Species-specific differences determine responses to a resource pulse and predation
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The effects of resource pulses on natural communities are known to vary with the type of pulse. However, less is known about mechanisms that determine the responses of different species to the same pulse. We hypothesized that these differences are related to the size of the species, as increasing size may be correlated with increasing competitive ability and decreasing tolerance to predation. A factorial experiment quantified the magnitude and timing of species’ responses to a resource pulse using the aquatic communities found in the leaves of the carnivorous pitcher plant, Sarracenia purpurea. We added prey to leaves and followed the abundances of bacteria and bacterivores (protozoa and rotifers) in the presence and absence of a top predator, larvae of the mosquito Wyeomyia smithii. Resource pulses had significant positive effects on species abundances and diversity in this community; however, the magnitude and timing of responses varied among the bacterivore species and was not related to body size. Larger bacterivores were significantly suppressed by predators, while smaller bacterivores were not; predation also significantly reduced bacterivore species diversity. There were no interactions between the effects of the resource pulse and predation on protozoa abundances. Over 67 days, some species returned to pre-pulse abundances quickly, others did not or did so very slowly, resulting in new community states for extended periods of time. This study demonstrates that species-specific differences in responses to resource pulses and predation are complex and may not be related to simple life history trade-offs associated with size.
KeywordsTop-down Bottom-up Resource control Stability Thresholds Consumer effects Protozoa Pitcher plants
The authors thank Casey terHorst, Abigail Pastore, and Jessie Mutz for comments as well as the very useful suggestions of the anonymous reviewers.
Author contribution statement
TEM and MLB conceived, designed, and conducted the experiment. TEM and CCG analyzed the data and wrote the manuscript.
This work was partially funded by grants from the National Science Foundation (DEB 0519170 and DEB 1456425 to TEM).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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