introduction to bryology joannes a. janssens hornworts liverworts mosses life cycle paleobotany moss...

INTRODUCTION TO BRYOLOGY

Joannes A. Janssens

• HORNWORTS

• LIVERWORTS

• MOSSES

• life cycle

• paleobotany

• moss flora

HORNWORTS

LIVERWORTS

MOSSES

The Life Cycle of Bryophytes

• bryophytes are diplohaplontic plants with a heteromorphic alternation of generations

• within the sporangium spores are formed by meiosis

• protonema and gametophores develop after germination

• antheridia and archegonia produce sperm and eggs

• after fertilization a new, attached sporophyte is formed

spor

gam

spor

gam

gam

spor

spor

gam

gam

spor

STREPTOPHYTE EVOLUTION

origin of embryophytes(Charophyceae)

Anthocerotophyta

Polysporangiophyta

Bryophyta

Marchiantiophyta

flavonoidsloss of pyrenoid

jacketsmulticellular sporophyte

calyptraestalked gametangia

loss of columella and stomataseta reduction

• vascular tissue• branched sporophyte• isomorphic phases• stoma

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?

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The Paleobotanical Record of Bryophytes

• Sporognites (Paleozoic, Devonian)

• Diettertia montanensis (Mesozoic, Cretaceous)

• Aulacomnium heterostichoides (Tertiary, Eocene)

• Calliergon aftonianum (Pliocene-interglacial Pleistocene)

Sporognites Halle (1913, 1936)

Diettertia montanensis Brown & Robinson (1974)

Aulacomnium

heterostichoides

Janssens et al.

(1979),

compared with

A.

heterostichum

Calliergon aftonianum Steere

(1942)

The Paleobotanical Record of Bryophytes: Conclusions

• earliest fossils are all liverworts (Silurian-Devonian), mosses are Carboniferous-Permian, hornworts first evidence only in Cretaceous

• no Paleozoic fossils can be attributed to any known class of bryophytes

• Mesozoic fossils suggest explosive evolution, and many lineages are presently extinct

• most present-day classes originated in Cretaceous (co-evolution with Angiosperms?) but no extant genera are known before the Eocene

• Tertiary fossils are very similar to extant taxa; present-day ranges were established

• Quaternary fossils are indistinguishable from present-day modifications of living species