Introduction To Lichens - Lasw

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’?