Dissertation Research: Habitat Partitioning by Notonectids: Temporal Patterns and the Role of Spatial Complexity

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9902177GilbertCoexistence of intraguild predators, potential competitors that are also mutually predaceous, is rarely predicted by models despite its commonplace occurrence. One mechanism by which conflict may be minimized is spatial partitioning of habitat. Such zonation has been observed in a small shallow pond with four notonectid species - voracious insect predators which share resources and readily feed on each other. Conflict may be reduced by this partitioning, but these patterns exhibit seasonal and diel shifts in ways that could substantially endanger or enhance coexistence. In this dissertation research, field study will quantitatively confirm the preliminary observations presented here. Mechanisms leading to spatial partitioning and temporal changes will be investigated in experimental microcosms. Mid-season distributional shifts of juveniles may be a response to a decline in adult predators, allowing juveniles to complete development in a high-resource habitat. Conversely, diel shifts in species distribution increase potential for conflict by increasing nocturnal overlap. Diurnal and nocturnal diet of field-collected notonectids will be compared, using electrophoretic gut content analysis, to determine whether intraguild predation increases at night as expected. In addition, a new hypothesis for diel horizontal migration is proposed: profitability of spatially complex and open habitat is reversed at night for predators using both vision and mechanoreception.