Modelling the effect of in-stream and terrestrial barriers on the dispersal of aquatic insect species: a case study from a Central European mountain catchment
Sondermann, Martin; Gies, Maria; Hering, Daniel; Schröder, Maria; Feld, Christian K.
published: Feb 1, 2015
ArtNo. ESP141018601005, Price: 29.00 €
Worldwide, lotic ecosystems are heavily impacted by anthropogenic disturbance, leading to a significant decline in freshwater biodiversity. In recent years, increasing efforts have been directed towards the restoration and revitalization of disturbed streams and rivers to reverse this trend. Although it is widely acknowledged that species dispersal is the key to the recolonization of restored streams and rivers and ultimately to their ecological recovery, dispersal often remains unaddressed in restoration ecology. In this study, we present an approach to predict larval (aquatic) and adult (terrestrial) dispersal ranges of three lotic insect species (Hydropsyche dinarica [Trichoptera], Calopteryx virgo [Odonata] and Dinocras cephalotes [Plecoptera]) within one life cycle. The actual species' distributions (presence / absence) were obtained from a total of 1,198 sites evenly distributed within the Ruhr catchment, North Rhine-Westphalia, Germany. The predictions for aquatic and terrestrial dispersal were made for two scenarios: with and without dispersal barriers included in the predictive modelling. In-stream dispersal barriers included weirs, dams, culverts and impounded water bodies, whereas terrestrial barriers were related to the stream corridor (degraded riparian vegetation) and different forms of land use (urban land use, coniferous and deciduous or mixed forest, open land, road infrastructure). We applied a least-cost modelling approach and combined each species' life-cycle-specific dispersal capabilities and the corresponding dispersal barrier's “friction” costs in a grid-based GIS model. Among the three model species, H. dinarica was the best disperser and was predicted to be able to reach between 81% (without barriers) and 67% (with barriers) of all river sections in the model catchment within one life cycle. Aerial (terrestrial) dispersal was by far the most important dispersal mechanism. For validation purposes, we conducted a logistic regression analysis to identify sample sites with environmentally suitable habitats. Within these sites that are not considered constrained by habitat limitations, the comparison of actual and predicted absences revealed a better match, if barriers were included in the dispersal models. At the same time the mismatch of actual absences and predicted presences decreased. Our results suggest that dispersal models can contribute to a better assessment of the potential recolonization of rivers. Yet, the dispersal of lotic insects may be considerably overestimated if dispersal barriers remain unaddressed.