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Temperature can play an important role in determining the feeding preferences of ectotherms. In light of the warmer temperatures arising with the current climatic changes, omnivorous ectotherms may perform diet shifts toward higher herbivory to optimize energetic intake. Such diet shifts may also occur during heat waves, which are projected to become more frequent, intense, and longer lasting in the future. Here, we investigated how heat waves of different duration affect feeding preferences in omnivorous anuran tadpoles and how these choices affect larval life history. In laboratory experiments, we fed tadpoles of three species on animal, plant, or mixed diet and exposed them to short heat waves (similar to the heat waves these species experience currently) or long heat waves (predicted to increase under climate change). We estimated the dietary choices of tadpoles fed on the mixed diet using stable isotopes and recorded tadpole survival and growth, larval period, and mass at metamorphosis. Tadpole feeding preferences were associated with their thermal background, with herbivory increasing with breeding temperature in nature. Patterns in survival, growth, and development generally support decreased efficiency of carnivorous diets and increased efficiency or higher relative quality of herbivorous diets at higher temperatures. All three species increased herbivory in at least one of the heat wave treatments, but the responses varied among species. Diet shifts toward higher herbivory were maladaptive in one species, but beneficial in the other two. Higher herbivory in omnivorous ectotherms under warmer temperatures may impact species differently and further contribute to changes in the structure and function of freshwater environments.

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In the Mediterranean basin, the globally increasing temperatures are expected to be accompanied by longer heat waves. Commonly assumed to benefit cold-limited invasive alien species, these climatic changes may also change their feeding preferences, especially in the case of omnivorous ectotherms. We investigated heat wave effects on diet choice, growth and energy reserves in the invasive red swamp crayfish, Procambarus clarkii. In laboratory experiments, we fed juvenile and adult crayfish on animal, plant or mixed diets and exposed them to a short or a long heat wave. We then measured crayfish survival, growth, body reserves and Fulton’s condition index. Diet choices of the crayfish maintained on the mixed diet were estimated using stable isotopes (13C and 15N). The results suggest a decreased efficiency of carnivorous diets at higher temperatures, as juveniles fed on the animal diet were unable to maintain high growth rates in the long heat wave; and a decreased efficiency of herbivorous diets at lower temperatures, as juveniles in the cold accumulated less body reserves when fed on the plant diet. Heat wave treatments increased the assimilation of plant material, especially in juveniles, allowing them to sustain high growth rates in the long heat wave. Contrary to our expectations, crayfish performance decreased in the long heat wave, suggesting that Mediterranean summer heat waves may have negative effects on P. clarkii and that they are unlikely to boost its populations in this region. Although uncertain, it is possible that the greater assimilation of the plant diet resulted from changes in crayfish feeding preferences, raising the hypotheses that i) heat waves may change the predominant impacts of this keystone species and ii) that by altering species’ trophic niches, climate change may alter the main impacts of invasive alien species.

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Deposits of coal combustion wastes, especially fly ash, are sources of environmental and health risks in industrial regions. Recently, fly ash deposits have been reported as habitat surrogates for some threatened arthropods in Central Europe. However, the potential environmental risks of fly ash have not yet been assessed in the region. We analysed concentrations of 19 minor and trace elements in 19 lignite combustion waste deposits in the Czech Republic. We assessed their environmental risks by comparison with the national and EU legislation limits, and with several commonly used indices. Over 50% of the samples exceeded the Czech national limits for As, Cu, V, or Zn, whilst only V exceeded the EU limits. For some studied elements, the high-risk indices were detected in several localities. Nevertheless, the measured water characteristics, the long-term presence of fly ash, previous leaching by acid rains, and the low amount of organic matter altogether can infer low biological availability of these elements. We presume the revealed high concentrations of some heavy metals at some studied sites can be harmful for some colonising species. Nevertheless, more ecotoxicological research on particular species is needed for final decision on their conservation potential for terrestrial and freshwater biota.

Permanent ponds are valuable freshwater systems and biodiversity hotspots. They provide diverse ecosystem services (ES), including water quality improvement and supply, food provisioning and biodiversity support. This is despite being under significant pressure from multiple anthropogenic stressors and the impacts of ongoing global change. However, ponds are largely overlooked in management plans and legislation, and ecological research has focused on large freshwater ecosystems, such as rivers or lakes. Protection of ponds is often insufficient or indirectly provided via associated habitats such as wetlands. This phenomenon is likely exacerbated due to lacking a full-scale understanding of the importance of ponds. In this review, we provided a detailed overview of permanent ponds across Europe, including their usages and the biodiversity they support. By discussing the concepts of pondscape and metacommunity theory, we highlighted the importance of connectivity among and between ponds and identified fluxes of emerging insects as another ES of ponds. Those insects are rich in essential nutrients such as polyunsaturated fatty acids (PUFA), which are delivered through them to the terrestrial environment, however the extent and impact of this ES remains largely unexplored. Several potential stressors, especially related to ongoing global change, which influence pond diversity and integrity were discussed. To conclude this review, we provided our insights on future pond management. Adaptive measures, taking into account the pond system per se within the pondscape, were found to be the most promising to mitigate the loss of natural ponds and restore and conserve natural small water bodies as refuges and diversity hotspots in increasingly urbanized landscapes.

Temperature changes alter the relative quality of plant and animal diets for ectotherms. Omnivorous amphibian tadpoles avoid protein-rich diets at higher temperatures simulating heat waves, and two out of three species benefit from this diet shift. Tadpoles may optimize energetic intake by increasing herbivory at higher temperatures.Recent climate change has unfolded many ecological questions, and the influence of temperature on nutrient acquisition by ectothermic organisms became the focus of several studies, whose results suggest that increasing herbivory should allow ectotherms to cope with the greater nutritional demands of higher temperatures. 1 Indeed, under the current climatic projections, a better understanding of temperature and nutrient interactions across ecological organization levels is crucial to realistically predict responses to global change. 2 Since most experimental research neglected the importance of discrete weather events as components of climate change, the authors decided to study the effects of heat waves on nutrient acquisition by aquatic omnivorous ectotherms.Temperature has different scaling effects on the various components of ectotherm metabolism, which may result in a greater assimilation of plant material at higher temperatures through two distinct pathways. First, through a passive effect upon nutrient assimilation, as the imbalanced temperature effects on metabolic processes may positively discriminate plant diets (carbohydrate-rich) at higher temperatures. By promoting a greater increase in feeding and gut passage rates than in assimilation rates at the intestine wall, higher temperatures may hamper the assimilation of slow digestion nutrients such as proteins, and favor the assimilation of smaller and structurally less complex nutrients, thereby increasing the relative assimilation efficiency of carbohydrates. Second, through an active modulation of ectotherm feeding preferences that increases the consumption of plant diets at higher temperatures. Plant diets are rich in carbohydrates, which are fast energy sources that should allow ectotherms to compensate for the lower assimilation efficiency at higher temperatures. Furthermore, high temperatures promote a greater increase in respiration than in growth, increasing the demand for carbon over nitrogen, which could motivate ectotherms to feed selectively and increase the consumption of plant diets at higher temperatures.The relationship between ectotherm diet and temperature may be of particular relevance in freshwater communities, as these are mainly composed of ectotherm species. Therefore, rising water temperatures resulting from global warming and extreme climatic events such as heat waves may induce generalized shifts in the trophic position of omnivorous ectotherms. This is especially significant because global climatic models project more frequent, intense and longer lasting heat waves in the areas of the globe currently afflicted by these climatic anomalies, such as the basin of the Mediterranean. Under this new regim...