Analyses On The Temperature Dependence Of Species Co-existence In Food Web Modules

Food web is the most important composition of an ecosystem.It is the pattern of energy flow and material flux among organisms. Recently, the biodiversity and the structure of food webs have been largely changed by the global warming. global warming.These changes have further influence on the stability and functions of ecosystems.Analyzing the the temperature dependence of the co-existence of species in a food web has important significance in both theory development and empirical. Complex food webs are built up by simple modules of species interactions. Among all these modules, intraguild predation modules and tri-trophic food chain modules are two most important ones, which are generally considered as the basic trophic modules of food webs. In this research, based on bioenergetic population dynamics model, the influence of warming on the co-existence of species in these two modules was analyzed through theoretical analyses and numerical simulations.A coefficient λ represented was applied to measrue the invasion ability of a consumer or predator. If λ> 0, the species could invade successfully and thus they can coexist.The results in tri-trophic modules showed that:(1) when consumers and producerscan co-exist at low temperatures, the consumers’invasion ability decrease with temperature, and warming destroyed the co-existence of producers and consumers. (2) When consumers and producers can co-exist at low temperatures, λC,R> 0, warming did not alter their co-existence. On this basis, the predator began to invade the system. If λP,CR>0, warming promoted the co-existence of the three species in the module,else warming restrained the co-existence of the three species. (3) When consumers and producers can co-exist at high temperatures, warming promoted their co-existence. On this basis, the predator began to invade the system. If λP,CR> 0, warming promoted the coexistence of the three species in the module,else λP,CR< 0, warming restrained the co-existence of the three species.The results in IGP modules showed that:(1) No matter how the temperature changed, if λC,R<0 and λP,R<0, warming not only inhibited the co-existence of consumers and producers, but also restrained the co-existence ofomnivorous predators and producers. (2) If λC,R>0 and λP,R>0, warming did not affect any two species’ co-existence. On this basis, the omnivorous predator invaded the system. If λP,CR>0, warming promotedthe coexistence of omnivorous predators and producers, and if λC,PR>0, warming promoted the coexistence of consumers and producers. (3) When any two species’ co-existence did ont vary with temperature, if λP,CR>0 and λC,PR>0 were always true, warming promoted the co-xistence of the three species in the module.This paper discusses the relationship between temperature and the species’ co-existence in basic trophic modules. It deepens our understanding of the temperature dependence of the co-existence of species in a complex food web.