Imagine a single species of predator or parasite that attacks two species of prey (or host). Parameters are defined in the text. Noonburg & Byers (2005) used a foodâweb model to explain coexistence of prey species when both exploitative and apparent competition occurred simultaneously. FIGURE 2: Transfer diagram for the three species model showing probabilities of moving from one state to another. See Apparent Competition and Biocontrol for the accompanying text. ent competition, and it is predicted that species will evolve to colonise enemy-free space (Jef-fries & Lawton 1984). Figures 2-8 follow. Apparent competition is a situation in which it appears that two species compete for limited resources, because the presence of one reduces the abundance of the other. The CAM-8 model illustrates the phenomenon of apparent competition in an explicitly spatial model. Their modeling of a singleâresource system, however, assumed that prey species must compete for the same resource in order to exist, whereas Holt's (1977) model assumed the opposite. The effect of a shared parasite on the dynamics between two host species has been investigated by mathematical models ( Hudson and Greenman, 1998 ; Greenman and Hudson 1999 , Greenman and Hudson 2000 ). The model was able to predict the actual relative abundances of D. aurita and M. nudicaudatus in the three empirical studies analyzed. But, the question still remains whether the observed behavior is dependent upon the spatial structure of the model, or whether it could also happen in a non-spatial version. caused by a small change in the harvest rate of another. Another reason for being cautious in our discussion of competition is the existence of what Holt (1977, 1984) has called 'apparent competition', and what others have called 'competition for enemy-free space' (Jeffries & Lawton, 1984, 1985). âApparent competitionâ is a phrase that today largely refers to an indirect negative interaction between individuals, populations, species, or entire functional groups, medi- ated through the action of one or more species of shared natural enemies. Our study presents quantitative support to the apparent competition theory; however, the model's applications to other groups still need to be verified. apparent competition in endangered species conservation, we have three primary objectives: (1) to review the me-chanics of apparent competition dynamics among predator and prey, including revisiting Holtâs (1977) original theore-tical model; (2) to review recent studies showing apparent competition and the sources of human-induced asymmetry In order to study the consequences of predator-mediated apparent competition in isolation from other complicating factors, a model community is analyzed in which there is no direct interspecific competition â¦ Joseph H. Connell, Apparent versus âRealâ Competition in Plants, Perspectives on Plant Competition, 10.1016/B978-0-12-294452-9.50006-0, (9-26), (1990). How-ever, the change in the mean density of one species. In competition theory, resources are often, but not always, assumed to have very simple dynamics, and intra- and inter- interpreted as apparent competition resulting from shared predation. This effect of apparent competition has been recently demonstrated by experiments using a hostâparasitoid system (Hassell and Bonsall). There are thus marked symmetries between competition and apparent competition, but there are also differences. described as apparent competition in this model.