evolutionary aspects

1. Phylogeny and evolution of lichens
Sidra Shahid
Roll # 14

2. Introduction
• 20,000 different kinds of lichen known,
• These are treated as species by lichenologists, but are not species in
the same sense as animal or plant species.
• Because lichens are formed through a combination of alga and fungus,
it is not possible to study the phylogeny of lichens, per specie.
• Rather, the relationships of the fungal partner and the algal partner
must both be studied.

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•Algal partner often
•a cyanobacterium, such as Nostoc or Scytonema.
•usually a unicellular pleurastrophycean green alga,
such as
•Trebouxia,
•Pseudotrebouxia, or Myrmecia,

4. Current topic
• Current topic on the phylogeny of lichens is focused
on the question of…
1. the origin of lichens
and particularly to answer
2. "How many times have lichens originated
among fungi?"

5. Morphology of Lichen
• Lichens occur in one of four basic growth forms, as
illustrated below:
• crustose - crustlike, growing tight against the substrate.
• squamulose - tightly clustered and slightly flattened
pebble-like units.
• foliose - leaflike, with flat sheets of tissue not tightly bound.
• fruticose - free-standing branching tubes.

6. Taxonomy of lichen
• Depending on the taxonomic classification
• 15–18 orders of the Ascomycota include lichen-
forming taxa,
• 8–11 of these orders (representing about 60% of the
Ascomycota species) contain both lichenized and non-
lichenized species.

7. Eumycota evolution and origins of lichen
associations
• This phylogram is based on parsimony analysis of
nearly complete (ca. 1700 nt) rDNA sequences.
• Bootstrap percentages of > 50 % (based on 200
bootstrap replications) are shown over thickened
branches. Distance is relative to line length (scale on
figure).
• Lichens are shown in green, animal pathogens in red.

9. Phylogenetic relationship with Ascomycota
• Phylogenetic reconstruction of Ophiocordyceps unilateralis
and an outgroup of Ascomycota.
• The order Hypocreales is highlighted in grey.
• The tree was rooted on Candida albicans and this branch is
not drawn to scale.
• Bootstrap values were 100, unless indicated otherwise.
Fungal lifestyles are indicated with different colors

10. Phylogenetic relationship with Ascomycota

11. Another example of lichen association
• Multilocus phylogeny of the lichen-forming fungal
genus Melanohalea (Parmeliaceae, Ascomycota)
• some Melanohalea taxa are truly widespread, a limited
number of clades appear to have much more restricted
distributional ranges. In most instances the
concatenated gene tree and multilocus species tree
approaches provided similar estimates of relationships.

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• However, nodal support was generally higher in the phylogeny
estimated from
•concatenated data,
•relationships among taxa within one major
clade were largely unresolved in the species
tree.

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• Major fungal lineages are derived from lichen
symbiotic ancestors
• Multiple origins of lichen symbioses in fungi
suggested by SSU rDNA phylogeny

15. References
• https://www.nature.com/articles/35082053
• https://www.scoop.it/t/lichen-
systematics/p/4017471126/2014/03/12/multilocus-phylogeny-of-the-
lichen-forming-fungal-genus-melanohalea-parmeliaceae-ascomycota-
insights-on-diversity-distributions-and-a-comparison-of-species-tree-and-
concatenated-topologies
• https://www.google.com.pk/search?q=phylogeny+of+lichens&dcr=0&sour
ce=lnms&tbm=isch&sa=X&ved=0ahUKEwjDjoz8r9fYAhUCOhQKHd5BBo4Q_
AUICigB&biw=1366&bih=662#imgdii=P9I2lb9V1YdilM:&imgrc=tPD9zYM1YS
2qJM
• http://www.sciencedirect.com/science/article/pii/S1055790312003703
• https://www.researchgate.net/figure/Phylogenetic-relationship-of-O-
unilateralis-s-l-with-other-ascomycetous-fungi_281098364