PLANT PATHOGENS AND THE THEORY OF r- AND K-SELECTION

r- and K-theory can be used to compare the life strategies of plant pathogens, at least during the parasitic phase. While, as a group, plant pathogens tend to be r-selected, individual species display certain tactics that may best be described by either r- or K-descriptors. Characteristics such as the ability to survive prolonged periods and the flexibility to time activities are more closely associated with "bet-hedging" than r- or K-selection. A conceptual model is proposed to show how pathogens can be positioned along an r-K continuum based on their relative allocation of resources to maintenance, growth, and reproduction. Superimposed on resource allocation is the nature of the parasite-host relationship, determined in part by whether the interaction is obligatory or facultative, whether nutrient is derived from living or dead cells of the host, and the extent of destruction of the host habitat. In general, obligately biotrophic parasites which exhibit narrow host ranges, specialization as biotypes or...