abstract: Though prey use a variety of information sources to assess predation risk, evolutionary cohistory with a predator could constrain information use, and nonnative prey might fail to recognize risk from a novel predator. Nonnative... more
abstract: Though prey use a variety of information sources to assess predation risk, evolutionary cohistory with a predator could constrain information use, and nonnative prey might fail to recognize risk from a novel predator. Nonnative prey might instead use generalized risk assessment, relying on general alarm signals from injured conspecifics rather than cues from predators. I tested the influence of shared predator-prey history on information use, comparing responses among three native and four nonnative prey species to chemical cues from a native predator and cues from injured con-specific prey. Nonnative prey demonstrated information generalism: (1) responding stronger to alarm cues released by injured conspecific prey than to cues from predators and (2) responding similarly to alarm cues as to cues from predators consuming injured conspecific prey. By contrast, for native prey, multiple information sources were required to elicit the greatest defense. The influence of other sources of chemical information was not predicted by cohistory with the predator: only one nonnative snail responded to the predator; digestion was important for only two native species; the identity of injured prey was important for all prey; and predator and prey cues contributed additively to prey response. Information generalism, hypothesized to be costly in coevolved interactions, could facilitate invasions as a driver of or response to introduction to novel habitats.
Background/Question/Methods Though it was originally supposed that prey in invaded predator-prey interactions would be unlikely to respond defensively to an evolutionarily novel predator, observations of this phenomenon are increasingly... more
Background/Question/Methods Though it was originally supposed that prey in invaded predator-prey interactions would be unlikely to respond defensively to an evolutionarily novel predator, observations of this phenomenon are increasingly common. Several mechanisms for recognition have been proposed, including adaptation, learning, and generalized risk assessment. The prevalence of any one of these mechanisms has implications for invasion ecology, potentially enabling managers to identify when invasive prey might elude biotic resistance, or when the impact of invasive predators is likely to be mitigated by appropriate prey responses. Moreover, invasive species offer an opportunity to test theory on the role of co-evolution in selecting for information strategies in risk assessment. In mesocosm experiments, I investigated the relative importance of single and combined chemical cues indicating predation risk (fed or starved native crab, injured conspecifics or bland prey) in influencing...
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Evidence of food uptake in the photosynthetic genus Dinophysis comes solely from the presence of food vacuoles, as no photosynthetic cells have ever been observed in the act of feeding. We examined the feeding ecology of D. acuminata in... more
Evidence of food uptake in the photosynthetic genus Dinophysis comes solely from the presence of food vacuoles, as no photosynthetic cells have ever been observed in the act of feeding. We examined the feeding ecology of D. acuminata in natural populations and under laboratory conditions. Using depth-integrated sampling of the water column, we determined the frequency of food vacuolated cells at 2-h intervals over a 24-h period in a shallow marine embayment. Food vacuoles in preserved cells were enumerated using Nomarski differential interference contrast microscopy; ultrastructural characters were recorded by transmission electron microscopy. A peak in the feeding activity was observed toward dusk for an abundant June population, with 26% of cells with at least one food vacuole. Mechanisms of concurrent carbon acquisition were evident from the presence of chloroplasts with starch grains and food vacuoles within the same cell. Vacuole content could not be identified. In a preliminary 2-wk long simulated grazing experiment, a mixture of two hypothesized preys, Rhodomonas salina and Dunaliella tertiolecta, was offered to D. acuminata; the Dinophysis populations decreased steadily and at the same rate, whether food was present or not. The evaluation of the food vacuole frequency will be repeated in the coming season to verify the observed pattern, while grazing experiments will include a variety of food items and incubation conditions. Our current inability to successfully culture any photosynthetic Dinophysis limits ecophysiological approaches, either at the population or cellular level, to manipulation of field samples.Supported by National Institutes of Health Grant GM62126-01A1.