Diversity patterns of native and exotic fish species suggest homogenization processes, but partly fail to highlight extinction threats

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http://hdl.handle.net/10138/302826

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Gavioli , A , Milardi , M , Castaldelli , G , Fano , E A & Soininen , J 2019 , ' Diversity patterns of native and exotic fish species suggest homogenization processes, but partly fail to highlight extinction threats ' , Diversity and Distributions , vol. 25 , no. 6 , pp. 983-994 . https://doi.org/10.1111/ddi.12904

Title: Diversity patterns of native and exotic fish species suggest homogenization processes, but partly fail to highlight extinction threats
Author: Gavioli, Anna; Milardi, Marco; Castaldelli, Giuseppe; Fano, Elisa Anna; Soininen, Janne
Contributor: University of Helsinki, Helsinki Institute of Sustainability Science (HELSUS)
Date: 2019-06
Language: eng
Number of pages: 12
Belongs to series: Diversity and Distributions
ISSN: 1366-9516
URI: http://hdl.handle.net/10138/302826
Abstract: Aim Exotic species are a major threat to biodiversity and have modified native communities worldwide. Invasion processes have been extensively studied, but studies on species richness and beta diversity patterns of exotic and native species are rare. We investigate such patterns among exotic and native fish communities in upland and lowland rivers to explore their relationship with environmental drivers. Location Northern Italy. Methods Exotic and native fish beta diversity patterns were investigated separately in lowland and upland sites using Local Contribution to Beta Diversity (LCBD) and Species Contribution to Beta Diversity (SCBD) analyses. To examine the main environmental variables affecting the LCBD, a Boosted Regression Trees (BRT) method was used. Community dispersion among and within stream orders was investigated with the PERMDISP test. Results In lowland sites, exotic species richness was higher than native species richness, especially in large rivers and drainage canals. An opposite trend was found in upland sites, where native species richness was higher than exotic species richness, especially in large rivers. No clear LCBD patterns were found along stream orders in the lowland, whereas higher stream orders in the upland showed the highest LCBD. Its patterns in upland and lowland sites were related to a number of factors, such as total suspended solids and total phosphorus. Community dispersion among stream orders did not show a relationship with environmental heterogeneity. SCBD values were positively correlated with species occupancy in the study area, and native species showed higher SCBD values than exotic species only in the uplands. Main conclusions Large rivers in the uplands are important in maintaining native fish diversity and should be protected against invasive fish. In contrast, most lowland rivers have suffered from biological homogenization. Some rare native species can show low contribution to beta diversity, but still need conservation actions due to their risk of local extinction.
Subject: Alien species
beta diversity
biodiversity conservation
freshwater
invasions
non-native species
species diversity
species richness
FRESH-WATER FISH
BETA-DIVERSITY
STREAM ORDER
MACROINVERTEBRATE COMMUNITIES
ASSEMBLAGE STRUCTURE
SITE CONTRIBUTIONS
BIODIVERSITY LOSS
OGLIO RIVER
IMPACTS
BASIN
1172 Environmental sciences
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