Cross‐ecosystem effects of terrestrial predators link treefrogs, zooplankton, and aquatic primary production

Predators can directly or indirectly shape food webs through a combination of consumptive and non‐consumptive effects. Yet, how these effects vary across natural populations and their consequences for adjacent ecosystems remains poorly resolved. We examined links between terrestrial predators and aquatic ecosystems through their effects on a locally abundant amphibian, the red‐eyed treefrog ( Agalychnis callidryas ), which has arboreal eggs (heavily predated by snakes and wasps) and aquatic larvae; embryos can escape terrestrial threats by hatching at an earlier age and smaller size. Our multi‐site field survey indicates that in natural populations, the relative contributions of these consumptive and non‐consumptive effects of predators can be substantial and remarkably similar. However, in mesocosms where we experimentally mimicked these predator effects, changes in the density and initial hatching age of tadpoles carried distinct consequences for aquatic food webs. Density‐dependent growth resulted in peak tadpole biomass at intermediate densities (reflecting intermediate predation), and early‐hatched tadpoles grew 16% faster and produced 26% more biomass than their late‐hatched counterparts. These changes in tadpole growth and size differentially affected zooplankton communities, and the production and stability of phytoplankton. Together, these results illustrate multiple pathways through which predators in one ecosystem can modulate the structure of adjacent food webs.