Prey and predator density-dependent interactions under different water volumes

Predation is a critical ecological process that directly and indirectly
mediates population stabilities, as well as ecosystem structure and
function. The strength of interactions between predators and prey may be
mediated by multiple density-dependences concerning numbers of predators
and prey. In temporary wetland ecosystems in particular, fluctuating water
volumes may alter predation rates through differing search space and prey
encounters rates. Using a functional response approach, we examined the
influence of predator and prey densities on interaction strengths of the
temporary pond specialist copepod Lovenula raynerae preying on cladoceran
prey, Daphnia pulex, under contrasting water volumes. Further, using a
population dynamic modelling approach, we quantified multiple predator
effects across differences in prey density and water volume. Predators
exhibited Type II functional responses under both water volumes, with
significant antagonistic multiple predator effects (i.e. antagonisms)
exhibited overall. The strengths of antagonistic interactions were,
however, enhanced under reduced water volumes and at intermediate prey
densities. These findings indicate important biotic and abiotic contexts
that mediate predator-prey dynamics, whereby multiple predator effects are
contingent on both prey density and search area characteristics. In
particular, reduced search areas (i.e., water volumes) under intermediate
prey densities could enhance antagonisms by heightening predator-predator
interference effects.