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Coexistence within an endangered predator–prey community in California vernal pools

Citation

Messerman, Arianne F. et al. (2021), Coexistence within an endangered predator–prey community in California vernal pools, Dryad, Dataset, https://doi.org/10.5061/dryad.zpc866t7x

Abstract

1. Globally endangered ecosystems, like ephemeral wetlands, are often critical habitat for multiple interacting imperiled species. To conserve this biodiversity, managers must consider both species-specific resource requirements and mechanisms for endangered species coexistence under variable habitat conditions.

2. We examined communities native to California playa pools, ephemeral wetlands that have declined by >90% from their historic extent. Specifically, we describe the diet of a federally Threatened amphibian (Ambystoma californiense), and characterize interactions between this amphibian and two federally Endangered macrocrustaceans (Branchinecta conservatio and Lepidurus packardi) across three rain years to understand how these imperiled species coexist under temporally variable conditions. We examined the dietary preferences of A. californiense larvae, metamorphs, juveniles, and breeding adults, and determined how prey electivity by larval A. californiense differs between natural playa pools and human-modified stock ponds.

3. Within playa pools, both breeding adult and larval A. californiense preyed extensively on L. packardi, whereas fully terrestrial juveniles had relatively empty stomachs. We provide evidence for size-moderated optimal foraging by larval A. californiense, and show that larval prey differed dramatically between playa pools and stock ponds. Additionally, an ontogenetic progression from smaller to larger prey gave the relatively large endangered macrocrustaceans an early-season temporal refuge, during which they reached maturity in all three rain years.

4. Consistent with complex life cycle theory, our results suggest that ephemeral wetland habitat offers abundant food resources for A. californiense relative to terrestrial habitat. Our findings also suggest that diet flexibility facilitates the persistence of this imperiled amphibian in human-modified stock ponds. Temporal offsets in prey maturation rates and ontogenetic shifts in predator diets likely facilitate coexistence among the focal endangered species.

5. We highlight the importance of accounting for spatial and temporal variation in interspecific interactions when predicting the effects of environmental change on biodiversity, particularly in highly threatened ecosystems.

Methods

Please see main manuscript for methodological details.

Usage Notes

Available files include:

  • An R script used to conduct some of our analyses and construct our data figures (Analyses-Figures.R). Analyses not performed in R v. 4.0.0 were conducted in JMP Pro v. 14.0.
  • All necessary data files to run the R script (Electivity-by-Pond.csv, Growth-Curve-2011.csv, Growth-Curve-2012.csv, Growth-Curve-2013.csv, Gut-Contents-Rev.csv, Ohlone-Electivities.csv, Olcott-Electivities.csv, Round-Electivities.csv. Sunol-Electivities.csv, Ontogenetic-Niche-Shift.csv, Stomach-Contents.csv).
  • A file documenting the prey identified at each study wetland based on aquatic field sampling, and calculating relative prey availability in each wetland (Environmental-Prey-Availability.xlsx).
  • A file showing the prey consumed by individual California tiger salamanders of distinct life stage/sex classes as identified by stomach flushing (Stomach-Contents-Calculations.xlsx). Additionally, this file includes calculations of relative prey consumption by percent of the total stomach content mass.
  • Calculations of the coefficients of variation for the prey captured at Olcott Lake and Round Pond across seine hauls (Seines-Spatial-Variation.xlsx).

Funding

Bureau of Reclamation

Solano County Water Agency

University of California, Davis

Solano County Water Agency