Patch size distribution affects species invasion dynamics in dendritic networks

Biological invasions are globally affecting ecosystems, causing local
species loss and altering ecosystem functioning. Understanding how such
biological invasions occur and succeed is thus of high priority. Both
local properties and the spatial network structure have been shown to be
determinants of invasion success, and the identification of spatial
invasion hubs directly promoting invasion dynamics is gaining attention.
Spatial dynamics, however, could also indirectly alter invasion success by
shaping pre- invasion local community structure: in many ecosystems, such
as riverine networks, regional properties such as patch size distribution
are known drivers of local community structures, which themselves may
affect the establishment success of invading species. Using microcosm
experiments in dendritic networks, we disentangled how inherent patch size
distribution and dispersal along specific network topologies shaped local
resident communities, and, subsequently, affected the establishment
success of invading species. After controlling for regional-scale effects
of connectivity on pre-invasion diversity, we find that patch size
distributions independently shaped pre-invasion community diversity and
invasion success, with no direct effect of pre-invasion diversity on
invasion success. Our results suggest that 1) landscape configuration
plays an underestimated role in invasion success and that 2) invasion
success should follow predictable landscape-scale patterns in riverine
networks given non-random patch-size distribution.