Chapter

Species, Their Diversity and Populations

Knowledge of a flute or a kettledrum is not sufficient to understand all the other instruments in a symphony orchestra or to predict their characteristic. Nor is knowledge of a single species, however complete, adequate for understanding diverse species. Diversity of research in the laboratory must at least dimly reflect the diversity of species in nature if the scope and beauty of evolutionary improvisations are to be appreciated and the genetic manipulations that brought them about are to be understood.

David D. Perkins

Fungi live in very diverse habitats and display great diversity in structure and biochemistry. Table 13.1 gives a sample of terms used to denote their diversity. The number of scientists with expertise in isolating and identifying fungi is rapidly dwindling. Our knowledge of fungi is therefore heavily biased on forms that are recognized unambiguously in nature, or of fungi that can be isolated from nature and induced to sporulate in pure culture. We know much less about the distribution of species in space and in time. Although the era of "model organisms" and of genomics is drawing attention away from the study of fungal populations, this may be a temporary phase because of the urge "to go places" to sample fungi for analyzing populations. Sooner or later, a student of fungal biology is confronted with the following questions. (i) What is meant by species? How can the number of species of fungi in nature be estimated? (ii) Of what value is fungal diversity? (iii) How can the similarities and variation between individuals within a population and the limits of such a population be determined? (iv) What are the possible causes of population changes and, ultimately, of evolutionary changes? How can the relative contributions of sexual and asexual modes of reproduction be ascertained in those fungi that possess both modes of reproduction? (v) How can the homology (affiliations) of confusing forms be resolved?

13.1 VALUE OF DIVERSITY 13.1.1 Applied Research

Most marketable biotechnology products still result from the traditional approach of isolation and screening of microbes from natural habitats and the exploitation of natural variability in populations. All biotechnology begins with a preferred fungal genome drawn from nature—a natural species and its numerous genetic strains. Some examples of inter- and intraspecies differences in enzyme productivity and properties of enzymes of commercial value can be

Table 13.1 Some Terms That Depict the Special Habitat and Diversity of Fungi

Term

Anthropophilic fungi Aquatic fungi (water molds)

Brown rot fungi

Coprophilous fungi

Corticolous fungi Dermatophyte

Edible fungi Endophytic fungi

Entomogenous fungi

Hypogeous fungi Keratinophilic fungi

Lichen forming fungi

Marine (saprobic) fungi

Mesophilic fungi Mildew

Mycorrhizal fungi Mycoparasites Necrotrophic fungi

Nematophagous (Predacious) fungi Osmotolerant fungi

Phylloplane fungi

Meaning

Infectious only to man Fungi resident in aquatic habitats Fungi which rot wood giving it a dark brown color Fungi growing on dung of herbivore animals Fungi growing on tree bark Fungi that live as parasites on skin, hair, or nails of man and other animals Fungi used as food

Symptompless parasitic fungi in mutualistic association with living plants Insect-parasitizing fungi

Fungi growing below ground Fungi growing on feathers, horns

Fungal symbiont of lichen thallus

Fungi growing and sporulating in marine or estuarine habitats Fungi thriving between

10-40°C Fungi producing whitish growth on living plants

Fungi in symbiotic association with living roots

Fungi parasitic on other living fungi

Parasitic fungi that kill host cells in advance of its hyphae and derive their organic nutrients from the dead cells Fungi parasitic on nematodes

Fungi capable of growth in solutions of high osmotic pressure Fungi growing on aerial surface of living leaves

Common example(s)

Trichophyton rubrum Saprolegnia

Fistulina, Daedalea,

Coniophora Pilobolus, Podospora, Coprinus

Trichophyton interdigitale, Microsporum canis, Arthobotrys sp. Agaricus campestris, Pleurotus versicolor Balansia sp., Curvularia sp.

Entomophthora, Cordyceps, Septobasidium, Beauveria Tuber sp.

Onygena equine, Nannizia

Cladonia cristellata, Xanthoria sp., Phaeographina fulgurata Dendryphiella salina, Mycosphaerella

Vast majority of fungi, e.g., Aspergillus niger Downy mildew (Peronospora viticola), powdery mildew (Erysiphe graminis) Mostly basidiomycetous fungi belonging to the families Agaricaceae, Boletaceae Trichoderma spp., Piptocephalius sp., Gliocladium roseum Pythium, Monilinia fruticola, Penicillium expansum

Arthobotrys sp., Dactylaria sp.

Aspergillus restrictus, A. flavus, A. amstelodami

Cladosporium herbarum, Alternaria alternata

Species, Their Diversity and Populations Table 13.1 (Continued)

Term

Meaning

Common example(s)

Psychrophilic fungi

Fungi growing at <10°C,

Mucor sp., Fusarium nivale,

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