-Remarkably, unlike other parts of Europe, the ecology of mayflies in the southeastern regions is still poorly known. Here we present the first comprehensive study of Ephemeroptera in the tufa-depositing habitats of the Dinaric Karst. The study was conducted in Plitvice Lakes National Park monthly during a one-year period (2007)(2008) in different types of habitats (springs, streams, mountainous rivers, tufa barriers). The aims of the study were to determine mayfly composition, abundance, spatial distribution and habitat preferences, and to examine the environmental factors important for the structuring of mayfly assemblages in Plitvice Lakes National Park. The mayfly fauna of tufa-depositing habitats was composed of 14 species (20 taxa). Water temperature, pH and ammonium concentration were the most important environmental variables explaining mayfly assemblages. Mayfly assemblages grouped according to habitat type. Generally, the most favourable habitat type was mountainous stream, tufa barriers were less favourable, and the least favourable were springs. Our results confirmed that mayflies are a powerful tool as descriptors of their environment, as the presence or absence of certain mayflies was strongly influenced by physico-chemical water properties.Keywords: case study / ecology / abiotic factors / Ephemeroptera / Southeast Europe Résumé -Facteurs environnementaux influençant la composition des éphémères dans les tufières du Karst Dinarique. De manière surprenante, et contrairement à d'autres parties de l'Europe, l'écologie des éphémères de la zone sud orientale est encore largement inconnue. Dans ce travail, nous présentons la première étude approfondie des éphémères habitant des tufières. L'étude a été menée au Parc National de Plitvice Lacs durant un an (2007)(2008) dans différents types d'habitats (sources, ruisseaux, rivières montagneuses, barrières de tuf). Les objectifs de cette étude étaient de déterminer la composition, l'abondance, la distribution spatiale et les habitats préférentiels des éphémères, d'une part, et d'examiner quels facteurs environnementaux étaient responsables de leur structuration, d'autre part. La faune des éphémères des tufières est composée de 14 espèces (20 taxons). La température de l'eau, le pH et la concentration en ammonium sont les variables environnementales les plus importantes qui expliquent la composition des éphémères. Celle-ci est fonction des types d'habitats. De manière générale, le type d'habitat le plus favorable est celui représenté par les ruisseaux, suivi par les barrières de tuf, les sources étant les moins favorables. Les résultats confirment la puissante capacité des éphémères à décrire leur environnement, puisque la présence ou l'absence de certaines espèces est fortement influencée par les propriétés physico-chimiques de l'eau.
Knowledge of the mayfly biodiversity in the Balkan Peninsula is still far from complete. Compared to the neighbouring countries, the mayfly fauna in Croatia is very poorly known. Situated at the crossroads of central and Mediterranean Europe and the Balkan Peninsula, Croatia is divided into two ecoregions: Dinaric western Balkan and Pannonian lowland. Mayflies were sampled between 2003 and 2013 at 171 sites, and a total of 66 species was recorded. Combined with the literature data, the Croatian mayfly fauna reached a total of 79 taxa. Of these, 29 species were recorded for the first time in Croatia while 15 species were not previously recorded in Dinaric western Balkan ecoregion. Based on the mayfly assemblage, sampling sites were first structured by ecoregion and then by habitat type. In comparison with the surrounding countries, the Croatian mayfly fauna is the most similar to the Hungarian and Bosnian fauna. Some morphologically interesting taxa such as Baetis cf. nubecularis Eaton, 1898 and Rhithrogena from the diaphana group were recorded. Ephemera cf. parnassiana Demoulin, 1958, the species previously recorded only from Greece, was also recorded.
The influences of river regulations on aquatic biota are insufficiently investigated. We assessed the level of ecological disturbance of the mayfly assemblages through the damming and flow alterations at two highly regulated Mediterranean rivers in Croatia: the Cetina River and its tributary, the Ruda. Contrary to our hypotheses, species richness, abundance and diversity of mayflies increased along the river’s course. At the sites directly influenced by the river regulations, mayfly assemblage changed: it was less diverse and less abundant. However, no obvious influence of the river regulation on the mayfly assemblages was detected for the sites that were indirectly influenced by these alterations. This was most likely due to specific karst hydrology, i.e., the presence of lateral springs along the course of the river. Multidimensional scaling analysis (MDS) revealed grouping of sites according to the similarity in physico-chemical water properties. The pH and water temperature were the most important environmental variables influencing mayfly assemblages. The data on ecology and distribution of mayflies presented in the current study represent a valuable background for further research and conservation practices in the Mediterranean region.
a b s t r a c tAquatic dance flies (Empididae; Clinocerinae and Hemerodromiinae) are important components of freshwater assemblages, especially in running waters. They are predators as larvae and adults and thus essential for understanding aquatic food webs. This study was conducted in Plitvice lakes National Park (Croatia) representing a wide variety of freshwater habitats (springs, streams, lakes and tufa barriers). Adults were collected monthly from March 2007 until March 2009 using pyramid-type emergence traps at 13 locations. A total of 3865 specimens comprising 18 species were collected. The dominant genus was Chelifera, while the most abundant species was Hemerodromia unilineata. All species were univoltine except Chelifera precabunda, Chelifera pyrenaica and Chelifera stigmatica that were bivoltine. Considerable differences in composition and structure of aquatic dance flies assemblages were recorded along a longitudinal gradient of studied sites, primarily related to differences in physical and chemical parameters of water. Water temperature was the main factor influencing the timing of emergence. Hemerodromia species preferred variable water temperature throughout the year while the majority of the Chelifera species preferred stable water temperature characteristic of spring sites. Furthermore, discharge affected assemblage composition of aquatic dance flies. The highest abundance of aquatic dance flies was recorded in lotic habitats with fast water current over substrates of moss, gravel and particulate tufa with detritus. These results give a new insight on microhabitat preference and their distribution on unique karstic habitats.
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