@article {940,
	title = {Defining and measuring the impact of dynamic traits on interspecific interactions},
	journal = {Ecology},
	volume = {88},
	year = {2007},
	note = {J
OCT},
	month = {2007///},
	pages = {2555 - 2562},
	abstract = {Trait- and density-mediated indirect effects describe different pathways by which indirect interactions in food webs are propagated from one species to another, through changes in intermediate species. A series of articles in Ecology has progressively altered the original definitions of "trait-mediated{\textquoteright}{\textquoteright} to the point where understanding is being impeded. The most recent of these articles are two meta-analyses that use "trait-mediated{\textquoteright}{\textquoteright} to describe the demographic costs to a prey species of employing anti-predator defenses. These same articles introduce a companion term, "density-mediated interaction,{\textquoteright}{\textquoteright} apparently to describe direct and indirect interactions that only involve changes in population density due to consumption by predators. This new terminology has many disadvantages, including ( 1) using a general term for a relatively narrow group of processes; ( 2) using "mediated{\textquoteright}{\textquoteright} in a manner inconsistent with existing terminology; ( 3) confusing the accepted definitions of different types of indirect effects; and ( 4) providing a highly incomplete measure of the impact of behavior on the predator - prey interaction. Solutions to these problems and the meaning of the meta-analyses are discussed},
	keywords = {defense, ecology, food webs, indirect effects, indirect interactions, interactions, INTERSPECIFIC INTERACTIONS, PREDATOR, predators, PREY},
	isbn = {0012-9658},
	url = {ISI:000250714200016},
	author = {Abrams,P.A.}
}
@article {941,
	title = {Does competition between resources change the competition between their consumers to mutualism? Variations on two themes by Vandermeer},
	journal = {American Naturalist},
	volume = {170},
	year = {2007},
	note = {J
NOV},
	month = {2007///},
	pages = {744 - 757},
	abstract = {How does competition between resources affect the interaction between consumer species that share those resources? Existing theory suggests that high resource competition can lead to mutualism. However, this is based on an analysis that need only apply near equilibrium, and experimental demonstrations of such mutualism are rare. Two alternative approaches to measuring food web mutualism are examined here. These are based on the population level effects of adding or removing a consumer species or on the amount of additional mortality that can be applied to one consumer without excluding it. Both measures suggest that mutualism is likely to be confined to two situations: when overlap in resource use by the consumers is very low and when the consumers are inefficient users of their resources. Competition between resources is also likely to increase the occurrence and magnitude of "hypercompetition" between consumers, where the reduction in population size caused by the introduced consumer is greater than that caused by a consumer that is identical to the resident species. Competition between resources can also increase the negative interaction between consumers by destabilizing the dynamics of the system. Such destabilization can cause negative indirect interactions between specialist consumers having no overlap in resource use},
	keywords = {COMPETITION, DYNAMICS, indirect interactions, interactions, MORTALITY, MUTUALISM, SIZE, theory},
	isbn = {0003-0147},
	url = {ISI:000249981500009},
	author = {Abrams,P.A. and Nakajima,M.}
}
@article {942,
	title = {Measuring the impact of dynamic antipredator traits on predator-prey-resource interactions},
	journal = {Ecology},
	volume = {89},
	year = {2008},
	note = {J
JUN},
	month = {2008///},
	pages = {1640 - 1649},
	abstract = {This article analyzes the limitations of the most widely used method for quantifying the impact of dynamic antipredator traits on food chain dynamics and discusses alternative approaches. The standard method for a predator-prey-resource chain estimates the effects of the prey{\textquoteright}s defensive behavior by comparing population densities or fitness measures in a {\textquoteright}{\textquoteright}predator cue{\textquoteright}{\textquoteright} treatment to those in a no-predator treatment. This design has been interpreted as providing a measure of the {\textquoteright}{\textquoteright}nonconsumptive effect{\textquoteright}{\textquoteright} of the predator on the prey and the {\textquoteright}{\textquoteright}trait-mediated indirect effect{\textquoteright}{\textquoteright} of the predator on the resource. Other approaches involve measurements of the impact of the behavior in the presence of functional predators. The questions addressed here are: (1) How consistent are the results of different approaches? (2) How time-dependent are their results? (3) How well do they correspond to theoretical measures of effect size? (4) How useful are the measurements in understanding system dynamics? A model of a tritrophic system in which the prey species adjusts a defensive trait adaptively is used to evaluate the experimental designs. Measures of changes in prey fitness or population density in a cue treatment generally include offsetting effects of the cost of the behavior and the benefit of more resources. This means that the sign of the effect, as well as its magnitude, may change depending on when the experiment is terminated. Because predation is not present in the cue treatment, few conclusions can be drawn about the impact of the behavior on population densities or fitness of the prey in a natural setting with predators. Cue experiments often do not accurately separate trait-mediated from density-mediated effects on the resource. Most scalar measures of effects are sensitive to experimental duration and initial densities. Use of a wider range of experimental designs to measure trait-related effects is called for},
	keywords = {DYNAMICS, interactions, predation, PREDATOR, predators, PREY, SIZE},
	isbn = {0012-9658},
	url = {ISI:000256540300017},
	author = {Abrams,P.A.}
}
