A new take on environmental filtering and habitat matching

Patterns and drivers of environmental filtering and habitat matching are context dependent on a macroecological scale.

Above: Panther Creek, Chattahoochee National Forest, Georgia.

Understanding how communities are assembled is the ‘what we do’ of community ecology: we want to know which species are present and why. With this guiding our work, we wanted to understand community assembly and if the environmental conditions of those communities match the expectations of the present species. Having both of these pieces could help us better anticipate community responses to ongoing environmental change in both space and time

Editors’ choice (free to read for two years):
Murray-Stoker, D., Murray-Stoker, K. M., Kong, F. P., & Amanat, F. (2022) Environmental filtering and habitat (mis)matching of riverine invertebrate metacommunities. Journal of Biogeography, 49, 2105– 2119. https://doi.org/10.1111/jbi.14501

Our project integrated disequilibrium theory (Blonder et al. 2015, Ecology) and functional traits to understand how environmental filtering and habitat matching play out in communities within river and stream ecosystems across ecoregions in the United States. Disequilibrium theory quantifies the degree of environmental filtering, or how much niche space is occupied by the local community: greater niche space than expected indicates environmental permissiveness, while lower niche space than expected indicates environmental filtering. The theory also quantifies habitat matching, or how different the center of the community niche is from expectations: greater differences than expected suggest habitat mismatch, while lower differences that expected suggest habitat matching.

Assortment of aquatic insects from the Chattooga River at Burrells Ford, on the South Carolina-Georgia border of the Southeastern United States. Top row: Helicopsyche (Trichoptera: Helicopsychidae), Isonychia (Ephemeroptera: Isonychiidae); Middle row: Ryhacophila (Trichoptera: Rhyacophilidae), Molanna (Trichoptera: Molannidae); Bottom row: Ectopria (Coleoptera: Psephenidae), Ephemerella (Ephemeroptera: Ephemerellidae).

We found that environmental filtering, but not habitat matching, varied strongly by ecoregion. Surprisingly, we found that both habitat matching and mismatch were common across all ecoregions, despite habitat matching generally thought to be a rare process. This result is intriguing, and also concerning, because it suggests many communities have experienced (or were experiencing)some disturbance that pushed communities into habitat mismatch. We also found that predictors of functional trait abundances varied by trait category and ecoregion, with habitat preference and dispersal traits primarily influenced by network variables. A common trend was that predictors of environmental filtering, habitat matching, or functional trait abundances were contingent, which brings us back to the common refrain of context dependency in community ecology. We embrace this context dependency, and suggest that it is not a problem but a pattern to be understood. In particular, a better understanding of the composition and diversity of regional species pools, both in terms of species and their functional traits, is a promising path forward

Moving forward, we want to use this work to guide the study of regional species pools and how this can be applied to conservation and management efforts in river and stream ecosystems. We also hope that it serves as a foundation on which other research is built, with the ultimate goal being causal explanations for our descriptive patterns

I first started working on this project in 2017 between shifts waiting tables at an Italian restaurant back in my hometown (Flowery Branch, GA, USA) and applying to graduate school. Once I started my PhD research at the University of Toronto, this project necessarily was set aside and in the background until it became increasingly relevant for Kelly’s PhD research. Over 5.5 years later, this work is finally getting out there because of this team of great people and great researchers.

Bearpen Creek in the Southern Appalachian Mountains
near Otto, North Carolina, United States

Written by:
David Murray-Stoker, Ph.D. Candidate, Department of Ecology and Evolutionary Biology, University of Toronto, Canada

Further information:
twitter: @dmurraystoker @_riverwitch @eebtoronto @UTMBiology

Published by Biogeography.news

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