untitled

chance of establishing in a new environment. The

larger mammals are good examples of this, as (in some

respects) are the Basidiomycota that produce perennial

fruiting bodies on trees (Fig. 11.2). So the distinction

between r- and K-selected organisms is, in essence, a

distinction between how these types of organism

invest their food resources for producing offspring.

A third factor, stress-tolerance, was added to the

two original life-history strategies, creating a triangle

(Fig. 11.1) representing the extreme expressions of

ruderal, stress-tolerant, or K-selected behavior. In the-

ory, any organism should be able to be placed within

this triangle, depending on its degree of expression

of the three primary strategies, ruderal behavior,

stress-tolerance, or K-selection, renamed combative

behaviorin the case of fungi. The value of this and

other theoretical models is discussed by Andrews

(1992).

The biochemical and molecular toolbox for

fungal ecology

Assessing the fungal content of natural

materials by biochemical “signature

molecules”

Several biochemical methods have been used to esti-

mate the fungal content of natural materials, but all

have limitations. One of the early methods developed

in the 1970s was to determine thechitin contentof

soils and other materials, by hydrolysing chitin to the

monomer N-acetylglucosamine, which can be assayed

colorimetrically. This method has also been used to

estimate the fungal content of plant tissues colonized

by plant pathogens or mycorrhizal fungi. The main

drawback is that the chitin content of fungal walls can

vary in different fungi, in different growth conditions,

or at different stages of a fungal life cycle. Also, it is

difficult to distinguish between the chitin of fungal

walls and the chitin of insect exoskeletons in natural

214 CHAPTER 11

Fig. 11.1A method of defining the life-history strategy
of a fungus according to its degree of expression of the
three “primary strategies” – ruderal behavior (R), K-selected
behavior, or combative behavior (K/C) and stress-tolerance.

Fig. 11.2Ganoderma adspersum, which exhibits predominantly K-selected behavior. This fungus progressively rots the
heartwood of standing trees (especially beech, Fagus sylvatica) and produces woody, perennial, hoof-like fruitbodies
which release millions of spores. The current year’s young growth is white.

(a) (b)