Competitive Interactions between Wood Decay Basidiomycetes

Author: Sally Fryar

Fryar, Sally, 1997 Competitive Interactions between Wood Decay Basidiomycetes, Flinders University, College of Science and Engineering

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The problem of the coexistence of competing species has been the focus of many ecological studies (eg Vincent and Vincent, 1996; Tilman, Lehman and Yin, 1997; Holt and Polis, 1997; Turner, Souza and Lenski, 1996; Morris, 1996; Hulme, 1996). Gause's law of competitive exclusion states that complete competitors cannot coexist (Hardin, 1960). Ever since this principle was developed (Gause, 1934) many ecologists have faced the problem that many competitors do coexist ( eg Jeltsch et al, 1996; Schwimming and Parsons, 1996; Connolly and Wayne, 1996; Wolff, 1996; Crook and Vuren, 1995; Blossey, 1995; Basset, 1997). This thesis is concerned with discovering mechanisms by which many competing species of wood decay fungi may coexist on the same substrate. The main theme is on testing for (1) indirect effects or interaction modifications between triplets of species and (2) intransitive competitive networks which have been shown to enhance species diversity (Karlson and Jackson, 1981 ). The influence of indirect effects and interaction modifications on the coexistence of species is observed.

Indirect effects and interactions modifications are the effects that one species has on another via a third ( or more) species. These are discussed in more detail in section 1.8. Intransitive competition occurs when species A outcompetes species B, species B outcompetes species C and species C outcompetes species A. The model organisms in this study are fungi that decay wood. The decomposition of a tree branch is a complex, multidimensional process which may follow a diverse array of optional pathways (Boddy, 1992). The process may involve many species of fungi and other organisms performing many different functions.

Interactions between species may be as diverse as the species themselves including mycophagy (Dowding, 1973), mutualism (Tanesaka 1993), parasitism (Hutchinson and Barron, 1996), competition (Holmer, Renvall and Stenlid, 1997) and predation (Tzean and Liou, 1993). Competition has been identified as a major factor in the structuring of wood decay fungal communities (Rayner et al, 1981; Coates and Rayner, 1985a, 1985b, 1985c). However almost all studies on fungal competition have only looked at pairwise interactions ( eg Holmer et al, 1997; Rayner and Hedges 1982; Owens, Reddy, and Grethein, 1994; Holmer and Stenlid, 1993). In more general ecological literature there is a growing concern that undue emphasis has been placed on direct two-species interactions. Ecologists have been turning more towards interactions within the context of the whole community such as indirect effects (eg Menge, 1995; Van Buskirk, 1988; Walters and Moriarty, 1993). Some negative interactions such as competition or predation, once placed into the context of the community, may actually be advantageous to coexistence (Stone and Roberts, 1991).

Keywords: fungi, taxonomy, fungal diversity, competition, indirect effects, transitivity

Subject: Biology thesis

Thesis type: Doctor of Philosophy
Completed: 1997
School: College of Science and Engineering
Supervisor: Greg Kirby