The importance of seawater tolerance and native status in mediating the distribution of inland fishes

Aim Unravelling the ecological and historical factors that underlie species distributions has challenged ecologists for a long time. Thus, our objective is to understand the role of environmental variables explaining the distribution of three major eco-evolutionary groups of inland fishes (Darlington's divisions: primary, i.e. strict freshwater; secondary, i.e. salt-tolerant; and peripheral, i.e. diadromous and marine origin), and how these variables are related to fish traits. Location Iberian Peninsula. Taxon 51 native and 17 alien inland fish species from the Iberian Peninsula. Methods We modelled distributions of the most common inland fish species across the Iberian Peninsula to compare the importance of different predictors among the three Darlington's divisions and between native and alien species. To explore the importance of specific environmental variables in determining the distribution of different traits of inland fish, variable importances obtained from species distribution models were subjected to a redundancy analysis. Results Darlington's divisions differ significantly in salinity tolerance, in distribution overlap, in the importance of distribution predictors and associated life-history traits. Topographic and climatic variables were generally more important than land use and anthropogenic factors in explaining fish distributions. We found significant differences in the importance of variables explaining the distribution of native vs. alien species and especially among Darlington's divisions. River basin was most important for primary native and many alien species. Increasing mean temperature and damming were positively associated with the presence of tolerant, large-bodied and warm-water alien species from more hydrologically stable habitats. Main conclusions Despite marked differences in the distribution patterns of native and alien species, evolutionary and introduction histories as well as seawater tolerance are central factors explaining the current distribution of inland fishes. Darlington's divisions proved useful for addressing ecological and biogeographical questions at broader spatial scales ​
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