the ”safe distance”. These experienced females had a significantly higher rate of oviposition than naive females or females foraging for an unattended host. Thus, the ability of the parasitoid to learn during interactions with an antagonist led to a prolonged retention time and a higher oviposition rate. By contrast, there was no evidence of learning in P. silvestris. Females of this species showed no behavioural change in response to ant encounters, and there was no difference in the foraging success of naive and experienced female parasitoids. Received: 7 December 1999 / Revised: 23 September 2000 / Accepted: 10 March 2000