DOI: 10.5061/dryad.rt201
title: Data from: A fresh approach reveals how dispersal shapes metacommunity structure in a human-altered landscape

description: To understand species losses from disturbed landscapes, it is important to
 distinguish the effects of degraded environmental conditions from those
 caused by barriers to dispersal between habitat patches. To assess the
 relative importance of these effects, we developed a new approach using
 permutation and association tests applied to rank abundance data, using
 the invertebrate fauna of two rivers in two seasons. Our study streams
 were Hughes Creek and Seven Creeks, in south-eastern Australia, which have
 both been degraded by agriculture in downstream sections. We collected
 benthic invertebrates and also dispersing individuals (drift, terrestrial
 adults) during two seasons in 2007–2008. Study sites spanned strong
 environmental gradients as well as the main dispersal route (up- and
 down-channel). Environmental data were analysed to set up permutation
 tests on rank abundances. Survey and disperser data were contrasted using
 contingency table analyses. The results suggest dispersal plays a strong
 role in community structure. Environmental effects were evident and
 strongest upstream, but evidence of environmental effects was weak over
 much of the gradient. Many species had different distributions in
 different data sets or dispersers that were abundant at locations distant
 from centres of benthic distribution. Our results differ from many
 studies, but few have been able to evaluate dispersal effects directly.
 Our method provides a practical approach for evaluating the role dispersal
 plays in driving species abundance patterns across landscapes, thus
 bridging a gap between theory and practice. Synthesis and applications.
 Managers typically use indices of ecosystem health that assume
 environmental conditions largely determine species diversity and
 abundance. Dispersal between habitat patches is known to be important, but
 there are no reliable methods to assess the role dispersal may play. We
 provide an approach that allows both dispersal and environmental effects
 on species distributions to be evaluated from survey data. This may open
 the way for dispersal information to be incorporated into management
 actions. Additionally, the approach should allow improved siting of
 restoration projects that depend greatly on successful dispersal of
 individuals for successful outcomes.
description: BenthicDataDensities (numbers per 0.09 metres squared) of different species of invertebrates collected at 8 sites in each of two streams in two seasons.Drift DataAverage numbers or individuals in the drift (over two hours) of multiple species of invertebrates sampled at 4 sites in each of two streams and two seasons.DriftData.csvList Of Species NamesA list of all species in the benthic and drift data sets with taxonomic classification and variable names.ListOfSpeciesNames.csvEnvironmental & Spatial VariablesVarious measures of environmental variation at 8 sites in each of two streams during summer plus the latitude and longitude for each site.Environmental&SpatialVariables.csvWater & Air TemperaturesAir and water temperatures recorded at two sites on each of Hughes Creek and Seven Creeks during summer and spring in 2008 and 2009.Water&AirTemperatures.csv