Distinctive macroinvertebrate communities in a subtropical river network

Abstract

Macroinvertebrates are widely used as bio-indicators in streams and rivers, and it is usually assumed that their community composition is primarily controlled by local environmental conditions. We examined the distribution of macroinvertebrates within the Guadalupe River basin (3256 km²) in Central Texas across physiographic gradients. Spatial analysis with variables that considers flow direction, connectivity and distances between sites (asymmetric eigenvector maps, AEM) detected distinctive communities in the lower reaches of the mainstem, in spring-influenced reaches, and in a tributary with intermittent reaches. Variation partitioning with redundancy analysis showed that large-scale factors, i.e. riverine network patterns (large-scale AEM variables), climatic variation and ecoregion explained a significant proportion (28%) of the variation in community composition within a river basin. The riverine network patterns were the most important factor, explaining 12% alone. Local environmental factors were significant, but completely confounded within these spatial patterns. We propose that there are distinctive macroinvertebrate communities depending on the location in the river network and this may apply to other (subtropical) rivers, which should be tested by future studies. We recommend spatial analysis that considers distances and connectivity within a river network as a powerful tool to recognize multiscale riverine network patterns, which can help to identify priority areas for conservation and to develop sound monitoring programs.

Keywords:

• metacommunity
• AEM spatial variables
• biomonitoring
• biogeography
• aquatic insects
• springs
• intermittent flow

Acknowledgements

We thank Gaby Timmins, Pete Diaz, and Nathaniel Dede-Bamfo for technical support, Rebecca Tucker for her help with sampling, and Don Apodaca for his help in the field and in the laboratory.

Disclosure statement

No potential conflict of interest was reported by the authors.

Funding

This work was supported by the Texas Parks and Wildlife Department through Texas Water Development Board under grant no. 1349311646.

Additional information

Notes on contributors

Rebecca Zawalski

Rebecca Zawalski was an MSc student co-advised by Drs. Nowlin and Schwalb during this study, but is now a Blue Thumb Field Educator at the Oklahoma Conservation Commission.

Weston H. Nowlin

Weston Nowlin is a professor of ecosystem ecology in the Biology Department at the Texas State University.

Karl Cottenie

Karl Cottenie is an associate professor of metacommunity ecology in the Department of Integrative Biology at the University of Guelph.

Archis Grubh

Dr. Archis Grubh is an aquatic biologist with research interests in macroinvertebrate community dynamics, and currently works for Texas Parks and Wildlife Division.

Astrid N. Schwalb

Astrid Schwalb is an assistant professor of stream ecology at the Texas State University.