Elton (1927) argued that the general constraint on food chain length may be largely related to the loss of energy in successive trophic levels due to low conversion efficiency in
consumer species. This argument extends from the basic thermodynamic principle that energy dissipates from a system as a consequence of inefficient transfer or conversion and has been expanded and refined by Lindeman (1942) and Yodzis (1984), among others.
Fishing has increasingly exerted pressure on fish species and affected the primary
consumer species. We hypothesized at Lake Iro fish catches were below optimal fish production levels, essentially due to excessive localized fishing efforts, and selective fishing techniques by fisherman.
Coexistence and limiting similarity of
consumer species competing for a linear arrayy of resources.
When borrowed by resistant
consumer species, however, they confer chemical defense against higher-order predators or operate in chemical communication as chemosensory excitants (Brown, 1984; Kvitek and Bretz, 2004, 2005; Williams et al., 2004; Narberhaus et al., 2005; Zimmer et at., 2006; Hara, 2011).
where R, C and P are resource, consumer and predator densities, respectively; K is the resource carrying capacity; [R.sub.0], [R.sub.02] are the half-saturation densities of the resource (R) and [C.sub.0] the half-saturation density of the consumer (C); [x.sub.c], [x.sub.p] are the mass-specific metabolic rates of consumer and predator species, respectively; [y.sub.c], [y.sub.pr] and [y.sub.pc] are measures of ingestion rate of
consumer species and predator (Yodzis and Innes, 1992; McCann and Yodzis, 1994a, b; McCann and Hastings, 1997).
Here we compare the population demography of a common but important
consumer species in eastern and mid-western grassland communities (Microtus pennsylvanicus) across three habitats that differ in the amount of time since reclamation following strip-mining (30, 25, and 15 years).
Small green frogs (Rana clamitans) were the focal
consumer species, small bullfrogs (R.
Exploitation competition is a reduction in a consumer resulting from the reduction of its prey by another
consumer species. Although a primary focus of ecology for years, exploitation competition was not appreciated as an indirect effect until relatively recently (e.g., Kerfoot and Sih 1987, Strauss 1991).
Moreover, toxins act as feeding attractants for
consumer species that are resistant to its adverse effects.
where [R.sub.[0.sub.i]] and [C.sub.[0.sub.i]] are half-saturation densities of the resource ([R.sub.i]) and consumer ([C.sub.i]), respectively; [x.sub.[c.sub.i]] and [x.sub.p] are mass-specific metabolic rates, measured relative to the production-to-biomass ratio of the resource population; and [y.sub.[c.sub.i]] and [y.sub.p] are measures of ingestion rate per unit metabolic rate of
consumer species i and the predator (McCann and Yodzis 1994, 1995).
1a illustrates a range of possible results observed in a field experiment designed to determine the effect of a
consumer species y on a target species x.
