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).     

Longitudinal Analysis of Attitudes Toward Wolves

Understanding individual attitudes and how these predict overt opposition to predator conservation or direct, covert action against predators will help to recover and maintain them. Studies of attitudes toward wild animals rely primarily on samples of individuals at a single time point. We examined longitudinal change in individuals’ attitudes toward gray wolves (Canis lupus). In the contiguous United States, amidst persistent controversy and opposition, abundances of gray wolves are at their highest in 60 years. We used mailed surveys to sample 1892 residents of Wisconsin in 2001 or 2004 and then resampled 656 of these individuals who resided in wolf range in 2009. Our study spanned a period of policy shifts and increasing wolf abundance. Over time, the 656 respondents increased agreement with statements reflecting fear of wolves, the belief that wolves compete with hunters for deer (Odocoileus virginianus), and inclination to poach a wolf. Endorsement of lethal control of wolves by the state and public hunting of wolves also increased. Neither the time span over which respondents reported exposure to wolves locally nor self‐reported losses of domestic animals to wolves correlated with changes in attitude. We predict future increases in legal and illegal killing of wolves that may reduce their abundance in Wisconsin unless interventions are implemented to improve attitudes and behavior toward wolves. To assess whether interventions change attitudes, longitudinal studies like ours are needed. Análisis Longitudinal de las Actitudes Hacia Lobos     

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     

Biodiversity Consequences of Genetic Variation in Bark Characteristics within a Foundation Tree Species

Abstract: The developing field of community genetics has the potential to broaden the contribution of genetics to conservation biology by demonstrating that genetic variation within foundation plant species can act to structure associated communities of microorganisms, invertebrates, and vertebrates. We assessed the biodiversity consequences of natural patterns of intraspecific genetic variation within the widely distributed Australian forest tree, Eucalyptus globulus. We assessed genetic variation among geographic races of E. globulus (i.e., provenances, seed zones) in the characteristics of tree‐trunk bark in a 17‐year‐old common garden and the associated response of a dependent macroarthropod community. In total, 180 macroarthropod taxa were identified following a collection from 100 trees of five races. We found substantial genetically based variation within E. globulus in the quantity and type of decorticating bark. In the community of organisms associated with this bark, significant variation existed among trees of different races in composition, and there was a two‐fold difference in species richness (7–14 species) and abundance (22–55 individuals) among races. This community variation was tightly linked with genetically based variation in bark, with 60% of variation in community composition driven by bark characteristics. No detectable correlation was found, however, with neutral molecular markers. These community‐level effects of tree genetics are expected to extend to higher trophic levels because of the extensive use of tree trunks as foraging zones by birds and marsupials. Our results demonstrate the potential biodiversity benefits that may be gained through conservation of intraspecific genetic variation within broadly distributed foundation species. The opportunities for enhancing biodiversity values of forestry and restoration plantings are also highlighted because such planted forests are increasingly becoming the dominant forest type in many areas of the world.     

Uncertainties in the assessment of “significant effect” on the Dutch Natura 2000 Wadden Sea site – The mussel seed fishery and powerboat race controversies

Natura 2000, the nature network based on the European Bird and Habitat Directives, is explicitly grounded on ecological science. To acquire a permit under the Dutch Nature Conservation Act, an appropriate assessment of significant effects must be conducted based on the best available scientific knowledge. In this way the scientific and policy world are directly linked. This article focuses on ‘significant effect’ as a boundary object to analyse how science–policy interactions shape the meaning and assessment of significant effect and how these interpretations influence the decision-making process. To this end, two conflicts over significant effect are investigated: the conflict over the 2006-spring permit for the mussel seed fishery, and the 2011 permit for the planned World Championship powerboat races. In both cases nature organisations started a court process against the government-granted permits in protest to the “no significant effect” claim, stating that there was insufficient certainty for this conclusion. These conflicts are approached as controversies between discourse coalitions with different interpretations of the ecological knowledge. We show how significant effect became a focal point in the controversies, limiting the debate to ecological arguments and science-based expertise, but also creating options for parties to advance their protest by articulating uncertainties. Only uncertainty of incomplete knowledge was explicitly addressed, excluding ambiguity of values and unpredictability of the actual ecosystem. We suggest that acknowledging the value aspect in disputes on significant effect would leave more space for effective solutions of the problems under debate.     

Specific Yield Functions for Estimating Evapotranspiration from Diurnal Surface Water Cycles

The White method has been routinely used to estimate evapotranspiration using diurnal variations in groundwater levels. Applications to surface water systems (e.g., wetlands) are less common. For applications to surface water systems, a stage‐dependent specific yield function must be defined. This is especially important for small wetlands formed in topographic depressions with bowl shaped bathymetries. Existing formulations of the specific yield function include weighting factors that impact the relative importance of the soil and open water specific yields on the composite value. Three formulations of the specific yield function from the literature were compared and found to produce varied results. Based on a comparison with empirical estimates of specific yield based on observed ratios of net precipitation to water level rise, one of the existing formulations is generalized and recommended for general use. The recommended function is dependent on wetland bathymetry, magnitude of the diurnal fluctuation, spatial extent of the equilibration area, and soil‐specific yield. A sensitivity analysis was conducted to examine the relative importance of these variables. The specific yield function is independent of wetland size and is strongly dependent on the basin profile coefficient (p), an indication of wetland shape. For most natural wetlands, bathymetry strongly influences specific yield.     

Scientists versus policy-makers: Building capacity for productive interactions across boundaries in the urban water sector

This paper critically reflects on a trial process for building the capacity of researchers to influence policy-makers in the urban water sector in Australia. Framed as an action research inquiry, this study brought together multidisciplinary teams of researchers to make policy pitches to simulated panels of current and former politicians, senior bureaucrats and industry representatives. The simulations were analysed with respect to tactics for pitching, methods of communication, use of evidence and participants’ reflections on the experience. Participants effectively used scientific research evidence to support a broad vision of water sensitive cities, but were less effective in articulating risk analyses, assessing economic impacts, and proposing appropriate policy instruments to enable their proposed visions to be operationalised. Dramaturgical analysis highlighted the implications of positioning scientists versus policy-makers, which ‘typecast’ participants in roles that restricted scientists’ ability to credibly argue policy ideas. It is proposed that teams of scientists and policy-makers ‘rehearse’ together to manage expectations, develop arguments that will cut through in policy contexts, and produce ideas that shape and are shaped and improved by the policy context.