The importance of spatial dynamics in pitcher plant metacommunities

 ABSTRACT- Patch numbers and dynamics, as well as spatial arrangements have been shown to affect
 persistence times in predator-prey metapopulations in both simulations and laboratory microcosm
 experiments. However, the significance of these factors for the long term stability of multispecies
 assemblages has not been satisfactorily tested in nature because of the lack of a suitable model system.
 The community of inquilines found in the leaves of the pitcher plant Sarracenia purpurea has provided a
 solution to this problem. The leaves of this carnivorous plant form natural microcosms in which a
 detritus-based aquatic food web composed of bacteria, protozoa, rotifers, insect larvae, and mites develops.
 Each pitcher represents a habitat patch within a bog landscape. Pitcher habitats are ephemeral; the
 metacommunity persists through the colonization of new pitchers. Four arthropod inquilines are habitat
 specialists found only in pitchers, while many protists and bacteria are cosmopolitan in their distributions,
 and probably habitat generalists. The habitat specificities of other common inquilines such as rotifers are
 unclear. Data from field censuses and experiments show that community composition varies spatially, and
 depends strongly on pitcher age, resources, colonization rates, and interspecific interactions. Persistence of
 weak competitors and taxa vulnerable to predation may be fostered by habitat patch heterogeneity which
 reduces their risk of extinction.