Role of regional and local factors in population dynamics of rock pools metacommunity along the gradient of species habitat specialization

Background/Question/Methods          Metacommunity theory explicitly recognizes the interplay between local and regional processes in structuring local communities.   Recently, using data from a rock pool invertebrate community we found that such a system can exhibit an internal differentiation of structuring processes, with habitat specialists governed predominantly by environmental factors and habitat generalists governed mainly by spatial factors.  In addition to, effect of environmental variability is higher on population synchrony of specialist than generalist species in the metacommunity. Specifically, we thus predicted that temporal dynamics of specialists is tied more to variability of environment because habitat specialists tend to be more tightly constrained by local conditions as compared to habitat generalists to whom environmental conditions in individual rock pools may appear more homogeneous. We tested these predictions using natural microcosms communities for which a long-term (9 year) environmental and population dynamics data were available. We focused on population synchrony, and the corresponding synchrony in variation of environmental factors, because synchrony captures well both the temporal and spatial dimensions of population dynamics.  We used cross-correlations function to determine the spatial population synchrony in population sizes.  We also assessed the effects of distance among pools and synchrony in variation of environmental variables on population synchrony of species.  Finally, we examined how these effects varied along the gradient of species habitat specialization.

Results/Conclusions

We found that the effect of environmental variability was increasing with the specialization (synchrony among specialists was correlated more with synchrony of physical variables in the same pools).  However the effect of distance on population synchrony did not significantly decline with the decline of specialization.   Thus, the study suggests that species of different habitat specialization show systematic differences with respect to local processes involving environmental characteristics  but fail to show such difference with respect to  regional processes involving distance, at least when long-term dynamics is concerned.