DIV 1 Lecture 11/3 - Ferns and Gymnosperms

Fern groups

extant lineages and 4 subclasses

• Polypodiidae (95%), 10,323 species

• Marattidae, 111 species

• Ophioglossidae, 129 species

• Equisetidae, 15 species

Fern Traits

• homospory: one type of spore for both sexes

• Polypodiidae: some heterospory, leptosporangia, sori

• Eusporangia: passive mechanism (wind dispersal)

• Leptosparangia: development → active mechanism

• Ophioglossidae: adaxial synangia (fused sporangia)

• Equisetidae: strobilus, nodes/ internodes

• Marattiidae: abaxinal synangia, large fronds

• all subclasses have roots EXCEPT OPHIOGLOSSIDAE

What is the rarest fern in the United States?

American Harts tongue fern

• listed as threatened species in the US

• habitat destruction and over collection, etc

How is the American harts tongue fern being conserved?

habitat protection (USF and WS), climatic and habitat analysis, genetic diversity analysis, in vitro propagation for restoration (argmentation and reintroduction), under consideration for delisting

Origin of seed plants: Carboniferous

• 359 to 299 mya

• dominated by lycophytes (spore → swimming sperms)

• warm and humid swamps

• cold and dry at the end of the Carboniferous

Origin of seed plants: Permian

• 299- 259 mya

• greatest consolidation of the continents (pangea)

• immense dry inland environment → lost a lot of ferns because it was dry

• seedless vascular plants become regulated to coastal, wet areas

• seed plants evolved under dry conditions and started to dominate

Environmental forces for evolution of the seed

• free living gametophytes of seedless plants are vulnerable

• retention of gametophytes on maternal parent is an advantage

Triassic (252 - 201 mya)

• began with an impoverished earth, with hot and dry climate

• favored planes pre-adapted to arid conditions

• seed plants became the dominate group

• further evolution of the seed and other innovations

• gymnosperms (naked seed plants → ovules not in an ovary)

Examples of further evolution of the seed and other innovations:

1) seed: seed coat, food source and young plant versus spore

2) pollen: contains male gametes

• reproduction becomes airborn

• allowed sexual reproduction to occur even in dry environments

Cycadophyta

• Cycads

• dominate group during Jurassic (201-145 mya)- still present today

• pinnately compound leaves

• frond clustered on top

• typically unbranched

• Xerophytic (thick and leathery fronds, hypodermis, sunken stomata

When was the ”age of the Cycads”?

the Jurassic period

Diversity of Cycads:

11 extant (alive) genra, 800 species, tropics to subtropics

Ginkgophyta

• peaked at jurassic

• 7 genra, 50 species → EXTICT

• Ginkgo biloba is the LONE SURVIVER

• unchanged for more then 150 mya (morphology conserved)

Ginkophyta traits

• simple, fan-like and bilobed leaves

• xerophic leaves

• dichotomous veins

• carkin-like reproductive structure

• paired ovules

Gnetophyla

• 3 families (Aphedra, Welwischia, Gnetum)

• 1 genus in each

• enigmatic group (morphological different)

• monophyletic group (molecular and anatomical data used to group them)

Aphedra

jointed stems, small and scale-like leaves, shrubs

Welwischia

2 strap-like leaves, short/ stout stem, herb

Gnetum

simple and laminar leaves, tree form

Coniferophyta

• Conifers

• most ecologically and economically important gymnosperms

• initial and subsequent diversification

Coniferophyta: initial diversification

• Triassic (252 - 201 mya)

• have rise to many families and genera that still exist today (ex. southern hemisphere: Ararcariaceae, Podocarpaceae, few pines)

Coniferophyta: subsequent diversification

• Jurassic (201 - 145 mya)

• Ex. Northern hemisphere: Pinaceae, Cupressaceae (Juniper, Cupressus, Thuja)

Gymnosperm phylogenetic tree

see image

Fern phylogenetic tree

see image