Flow intermittence changes the occupancy frequency distribution of stream chironomid assemblages
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| Year of publication | 2024 |
| Type | Conference abstract |
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| Description | In community ecology research, the characterisation of species occupancy frequency distribution (OFD) patterns has been proven to be a suitable method to understand the mechanisms underlying the organisation of the communities on a regional scale. OFDs provide information on the relative dominance of rare and common species in the communities by multiple shapes of histograms based on the occurrence frequencies of the species. Among them, unimodal (characterised by rare species) and bimodal (characterised by additional common species) patterns might indicate wellstructured communities, organised by various local and regional filters. In the case of passive dispersers, like Chironomidae, a right-skewed unimodal OFD pattern is expected in undisturbed conditions at a regional scale. We studied the OFD pattern of stream-dwelling chironomid assemblages in drying river networks (DRNs) suffering from various degrees of intermittency. We assumed that flow intermittency, as an environmental disturbance, can cause changes in the organisation of the assemblages. Quantitative samples were taken bimonthly within the framework of the DRYvER project (Horizon2020 #869226) through six sampling campaigns in 2021. Chironomid larvae were identified morphologically to the lowest possible taxonomic level (targeting species level) from Hungarian, Croatian and Czech DRNs. In contrast with our expectations, in the permanent sites, the chironomid assemblages showed bimodal OFD pattern characterised by many rare, relatively few moderately frequent and several common species. On the contrary, the assemblages in intermittent streams were characterised by a rather right-skewed unimodal OFD pattern, with a high number of rare species but few common species, and relatively high proportion of moderately frequent species. Species that were common in permanent streams become moderately frequent or rare in intermittent streams. It suggests that previously suitable habitat decreased in the area due to flow intermittence. Our results demonstrate that drying events can have a remarkable influence on the processes that shape the chironomid assemblages at a regional scale. |
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