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Environment-induced plastic responses in chemical defences of a vertebrate

Final Report Summary - CHEMICAL DEFENCES (Environment-induced plastic responses in chemical defences of a vertebrate)

The main aim of the project was to study various aspects of environmental effects on the chemical defences of a vertebrate, the common toad (Bufo bufo) and their larvae. We performed laboratory- and field-based experiments, as well as field observations. Our experiments provide the first evidence for toxin synthesis in larval amphibians. In correlative studies we detected signs of competition-induced changes in toxin production. Our experimental studies confirmed this result and thereby provide the first evidence that the intensity of competition may induce changes in the chemical defences in any vertebrate. Interestingly, enhanced toxin production was more pronounced in the presence of conspecific tadpoles and less in the presence of heterospecifics, and we did not detect an allelopathic effect of enhanced toxin production. Furthermore, we also detected altered toxin production in response to predators: tadpoles raised with chemical cues of predation risk produced higher numbers of bufadienolide compounds and larger total bufadienolide quantities than their predator-naive conspecifics. Further, the intensity of responses in chemical defence depended on the predator species present. This result delivers the first evidence for potentially adaptive predator-induced changes in chemical defences in a vertebrate. We also performed studies investigating effects of pathogens on toxin production, but did not observe any clear effect in experimental studies. We documented ontogenetic changes in toxin production of larval and post-metamorphic toads: the quantity of toxins produced first increases in the most vulnerable life-stage and later decreases, when tadpoles become larger and less susceptible to predators. In two studies we were looking for costs of toxin production, but these delivered no positive result, suggesting relatively low costs arising from the synthesis of toxins. In an experiment we assessed the temporal aspect of toxin replenishment in tadpoles following artificially induced release of defensive chemicals and observed that quantities of toxin compounds reached initial levels already twelve hours after toxin release, proving the ability of quick replenishment. Finally, we detected an unexpected effect of pesticide-exposure on skin toxin production, suggesting that tadpoles developing in waters contaminated with glyphosate-based herbicides may boost their toxin synthesis. In addition to the studies primarily concerned with chemical defences, we also performed studies on predator recognition in amphibian larvae, on their sensitivity to climate change and agricultural contaminants, on predator-prey interactions between an agricultural pest and its predators, as well as on the ontogeny of animal personality. For details see the homepage of the ‘Lendület’ Evolutionary Ecology Research Group (LEERG) at http://evolecol.hu/ and the publications made available there.
With the help of the MC CIG the fellow strengthened, expanded and equipped the newly founded LEERG at the Host Institute (Plant Protection Institute, Centre for Agricultural Research, Hungarian Academy of Sciences). The LEERG currently consists of four post-docs, four pre-docs, one PhD-student, four MSc students and a technician. During the project period, while supported by the MC CIG and in collaboration with the rest of the LEERG, the fellow:
- published 23 papers in international scientific journals, and thereby significantly contributed to the scientific output of the Host Institute,
- presented results at 9 national and 8 international conferences,
- published press releases on results of three studies and wrote two articles for popular scientific journals,
- participated as a scientific advisor and an interviewee in the production of educative films on amphibians targeting teenaged schoolchildren,
- gave three invited talks (at the Department of Ecology, Institute of Biology, Szent István University, at the Bolyai Collegium, Eötvös Loránd University and at the Department of Ecology, Institute of Biology, University of Veterinary Medicine Budapest),
- obtained a medium sized and two small research grants, as well as three post-doc fellowships,
- supervised the research of 4 PhD students as well as 8 MSc students,
- organized three workshops for young scientists of the Host Institute,
- participated in the teaching activities of two universities,
- contributed to the Hungarian and the English versions of the webpage of the Host Institute (http://novi.agrar.mta.hu/hu/ and http://novi.agrar.mta.hu/en/) and kept the English webpage of the LEERG up to date (http://evolecol.hu)
- developed and maintained tight collaborations with four research groups within the Host Institute and several other groups outside the Host, embarked on a project involving agricultural pests, and studied effects of herbicides on non-target organisms;
- helped other members of the LEERG reach success (supervised MSc student won the yearly competition of the National Scientific Students' Associations Conference (OTDK 2017) in the section Animal Ecology; supervised PhD student was elected ‘Young Ethologist of the Year 2017’ by the Hungarian Ethological Society; another supervised PhD student obtained a small research grant from the Otto Kinne Foundation; a third supervised PhD student was elected first at the Young Researchers’ Yearly Hearing at the Hungarian Academy of Sciences (HAS); a fourth supervised PhD student obtained a twelve-months research fellowship to Mexico from the Tempus Public Foundation; one of the senior post-docs obtained a research grant of the National Research, Development and Innovation Office (NKFIH) and a Young Researcher Position from the HAS; the other senior post-doc obtained a prestigious MTA Premium Post-doctoral Fellowship and another Young Researcher Position from the HAS).
Thus, over the course of the project period, the fellow and the LEERG, aided by the MC-CIG, contributed to the training of young researchers, widely disseminated research results, obtained further funding, became fully integrated in the Host Institute and obtained a respected status in the Hungarian, as well as in the international research landscape.