Plant Systematics: General Overview


Systematics is the study of diversity. In particular, it focuses on describing and classifying species. Recently, classifications following phylogenetic (evolutionary) relationships have been attempted (see Judd et al., 1999). Here, I do not provide a description of particular species (I recommend reading field guide books as a place to start for that), but rather I provide a general overview of the various groups of the plant kingdom and of plant-like protists. This is by no means intended to be exhaustive. The information presented here is from a variety of sources referenced at the bottom of this page.

Plant-like Protists:

  • Phaeophyta -- brown algae
  • Rhodophyta -- red algae
  • Chrysophyta -- diatoms, gold-brown algae
  • Xanthophyta -- yellow-green algae
  • Pyrrophyta -- dinoflagellates
  • Euglenophyta -- euglenoids
  • Chlorophyta -- green algae
    • Chlorophyceae
    • Ulvophyceae
    • Charophyceae
      • Charales
      • Coleochaetales
      • Zygnematales
      • Klebsormidiales
      • Chlorokybales

Land plants probably arose about 450 to 470 MYA, and are believed to have evolved directly from a freshwater charophycean green algal ancestor (and probably from the order Charales)(Graham, 1993). Land plants have been historically divided into two main groups: non-vascular plants and vascular plants. The non-vascular plants is composed of the “bryophytes”, which is a general term used to collectively refer to hornworts, liverworts, and mosses.

The “bryophytes”:

  • Hepatophyta (liverworts)
  • Anthocerophyta (hornworts)
  • Bryophyta (mosses)

The vascular plants (or “tracheophytes” -- “tracheo” refers to tracheids, which are types of water conducting cells) have been divided into two groups: the pteridophytes (ferns and fern allies) and the seed plants. The pteridophytes are a non-monophyletic group and have been referred to as the “free-sporing tracheophytes” since they all produce spores for dispersal (Judd et al., 1999). Alternatively, they have been referred to as “seedless vascular plants”. Three divisions of seedless vascular plants (Rhyniophyta, Zosterophyllophyta, and Trimerophyta), which lived in the Devonian peroid, went extinct about 360 MYA (Raven, 1992).

Pteridophytes:

  • Lycopodiophytes
  • Psilotophytes
  • Equisetophtyes
  • Leptosporangiate ferns

The seed plants are divided into the gymnosperms and angiosperms. The gymnosperms are a non-monophyletic group, and have naked seeds (i.e. seeds are not enclosed by a carpellary structure as in the angiosperms). Double fertilization, which forms triploid endosperm in the angiosperms, does not occur in gymnosperms. The following information on gymnosperms and angiosperms was taken from Plant Systematics, A Phylogenetic Approach by Judd et al. (1999).

I will use the following symbols to represent the total number of taxonomic levels that are present per group:

Order = O
Family = F
Genera = G
Species = S

For the gymnosperms, I have included the common/general name of the particular group of families. Then, for each family, the ‘official’ name is given (with the suffix ‘-aceae’) followed by the common family name in parentheses, after which examples of genera or species are given. I have labelled certain angiosperm family names (or orders) in bold which may be of particular interest (since they contain either common species of weeds, crop plants, medicinal plants, ornamentals, or house plants).

Gymnosperms:

  • Cycads [F=3; G=10; S=130]:
    • Cycadaceae (Cycad family) [G=1, S=20]
      Cycas sp.
    • Stangeriaceae [G=1]
      Stangeria sp.
    • Zamiaceae (Coontie family) [G=8; S=110]
      Zamia sp.
  • Ginkgos (F=1; G=1; S=1):
    • Ginkgoaceae (Maidenhair Tree family)
      Ginkgo biloba
  • Conifers [F=7; G=65; S>600]:
    • Cupressaceae (Cypress or Redwood family) [G=29; S=130]
      e.g. Juniperus, Thuja, Taxodium, Sequoia
    • Pinaceae (Pine family) [G=10; S=220]
      e.g. Pinus (pine), Abies (fir), Picea (spruce), Larix (larch), Tsuga (hemlock), Pseudotsuga (Douglas fir), Cedrus (cedar)
    • Podocarpaceae (Podocarp family) [G=17; S>170]
    • Taxaceae (Yew family) [G=5; S=20]
      e.g. Taxus, Torreya
  • Gnetophytes [F=3; G=3]:
    • Ephedraceae (Mormon Tea family) [G=1; S=50]
      Ephedra sp.
    • Gnetaceae [G=1; S=40]
      Gnetum sp.
    • Welwitschiaceae [ ]
      Welwitschia sp.

Judd et al. (1999) have divided the angiosperms (or ‘flowering plants’) into four groups. These are 1) the “Non-Monocot Paleoherbs”, 2) the Monocots, 3) the “Magnoliid Complex”, and 4) the Tricolpates (or Eudicots, which are divided into the “Basal Tricolpates” and the Core Tricolpates). In some of the following, the order name is given first (i.e. with the suffix ‘-ales’), and then the family name. Genus names with a number in parentheses refers to the number of species that have been found for that genus.

“Non-Monocot Paleoherbs”:

  • Nymphaeales
  • Ceratophyallales
  • Aristolochiales
  • Piperales
    • Saururaceae [G=4; S=6]
    • Piperaceae (Pepper family) [G=6; S=2020]
      e.g. Peperomia (1000), Piper (1000)

Monocots:

  • Acorales
  • Alismatales
    • Araceae (Arum family) [G=108; S=2830]
      e.g. Philodendron (500), Dieffenbachia (40; dumbcane), Pothos (50), Syngonium (30; arrowhead), Lemna (duck weed), Xanthosoma (40; elephant’s ear)
    • Alismataceae (Water Plantain family) [G=16; S=100]
      e.g. Sagittaria
    • Hydrocharitaceae (Tape Grass family) [G=16; S=100]
      e.g. Vallisneria
  • Lilianae
    • Liliales
      • Liliaceae (Lily family) [G=13; S=400]
        e.g. Lilium (80; lily), Tulipa (80; tulips)
    • Asparagales
      • Convallariaceae (Lily of the Valley family) [G=24; S=300]
        e.g. Dracaena (80), Sansevieria (50), Polygonatum (50; Solomon’s seal), Maianthemum (33; false Solomon’s seal)
      • Asphodelaceae (Aloe family) [G=15; S=750]
        e.g. Aloe (380), Haworthia (70)
      • Agavaceae (Agave family) [G=9; S=300]
        e.g. Agave (250), Yucca (40)
      • Alliaceae (Onion family) [G=19; S=645]
        e.g. Allium (550; garlic, onions, shallots, chives, leeks, ramps)
      • Amaryllidaceae (Amaryllis or Daffodill family) [G=50; S=870]
        e.g. Amaryllis, Narcissus (daffodill)
      • Iridaceae (Iris family) [G=78; S=1750]
        e.g. Crocus, Iris
      • Orchidaceae (Orchid family) [G=775; S=19500]
        e.g. Vanilla planifolia (vanilla)
    • Dioscoreales
      • Dioscoreaceae (Yam family) [G=5; S=625]
        e.g. Dioscorea (600)
  • Commelinanae
    • Arecales
      • Arecaceae (Palm family) [G=200; S=2780]
    • Bromeliales
      • Bromeliaceae (Bromeliad family) [G=51; S=1520]
    • Philydrales
      • Pontederiaceae (Water Hyacinth family) [G=4; S=35]
        e.g. Pontederia, Eichhornia
    • Commelinales
      • Commelinaceae (Spiderwort family) [G=40; S=640]
        e.g. Tradescantia (60)
    • Typhales
      • Typhaceae (Cattail family) [G=2; S=28]
        e.g. Typha (13; cattails), Sparaganium (15; bur reeds)
    • Juncales
      • Juncaceae (Rush family) [G=6; S=400]
      • Cyperaceae (Sedge family) [G=122; S=4500]
    • Poales
      • Poaceae (Grass family or Gramineae) [G=650; S=8700]
        e.g. Triticum (wheat), Hordeum (barley), Avena (oats), Sorghum (sorghum millet), Pennisetum (pearl millet), Oryza sativa (rice), Zizania aquatica (wild rice), Zea mays (maize), Saccharum officinale (sugar cane), Bambusa (bamboo), Secale cereale (rye), Andropogon, Aegilops
    • Zingiberales

“Magnoliid Complex”:

  • Magnoliales
  • Laurales
  • Illiciales

Tricolpates (Eudicots): “Basal Tricolpates”

  • Ranunculales
    • Ranunculaceae (Buttercup family) [G=47; S=2000]
      e.g. Rannunculus (400), Clematis (250), Anemone (150)
    • Berberdaceae
    • Papaveraceae (Poppy family) [G=40; S=770]
      e.g. Papaver (100), P. somniferum (opium, morphine, heroin, codeine), Dicentra
    • Menispermaceae
  • Proteales
    • Plantanaceae (Sycamore Tree family, Plananus) [G=1; S=9]

Tricolpates (Eudicots): Core Tricolpates

  • Vitales
    • Vitaceae (Grape family) [G=12; S=700]
      e.g. Vitis (60), Parthenocissus
  • Saxifragales
    • Saxifragaceae
    • Crassulaceae (Stonecrop family) [G=35; S=1500]
    • Hamamelidaceae
    • Altingiaceae
    • Grossulariaceae
    • Haloragaceae
    • Ceridophyllaceae
    • Iteaceae
  • Santalales
  • Caryophyllanae*
  • Rosids*
  • Asterids*

*The composition of three groups in the ‘core tricolpates’ (Caryophyllanae, Rosids, and the Asterids), are shown below.

Caryophyllanae:

  • Caryophyllales
    • Caryophyllaceae (Carnation family) [G=70; S=2200]
      e.g. Silene (700), Dianthus (carnations)
    • Phytolaccaceae (Poke Weed family)
      e.g. Phytolacca (pokeweed)
    • Nyctaginaceae (Four O’Clock family)
      e.g. Mirabilis (four o’clock)
    • Amaranthaceae (Amaranth family)
      e.g. Beta vulgaris (beet), Spinacia oleracea (spinach)
    • Aizoaceae (Stone Plant family)
    • Cactaceae (Cactus family) [G=93; S=1400]
    • Petiveraceae
  • Polygonales
    • Droseraceae (Sundew family) [G=4; S=110]
      e.g. Drosera (sundew), Dionaea (Venus’s flytrap)
    • Polygonaceae (Knotweed family, G=43; S=1100)
      e.g. Rumex (200; rhubarb), Fagopyrum (buckwheat)
    • Plumbaginaceae
    • Nepenthaceae
The Rosid Clade:
  • Zygophyllales
  • Geraniales
    • Geraniaceae (Geranium family) [G=7; S=750]
      e.g. Geranium (300), Pelargonium (250)
  • Eurosids I
    • Celatrales
    • Malpighiales
      • Malpighiaceae
      • Euphorbiaceae
      • Clusiaceae (St. John’s-Wort family) [G=38; S=1100]
        e.g. Hypericum (360)
      • Rhizophoraceae
      • Violaceae (Violet family) [G=22; S=950]
        e.g. Viola (500)
      • Passifloraceae (Passionflower family) [G=18; S=630]
        e.g. Passiflora (400), Adenia (100)
      • Salicaceae (Willow family) [G=3; S=386]
        e.g. Salix (350), Populus (35)
    • Oxalidales
      • Oxalidaceae
      • Cephalotaceae
      • Cunoniaceae
    • Fabales
  • Fabaceae (Legume or Bean family) [G=630; S=18000]
    e.g. Arachis (peanuts), Cicer (chickpeas), Lens (lentils), Glycine (soybeans), Phaseolus (beans), Pisum (pea), Medicago (alfalfa), Melilotus (sweet clover), Trifolium (clover), Vicia (vetch), Acacia, Lathyrus (sweet pea), Gleditsia (honey locust)
  • Polygalaceae
  • Suraniaceae
  • Rosales
    • Rosaceae (Rose family) [G=85; S=3000]
      e.g. Malus (apple), Pyrus (pear), Prunus (peaches, plums, cherries, apricots, almonds, nectarines), Rubus (blackberry, raspberry), Fragaria (strawberry), Cydonia (quince), Potentilla (cinquefoil), Crataegus (hawthorn), Rosa (rose), Sorbus (mountain ash)
    • Rhamnaceae (Buckthorn family)
    • Ulmaceae (Elm family) [G=6; S=40]
      e.g. Ulmus
    • Celtidaceae
    • Moraceae (Fig family) [G=53; S=1500]
      e.g. Ficus (fig), Morus (mulberries)
    • Urticaceae (Nettle family) [G=40; S=900]
    • Ceropiaceae
    • Cannabaceae
      e.g. Cannabis
  • Cucurbitales
    • Cucurbitaceae (Cucurbit family) [G=118; S=825]
      e.g. Cucurbita (pumpkin, squash, gourds), Cucumis (cantaloupe, muskmelon, honeydew melon, cucumber), Citrullis (watermelon) Luffa (loofah)
    • Begoniaceae
  • Fagales
    • Fagaceae (Beech or Oak family) [G=9; S=900]
      e.g. Quercus (450; oak), Q. suber (cork), Fagus (beech)
    • Betulaceae (Birch family, G=6; S=157)
      e.g. Betula (60), Corylus (hazelnuts), Carpinus (ironwood)
    • Casuarinaceae
    • Myricaceae (Bayberry family)
    • Juglandaceae (Walnut family) [G=8; S=59]
      e.g. Juglans (20; walnut), Carya (25; pecan)
  • Eurosids II
    • Myrtales
      • Lythraceae (Loosestrife family) [G=30; S=600]
        e.g. Lythrum (35)
      • Onagraceae (Evening Primrose family) [G=16; S=650]
        e.g. Oenothera (120), Clarkia (45)
      • Myrtaceae (Myrtle family) [G=144; S=3100]
        e.g. Eucalyptus (500)
      • Melastomataceae
      • Combretaceae
      • Vochysiaceae
      • Memecylaceae
    • Brassicales
      • Brassicaceae (Mustard family) [G=419; S=4130]
        e.g. Brassica oleracea (cabbage, kale, broccoli, cauliflower, Brussels sprouts), B. rapa (chinese cabbage, turnip), B. nigra (black mustard), B. napus (canola, rapeseed oil), Sinapis alba (white mustard), Armoracia rusticana (horseradish), Raphanus sativus (radish), Arabidopsis thaliana (thale or mouse-ear cress), Rhaphanobrassica
      • Bataceae
      • Caricaceae
      • Resedaceae
      • Moringaceae
    • Malvales
    • Sapindales
      • Rutaceae
      • Meliaceae (Mahogany family)
      • Simaroubaceae
      • Anacardiaceae (Sumac or Poison Ivy family) [G=70; S=600]
        e.g. Toxicodendron (30; poison ivy, poison oak, poison sumac), Rhus (sumac), Mangifera indica (mango), Anacardium occidentale (cashew), Pistachia vera (pistachio)
      • Sapindaceae
      • Burseraceae

    Asterid Clade:

    • Cornales
      • Hydrangeaceae (Hydrangea family)
      • Cornaceae (Dogwood family)
      • Loasaceae
    • Ericales
      • Sapotaceae
      • Primulaceae (Primrose family) [G=20; S=1000]
        e.g. Primula
      • Myrsinaceae
      • Theaceae (Tea family)
      • Ericaceae (Heath family)
      • Sarraceniaceae (Pitcher-plant family)
      • Polemoniaceae (Phlox family)
    • Euasterids I
      • Garryales
      • Solanales
        • Solanaceae (Potato family) [G=147; S=2930]
          e.g. Solanum (1400), S. tuberosum (potato), S. dulcamara (Bittersweet nightshade), S. melongena (eggplant), S. lycopersicon (tomatoes), S. betacea (tree tomatoes), Nicotiana (100), Capsicum (cayenne, green and red peppers), Datura (jimsonweed), Physalis ixocarpa (tomatillos), Petunia, Cestrum, Brunfelsia
        • Convolvulaceae (Morning Glory family G=55; S=1930)
          e.g. Ipomoea
      • Gentianales
        • Gentianaceae
        • Rubiaceae (Coffee family) (G=550; S=9000]
          e.g. Coffea arabica and C. robusta (coffee)
        • Apocynaceae (Milkweed family) [G=355; S=3700]
          e.g. Asclepias (230)
      • Lamiales
        • Oleaceae (Olive family) [G=29; S=600]
        • Plantaginaceae (Snapdragon family)
          e.g. Antirrhinum (40; snapdragon), Linaria (120), L. vulgaris (butter-and-eggs), Plantago (215; plantain), Mimulus (150), Digitalis (20)
        • Scrophulariaceae
        • Orobanchaceae
        • Bignoniaceae
        • Acanthaceae
        • Gesneriaceae
        • Lentibulariaceae (Bladderwort family)
        • Lamiaceae (Mint family) [G=258; S=6970]
          e.g. Mentha (peppermint, spearmint), Lavandula (lavender), Marrubium (horehound), Nepeta (catnip), Ocimuum (basil), Origanum (oregano), Rosmarinus (rosemary), Salvia (sage), Satureja (savory), Thymus (thyme)
    • Euasterids II
      • Aquifoliales (Holly family)
      • Apiales
        • Apiaceae (Carrot family) [G=460; S=4250]
          e.g. Daucus (carrot; Queen Anne’s Lace), Anethum (dill), Apium (celery), Carum (caraway), Foeniculum (fennel), Pastinaca (parsnip), Petroselinum (parsley), Conium (hemlock), Cicuta (water hemlock), Panax ginseng (ginseng), Aralia (wild sarsaparilla)
      • Dipsacales
        • Caprifoliaceae (Honeysuckle family)
      • Asterales
        • Asteraceae or Compositae (Aster family) [G=1535; S=23000]
          e.g. Aster (250), Solidago (100; goldenrod), Cichorium (chicory), Helianthus (sunflower), Taraxacum (dandelion), Ambrosia (ragweed), Pulicaria (fleabane), Lactuca (lettuce), Cirsium, Senecio, Artemisia, Tragopogon, Cynara (artichoke), Calendula (marigold), Leucanthemum (chrysanthemum), Zinnia
        • Calceraceae
        • Campanulaceae (Lobelia family)
        • Stylidiaceae
        • Menythaceae
        • Goodeniaceae

    References:

    1. Graham, L.E. (1993) Origin of Land Plants. John Wiley & Sons: New York.
    2. Judd, W.S., Campbell, C.S., Kellogg, E.A., and Stevens, P.F. (1999) Plant Systematics, A Phylogenetic Approach. Sinauer Associates, Inc: USA.
    3. Stewart, W.N. and Rothwell, G.R. (1992) Paleobotany and the Evolution of Plants, 2nd edt. Cambridge University Press:USA.
    4. Raven, P.H., Evert, R.F, and Eichhorn, S.E. (1992) Biology of Plants, 5th edt. Worth Publishers: USA.

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