Food Web Architecture and Population Dynamics in Laboratory Microcosms of Protists

Abstract

In theory, food chain length and omnivory are pivotal elements of food web structure that can affect the population dynamics of species within the web. Long food chains are thought to be less stable than shorter food chains, and omnivores are thought to destabilize food webs, although populations of omnivores may be more stable than populations of nonomnivores. In three of four simple food webs assembled from bacteria and protists in laboratory microcosms, the abundance of bacterivorous protists varied more over time when the species occurred in longer versus shorter food chains. The abundance of protists attacked by omnivorous top predators was either more or less temporally variable than in webs where top predators fed only at one adjacent trophic level, depending on the particular combination of interacting species. The abundance of omnivorous top predators varied less over time than the abundance of top predators restricted to feeding only at an adjacent trophic level. Observations of increased temporal variation in prey abundance in longer food chains and low temporal variation in omnivore abundance agree broadly with several predictions of food web theory. The observation that different species in similar trophic positions can exhibit very different dynamics suggests that stability may depend on complex interactions between species-specific life-history traits and general patterns of food web architecture.

The inflationary effects of environmental fluctuations in source–sink systems

“…All populations of P. tetraurelia were maintained with standard protozoan culture methods (28). Replicate microcosms consisted of 100 ml of nutrient medium [made from autoclaved and filtered pond water to every liter of which a single (0.70 g) Carolina Biological Supply protozoan pellet was added] contained within 175-ml glass bottles, covered with an aluminum foil lid.…”

Forest structure affects resource partitioning between pygmy and white-breasted nuthatches

“…Resource partitioning can occur when species forage in different habitats/ micro-habitats (MacArthur 1958;Hutchinson 1961;Alatalo & Alatalo 1979;Török 1990;Steen et al 2007) and at different times (Bosakowski & Smith 1992;Lawler & Morin 1993;Kronfeld-Schor & Dayan 2003;Lara et al 2009). Furthermore, coexisting species often use different hunting tactics that result in the capture of different prey items (Pulliam 1985;Kent 1986aKent , 1986bKiszka et al 2011).…”

Mercury Trophic Transfer in a Eutrophic Lake: The Importance of Habitat‐specific Foraging

“…This suggests that there are inherent properties of food webs that affect Hg transfer. Food webs are extremely complex with extensive omnivory and a great deal of spatial and temporal variability (Winemiller 1990, Polis 1991, Lawler and Morin 1993, Dunne et al 2002. They consist of a network of weak and strong trophic interactions (linkages) that vary both temporally and spatially (Dunne et al 2002).…”