The effects of spatial network topology on metacommunity dynamics

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Paulina A. Arancibia, Graduate Program in Ecology & Evolution, Rutgers University, New Brunswick, NJ

Background/Question/Methods
The study of metacommunity dynamics is increasingly important due to the rising rates of habitat loss and fragmentation. Not only it is necessary to understand how metacommunities respond to these pressures but also to identify which local communities are more susceptible to biodiversity loss, what measures can be taken to mitigate losses, and how to prevent their negative effects on ecosystem functioning. Although ecological factors such as community composition and dispersal—among others—can affect metacommunity dynamics, the spatial configuration (i.e. topology) of the network of habitats can also affect biodiversity patterns. Previous studies have suggested network topology can alter metapopulation dynamics, but it is unclear if these patterns hold after increasing community complexity. In this study I used a food web module composed of three species of aquatic ciliates (two preys and one predator) to understand how spatial configuration affects regional metacommunity dynamics. For this purpose, I designed metacommunities of 24 patches arranged as random and scale free networks, and evaluated their occupancy patterns, diversity, biomass, and community stability and persistence for ∼30 protist generations.
Results/Conclusions
The results show a consistent effect of network topology on metacommunity dynamics. The full food web module studied, persisted for almost 10 generations longer in metacommunities arranged as scale free networks. Moreover, these topologies consistently had higher occupancy, biomass, richness and diversity throughout the experiment. I also observed that scale free metacommunities had higher stability (measured as the coefficient of variation of biomass) and lower community synchrony levels. I suggest that scale free networks being more heterogenous in terms of connectivity than random networks, allow the possibility of spatial refugia from both competition and predation, which ultimately results in increased metacommunity persistence and function. Unsurprisingly, this pattern contrasts with observations from a previous study about metapopulation dynamics of one of the prey species, that describes higher occupancy and abundance in random networks. This indicates the importance of species interactions in these systems. Altogether, these results highlight the importance of studying metacommunity patterns in a spatially explicit context.