EVALUATION OF PARASITE OR PREDATOR RESPONSES

摘要: The behaviour of searching parasites and predators in relation to varying populations their hosts or prey is unlikely be simple. Early theorists sought describe the relationship by a single constant (Lotka 1925; Volterra 1931; Thompson 1930; Nicholson 1933; & Bailey 1935). Solomon (1949) first suggested terms functional numerical for more complex responses prey. These have since been used several authors, not always as they were originally defined. They are suitable describing effects host density on reproduction parasite predator concerned, but parasitism predation population. purpose this paper review some uses terminology literature introduce new precise system classifying density. It should added, however, that it almost an impossible task find any kind caters all cases, there will certainly instances which proposed unsuitable. stated '. . dependent, enemy must respond changes numbers (cf. Varley 1947). nature response commonly twofold. First, FUNCTIONAL (say) increase density, because increased availability victims: rises, each attack individuals, fixed number rapidly. A frequent, invariable result (a NUMERICAL influence) due rate survival reproduction, both; may sufficient produce PROPORTION enemies increasing hosts'. important realize weak insufficient density-dependent mortality, proportion taken increases. Likewise, delayed density-dependency proportionate compared with those necessary. Holling (1959a) elaborated these his study cocoons Neodiprion sertifer (Geoff.) small mammals Canada. was defined consumed predator, at different densities. divided into three basic types expressed them graphically plotting per unit time dependent variable against (Fig. la). Similarly, subdivided (direct, none inverse) area 2, A, B C). Gradwell (1963a) sense implied resulted mortalities occurring when local concentrations