Estimates of niche position and breadth vary across spatial scales for native and alien inland fishes

Abstract

We estimate and compare niche position, marginality and breadth of Iberian inland fishes at three geographical extents (regional, restricted to the species’ range and global) to understand the effect of spatial scale on niche metrics. Furthermore, we investigate differences in niche metrics between native and alien fish, and test for associations with introduction date of alien species and niche characterization to better understand their invasion process. Location: Iberian Peninsula and global. Time period: 2000–2020. Major taxa studied: Fifty-one native and 17 alien inland fish species from the Iberian Peninsula. Methods: Outlying mean index (OMI) analyses were used to estimate the niche position, marginality and breadth of Iberian inland fishes. Climatic OMI analyses were computed at three different scales (regional, restricted to the species’ range and global). Permutational analyses of variance (PERMANOVAs) were used to test for differences in niche position, marginality and breath among native and alien species. Results: Niche metrics differed depending on the geographical extent of the investigation, as well as with respect to species origin (native versus alien). Differences in climatic niche position between native and alien species observed at the global scale were non-existent at the regional scale. The niche breadth of widely distributed alien species was highly underestimated when only considering the invaded region, and further influenced by the first date of of species introduction. Main conclusions: Estimating niches of freshwater species, especially of alien invaders, should carefully consider the geographical extent of the investigation. We suggest that analyses that jointly consider regional and global scales will improve the estimation of niche metrics of widely distributed organisms, particularly regarding species climatic niche, and the assessment of the invasive potential of species

Research funding: Generalitat de Catalunya. Grant Number: ref. 2017 SGR 548 & Ministerio de Ciencia e Innovación. Grant Numbers: CGL2016-80820-R, PID2019-103936GB-C21, ref. BES-2017-081999