A re-examination of geographical variation in Nepenthes food webs

The metazoan food webs of Nepenthes pitcher plants exhibit marked geographical variation In previous studies this was attributed lo a number of biogeographical factors including island area. local arthropod biodiversity and degrees of spatial and temporal variation of the host Nepenthes species. Recent investigations showed that some assumptions made in compiling these webs are erroneous and that predation is more widespread in these communities than previously assumed. In this study the new data are used to revise several webs from the geographical studies for comparison with the original versions. Conneetance values and predator:prey ratios increased significantly after revision (though all other food web statistics did not), providing evidence for widespread predation. This is presumed to be a result of some metazoan species adopting variable feeding strategies, depending on which food sources are available in their piteher. Despite this, the geographical patterns are still evident alter revision of the webs. Whether or not these are actually due to geographical Victors is discussed, h is suggested that the structure of Nepenthes webs is influenced by tour major factors- "geographical, deterministic, stochastic and host pitcher (the latter was discounted in previous studies), but that the relative importance of each factor is highly variable and cannot be quantified at present.