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RESEARCH PRODUCT

Effects of environmental and spatial variables on lotic ostracod metacommunity structure in the Iberian Peninsula

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The heterogeneous distribution of aquatic species in lotic environments has been studied little in terms of metacommunity theory. Previous empirical tests have found significant spatial and environmental effects in pond and lake communities, but this has not yet been clearly established for stream networks. We conducted a multi-season survey of mountain streams in the Iberian Peninsula. We recorded GIS and in situ environmental data and collected biological samples to determine ostracods and macroinvertebrates and identified 41 ostracod species, the most common belonging to genera Herpetocypris , Sarscypridopsis , and Ilyocypris . A generalized linear model analysis showed that thermal range, alkalinity, slope, and the Iberian Average Score Per Taxon (IASPT) macroinvertebrate biotic index negatively influenced ostracod presence, whereas the Iberian Bio-Monitoring Working Party (IBMWP) biotic index and nitrite concentration had a positive effect. Conductivity, mean air temperature, slope, and IBMWP were the most statistically significant environmental factors affecting ostracod species distribution according to a canonical correspondence analysis, together with large-scale spatial factors identified with a principal coordinates neighbour matrix (PCNM) analysis. Both environment and space, although markedly overlapping, contributed significantly to the explanation of ostracod metacommunity structure. We conclude that both colonisation histories and environmental adaptations affect the patterns of distribution of aquatic organisms in riverine environments, extending beyond intra-basin connectivity.