Effects of dispersal mode on the environmental and spatial correlates of nestedness and species turnover in pond communities

Advances in metacommunity theory have made a significant contribution to understanding the drivers of variation in biological communities. However, there has been limited empirical research exploring the expression of metacommunity theory for two fundamental components of beta diversity: nestedness and species turnover. In this paper, we examine the influence of local environmental and a range of spatial variables (hydrological connectivity, proximity and overall spatial structure) on total beta diversity and the nestedness and turnover components of beta diversity for the entire macroinvertebrate community and active and passively dispersing taxa within pond habitats. High beta diversity almost entirely reflects patterns of species turnover (replacement) rather than nestedness (differences in species richness) in our dataset. Local environmental variables were the main drivers of total beta diversity, nestedness and turnover when the entire community was considered and for both active and passively dispersing taxa. The influence of spatial processes on passively dispersing composition, total beta diversity and nestedness was significantly greater than for actively dispersing taxa. Our results suggest that species sorting (local environmental variables) operating through niche processes was the primary mechanism driving total beta diversity, nestedness and turnover for the entire community and active and passively dispersing taxa. In contrast, spatial factors (hydrological connectivity, proximity and spatial eigenvectors) only exerted a secondary influence on the nestedness and turnover components of beta diversity

Heino & Tolonen_Ecography

This table includes information on species' regional occupancy (number of sites occupied), abundance (total abundance across 48 lakes), niche features, traits and taxonomic position

data for pairwise site beta diversity

data for pairwise site beta diversit

Environmental variables and bacterial and fungal OTUs

Measured environmental variables for the study sites and occurrences of bacterial and fungal OTUs obtained using pyrosequencing. Units for environmental variables are provided in column headings. Unit for particle size is explained in a separate row below the data

data for multiple site beta diversity

data for multiple site beta diversit

StudyDataDryas

The data contains species names and used explanatory variables in the study published in Oikos. For further information, please contact Janne Alahuhta

Appendix C. Tests of models assumptions.

Tests of models assumptions

Appendix A. Schematic representation of the main analyses used in this study.

Schematic representation of the main analyses used in this study

Appendix B. Loadings from PCA, PERMANOVA, and PERMDISP results, scatterplots, and results from GLM and matrix comparisons.

Loadings from PCA, PERMANOVA, and PERMDISP results, scatterplots, and results from GLM and matrix comparisons

Supplementary Information files for Invasive crayfish alter the long‐term functional biodiversity of lotic macroinvertebrate communities

Supplementary Information files for Invasive crayfish alter the long‐term functional biodiversity of lotic macroinvertebrate communities. 1. Invasive species represent one of the primary threats to global biodiversity. Despite acknowledged implications for taxonomic properties of ecological communities following invasion, functional measures remain poorly understood.2. We examined the long-term implications of invasion by a crayfish species (Pacifastacus leniusculus) on functional alpha and beta diversity properties of lotic macroinvertebrate communities in three English regions. The dataset comprised 477 samples collected predominantly between 1990 and 2013. Unlike many invasion studies, we employed before and after invasion comparisons, in association with control rivers not invaded by crayfish.3. Functional richness and divergence metrics displayed the strongest responses to invasion, highlighting that P. leniusculus may alter the range of functional niches and extreme trait values (likely reflecting resistance and resilience mechanisms) displayed by macroinvertebrate communities. Interestingly, in one region, biodiversity gains seen in control rivers were not mirrored in invaded rivers, potentially suggesting that invasion inhibited4. Invasion by signal crayfish resulted in functional compositional changes in two of the three English regions studied, with these rivers yielding greater ecological differences between pre- and post-invasion periods relative to control rivers. This change was primarily driven by higher nestedness values in invaded rivers, with communities containing functional subsets relative to control rivers. The third region demonstrated no functional compositional changes or alterations in functional beta diversity associated with invasion.5. Our findings indicated that in most instances, the functional properties of macroinvertebrate communities responded to crayfish invasion and may therefore represent a complementary means to monitor the ecological condition of lotic ecosystems. Given their spatial transferability, functional traits could provide a platform to guide regional management practices in the face of biological invasions.</div