Fungal Classification

Question 1

Describe taxonomy

Answer 1

the categories used to group named and identified organisms that share similar characteristics

Question 2

How are taxonomical categories arranged?

Answer 2

as a hierarchy with the ranks representing the degree of the relationship between the members

Question 3

What are taxonomical categories based on?

Answer 3

characters

which can be DNA sequences, amino acid sequences, morphology

Question 4

What is the purpose of systematics? how is it informed?

Answer 4

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

Question 5

What are the taxonomic categories?

Answer 5

Phylum
Class
Order
Family
Genus
Species

Question 6

What are the 2 clades of fungi?

Answer 6

Stramenopiles clade or Heterokonta (pseudo-fungi)
Opisthokonta (true fungi)

Question 7

What phylum is included in the stramenopiles/heterokonta clade?

Answer 7

Oomycota

Question 8

What class is included in the stramenopiles/heterokonta clade?

Answer 8

Oomycetes

Question 9

What phylum is included in the opisthokonta clade?

Answer 9

Basidiomycota

Question 10

What class is included in the opisthokonta clade?

Answer 10

Agaricomyetes

Question 11

What is the suffix for phyla of fungi?

Answer 11

-mycota

Question 12

What is the suffix for classes of fungi?

Answer 12

-mycetes

Question 13

What is the suffix for orders of fungi?

Answer 13

-ales

Question 14

What is the suffix for family of fungi?

Answer 14

-aceae

Question 15

Is there a fixed suffix for genera or species of fungi?

Answer 15

no, these depend

Question 16

Describe the historical approach to fungal taxonomy - what is problematic about it?

Answer 16

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

Question 17

Describe phylogenetics

Answer 17

organization of organisms into a classification system based on the evolutionary history and relationships of the organisms - the relatedness

Question 18

Describe the current approach to fungal taxonomy - what is problematic about it?

Answer 18

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)

Question 19

WHat is the primary fungal barcode formally recognized?

Answer 19

ITS - an rDNA region

Question 20

What does the secondary barcode gene loci include?

Answer 20

ribosomal LSU
actin (ACT)
beta-tubulin (TUB2)
translation elongation factor 1 (TEF1)
etc

Question 21

How can DNA sequencing be used to resolve discrepancies in current classifications?

Answer 21

it can be combined with morphology to make better distinctions

Question 22

Why is defining a fungal species so difficult?

Answer 22

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

Question 23

What is the best current practice for identifying fungal species?

Answer 23

combining molecular (DNA) and morphological data

Question 24

What are the 6 types of gill morphology that are often used as one morphological characteristic to help classify groups?

Answer 24

free
adnate
adnexed
sinuate
decurrent
emarginate

Question 25

Define anamorph

Answer 25

the asexual phase of a fungal life cycle

Question 26

Define teleomorph

Answer 26

the sexual phase of a fungal life cycle

Question 27

define holomorph

Answer 27

the complete life cycle of a fungus (including both anamorph and teleomorph phases if present)

Question 28

T or F: all fungal species have both an anamorph and teleomorph phase

Answer 28

false! some only have an anamorph phase and no sexual stage

Question 29

How does using morphology as a tool cause issues in fungal nomenclature?

Answer 29

because some fungi have different morphologies at different life stages (ex. anamorph vs. teleomorph), they have been defined as different species in literature

Question 30

Which class of fungi contains the most species that have been identified as 2 for their different life stages?

Answer 30

Ascomycete

Question 31

What is an example of convergent evolution of a fungal form?

Answer 31

puffballs - they have evolved repeatedly and separately in different phyla (ie., polyphyletic form) ex. order Agaricales and order Hysterangiales (false truffles) have puffballs

Question 32

What does polyphyletic mean?

Answer 32

the character evolved separately in different phyla (ie., convergent evolution)

Question 33

Give an example of a fungus that was historically described many species, but turned out to be MANY species

Answer 33

apple scab has been given 59 different anamorph names described as unique morphological species

Question 34

Give an example of a fungus that was historically described as one species, but turned out to be many

Answer 34

Honey fungus - once considered a polymorphic species from morphology has since been found to be > 6 distinct species based on genetic analyses

Question 35

What are opisthokonts?

Answer 35

the group of eukaryotes that includes true fungi, animals and choanoflagellates (unicellular)

Question 36

What are stramenopiles (heterokonts)?

Answer 36

the group of eukaryotes that includes the false-fungi (Oomycetes), autotrophic unicellular algae (diatoms) and multicellular kelp

Question 37

How many accepted phyla are there for fungi according to current molecular phylogenetics?

Answer 37

7

Question 38

What are the 7 accepted phyla of fungi? What is the controversial 8th?

Answer 38

Microsporidia (single-celled animal parasites) Chytridiomycota (zoosporic) Blastocladiomycota (zoosporic, aquatic) Neocallimastigomycota (anaerobic, in herbivores) Glomeromycota (endomycorrhizal) Ascomycota Basidiomycota controversial: Zygomycota

Question 39

Where are Oomycetes found?

Answer 39

terrestrial in damp soils or humid enviros freshwater systems

Question 40

What are the major differences between Oomycota and true fungi?

Answer 40

1. 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) 2. CELL WALL: Oomycota cell walls contain cellulose and glucans; true fungal cell walls contain chitin and glucans 3. SEPTA: Oomycetes have no septa; true fungi often have septa 4. LIFESTYLES (SYMBIONTS): Oomycetes have no known symbionts; true fungi often have symbiotic relationships

Question 41

What are major similarities between the Oomycetes and true fungi?

Answer 41

1. Both have filamentous growth 2. both are heterotrophic and digest/absorb nutrients externally 3. both produce spores 4. both can have lifestyles that include saprophytes, parasites, and pathogens (but true fungi can also be symbionts) 5. both have glucans in their cell walls (but contain other different constituents like cellulose v. chitin)