Background/Question/Methods   The effects of productivity on diversity have been a question of much debate. Despite much research effort, the form of the relationship between primary productivity and diversity, as well as the mechanisms responsible for this relationship, remain unclear. The issue becomes even more complex when one considers the potential effects of spatial subsidy on the dynamics of a target ecosystem. In this paper, we used trapping of tenebrionids as well as plant and carrion censuses on 18 islands in the archipelago of Bahia de los Angeles to investigate the effect of allochthonous input by seabirds on the diversity of tenebrionid beetles on islands of the Gulf of California.

Results/Conclusions   Seabird input decreased species richness and evenness (i.e., causes more heterogeneity of the assemblage), but did not affect diversity (the probability that two individuals belong to different species) or dominance. Seabird input also affected the occurrence and abundance of species on islands. Interestingly, species occurring significantly in a lower proportion of islands than expected were those that also showed a significantly lower relative abundance. This is the case of Triphalopsis spp., occurring in lower number of nesting islands, and when occurring, they did so in significantly lower relative abundance. Our results have conservation implications, in that they showed that diversity in closed communities isolated in habitat fragments yet open to external inputs are negatively affected, decreasing their diversity. Thus, species lost will occur not only due to the decrease in area of the habitat, but also because of the potential effects of disturbance due to external inputs (e.g., fertilizers entering the area from neighboring crops, input of prey from other areas, animals feeding on crops and dumps, etc.).