Biogeographic classification of streams using fish community– and trait–environment relationships

• DOI: 10.1111/ddi.13001
• Publication Date: 2019-11-06T11:42:56Z
• Authors: Matthew J. Troia; Ryan A. McManamay
• Keywords: Biota; Environmental gradient

Abstract Aim Present a hybrid biogeographic and environmentally constrained clustering approach to classify ~853,000 stream reaches in the eastern United States. Examine frequency of typologies landscape relative anthropogenic stressors identify potential conservation needs. Location Eastern Methods Fish communities at 956 least‐disturbed sampling were characterized using taxonomic functional composition native species. Environmental variables summarized within included discharge, channel gradient, hydrologic regime, summer water temperature boundaries freshwater ecoregions. Multivariate regression trees used relate environmental fish while simultaneously developing taxa‐ trait‐specific classifications. We then overlaid classifications with indices disturbances evaluate rarity risk complete loss natural representation types. Results Taxonomically based classes represented combination ecoregional gradients, whereas gradients most important differentiating composition. An optimal taxonomy‐based classification contained 13 explained 26.4% community variation, trait‐based 6 classes, explaining 25.2% variation. Overlaying class maps an disturbance index revealed substantial variation severity degradation among their abundance landscape, especially rare (i.e., large rivers cold headwater systems). Main conclusions demonstrate value integrating local, regional historical factors characteristics biota ecosystems on mechanistic biota–environment relationships. This is addressing challenge that reconcile drivers trait constraints regionality spatial scales. Furthermore, spatially explicit high‐resolution disseminated here can uniquely inform management decisions regarding threats biodiverse freshwaters