Classification and Nomenclature of Fungi
Fungi are small, generally microscopic, eukaryotic, usually filamentous, branched, spore-bearing organisms that lack chlorophyll. Fungi have cell walls that contain chitin and glucans (but no cellulose) as the skeletal components.What is Phylogenetic Classification?
A classification based on the evolutionary relationships is known as Phylogenetic classification.
IMPORTANCE
Although classification can be done on the basis of any criteria but classifying on the basis of phylogenetic relationships aid us
� in understanding the evolutionary changes and
� allow one to make prediction on the basis of what is known about an organism and its close relatives.
Traditional Classification of Fungi
u In the 2 kingdom system of classification, fungi were placed under kingdom Plantae.
Modern Classification of Fungi
u According to Hawksworth et al., 1995 and Alexopoulos and Mims, 1979:
The organisms once considered fungi are now considered under three different kingdoms.
1. Kingdom Fungi
2. Kingdom Stramenopila
3. Kingdom Protista
u This is due to classifying organisms in monophyletic groups.
This classification recognizes that the organisms which have been called �fungi� are not closely related.
 |
| Classification of groups of organisms which were once considered as 'Fungi' |
What is monophyletic and polyphyletic grouping?
u A monophyletic group consists of an ancestor and all its descendents.
u Polyphletic groups do not share a close common ancestor.
NOMENCLATURE OF FUNGI
u All the activities of nomenclature of fungi fall under the rules of International Code of Botanical Nomenclature (ICBN).
u The �Biological Code� now makes it clear that it includes all the groups that have been traditionally considered as plants.
COMMITTEE OF FUNGI
u At each International Botanical Congress (held every four years) a Committee for Fungi is formed.
FUNCITONS:
u To make recommendations on proposals to conserve or reject names and
u To comment on changes being considered in the rules relating to fungal nomenclature.
u When modification of the existing code are approved at the congress, the code is updated.
Rule of PRIORITY
Priority is the provision of the code that helps to determine the correct name for a taxon. For example;
- If a single species is described by two mycologists; then the species described first is said to have priority and accepted as the correct one.
- Sometimes the description of a new taxon is unknown to a second worker because both publications are in press in two different journals.
In such case, the exact date of issue of the journal is important in determining priority.
Confusion of Anamorphs & Telomorphs Nomenclature
Fungi may exist in many forms (=morphs), that is, they are Pleomorphic. The existence of different morphs in the life cycles of fungi has nomenclature significance since this lead to different names for the same fungus. Later on, genetic connection was established between sexual and asexual forms. But anamorphic names are still common.
Telemorph
u Greek, teleos = perfect, entire; morphe = form
u The morph which include the sexually produced spore form is called telomorph. Previously known as perfect stage of fungus.
u For example; Ascocarps of ascomycetes and basidiocarps of basidiomycetes.
Anamorph
u Greek, ana = similar to, thorough out
u The asexual morphs are called anamorphs.
Or
u The asexual stage of fungal life cycle is called anamorph.
u Previously known as Imperfect stage of fugus.
u This characteristic of fungi lead to the formation of group of fungi called �Fungi Imperfecti� or �Deuteromycetes�.
u This group only contains fungi which reproduce asexually and have no sexual stage reported.
The CONFUSION�!
u In some cases anamorphic names are very common and telomorphic names are not.
For example; Aspergillus nidulans is name for conidial stage (Anamorph)of same fungus but Emericella nidulans is name forascocarp stage (telemorph).
Comments
Post a Comment