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GYMNOSPERMS, unlike Angiosperms, bear their ovules openly on megasporophylls. In the absence of an ovary, style and stigma the pollen grains reach directly to ovules and fertilize it. Consequently, ovules mature into seeds but there is no outer covering of the ovary wall and seeds are naked. These are thus fruitless seed plants. Gymnosperms dominated the seed plant diversity in late Paleozoic and Mesozoic Era in the ancient past. Today, extant members represented by merely 884-1420 species under 82-84 genera of 12 families (Christenhusz et al. 2011; Christenhusz & Byng 2016; Mabberley 2017; CoL 2021) are relicts, survivors of rich ancient flora. Read more about the Gymnosperms at 'The Gymnosperm Database' [https://www.conifers.org/index.php] and 'World List of Cycads' [https://cycadlist.org/index.php].
In the area of Pantnagar, no Gymnosperm species is known to occur naturally, though, some species are cultivated here.
The following families of Gymnosperm are known in the Pantnagar area:
Araucariaceae Henkel & W.Hochst.
Cupressaceae Gray
Cycadaceae Pers.
Pinaceae Spreng. ex Rudolphi
Zamiaceae Horan.
The evolution of vascular cambium in land plants paved the way for the evolution of large plants with secondary growth and monophyletic clade 'lignophytes' (woody plants) evolved. This was followed by the evolution of seeds within this clade giving rise to 'spermatophytes' (seed-bearing plants). The living spermatophytes are often classified into two groups mainly based on the nature of the ovule; plants with naked ovules- 'Gymnosperms', and plants with ovules contained in the ovary- 'Angiosperms'. Recent cladistic analyses strongly suggest these two groups as sister clades which separated from each other as far back as 310-350 million years ago. However, the evolutionary relationships of all groups of living spermatophytes and their extinct ancestors are not known exactly. The extant Gymnosperms (often called Acrogymnosperms or Acrogymnospermae) are a very small group represented by relicts of a very large group of plants that existed in the upper Paleozoic and Mesozoic eras.
Outlines of some traditional and cladistic (and rankless) classifications of Gymnosperms are given below:
Classification by K.R. Sporne (1965, 74)
Classification by K.R. Sporne (1965, 74)
CLASS- CYCADOPSIDA
ORDER- PTERIDOSPERMALES*
Family- Lyginopteridaceae*
Family- Medullosaceae*
Family- Calamopityaceae*
Family- Glossopteridaceae*
Family- Peltaspermaceae*
Family- Corystospermaceae*
Family- Caytoniaceae*
ORDER- BENNETTITALES* (=CYCADEOIDEALES)
Family- Williamsoniaceae*
Family- Wielandiellaceae*
Family- Cycadeoideaceae*
ORDER-PENTOXYLALES*
Family- Pentoxylaceae*
ORDER- CYCADALES
Family- Nilssoniaceae*
Family- Cycadaceae
CLASS- CONIFEROPSIDA
ORDER- CORDITALES*
Family- Eristophytaceae*
Family- Cordaitaceae*
Family- Poroxylaceae*
ORDER- CONIFERALES
Family- Lebachiaceae*
Family- Voltziaceae*
Family- Palissyaceae*
Family- Pinaceae
Family- Taxodiaceae
Family- Cupressaceae
Family- Podocarpaceae
Family- Cephalotaxaceae
Family- Araucariaceae
ORDER- TAXALES
Family- Taxaceae
ORDER- GINKGOALES
Family- Trichopityaceae*
Family- Ginkgoaceae
CLASS- GNETOPSIDA
ORDER- GNETALES
Family- Gnetaceae
Family- Welwitschiaceae
Family- Ephedraceae
*completely extinct group
Classification in Mabberley (2017)
Classification in Mabberley (2017)
SUBCLASS- GINKGOIDAE
ORDER- GINKGOALES
Family-Ginkgoaceae
SUBCLASS- CYCADIDAE
ORDER- CYCADALES
Family- Cycadaceae
Family- Zamiaceae
SUBCLASS- PINIDAE
ORDER- PINALES
Family- Pinaceae
Family- Araucariaceae
Family- Podocarpaceae
Family- Sciadopityaceae
Family- Taxaceae
Family- Cupressaceae
SUBCLASS- GNETIDAE
ORDER- GNETALES
Family- Gnetaceae
Family- Ephedraceae
Family- Welwitschiaceae
Classification by Cantino et al. (2007)
Classification by Cantino et al. (2007)
Rankless phylogenetic classification
TRACHEOPHYTA
EUPHYLOPHYTA
LIGNOPHYTA
SPERMATOPHYTA
ACROGYMNOSPERMAE
CYCADOPHYTA
CONIFERAE
PINACEAE
CUPRESSOPHYTA
GNETOPHYTA
Extant Gymnosperm clades in BOLD LETTERS
Classification in Simpson (2019)
Classification in Simpson (2019)
Rankless phylogenetic classification
SPERMATOPHYTA
GYMNOSPERMAE (ACROGYMNOSPERMAE)
CYCADOPHYTA
Cycadaceae
Zamiaceae
GINKOOPHYTA
Ginkgoaceae
CONIFERAE
PINOPSIDA
Pinaceae
CUPRESSOPSIDA
Araucariaceae
Cupressaceae
Phyllocladaceae
Podocarpaceae
Sciadopityaceae
Taxaceae (includes Cepalotaxaceae)
GNETALES
Ephedraceae
Gnetaceae
Welwitschiaceae
ANGIOSPERMAE
Classification by Christenhusz et al. (2011)
Classification by Christenhusz et al. (2011)
SUBCLASS- CYCADIDAE
ORDER- CYCADALES
Family- Cycadaceae
Family- Zamiaceae
SUBCLASS- GINKGOIDAE
ORDER- GINKGOALES
Family-Ginkgoaceae
SUBCLASS- GNETIDAE
ORDER- WELWITSCHIALES
Family- Welwitschiaceae
ORDER- GNETALES
Family- Gnetaceae
ORDER- EPHEDRALES
Family- Ephedraceae
SUBCLASS- PINIDAE
ORDER- PINALES
Family- Pinaceae
ORDER- ARAUCARIALES
Family- Araucariaceae
Family- Podocarpaceae
ORDER- CUPRESSALES
Family- Sciadopityaceae
Family- Cupressaceae
Family- Taxaceae
Classification in The Gymnosperm Database (Earle, 1997-2021)
Classification in The Gymnosperm Database (Earle, 1997-2021)
SUBCLASS- CYCADIDAE
ORDER- CYCADALES
Family- Cycadaceae
Family- Zamiaceae
SUBCLASS- GINKDODAE
ORDER- GINKGOALES
Family- Ginkgoaceae
ORDER- Welwitschiales
Family- Welwitschiaceae
SUBCLASS- GNETIDAE
ORDER- GNETALES
Family- Gnetaceae
ORDER- EPHEDRALES
Family- Ephedraceae
SUBCLASS- PINIDAE
ORDER- PINALES
Family- Pinaceae
ORDER- ARAUCARIALES
Family- Araucariaceae
Family- Podocarpaceae
ORDER- CUPRESSALES
Family- Sciadopityaceae
Family- Cupressaceae
Family- Taxaceae
Cladogram of Embryophytes (Land plants) based on Cantino et al. (2007) showing Extant Gymnosperm clades
Cladogram of woody and seed plants redrawn after Simpson (2019)
Evolutionary relationships of major gymnosperm groups are drawn in the above two cladograms. The Coniferae group of Cantino et al. (2007) includes Pinaceae, and Cupressophyta but excludes Gnetophyta (Gnetum, Welwitschia, Ephedra). While the cladogram based on Simpson (2019) contains Pinaceae, Gnetales (Gnetum, Welwitschia, Ephedra) and Cupressophyta.
A more recent cladogram showing the relationship of major Gymnosperm clades and other seed plants based on molecular phylogenetics is drawn below. Here the conifers are divided into two separate groups (Pinaceae and non- Pinaceae conifers) refuting their monophyletic origin. Pinaceae are the sister group to Gnetales (Gnetum, Welwitschia, Ephedra) and these two constitute a clade which is sister to non-Pinaceae conifers. These three major clades (non-Pinaceae conifers, Gnetales and Pinaceae) together constitute a sister group of basal most clade of living Gymnosperms containing cycads and Ginkgo. All these Gymnosperm clades together are sister groups to Angiosperms. Since molecular data for the majority of Gymnosperm taxa are not available due to their extinction exact phylogenetic relationships between extant taxa and extinct taxa will be hard to achieve in near future (Earle, 2021).
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