The price of connectivity in stable vs. disturbed conditions

High connectivity is usually linked with high dispersal, generally a positive characteristic in a stable metapopulation.  However, high dispersal might not always be a good thing, especially when ecosystems switch between stable and disturbed states, such as when seen under changing temperatures.  In their recent paper in Oikos, de Boer et al. look at the potential trade-off between high dispersal between local populations during stable environmental conditions, and how this dispersal impacts community structure once a disturbance moves through.  They use periphyton metacommunities (a mixture of benthic microalgae, mostly diatoms) as their model system, and subject them to a simulated heat wave.  They hypothesize that in stable conditions, high dispersal leads to lower biomass accumulation due to homogenization of local communities, but following a disturbance, high dispersal allows faster regional recovery through the spread of well-adapted individuals.

By manipulating dispersal ability, temperature, and light regimes for periphyton communities, de Boer and colleagues were able to test how dispersal affected community structure following disturbance.  Their results show that communities did in fact recover quicker when allowed greater dispersal following disturbance, but this benefit of greater connectivity was mitigated by reduced biomass accumulation during stable conditions due to homogenization.  This tradeoff between capacity for recovery and maximizing heterogeneity means that managing connectivity on a landscape level requires creating a balance between too much and too little.  Although there is a strong potential for communities connected by dispersal to recover successfully after an environmental stress such as increased temperatures, the persistent threat of climate change may continue to affect community composition and structure in the long term.