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Ludwigia hexapetala is an alien aquatic plant considered highly invasive in Europe since it alters freshwater habitats by forming dense mats both in water and along banks, outcompeting natives. Ludwigia effects on the native carnivorous plant Utricularia australis were investigated here. A 21-day indoor experiment was performed by setting up some separate tests in which Utricularia was made to grow both alone (control tests) and together with Ludwigia (arena tests). Water chemical and physical parameters and growth and morphological traits of Utricularia and Ludwigia were analysed weekly. Water samples were also analysed by UV-visible spectra to verify allelochemical (quercitrin) production by Ludwigia. In arena tests, oxygen concentration and pH were lower and conductivity higher than in control tests. Utricularia grew significantly less in arena tests in both shoot length and internode number, and its fresh weight, trap number and internode length decreased more than the control. Quercitrin was found only in arena tests as an allelochemical product released by Ludwigia. Overall, this study demonstrated Ludwigia significantly alters water parameters and negatively affects the growth of Utricularia, showing aggressive and competitive behaviour against this native species. Such evidence suggest that the widespread of L. hexapetala can represent a serious threat to the conservation of native plant diversity occurring in the freshwater habitats it invades. [ABSTRACT FROM AUTHOR]

Although freshwater habitats, especially springs, are widely recognized as top-priority habitats for monitoring and conservation procedures, their fauna, especially water beetles, are still poorly studied in the southeastern part of Europe. Thus, the dominant water beetle in these habitats, E. bosnica (Zaitzev, 1908) (Insecta: Coleoptera: Elmidae), has been completely ignored and misidentified. This study represents the first review of its taxonomy and its population and ecological traits. Both published and unpublished data are presented and discussed, as well as the results of field sampling in 46 springs and other waterbodies conducted in this region from 2004 to 2019. The identification characters of the male genitalia and the first DNA barcode of the species are presented. The results confirm the close phylogenetic relationship of E. bosnica with E. aenea (Müller, 1806) and E. rioloides (Kuwert, 1890). The species proved to be a useful environmental descriptor and can easily be used as a biological indicator due to its easy identification. The species shows remarkable sensitivity to environmental conditions and inhabits sites that are potentially under increased anthropogenic pressure and could disappear at an alarming rate. Thus, karstic habitats should be included in future conservation and monitoring procedures in this part of Europe. [ABSTRACT FROM AUTHOR]

Simple Summary: This study aims to understand if the threats to freshwater-dependent species identified by The International Union for Conservation of Nature Red List of Threatened Species are correctly supported by valid literature. The results show that 99% of threats are not supported by validated published scientific knowledge. This may lead to ineffective conservation and management plans. Funding to study and fill baseline knowledge gaps about threats should be a priority. Freshwater ecosystems are disproportionally important for biodiversity conservation, as they support more than 9% of known animal species while representing less than 1% of the Earth's surface. However, the vast majority of the threats (99%, or 826 out of 837) identified by the International Union for Conservation of Nature Red List of Threatened Species known to affect the 434 known freshwater-dependent fish and lampreys of Europe are not supported by validated published scientific knowledge. This general lack of information about freshwater-dependent fish and lamprey species may have deleterious effects on species conservation, and additional funding is required to fill baseline knowledge gaps. [ABSTRACT FROM AUTHOR]

Caves are the best studied aquatic subterranean habitat, but there is a wide variety of these habitats, ranging in depth below the surface and size of the spaces (pore or habitat size). Both factors are important in setting limits to species composition and richness. In addition to caves, among the most important shallow aquatic subterranean habitats are the hyporheal (underflow of rivers and streams), the hypotelminorheal (very superficial drainages with water exiting in seeps), epikarst, and calcrete aquifers. Although it is little studied, both body size and species composition in the different habitats is different. Because of high levels of endemism and difficulty in access, no subterranean habitats are well sampled, even caves. However, there are enough data for robust generalizations about some geographic patterns. Individual hotspot caves are concentrated in the Dinaric region of southern Europe, and overall, tropical regions have fewer obligate aquatic cave dwellers (stygobionts). In all subterranean aquatic habitats, regional diversity is much higher than local diversity, but local diversity (especially single cave diversity) may be a useful predictor of regional species richness. In Europe there is a ridge of high aquatic subterranean species richness basically extending east from the French–Spanish border. Its cause may be either high productivity or that long-term temperature oscillations are at a minimum. With increased collecting and analysis, global and continental trends should become clearer. [ABSTRACT FROM AUTHOR]