Disentangling the effects of habitat suitability, dispersal, and fragmentation on the distribution of river fishes

Abstract

Habitat suitability, dispersal potential, and fragmentation influence the distribution of stream fishes; however, their relative influence and interacting effects on species distributions are poorly understood, which may result in uncertain outcomes of river rehabilitation and conservation. Using empirical data describing 17 relatively common stream fishes, we combine (1) species habitat suitability models (MaxEnt) with a (2) species dispersal model (FIDIMO) and a (3) worst-case scenario of the influence of river fragmentation on dispersal. Using generalized linear mixed models, we aimed to uncover the role of these factors in explaining the probability of presence. Simulations over nine years allowed for assessing the relative importance of dispersal over time for structuring species occurrences vs. the importance of habitat suitability. Models combining all three structuring factors performed consistently better in predicting the spatial occurrence patterns than models including only single factors. Our results confirmed that distribution patterns of stream fishes are jointly controlled by species dispersal and habitat suitability. An increase of 0.1 habitat suitability probability more than doubled the odds of species occurrence; an increase of 0.1 dispersal probability yielded a 14-fold increase of the odds of species occurrence. Temporal simulations revealed that over short time frames (1-2 years) dispersal from nearby source populations is four times more important than habitat suitability for species presence. However, over longer time periods, the importance of habitat suitability increases relative to the importance of dispersal. Surprisingly, fragmentation by migration barriers did not appear as a significant driver of occurrence patterns. Concluding, these findings demonstrate the importance of the spatial arrangement of suitable habitats and potential source populations, as well as their relative position in relation to barriers. We emphasize considering the direction of connections within river networks and the dispersal abilities of fishes, as well as providing (access to) new, suitable habitat for successful river rehabilitation.

Spatiotemporal patterns of mountain whitefish (Prosopium williamsoni) in response to a restoration of longitudinal connectivity

“…This finding is in contrast to recent studies that found artificial barriers were generally not important in explaining the distribution of riverine fish in some study systems (Branco, Segurado, Santos, Pinheiro, & Ferreira, 2012;Radinger & Wolter, 2015). This finding is in contrast to recent studies that found artificial barriers were generally not important in explaining the distribution of riverine fish in some study systems (Branco, Segurado, Santos, Pinheiro, & Ferreira, 2012;Radinger & Wolter, 2015).…”

The effect of river restoration on fish, macroinvertebrates and aquatic macrophytes: A meta-analysis

“…This is consistent with the higher mean effect on macroinvertebrate abundance ( r = 0.21) compared to richness ( r = 0.08) reported in Miller et al (2010) and recent empirical and modelling studies which showed that the species pool and source populations for colonization are often sparse and limit the effect of restoration on species richness (Radinger and Wolter, 2015;Stoll et al, 2014;Tonkin et al, 2014).…”

Climate change increases ecogeographical isolation between closely related plants

“…As shown by our analysis, accounting for dispersal limitation in predicting where a species could occur is therefore important, because although suitable habitat may be available, the ability of a species to migrate to that habitat is critical in determining their occurrence. For example, Radinger and Wolter () found that the dispersal ability of river fishes is more than four times more important as a predictor than habitat suitability for determining species presence at a particular location. Although ants disperse seeds of Pulmonaria species, taxon‐specific differences in ant ability to disperse seeds and whether different Pulmonaria species use different ant taxa to disperse seeds remain to be tested.…”