DOI: 10.5061/dryad.b1c58f8
title: Data from: A trait-based framework for discerning drivers of species co-occurrence across heterogeneous landscapes

description: Null model analysis of species co-occurrence patterns has long been used
 to gain insight into community assembly but is often limited to
 identifying non-random patterns without providing clarity about underlying
 ecological mechanisms. This challenge is especially apparent when sampling
 units are spread across a heterogeneous landscape or along an
 environmental gradient because multiple mechanisms can produce similar
 co-occurrence patterns. We developed a trait-based approach for
 discriminating between environmental filtering and biotic interactions as
 the probable driver of co-occurrence patterns across environmentally
 heterogeneous sites. We demonstrate our framework by analyzing the
 co-occurrence of small mammals over elevation in three independent
 mountain ranges in the Great Basin of the western United States. Our
 sampling design accounts for landscape scale environmental variability and
 within-site habitat heterogeneity. We identified 52 non-random species
 pairs, of which 36 were aggregated and 16 were segregated. For each pair,
 we determined which mechanism was the likely ecological explanation using
 a hypothesis-testing framework based on functional trait similarity.
 Expectations of biotic interactions were based on similarity of diet and
 body size whereas habitat affinity and geographic range were used for
 environmental filtering. Only four pairs were consistent with expectations
 under biotic interactions, including pairs for which competitive exclusion
 has previously been documented. In addition to analyzing individual pairs,
 we used binomial tests of observed versus expected totals of intra- and
 inter-guild pairs to determine assemblage-wide deviations from random
 community structure. Signatures of environmental filtering were consistent
 across mountain ranges and scales. Despite differences in species
 composition and significant pairs among data sets, our approach revealed
 consistent mechanistic conclusions, emphasizing the value of trait-based
 methods to co-occurrence and community assembly.
description: RubySites_OccMatrixSpecies by Site occurrence matrix for Ruby Mountains. Used as input matrix for Program Pairs.RubyTraplines_OccMatrixSpecies by Trapline occurrence matrix for Ruby Mountains. Used as input matrix for Program Pairs.SnakeSites_OccMatrixSpecies by Site occurrence matrix for Snake Range. Used as input matrix for Program Pairs.SnakeTraplines_OccMatrixSpecies by Trapline occurrence matrix for Snake Range. Used as input matrix for Program Pairs.ToiyabeSites_OccMatrixSpecies by Site occurrence matrix for Toiyabe Range. Used as input matrix for Program Pairs.ToiyabeTraplines_OccMatrixSpecies by Trapline occurrence matrix for Toiyabe Range. Used as input matrix for Program Pairs.Ruby_PairsOutputFull Pairs output for Ruby Mountains. Output from site and trapline analyses are both contained in this file.Snake_PairsOutputFull Pairs output for Snake Range. Output from site and trapline analyses are both contained in this file.Toiyabe_PairsOutputFull Pairs output for Toiyabe Range. Output from site and trapline analyses are both contained in this file.