Physical disturbance has been proposed as a factor mediating the effects of predators on herbivore populations. This study assessed the differential impact of tidal inundation on the spatial distributions of arthropod predators and prey and the possibility that such disturbance creates temporary spatial refuges for herbivores and promotes outbreaks. We examined this issue on a mid-Atlantic salt marsh where planthoppers and their invertebrate predators are the dominant players in the terrestrial food-web. Planthoppers often reach outbreak densities in low marsh habitats characterized by greater tidal inundation. We hypothesized that three of the most abundant predators of planthoppers, the lycosid spider Pardosa littoralis, the sheet-web building spider Grammonota trivitatta, and the mirid egg predator Tytthus vagus, would be more adversely affected by rising tidewaters than are planthoppers. We measured densities of planthoppers and predators during different phases of the tide cycle at different elevations within and across habitats. Prey were most abundant in low-elevation marsh habitats and their distribution was unaffected by tidal inundation. In contrast, all three predator taxa shifted their distribution toward higher elevations during extremely high tides. Spatial shifts in predator distribution created a potential refuge for prey at low elevations, where indeed prey outbreaks are most frequently observed. Thus, even temporary refuges created by tidal disturbance can have important consequences for the coupling of predator-prey interactions and outbreak dynamics of insect herbivores.
Species 1: Araneae Lycosidae Pardosa littoralis (wolf spider)
Species 2: Homoptera Delphacidae Prokelisia marginata
Species 3: Heteroptera miridae Tytthus vagus
Keywords: Physical disturbance, Predator-prey interaction
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