Prey‐driven control of predator assemblages: zooplankton abundance drives aquatic beetle colonization

Abstract

Trophic interactions are critical determinants of community structure and ecosystem function. In freshwater habitats, top predators are traditionally viewed as drivers of ecosystem structure, shaping populations of consumers and primary producers. The temporary nature of small water bodies makes them dependent on colonization by many organisms, particularly insects that form highly diverse predator assemblages. We conducted mesocosm experiments with naturally colonizing populations of aquatic beetles to assess how prey (zooplankton) abundances influenced colonization and assemblages of natural populations of aquatic beetles. We experimentally demonstrate that zooplankton populations can be proximate regulators of predator populations and assemblages via prey-density-dependent predator recruitment. Our results provide support for the importance of prey populations in structuring predator populations and the role of habitat selection in structuring communities. We indicate that traditional views of predators as drivers of ecosystem structure in many systems may not provide a comprehensive picture, particularly in the context of highly disturbed or ephemeral habitats.

River habitat homogenisation enhances trophic competition and promotes individual specialisation among young of the year fish

“…A similar response has been reported by Hoogenboezem, Lammens, van Vugt, and Osse () for the common bream under zooplankton abundance lower than 500 ind/L. For many cyprinids and percids, switching from water column feeding to a selective capture of benthic prey could decrease the relative energy gain (Nunn et al., ) and enhance competition, which could be mitigated by habitat diversity and presence of alternative resources (Pintar & Resetarits, ).…”

Colonization across gradients of risk and reward: Nutrients and predators generate species‐specific responses among aquatic insects

“…Even though predaceous beetle species do not directly feed on the rabbit chow or leaf litter, base resources and nutrients support higher primary productivity, which in turn supports higher abundances of prey taxa (zooplankton, larval insects) as well as food for the omnivorous hydrophilids. The predaceous dytiscids select habitats with higher abundances of zooplankton, whereas hydrophilids do not, while both families select patches with more leaf litter (Pintar & Resetarits, , ). This indicates that aquatic beetles can be responsive to both the resources they directly use and the overall nutrient availability.…”

“…Habitat selection plays an important role in determining the colonization rate and resulting community structure both within and among habitat patches for aquatic insects (Binckley & Resetarits, ; Vonesh et al., ). Both predator presence and identity, and resource abundance and quality, can cause differential colonization rates that result in aquatic beetle assemblages that vary based on these patch characteristics (Pintar & Resetarits, , ; Resetarits & Pintar, ). While we observed species‐specific colonization in response to variation in nutrients and predator presence, overall assemblage structure of colonists was driven by predator presence alone, again reflecting the primacy of predation risk in freshwater habitats.…”

“…2D stress = 0.21; 3d stress = 0.15 the omnivorous hydrophilids. The predaceous dytiscids select habitats with higher abundances of zooplankton, whereas hydrophilids do not, while both families select patches with more leaf litter (Pintar & Resetarits, 2017a, 2017b. This indicates that aquatic beetles can be responsive to both the resources they directly use and the overall nutrient availability.…”

Aquatic beetles influence colonization of disparate taxa in small lentic systems

“…We later counted and identified to order zooplankton in 1 ml subsamples from each 50 ml sample (Wetzel & Likens, 2000). We initially included total zooplankton abundance as a covariate in dytiscid analyses as higher zooplankton abundances may lead to higher colonization by dytiscids (Pintar & Resetarits, 2017a), but there was no effect here ( p > .37), and we excluded this factor from all analyses. We terminated the experiment on 9 June and exhaustively collected beetles below the screens and sampled other insects by sweeping a fine mesh net around the pool until no debris remained.…”