Density-related Effects on the Components of Fitness and Population Dynamics of Planthoppers

Abstract

The extent to which populations are “regulated” or suppressed by density-dependent factors continues to be the subject of extensive ecological debate (see Slade 1977; Strong 1984; Vickery and Nudds 1984; Hassell 1985a, 1986a; Dempster and Pollard 1986; den Boer 1988). Traditionally, discussions of density dependence have focused on its statistical detection (Morris 1959; Varley and Gradwell 1963; Eberhardt 1970; It 1972; Kuno 1973a; Bulmer 1975; Slade 1977; Vickery and Nudds 1984; Dempster and Pollard 1986; Hassell 1986a; Mountford 1988), its potential “stabilizing” role in population dynamics (Varley et al. 1973; Dempster 1983; Hassell 1985a; Dempster and Pollard 1986; den Boer 1986, 1988; Latto and Hassell 1987; Poethke and Kirchberg 1987), and its relative strength and frequency in natural populations (Murdoch 1970; Chesson 1978; Strong 1984, 1986). Despite the history of controversy, there currently appears to be widespread agreement that the dynamics of persisting populations result from both density-dependent and density-independent processes and that the variance associated with density relationships is an important consideration (Strong 1984, 1986; Hassell 1986a).