Environmental factors and river network position allow prediction of benthic community assemblies: A model of nematode metacommunities

Birgit Gansfort,Walter Traunspurger

doi:10.1038/s41598-019-51245-2

Abstract

The field of metacommunity studies is growing rapidly, including recent applications to river networks. Most of these studies have targeted a single river network but whether their findings are relevant to other river systems is unknown. This study investigated the influence of environmental, spatial and temporal parameters on the community structure of nematodes in the river networks of the Elbe and Rhine. We asked whether the variance in community structure was better explained by spatial variables representing the watercourse than by overland distances. After determining the patterns in the Elbe river network, we tested whether they also explained the Rhine data. The Elbe data were evaluated using a boosted regression tree analysis. The predictive ability of the model was then assessed using the Rhine data. In addition to strong temporal dynamics, environmental factors were more important than spatial factors in structuring riverine nematode communities. Community structure was more strongly influenced by watercourse than by Euclidean distances. Application of the model’s predictions to the Rhine data correlated significantly with field observations. Our model shows that the consequences of changes in environmental factors or habitat connectivity for aquatic communities across different river networks are quantifiable.

Highlights

Given that habitat fragmentation and environmental change are progressive, a theoretical framework is needed that allows prediction of the consequences for ecological communities
(2) We examined the extent to which the patterns observed in the Elbe river network could be transferred to distinct river systems, by testing the overlap between predictions based on a model developed using the Elbe data and real observations from the Rhine river network
The sampling sites of Elbe river system were located in 10 rivers, with 39 samples taken from tributaries and 76 along the Elbe itself

Summary

Introduction

Given that habitat fragmentation and environmental change are progressive, a theoretical framework is needed that allows prediction of the consequences for ecological communities. This metacommunity concept has become a powerful tool for determining the relative importance of spatial (i.e. regional, dispersal-related) and environmental (local, niche-based) processes in structuring communities[2]. Quantifying the amount of connectivity between sites remains challenging[3], as the dispersal rates within different ecosystems and for entire species assemblages are not formulated[4]. An alternative approach is to use spatial variables as proxies for dispersal intensity, as shorter physical distances between sites imply stronger connectivity between communities via dispersal. The importance of these two dispersal proxies for community assemblies widely varied according to the studied organismal group, showing that different taxa respond differently to isolation effects in stream networks[7]. Different processes might drive the presence vs. abundance of species, requiring that both be taken into account[11]

Methods

Results

Discussion

Conclusion