Abstract
The functional response of a predatory nematode and the influence of different prey sizes and habitat structure on the concerning parameters were analyzed. We hypothesized that the handling of small prey would be less time-consuming, whereas feeding on larger prey would be more efficient. Therefore, type II functional response curves were expected for large prey and a trend towards type III curves for small prey. We expected the introduction of prey refuges to shift the functional response curves from hyperbolic to sigmoidal and that the effect would be even more pronounced with smaller prey. P. muscorum consumed large amounts of small and large C. elegans, with daily per capita ingestion of prey reaching a maximum of 19.8 µg fresh weight, which corresponds to 4.8 times the predator’s biomass. Regardless of prey size and habitat structure, P. muscorum exhibit a type III functional response. Overall, the allometric effect of prey size had a greater effect on the predator’s functional response than did the addition of substrate, presumably due to the similar body shape and mobility of the two nematode species. Our results demonstrate that individual factors such as feeding behavior are important determinants of functional responses and therefore of ecosystem stability.
Highlights
The quantitative characteristics of consumer-resource interactions determine our understanding of the stability of population dynamics, complex food webs and ecosystem function
The maximum per capita ingestion of nematode prey per 4 h in the treatments without substrate occurred at a prey density of 300 nematodes, with 73 small and 52 large C. elegans individuals consumed in the respective treatments (Fig. 1)
This study shows for the first time that there is a strong interaction of predatory nematodes with nematodes as prey, both with and without substrate
Summary
The quantitative characteristics of consumer-resource interactions determine our understanding of the stability of population dynamics, complex food webs and ecosystem function. Nematodes are the most abundant metazoan group within the meiofauna, reaching maximum densities >106 individuals per m2 in the sediment and periphyton of stony hard-substrates of freshwater habitats[26,27] They colonize all types of habitats and climatic zones and establish a permanent standing stock in the course of the year, comprising many different species[28,29,30,31]. A recent study[46] demonstrated that an increase in the amount of predator-free space causes a shift from a type II to a type III functional response, with effects on the stability of predator- prey dynamics based on an accelerated predation risk at low resource densities
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