The role of dispersal on the persistence of patchily-distributed populations has been well studied; however, the effects of dispersal on community processes such as predation and competition have only recently begun to be investigated. Metacommunity theory predicts that intermediate levels of dispersal among suitable habitat patches will increase the persistence time of both predators and their prey in fragmented landscapes, but there have been few empirical studies to test these predictions. There are even fewer studies which examine how varying the dispersal rate among habitat patches affects predation rate and persistence of the metacommunity. We used an insect-red clover metacommunity to test the hypothesis that varying dispersal rate and predator density would affect predation rate and prey persistence. Red clover is commonly planted as a cover crop in agricultural systems, the leafhopper Agallia constricta is a common pest of red clover, and damsel bugs (Nabis spp.) are generalist predators common in many agricultural systems. Three experimental mesocosms were connected by plastic tubing into a triangular shape, and dispersal rates among habitat patches were controlled by varying the amount of time the connecting tubes were open to movement of insects. Three dispersal treatments were used to simulate a single, patchy community, a metacommunity, and isolated communities.
Results/Conclusions
Less than 5% of the leafhopper population moved among habitat patches in all treatments, suggesting that each individual mesocosm was operating as a single, isolated community. Neither dispersal level nor damsel bug density significantly affected leafhopper survival time, but the treatment simulating a single, patchy community trended towards lower leafhopper survival times. When damsel bugs were absent, there was no difference in A. constricta survival time among the three dispersal treatments, and density-dependent dispersal of leafhoppers was not observed. These results suggest that leafhoppers may only disperse among habitat patches when conspecific densities reach levels greater than would normally be observed in the field. Damsel bugs were also able to consume a large proportion of A. constricta in each mesocosm per day, suggesting that they may be a candidate to control this leafhopper in the field since no specialist parasitoid is known for A. constricta.
