How characteristic is the species characteristic selection scale?. Issue 12 (11th September 2019) - Stuber, Erica F.
Abstract: Aim: The importance of framing investigations of organism–environment relationships to interpret patterns at relevant spatial scales is increasingly recognized. However, most research related to environmental relationships is single‐scaled, implicitly or explicitly assuming that a "species characteristic selection scale" exists. We tested the premise that a single characteristic scale exists to understand species–environment relationships within species by asking (a) what are the characteristic scales of species' relationships with environmental predictors, and (b) is within‐species, cross‐predictor consistency in characteristic scales a general phenomenon. Location: Nebraska, USA. Time period: 2016. Major taxa studied: Birds. Methods: We used data from 86 species at > 500 locations to build hierarchical N‐mixture models relating species abundance to land cover variables. By incorporating Bayesian latent indicator scale selection, we identified the spatial scales that best explain species–environment relationships with each land cover predictor. We quantified the extent of cross‐predictor consistency in characteristic scales, and contrasted this to the expectation given a single species' characteristic scale. Results: We found no evidence for a characteristic spatial scale explaining all abundance–environment relationships within species, rather we found substantial variation in scale‐dependence across multiple environmental attributes. Furthermore, 33% of species displayed evidence of multiple important spatial scales within environmental attributes. Major conclusions: Within species there is little evidence for a single characteristic scale of environmental relationships and considerable variation in species' scale dependencies. Because species may respond to multiple environmental attributes at different spatial scales, or single environmental attributes at multiple scales, we caution against any unoptimized single‐scale studies. Our results demonstrate that until a framework is developed to predict the scales at which species respond to environmental characteristics, multi‐scale investigations must be performed to identify and account for multi‐scale dependencies. Natural selection acting on species' response to distinct environmental attributes, rather than natural selection acting on species' perception of spatial scales per se, may have shaped patterns of scale dependency and is an area ripe for investigation.