Résumé
Landscape connectivity structure, specifically the dendritic network
structure of rivers, is expected to influence community diversity dynamics
by altering dispersal patterns, and subsequently the unfolding of species
interactions. However, previous comparative and experimental work on
dendritic metacommunities has studied diversity mostly from an equilibrium
perspective. Here we investigated the effect of dendritic versus linear
network structure on local (α-diversity), among (β-diversity) and total
(γ-diversity) temporal species community diversity dynamics. Using a
combination of microcosm experiments, which allowed for active dispersal
of 14 protists and a rotifer species, and numerical analyses, we
demonstrate the general importance of spatial network configuration and
basic life history tradeoffs as driving factors of different diversity
patterns in linear and dendritic systems. We experimentally found that
community diversity patterns were shaped by the interaction of dispersal
within the networks and local species interactions. Specifically,
α-diversity remained higher in dendritic networks over time, especially at
highly connected sites. β-diversity was initially greater in linear
networks, due to increased dispersal limitation, but became more similar
to β-diversity in dendritic networks over time. Comparing the experimental
results with a neutral metacommunity model we found that dispersal and
network connectivity alone may, to a large extent, explain α- and
β-diversity dynamics. However, additional mechanisms, such as variation in
carrying capacity and competition–colonization tradeoffs, were needed in
the model to capture the detailed temporal diversity dynamics of the
experiments, such as a general decline in γ-diversity and long-term
dynamics in α-diversity.