On the coexistence of perennial plants by the competition-colonization trade-off.

Abstract

A competitively inferior species can coexist with a superior competitor in a metapopulation provided that the inferior species is a better colonizer of empty habitats (Levins and Culver 1971; see also Nee and May 1992; Dytham 1994; Moilanen and Hanski 1995). The same trade-off between competition and colonization can also maintain coexistence within a single population of plants that live in small patches supporting a single adult (henceforth called “sites”) and disperse their seeds randomly. With local populations interpreted as individual sites, the metapopulation model of Levins and Culver (1971) has been applied to model within-population coexistence of perennial plant species (e.g., Tilman 1994). However, Yu and Wilson (2001) pointed out that there may be an important difference between metapopulation dynamics and the site dynamics of plants: in the metapopulation model, it is assumed that dispersers of the competitively superior species displace established populations of the inferior species (displacement competition). In plants, seedlings may or may not be able to displace established adults; in the latter case, seedlings compete with one another only for the sites vacated by adult death (replacement competition). Yu and Wilson (2001) argued that under replacement competition, perennial species cannot coexist by the competitioncolonization trade-off alone. In this note, we show that the competition-colonization trade-off does maintain coexistence provided that seed numbers within individual sites are subject to demo-