Species often exist in groups of populations that are geographically separated but have the potential to exchange individuals (i.e. a metapopulation). Metapopulation synchrony is the fluctuation of population densities in a synchronous fashion within a metapopulation. Synchrony has been observed in many taxa, including fish, amphibians, mammals and it is crucial to understanding the causes of synchrony. The interaction of spatial and temporal variables is key. As a measure of spatial variables, we used the Watts-Strogatz model to generate metapopulation networks of size ten. We varied the network structure from regular-irregular-random structures and looked at various levels of connectedness within a network. For the temporal variables, we generated environmental noise based on the Chambers method that allows one to generate random environmental noise from a frequency input. The generated environmental noise has a frequency-specific environmental synchrony on different time scales. We also looked at how these spatial and temporal variables interact over differing rates of dispersal and population dynamics (undercompensating, overcompensating, cycles and chaos). We ran simulations of metapopulation models to investigate how the metapopulation extinction risk is affected by the interaction of different networks of dispersal, rates of dispersal, the frequency-specificity of environmental noise and the population dynamics.
Results/Conclusions
My preliminary results are based on a network that has the regular network structure in which patches form a ring with various levels on connectedness among the patches. Several inferences can be made based on these preliminary results. As the level of connectedness within a metapopulation increases from the two closest neighbors to the six closest to the eight closest, the probability of a metapopulation extinction decreases across all population dynamics. Increasing dispersal level from 0 to 0.3 per population decreases the probability of a metapopulation extinction; however the extinction probability increases as the dispersal level is increased beyond 0.4 per population. Environmental fluctuations which are positively correlated over long time scales (red-shifted) enhance the probability of metapopulation extinction. These interactions also depend on the type of population dynamics. Understanding the consequences of metapopulation synchrony could lead to better natural resource management and conservation decisions as it would allow us to further understand how combinations of exogenous and endogenous variables (environmental noise, dispersal network and growth rate) could potentially affect the probability of a metapopulation extinction.