Abstract
Niche-based species distribution models (SDMs) play a central role in studying species response to environmental change. Effective management and conservation plans for freshwater ecosystems require SDMs that accommodate hierarchical catchment ordering and provide clarity on the performance of such models across multiple scales. The scale-dependence components considered here are: (a) environment spatial structure, represented by hierarchical catchment ordering following the Strahler system; (b) analysis grain, that included 1st to 5th order catchments; and (c) response grain, the grain at which species respond most, represented by local and upstream catchment area effects. We used fish occurrence data from the Danube River Basin and various factors representing climate, land cover and anthropogenic pressures. Our results indicate that the choice of response grain – local vs. upstream area effects – and the choice of analysis grain, only marginally influence the performance of SDMs. Upstream effects tend to better predict fish distributions than corresponding local effects for anthropogenic and land cover factors, in particular for species sensitive to pollution. Key predictors and their relative importance are scale and species dependent. Consequently, choosing proper species dependent spatial scales and factors is imperative for effective river rehabilitation measures.
Highlights
The majority of studies describing distributions of freshwater species rely on niche-based species distribution models (SDMs) (Buisson et al, 2008; Lassalle et al, 2010; Markovic et al, 2012)
Our results indicate that the choice of response grain – local vs. upstream area effects – and the choice of analysis grain, only marginally influence the performance of SDMs
In our recent study (Kärcher et al, 2019), we have shown that the choice of the analysis grain, reflected by the hierarchical catchment order, only marginally influences the mean performance of SDMs
Summary
The majority of studies describing distributions of freshwater species rely on niche-based species distribution models (SDMs) (Buisson et al, 2008; Lassalle et al, 2010; Markovic et al, 2012). Following Mertes and Jetz (2018), the scale-dependence components of species-environment relationships are: (1) spatial structure of the environment; (2) analysis grain, the grain at which analyses are conducted; and (3) response grain, the grain at which species respond most strongly to their environment. Domisch et al (2013) and Kärcher et al (2019) have shown that the second scale component – analysis grain – only marginally influences the performance of SDMs; to address the effects of the above-defined three scale components on the performance of SDMs tailored to freshwater species, an integrated modelling framework is needed. In the era of urgent management response to high environmental pressures to freshwater ecosystems, catchment scale hold great promise where fine grain (e.g. reach scale) survey data are unavailable. Given the high vulnerability of freshwater ecosystems to environmental change (Woodward et al, 2010; Markovic et al, 2017) and the fact that
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