untitled

consort. The types of organisms that are active in
these communities can vary, but the overall course
of decomposition is similar in many situations (Fig. 11.5)
because it involves an overlapping sequence of activ-
ities of fungi with different patterns of behavior and

different abilities to degrade particular types of substrate

(Table 11.1).

In this section we will look at the main stages in

a generalized decomposition sequence, starting with

the organisms that colonize the surfaces of living

FUNGAL ECOLOGY: SAPROTROPHS 217

Epiphytic fungi

Weak parasites

Pioneer saprotrophic fungi

Host death

V

Polymer-degrading fungi

Secondary opportunistic fungi

Degraders of recalcitrant compounds

Fig. 11.5Representation of the overlapping phases of activity of different types of fungi in a decomposition sequence.

Table 11.1The main behavioral groupings of decomposer fungi.

Group

1. Resident microbes on
   living tissues


2. Endophytes, weak
   parasites and pathogens


3. Pioneer saprotrophic fungi


4. Polymer-degrading fungi


5. Degraders of recalcitrant
   materials


6. Secondary opportunists

Features

(i) Grow on generally low levels of available substrates

(ii) Often tolerate stress conditions

(iii) Are usually displaced when the host tissues die

(i) Grow initially by tolerating host resistance factors or other special conditions

(ii) Generally utilize simple soluble substrates or storage compounds but not

structural polymers

(iii) Generally poor competitors for dead organic matter

(i) Generally utilize simple soluble substrates or storage compounds but not

structural polymers

(ii) Good competitors, with fast growth, etc. and short life cycles

(iii) Cannot defend a resource against subsequent invaders

(i) Degrade the main structural polymers (cellulose, hemicelluloses, chitin, etc.)

(ii) Have an extended growth phase, defending a resource by antibiosis or by

sequestering mineral nutrients, etc.

(iii) Substrate-specialized, and sometimes tolerant of stress factors (extremes of

temperature, pH, etc.)

(i) Specialized to degrade recalcitrant organic materials (lignin etc.) and gain

access to polymers (cellulose etc.) complexed with them

(ii) Long growth phase, and defend a resource by antagonism or mutual

inhibition (deadlock)

(iii) Can gain access to mineral nutrients (nitrogen, etc.) that previous colonizers

have exploited

(i) Nutritionally opportunistic: grow on dead remains of other fungi, insect

exoskeletons, etc., or parasitize other fungi, or grow commensally with

polymer-degraders.

(ii) Tolerant of the metabolic byproducts of other fungi

(iii) Often antagonistic