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28 septembre 2017

Competition induces increased toxin production in toad larvae without allelopathic effects on heterospecific tadpoles [Functional Ecology]

Keywords : allelopathy, amphibian toxins, chemical defence, chemical interference, growth-defence trade-off, growth inhibition, inducible defences, phenotypic plasticity

1.Inducible defences are a form of phenotypic plasticity by which organisms respond to and mitigate the threat posed by predators, parasites and competitors. While anti-predatory defences are often in trade-off with anti-competitor responses, chemicals that deter predators may have negative effects on competitors as well. Allelopathy is well known in plants and plant-like animals, but whether the toxins of mobile, behaviourally and morphologically complex animals are induced by and exert allelopathic effects on competitors is poorly known.
2. Common toads Bufo bufo synthesize bufadienolides which make them unpalatable or toxic to many predators. However, bufadienolide content of toad tadpoles correlates positively with the density of competitors in natural populations, suggesting that they may upregulate their toxin production to inhibit their competitors, such as heterospecific tadpoles that may be vulnerable to toad toxins.(...)

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27 septembre 2017

How to fight multiple enemies : target-specific chemical defences in an aposematic moth [Proceedings of the Royal Society B - Biological Sciences]

Keywords : predator–prey interactions, chemical defences, aposematism, pyrazines

Animals have evolved different defensive strategies to survive predation, among which chemical defences are particularly widespread and diverse. Here we investigate the function of chemical defence diversity, hypothesizing that such diversity has evolved as a response to multiple enemies. The aposematic wood tiger moth (Arctia plantaginis) displays conspicuous hindwing coloration and secretes distinct defensive fluids from its thoracic glands and abdomen. We presented the two defensive fluids from laboratory-reared moths to two biologically relevant predators, birds and ants, and measured their reaction in controlled bioassays (no information on colour was provided). We found that defensive fluids are target-specific : thoracic fluids, and particularly 2-sec-butyl-3-methoxypyrazine, which they contain, deterred birds, but caused no aversive response in ants. By contrast, abdominal fluids were particularly deterrent to ants, while birds did not find them repellent. Our study, to our knowledge, is the first to show evidence of a single species producing separate chemical defences targeted to different predator types, highlighting the importance of taking into account complex predator communities in studies on the evolution of prey defence diversity.

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27 septembre 2017

Anthropogenic noise pollution from pile-driving disrupts the structure and dynamics of fish shoals [Proceedings of the Royal Society B - Biological Sciences]

Keywords : noise, collective behaviour, global change, shoaling, pile-driving

Noise produced from a variety of human activities can affect the physiology and behaviour of individual animals, but whether noise disrupts the social behaviour of animals is largely unknown. Animal groups such as flocks of birds or shoals of fish use simple interaction rules to coordinate their movements with near neighbours. In turn, this coordination allows individuals to gain the benefits of group living such as reduced predation risk and social information exchange. Noise could change how individuals interact in groups if noise is perceived as a threat, or if it masked, distracted or stressed individuals, and this could have impacts on the benefits of grouping.(...)

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27 septembre 2017

Alteration of plant species assemblages can decrease the transmission potential of malaria mosquitoes [Journal of Applied Ecology]

Keywords : disease, fecundity, integrated vector management, malaria, mosquito, nectar, pathogen transmission, plant species assemblages, survival, vectorial capacity

1. Knowledge of the link between a vector population’s pathogen-transmission potential and its biotic environment can generate more realistic forecasts of disease risk due to environmental change. It also can promote more effective vector control by both conventional and novel means.
2. This study assessed the effect of particular plant species assemblages differing in nectar production on components of the vectorial capacity of the mosquito Anopheles gambiae s.s., an important vector of African malaria.(...)

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27 septembre 2017

Fungal community homogenization, shift in dominant trophic guild, and appearance of novel taxa with biotic invasion [Ecosphere]

Keywords : Alliaria petiolata, DNA sequencing, fungal community structure, fungi, garlic mustard, microbiome, mycorrhizae

Invasion by non-native plants may fundamentally restructure the soil fungal community. The invasive plant, Alliaria petiolata, produces secondary compounds suppressive to mycorrhizal fungi and may therefore be expected to have generally negative effects on other components of the fungal community. Here, we compared fungal biomass, diversity, community composition, and the relative abundance of fungal trophic guilds, along with edaphic properties of soils collected from uninvaded and invaded plots across six temperate forests. (...)

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