Taxonomic rarity and functional originality of freshwater fishes and their responses to anthropogenic habitat alterations

• Published in: Aquatic conservation Vol. 32; no. 3; pp. 484 - 494
• Main Authors: Tóth, Rita, Czeglédi, István, Takács, Péter, Tedesco, Pablo A., Erős, Tibor
• Format: Journal Article
• Language: English
• Published: Oxford Wiley Subscription Services, Inc 01.03.2022; Wiley
• Subjects: Anthropogenic factors; Biodiversity; Conservation; Endemism; Environmental degradation; Environmental policy; Environmental Sciences; Fish; Freshwater; Freshwater fish; functional rarity; functional uniqueness; Functionals; Habitats; Inland water environment; Land degradation; rare species; Rivers; Species; species level conservation; Specificity; stream fish; taxonomic rarity; Taxonomy
• ISSN: 1052-7613; 1099-0755
• DOI: 10.1002/aqc.3768

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.