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INTRODUCTION TO LICHENS
What is a lichen?
Lichens are fungi that associate with algae. Most are ascomycetes, a few are basidiomycetes.
ascomycetes basidiomycetes
Are lichens a ‘natural’ group?
they have evolved many separate times
Are lichens a ‘natural’
group?
they have evolved in
basidiomycetes as well
all lichens contain algae
or cyanobacteria
upper cortex
algal layer
medulla
lower cortex
photobionts
photobionts - Trentepohlia
photobionts - cyanolichenssometimes look grey, or the dull blue-grey cyanobacteria seen when thallus is broken
photobionts - cyanolichens
some cyanolichens swell when moist (but most do not)
photobionts - cephalodia
lichen growth forms
crustose
foliose
fruticose
crustose lichens - cracked
crustose lichens - smooth
crustose lichens - leprose
crustose lichens - endolithic
squamulose lichens
squamulose lichens
foliose lichens
fruticose lichens
fruticose lichens
fruticose lichens – can be flattened
fruticose lichens – can be flattened
crustose with lobes: placodioid
filamentousshape is determined by photobiont
foliose lichens - rhizines
foliose lichens - cilia
pseudocyphellae
vegetative reproductionthe lichen needs to disperse the fungus and the alga
together
vegetative reproduction
soredia isidia
(in a soralium)
vegetative reproductionsoralia
vegetative reproduction - soralia
vegetative reproduction - soralia
vegetative reproduction – soralia
position is useful in species identification
vegetative reproduction – isidia
vegetative reproduction – phyllidia
vegetative reproduction – pseudoisidia
vegetative reproduction
isidioid soredia/isidiomorphs
– soredia which stay in place and become corticate
vegetative reproduction
blastidia schizidia
vegetative reproduction - blastidia
often very similar to soredia
sexual reproduction
apothecium perithecium
sexual reproduction - apothecia
sexual reproduction - apothecia
sexual reproduction – apotheciano thalline margin thalline margin
(lecideine) (lecanorine)
sexual reproduction – apothecia
no thalline margin
sexual reproduction – apothecia
convex; margin absent or almost
sexual reproduction – apotheciaelongated apothecium (lirella)
sexual reproduction – apothecia
Stalked, with a dry spore-mass
sexual reproduction – perithecia
sexual reproduction – perithecia
perithecia sunk in pits in limestone
asexual spores
called conidia
usually in pycnidia
asexual spores
apothecia together with pycnidia
asexual spores
apothecia together with pycnidia, immersed in surface of limestone
basidiolichens
basidiolichens
When is it not a lichen?
When is it not a lichen,but it is a ‘lichen’?
