Some effects of parasitism on food web structure: a topological analysis
WeiPeng Kuang, WenJun Zhang
So far most of the food webs lack parasitism. It has been found that parasites can profoundly affect food web properties. In this study we tried to consider parasitism in the food web analysis in order to provide a basis for further and more complete theory development. The data for topological analysis of food webs was from the food web studies of Lafferty et al. Pajek software was used to conduct topological analysis on food webs. The results revealed that in the food web the number of base species kept to be constant but the number of top species declined remarkably and the number of intermediate species increases sharply when parasitism was considered. Parasitism increased the food chain cycles. There were 508 cycles in the parasite-parasite sub-web but not any cycle was found in the predator-prey sub-web. The connectance and link density increased after parasitism was added. The links between predators and parasites were greater than the links between predators and preys. The connectance of predator-prey sub-web, predator-parasite sub-web, parasite-host sub-web, and parasite-parasite sub-web is 0.29, 0.16, 0.24, and 0.34, respectively. The link density of predator-prey sub-web, predator-parasite sub-web, parasite-host sub-web, and parasite-parasite sub-web is 11.95, 9.84, 15.5, and 7.64, respectively. Chain length increased slightly and omnivorous species and omnivory increased also. The present study revealed that parasitism would yield substantial effects on food web structure.
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