Data from: As time goes by: 20 years of changes in the aquatic macroinvertebrate metacommunity of Mediterranean river networks

Aim: to analyse temporal metacommunity dynamics in river networks in
relation to hydrological conditions and dispersal. Location: 15 river
reaches from the Llobregat, Besòs and Foix catchments in the North-Eastern
Iberian Peninsula. Taxon: aquatic macroinvertebrates belonging to 99
different families. Methods: we sampled aquatic macroinvertebrate
communities during spring in 20 consecutive years. We built two
environmental distances (one related with water chemistry and another one
with river flow regime) and two spatial distances (network distance and
topographic distance). Then we used Mantel tests (accounting for spatial
autocorrelation) to relate macroinvertebrate dissimilarity with
environmental and spatial distances. Additionally, we determined the dry
and wet years using the Standardised Precipitation Index (SPI) and we
classified macroinvertebrate families based on their ability to fly and to
drift. Finally, we ran a linear regression model including the correlation
value (r) of each Mantel test as response variable and distance type
(environmental or spatial), SPI, dispersal mode, their pairwise
interactions and a three-way interaction as predictor variables. Results:
metacommunity organization varied over time and it was significantly
affected by precipitation, which can be related to river network
connectivity. The environmental filters, mainly the flow regime, were
generally more important than the spatial filters in explaining community
dissimilarity over the study period. However, this depended on the
dispersal abilities of the organisms. Network fragmentation due to flow
intermittence during the dry years significantly reduced the dispersal
capacity of strong aerial dispersers, leading to spatially structured
metacommunities. For strong drift dispersers, community dissimilarity
patterns were generally best explained by environmental filters regardless
of SPI. Main conclusions: a significant temporal variation in
metacommunity organization can be expected in highly dynamic systems (e.g.
Mediterranean rivers) and it might depend on the dispersal modes and
abilities of the organisms, since they determine the response to changes
in environmental and landscape filters.