Invasions of alien species are a great threat to biodiversity and native species communities. There are many examples in the literature on how the invasive plants affect the natural environment. Beside reports on negative effects of these invasions, there are also several studies indicating a positive impact of the invaders. Canadian goldenrod (Solidago canadensis) is one of the most invasive plant species all over Europe. Earlier studies showed that the goldenrod affects natural plant communities and has a negative impact on many animals, both vertebrates and arthropods. However, all the studies were conducted during goldenrod flowering. In contrast, this study has tested the novel hypothesis that Canadian goldenrod has a positive effect on native spider hunting success and increases spider abundance in farmland outside the growing season. Observations were made during spring on 13 meadows: 7 invaded and 6 non-invaded by goldenrod. All tall plants from experimental plots (1 m 2 each) were examined for the presence of spiders, their nets and prey. Prey items were counted only in spider webs. The results support the hypothesis that S. canadensis is a favourable foraging habitat for spiders: 14.6 spiders/m 2 on invaded plots versus 2.2 on non-invaded ones. Many spiders of the families Theridiidae and Araneidae were found on goldenrod plants, but on native plants only the Araneidae were found. Moreover, on invaded plots, much more prey items/m 2 were present in spiders webs than on non-invaded plots (155.3 vs. 13.8). The study is a rare example of a positive influence of invasive plants on the native arthropod community. This is also a novel approach that shows the importance of dry goldenrod stems in invaded ecosystems. Keywords Invasive ecology Á Alien species Á Ecosystem services Á Agriculture Á Biological pest control Á Biodiversity Handling Editor: Heikki Hokkanen.

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Antagonistic interactions between insects and amphibians are the subject of many scientific articles, mostly concerning amphibian predation on insect, but many fewer examples exist of the opposite situation. In this article we review available information from the literature and add our own observations collected during amphibian pitfall trap monitoring in 2012–2016 in Western Poland, as well as discuss potential conservation implications of observed behavior. We identified a total of 29 cases involving 94 individual ants attacking four species of Anura, Rana temporaria, Pelophylax esculentus complex, Bufo bufo, and Pelobates fuscus, and biting their back, cloaca, armpits, or hind legs. Bites were inflicted by three ant species: Myrmica rubra, Lasius fuliginosus, and Formica polyctena. The number of ants found on an amphibian was positively and significantly correlated with its body length. To date, direct damage by ants on amphibians was reported mainly from the tropics in general predation accident. However, as we document here, it is probably a more common phenomenon, especially in some ecological traps or during pitfall trapping, which is a common method to mitigate road mortality of frogs and toads.

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