List of the largest genera of flowering plants

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Agamospecies in the Ranunculus auricomus complex help to swell the number of species in the genus Ranunculus. Ranunculus auricomus.jpg
Agamospecies in the Ranunculus auricomus complex help to swell the number of species in the genus Ranunculus .

There are over 56 genera of flowering plants estimated to contain at least 500 described species. The largest of these is currently the legume genus Astragalus (milk-vetches), with over 3,000 species. [1]

The sizes of plant genera vary widely from those containing a single species to genera containing thousands of species, and this disparity became clear early in the history of plant classification. The largest genus in Carl Linnaeus' seminal Species Plantarum was Euphorbia , with 56 species; Linnaeus believed that no genus should contain more than 100 species. [2]

Part of the disparity in genus sizes is attributable to historical factors. According to a hypothesis published by Max Walters in 1961, the size of plant genera is related to the age, not of the taxon itself, but of the concept of the taxon in the minds of taxonomists. [3] Plants which grew in Europe, where most of the early taxonomy was based, were therefore divided into relatively small genera, while those from the tropics were grouped into much larger and more heterogeneous genera. [3] [4] Likewise, plants which shared common medicinal properties, such as the many species of Euphorbia , were united into a single genus, while plants of diverse uses, such as the grasses, were split into many genera. [3] Where there were many classical names for groups of plants, such as in Apiaceae / Umbelliferae or Brassicaceae / Cruciferae, small genera were defined, whereas groups not subdivided by classical authors remained as larger genera, such as Carex . [3] [4] A number of biological factors also influence the number of species. For instance, the occurrence of apomixis allows the recognition of large numbers of agamospecies, and such taxa have helped to bolster genera such as Ranunculus and Potentilla . [2]

The introduction of infrageneric taxa (such as the subgenus, section and series) in the 19th century by botanists including Augustin Pyrame de Candolle allowed the retention of large genera that would otherwise have become unwieldy. E. J. H. Corner believed that studying large genera might enable greater insights into evolutionary biology, and he concentrated his efforts on large tropical genera such as Ficus . [2]

Largest genera

According to a 2004 analysis by the botanical taxonomist David G. Frodin, a total of 57 genera of flowering plants contain at least 500 species. [2] It is clear that there are other genera with over 500 species, as the work of taxonomists continues. [4] Currently the number of species included in many genera is very different (e.g. see Psychotria ), so their ranking is subject to changes. The actual numbers of species are imprecisely known also because of different approaches of taxonomists, and many of the genera have not been the subject of recent monographs. For instance, estimates of the number of species in the orchid genus Pleurothallis range from 1,120 to 2,500. Genera from some other groups of vascular plants (like pteridophytes), which have similarly large numbers of species, include Selaginella , Asplenium and Cyathea . [2]

Astragalus is the largest flowering plant genus, with more than 3,200 species, including Astragalus agnicidus. Astragalusagnicidus.jpg
Astragalus is the largest flowering plant genus, with more than 3,200 species, including Astragalus agnicidus .
Bulbophyllum is the second largest flowering plant genus, with more than 2,000 species, including Bulbophyllum guttulatum. Bulbophyllumguttulatum24.JPG
Bulbophyllum is the second largest flowering plant genus, with more than 2,000 species, including Bulbophyllum guttulatum .
Psychotria is the third largest flowering plant genus, with more than 1,900 species, including Psychotria mariniana. Starr 020925-0087 Psychotria mariniana.jpg
Psychotria is the third largest flowering plant genus, with more than 1,900 species, including Psychotria mariniana .
Euphorbia is the fourth largest flowering plant genus, with more than 1,800 species, including Euphorbia amygdaloides. Euphorbia amygdaloides - Berlin Botanical Garden - IMG 8500.JPG
Euphorbia is the fourth largest flowering plant genus, with more than 1,800 species, including Euphorbia amygdaloides .
Carex is the fifth largest flowering plant genus, with more than 1,700 species, including Carex pilulifera. Carex pilulifera habitus.jpeg
Carex is the fifth largest flowering plant genus, with more than 1,700 species, including Carex pilulifera .
Genera of flowering plants with at least 500 species in 2025 [2] [1]
RankGenusSpeciesFamilySpecies list
1 Astragalus Fabaceae List of Astragalus species
2 Piper Piperaceae List of Piper species
3 Bulbophyllum Orchidaceae List of Bulbophyllum species
4 Begonia Begoniaceae List of Begonia species
5 Carex Cyperaceae List of Carex species
6 Euphorbia Euphorbiaceae List of Euphorbia species
7 Miconia Melastomataceae List of Miconia species
8 Epidendrum Orchidaceae List of Epidendrum species
9 Ranunculus Ranunculaceae List of Ranunculus species
10 Psychotria Rubiaceae List of Psychotria species
11 Dendrobium Orchidaceae List of Dendrobium species
12 Senecio Asteraceae List of Senecio species
13 Peperomia Piperaceae List of Peperomia species
14 Anthurium Araceae List of Anthurium species
15 Syzygium Myrtaceae List of Syzygium species
16 Solanum Solanaceae List of Solanum species
17 Eugenia Myrtaceae List of Eugenia species
18 Lepanthes Orchidaceae List of Lepanthes species
19 Croton Euphorbiaceae List of Croton species
20 Impatiens Balsaminaceae List of Impatiens species
21 Rhododendron Ericaceae List of Rhododendron species
22 Allium Amaryllidaceae List of Allium species
23 Acacia Fabaceae List of Acacia species
24 Phyllanthus Phyllanthaceae List of Phyllanthus species
25 Salvia Lamiaceae List of Salvia species
26 Cyperus Cyperaceae List of Cyperus species
27 Justicia Acanthaceae List of Justicia species
28 Silene Caryophyllaceae List of Silene species
29 Habenaria Orchidaceae List of Habenaria species
30 Ficus Moraceae List of Ficus species
31 Erica Ericaceae List of Erica species
32 Diospyros Ebenaceae List of Diospyros species
33 Centaurea Asteraceae List of Centaurea species
34 Indigofera Fabaceae
35 Ardisia Primulaceae List of Ardisia species
36 Crotalaria Fabaceae List of Crotalaria species
37 Cyrtandra Gesneriaceae List of Cyrtandra species
38 Eucalyptus Myrtaceae List of Eucalyptus species
39 Cousinia Asteraceae List of Cousinia species
40 Galium Rubiaceae List of Galium species
41 Ipomoea Convolvulaceae List of Ipomoea species
42 Dioscorea Dioscoreaceae
43 Berberis Berberidaceae List of Berberis species
44 Pleurothallis Orchidaceae List of Pleurothallis species
45 Oxalis Oxalidaceae List of Oxalis species
46 Helichrysum Asteraceae List of Helichrysum species
47 Pandanus Pandanaceae List of Pandanus species
48 Ixora Rubiaceae List of Ixora species
49 Potentilla Rosaceae List of Potentilla species

NB - all species counts have been updated to the 3rd of March 2025 as accepted by Plants of the World Online (POTWO) and genera with lower than 500 species as of then have been removed, but no genus has been added to this list differing from the 2004 list so there may be some missing relevant genera.

References

  1. 1 2 "Plants of the World Online | Kew Science". Plants of the World Online. Retrieved 2025-03-04.
  2. 1 2 3 4 5 6 David G. Frodin (2004). "History and concepts of big plant genera". Taxon . 53 (3): 753–776. doi:10.2307/4135449. JSTOR   4135449.
  3. 1 2 3 4 Max Walters (1961). "The shaping of angiosperm taxonomy". New Phytologist . 60 (1): 74–84. doi: 10.1111/j.1469-8137.1961.tb06241.x . JSTOR   2429789.
  4. 1 2 3 David J. Mabberley (2008). "Introduction". Mabberley's Plant-book: a Portable Dictionary of Plants, their Classification and Uses (3rd ed.). Cambridge University Press. pp. vii–xv. ISBN   978-0-521-82071-4.