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Variation in phenology and density differentially affects predator-prey interactions between salamanders.

Thomas L Anderson1,2, Freya E Rowland3, Raymond D Semlitsch3

  • 1Division of Biological Sciences, University of Missouri, 105 Tucker Hall, Columbia, MO, 65211, USA. anderstl@gmail.com.

Oecologia
|September 13, 2017
PubMed
Summary

Density dependence significantly impacts amphibian interactions, often overriding phenological variation effects. High ringed salamander density negatively affected spotted salamanders and lower trophic levels, regardless of breeding timing.

Keywords:
AmbystomaCompetitionIntraguild predationPhenological shiftPriority effects

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Area of Science:

  • Ecology
  • Amphibian Biology
  • Community Ecology

Background:

  • Phenological variation influences species interactions and community structure by altering body size differences.
  • Density-dependent competition can further modify body size disparities, but combined effects of density and phenology are understudied.

Purpose of the Study:

  • To investigate how experimental variation in breeding phenology and density affects interspecific interactions between ringed salamanders (Ambystoma annulatum) and spotted salamanders (Ambystoma maculatum).
  • To determine if these altered salamander dynamics lead to trophic cascades.

Main Methods:

  • Outdoor mesocosms were used to experimentally manipulate ringed salamander density (low/high) and breeding phenology (early/late) for both species.
  • Measurements included body size at metamorphosis, development, growth rates, and survival for both salamander species.
  • Trophic cascades were assessed by measuring the biomass of lower trophic levels.

Main Results:

  • Ringed salamander body size, development, and growth were reduced at high densities. Delayed phenology increased hatchling size but reduced relative growth rates.
  • Spotted salamander growth, size at metamorphosis, and survival were negatively impacted primarily by high ringed salamander density.
  • The biomass of lower trophic levels was also reduced by high ringed salamander density, indicating a trophic cascade.

Conclusions:

  • Density dependence effects on fitness-related traits can modify or supersede those of phenological variation in amphibians.
  • Direct interactions, such as predation, are key mechanisms by which dominant species (ringed salamanders) limit subordinate species (spotted salamanders).
  • Understanding context dependencies, like density and phenology interactions, is crucial for predicting how phenological variation impacts species interactions.