Complex relationships between species niches and environmental heterogeneity affect species co-occurrence patterns in modelled and real communities

Abstract

ResearchCite this article: Bar-Massada A. 2015 Complex relationships between species niches and environmental heterogeneity affect species co-occurrence patterns in modelled and real communities. Proc. R. Soc. Species co-occurrence analysis is commonly used to assess how interspecific interactions dictate community assembly. Non-random co-occurrences, however, may also emerge from niche differences as well as environmental heterogeneity. The relationships between species co-occurrence patterns, environmental heterogeneity and species niches are not fully understood, due to complex interactions among them. To analyse the relationships among these patterns and processes, I developed synthetic community models and analysed a large dataset of tree species across the conterminous United States. Niche overlap and environmental heterogeneity had significant and contrasting effects on species co-occurrence patterns, in both modelled and real communities. Niche breadth, in turn, affected the effect sizes of both variables on species cooccurrence patterns. The effect of niche breadth on the relationship between co-occurrence and niche overlap was markedly consistent between modelled and real communities, while its effect on the relationship between co-occurrence and environmental heterogeneity was mostly consistent between real and modelled data. The results of this analysis highlight the complex and interactive effects of species niche overlap, niche breadth and environmental heterogeneity on species co-occurrence patterns. Therefore, inferring ecological processes from co-occurrence patterns without accounting for these fundamental characteristics of species and environments may lead to biased conclusions.

Environmental Selection, Dispersal, and Organism Interactions Shape Community Assembly in High-Throughput Enrichment Culturing

“…To that end, pairs of taxa were identified as potentially interacting if they were found more or less frequently together than expected by random chance. Given that every local environment is initially identical, cooccurrence patterns are not linked to initial abiotic conditions and "habitat-filtering," a common problem for studies done in situ (32). Overall, we observed a larger number of interactions in the anaerobic samples than in the aerobic samples (Table 1 and Fig.…”

Non‐stationarity in the co‐occurrence patterns of species across environmental gradients

“…This study is unique as it explicitly examined several confounding factors that are often ignored (Bar‐Massada ), but may substantially bias the results of co‐occurrence analyses. For example, species co‐occurrence analyses typically conflate species interactions with environmental filtering, making separating the two difficult.…”

“…Previous studies have shown that non‐random species co‐occurrence patterns might emerge simply due to the degree of similarity in species’ niches, the amount of cohesion in their geographic distributions, and the environmental heterogeneity of the regions they inhabit (Connor, Collins & Simberloff ; Bar‐Massada ; Royan et al . ).…”

“…). For example, increasing levels of niche overlap between tree species leads to more aggregated co‐occurrence patterns, while increased environmental heterogeneity leads to more segregated patterns (Bar‐Massada ). Co‐occurrence analyses should account for these confounding factors if one attempts to gain insight about relationships between co‐occurrence patterns and biotic interactions.…”

“…However, these analyses are confounded by several factors that can lead to non‐random co‐occurrence patterns even in the absence of interspecific interactions. These factors include similarities between species’ environmental preferences (Bar‐Massada ; Royan et al . ), environmental heterogeneity (Heino & Grönroos ; Bar‐Massada ) and differences in geographic ranges (Connor, Collins & Simberloff ; Pollock et al .…”