Hierarchical metapopulation dynamics of two aphid species on a shared host plant.

We modeled hierarchical multiscale colonization-extinction dynamics of two aphid species living in a shared host plant. We parameterized the model with data collected at the level of individual ramets of the host plant, with the plants being organized as groups within islands. As expected, the extinction rates and per capita colonization rates decreased with increasing spatial scale. The per capita colonization rates were greater for winged than for unwinged individuals, but as the unwinged individuals were much more abundant, they actually performed most of the colonizations. Colonizations and extinctions were negatively correlated, so that when the colonization rate in a given island was high, the extinction rate in the same island was low. There was a clear indication of interspecific interaction, with the presence of one species increasing the extinction rate and decreasing the colonization rate of the other species. Further simulation results based on the parameterized model show a contrasting pattern between the two species, with Metopeurum fuscoviride (with relatively stable dynamics) being favored by a highly aggregated distribution of the ramets, whereas for Macrosiphoniella tanacetaria (with a high turnover rate), an equally high persistence time follows if the plants are distributed in a segregated manner over several islands.