Fungal Classification Flashcards
Describe taxonomy
the categories used to group named and identified organisms that share similar characteristics
How are taxonomical categories arranged?
as a hierarchy with the ranks representing the degree of the relationship between the members
What are taxonomical categories based on?
characters
which can be DNA sequences, amino acid sequences, morphology
What is the purpose of systematics? how is it informed?
systematics is informed from taxonomic studies of relationships between taxa
its purpose is to study the evolutionary history of a taxonomic group - ie., the diversity and evolutionary relationships
What are the taxonomic categories?
Phylum
Class
Order
Family
Genus
Species
What are the 2 clades of fungi?
Stramenopiles clade or Heterokonta (pseudo-fungi)
Opisthokonta (true fungi)
What phylum is included in the stramenopiles/heterokonta clade?
Oomycota
What class is included in the stramenopiles/heterokonta clade?
Oomycetes
What phylum is included in the opisthokonta clade?
Basidiomycota
What class is included in the opisthokonta clade?
Agaricomyetes
What is the suffix for phyla of fungi?
-mycota
What is the suffix for classes of fungi?
-mycetes
What is the suffix for orders of fungi?
-ales
What is the suffix for family of fungi?
-aceae
Is there a fixed suffix for genera or species of fungi?
no, these depend
Describe the historical approach to fungal taxonomy - what is problematic about it?
the historical approach of phylogenetics was based on morphology
problems:
- convergent evolution may cause 2 unique organisms to be classified in the same taxa
- fungal fossil record is limited
- lack of useful traits in some taxa
- different life stages or growth stages can have different morphologies and lead to the same species being identified more than once
Describe phylogenetics
organization of organisms into a classification system based on the evolutionary history and relationships of the organisms - the relatedness
Describe the current approach to fungal taxonomy - what is problematic about it?
currently, DNA sequencing for conserved genes is being used to determine phylogeny
challenges:
- selecting the most suitable gene locus to identify unique taxa may be challenging
- level of resolution may differ (inter-specific vs. intra-specific) and may be challenging to apply
- varying quality of reference sequence data in databases (ex. Genbank) for comparisons
- primary and secondary barcode loci in public databases may be limited/not available (esp for understudied or new species)
WHat is the primary fungal barcode formally recognized?
ITS - an rDNA region
What does the secondary barcode gene loci include?
ribosomal LSU
actin (ACT)
beta-tubulin (TUB2)
translation elongation factor 1 (TEF1)
etc
How can DNA sequencing be used to resolve discrepancies in current classifications?
it can be combined with morphology to make better distinctions
Why is defining a fungal species so difficult?
it is difficult to apply the biological species concept for a definition because many fungi cannot be cultured in a lab and sexual events cannot be observed
BSC: a species is a group of individuals (a population) that interbreed and produce viable, fertile offspring and are reproductively isolated from other populations
the morphological definition is challenging because morphology does not equate biological species and morphology is subjective, as well as many fungi having different morphologies throughout their life cycle
What is the best current practice for identifying fungal species?
combining molecular (DNA) and morphological data
What are the 6 types of gill morphology that are often used as one morphological characteristic to help classify groups?
free
adnate
adnexed
sinuate
decurrent
emarginate
Define anamorph
the asexual phase of a fungal life cycle
Define teleomorph
the sexual phase of a fungal life cycle
define holomorph
the complete life cycle of a fungus (including both anamorph and teleomorph phases if present)
T or F: all fungal species have both an anamorph and teleomorph phase
false! some only have an anamorph phase and no sexual stage
How does using morphology as a tool cause issues in fungal nomenclature?
because some fungi have different morphologies at different life stages (ex. anamorph vs. teleomorph), they have been defined as different species in literature
Which class of fungi contains the most species that have been identified as 2 for their different life stages?
Ascomycete
What is an example of convergent evolution of a fungal form?
puffballs - they have evolved repeatedly and separately in different phyla (ie., polyphyletic form)
ex. order Agaricales and order Hysterangiales (false truffles) have puffballs
What does polyphyletic mean?
the character evolved separately in different phyla (ie., convergent evolution)
Give an example of a fungus that was historically described many species, but turned out to be MANY species
apple scab has been given 59 different anamorph names described as unique morphological species
Give an example of a fungus that was historically described as one species, but turned out to be many
Honey fungus - once considered a polymorphic species from morphology has since been found to be > 6 distinct species based on genetic analyses
What are opisthokonts?
the group of eukaryotes that includes true fungi, animals and choanoflagellates (unicellular)
What are stramenopiles (heterokonts)?
the group of eukaryotes that includes the false-fungi (Oomycetes), autotrophic unicellular algae (diatoms) and multicellular kelp
How many accepted phyla are there for fungi according to current molecular phylogenetics?
7
What are the 7 accepted phyla of fungi? What is the controversial 8th?
Microsporidia (single-celled animal parasites)
Chytridiomycota (zoosporic)
Blastocladiomycota (zoosporic, aquatic)
Neocallimastigomycota (anaerobic, in herbivores)
Glomeromycota (endomycorrhizal)
Ascomycota
Basidiomycota
controversial: Zygomycota
Where are Oomycetes found?
terrestrial in damp soils or humid enviros
freshwater systems
What are the major differences between Oomycota and true fungi?
- MOTILE SPORES
Oomycota have motile spores (zoospores + 2 flagella); true fungi commonly do not have motile spores (some have 1 flagellum at 1 life stage) - CELL WALL:
Oomycota cell walls contain cellulose and glucans; true fungal cell walls contain chitin and glucans - SEPTA:
Oomycetes have no septa; true fungi often have septa - LIFESTYLES (SYMBIONTS):
Oomycetes have no known symbionts; true fungi often have symbiotic relationships
What are major similarities between the Oomycetes and true fungi?
- Both have filamentous growth
- both are heterotrophic and digest/absorb nutrients externally
- both produce spores
- both can have lifestyles that include saprophytes, parasites, and pathogens (but true fungi can also be symbionts)
- both have glucans in their cell walls (but contain other different constituents like cellulose v. chitin)
