DOI: 10.5061/dryad.zpc866t7x
title: Coexistence within an endangered predator–prey community in California vernal pools

description: 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
 &gt;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.
description: Please see main manuscript for methodological details.
description: 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).