Increasing agriculture and urbanization inevitably lead to changes in the biodiversity of stream ecosystems. However, few studies examined comprehensively how biodiversity is distributed within and among protected, agricultural and urban land use types in streams. We studied environmental characteristics of streams and patterns of species richness and other community attributes of stream fish communities in these three characteristic land use types in the catchment of the Danube River, Hungary. Land use separated streams to some degree based on their environmental characteristics. However, both between stream environmental and fish community variability were high in most types, and comparable to land use type level differences in case of many streams. A variety of environmental gradients influenced fish community structure rather independently of land use type, which was also influenced by spatial drivers. Non-native fishes modified the structure of native fish communities, especially in agricultural streams, although their modification effect varied more among individual streams than among land use types. In conclusion, land use type proved to be a poor predictor of fish communities in this human modified landscape. We found that even intensively managed areas (i.e. agricultural and urban) can contribute to the maintenance of fish diversity in this biogeographic region, or at least their potential can be comparable to those streams which flow in protected areas. Thus, conservation management should focus on maintaining streams in more natural condition in protected areas and/or use the potential of non-protected agricultural and urban streams in maintaining fish diversity in human modified landscapes.

No abstract

No abstract

The human alteration of habitats is a major driver in the decline of biodiversity worldwide. However, the relationships between different forms of rarity, including both taxonomic and functional aspects, are poorly known. Two relationships were examined in this study: (i) between the different forms of taxonomic rarity and functional originality of lotic fishes; and (ii) between rarity indices and the degree of human alterations. Stream fish communities at 429 stream and river sites were sampled between 2013 and 2018. The taxonomic rarity of fishes was characterized based on their local rarity, habitat specificity and geographical restrictedness. The functional originality of each species was also quantified by using ecomorphological traits, and the relationships between the different indices and their responses to human habitat degradation were explored. Only weak or medium level correlations were found among the indices of taxonomic rarity. A combined taxonomic rarity index showed that overall taxonomic rarity was determined most strongly by local rarity, followed by habitat specificity, and finally, geographical restrictedness. Functional originality was not related either to individual rarity indices or the combined taxonomic rarity index. Mean taxonomic rarity of species was correlated with the degree of habitat degradation of the sites. Contrary to taxonomic rarity, mean functional originality of species increased with the degree of human alteration. This study shows that a more exact characterization of species rarity requires multiple metrics, including functional ones, because these indices respond differently to human alterations. Combined indices of rarity can help to prioritize species level conservation actions, although single rarity metrics are still needed to adapt these actions to species attributes (e.g. endemism or unique functions). Species level conservation would benefit from including the evaluation of functional rarity into conservation policy.