Overview of Green Plant Phylogeny

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Overview of Green Plant Phylogeny

• Plant Systematics (PBIO 309/509)
• Harvey Ballard

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Cycads

• First cycad fossils from late Carboniferous (290
  mya)
• Most abundant from Cretaceous through Triassic,
  65-255 mya)
• Presently ca. 130 spp.

Cycas revoluta
Photo from Digital Flora of Texas website (2006)
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Cycads

• Dioecious, both types of strobili large
• Several features may be ancestral for seed plants
• Haustorial male gametophytes
• Gigantic multiflagellate sperm

Cycas rumphii
Drawing from Judd et al. (2002) photo from
Digital Flora of Texas website (2006)
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Geologic Origins of Major Groups
Era Period Duration (mya)
Fossils Found
Cycads
Progymnosperms Pteridosperms
Marattiales Polypodiales
Equisetophytes
Lycophytes
Trimerophytes
Rhyniophytes
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Ginkgos

• Single extant species, Ginkgo biloba,
  rediscovered in 1956 in mountains of China
• Possible preginkgophyte Dichophyllum in Upper
  Carboniferous (345 mya)
• Dioecious group
• Like cycads, have haustorial male gametophyte,
  swimming sperm

Ginkgo biloba
Digital Flora of Texas website (2006)
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Ginkgos

• Later fossils definitely attributable to
  Gingkoales extend to Lower Cretaceous (120 mya)
• Specimens resembling G. biloba appear in Jurassic
  but extensive in Tertiary (60-160 mya)
• By Oligocene (38 mya), only G. biloba and G.
  adiantoides survived (latter extinct)

Judd et al. (2002)
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Geologic Origins of Major Groups
Era Period Duration (mya)
Fossils Found
Ginkgos
Cycads
Progymnosperms Pteridosperms
Marattiales Polypodiales
Equisetophytes
Lycophytes
Trimerophytes
Rhyniophytes
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Gnetophytes

• Fossil record sparse, from Upper Triassic to
  Tertiary, abundant during mid-Cretaceous (60-205
  mya)
• Extant genera Ephedra, Gnetum, Welwitschia

Ephedra
Photo from Digital Flora of Texas website (2006)
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Gnetophytes
Welwitschia

• One fossil interpretable as gymnosperm or
  angiospermraises issues of synapomorphies
  distinguishing latter
• Earlier analyses supported anthophyte
  hypothesis, with gnetophytes, Benettitales and
  angiosperms together
• Recent studies places gnetophytes w/conifers

Drawing from Judd et al. (2002) photo from
Digital Flora of Texas website (2006)
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Geologic Origins of Major Groups
Era Period Duration (mya)
Fossils Found
Gnetophytes
Ginkgos
Cycads
Progymnosperms Pteridosperms
Marattiales Polypodiales
Equisetophytes
Lycophytes
Trimerophytes
Rhyniophytes
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Conifers
Larix

• Progymnosperms of Devonian perhaps ancestral to
  conifers
• Cordaitaceae first conifers, from
  mid-Carboniferous (320 mya), became common in
  later Carboniferous

Pinus
Digital Flora of Texas website (2006)
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Conifers

• Ca. 600 living spp.
• Mostly trees and shrubs
• Moneocious or dioecious
• Molecular and morphological data indicate
  ancestral split between Pinaceae and remaining
  conifers

Judd et al. (2002)
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Geologic Origins of Major Groups
Era Period Duration (mya)
Fossils Found
Conifers
Ginkgos
Cycads
Progymnosperms Pteridosperms
Marattiales Polypodiales
Equisetophytes
Lycophytes
Trimerophytes
Rhyniophytes
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Angiosperms

• Over 257,000 extant spp.
• Account for most of the diversity of plant life
  on earth
• Relationships remain unclear
• First unequivocal fossils date from Lower
  Cretaceous (ca. 120 mya)followed by abrupt
  extensive diversification

Judd et al. (2002)
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Angiosperms

• Synapomorphies
• Seeds enclosed within a carpel
• Reduced female gametophyte
• Double fertilization w/endosperm
• Recent DNA and other evidence supports a few
  basal dicot families sister to core angiosperms

Judd et al. (2002)
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Geologic Origins of Major Groups
Era Period Duration (mya)
Fossils Found
Angiosperms
Conifers
Ginkgos
Cycads
Progymnosperms Pteridosperms
Marattiales Polypodiales
Equisetophytes
Lycophytes
Trimerophytes
Rhyniophytes
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References

• Judd, W. S., C. S. Campbell, E. A. Kellogg, P. F.
  Stevens, and M. J. Donoghue. 2002. Plant
  systematicsA phylogenetic approach, 2nd ed.
  Sinauer Associates, Sunderland, MA. pp. 153-184.
• Stewart, W. N. and G. W. Rothwell. 1993.
  Paleobotany and the evolution of plants, 2nd ed.
  Cambridge Univ. Press, Cambridge, UK.