Spatio-temporal variation of macroinvertebrate metacommunity organization in a monsoon-climate region

Aim Disentangling the drivers of community assembly and species diversity in space and time is critical to elucidating metacommunity theory. However, our understanding of how metacommunity structuring will change over time remains insufficient, especially in rivers in the monsoon climate zone. We examined whether (1) the idealized metacommunity structure is different among seasons and (2) the relative importance of underlying mechanisms on community assembly varies within and across tributaries as well as among seasons. Location Five tributaries in the Hanjiang River Basin. Taxon Macroinvertebrates. Methods Benthic macroinvertebrates and environmental data were collected seasonally (i.e. spring, summer, autumn and winter) from the same 70 sampling sites. The elements of metacommunity structure (EMS) framework was employed to identify which idealized topology best characterizes the actual metacommunity. Redundancy analysis and variance partitioning procedures were applied to determine key environmental and spatial factors and to examine their relative contributions to variation in community structure in different seasons. Results The best-fit metacommunity typologies were consistent over time, with metacommunity structure in each season displaying Clementsian gradients, characterized by high degrees of coherence and turnover, and positive boundary clumping. Environmental control prevailed over spatial processes in structuring macroinvertebrate communities, but their relative influence on community variation was context-dependent. Particularly, environmental filtering was the predominant mechanism at the intermediate spatial scale. However, spatial processes had gradually stronger effects at smaller and larger extents. Main conclusions Both EMS analysis and the variance partitioning approach suggested environmental filtering was the principal structuring processes for macroinvertebrate assemblages throughout the year, although mass effects and dispersal limitation also played significant roles at smaller and larger spatial extents respectively. Considering that the most influential environmental factors shaping macroinvertebrate communities were variable across seasons, we argue that spatio-temporal investigations would provide more information on community assembly than single snapshot studies.