Phytochorion

A phytochorion, in phytogeography, is a geographic area with a relatively uniform composition of plant species. Adjacent phytochoria do not usually have a sharp boundary, but rather a soft one, a transitional area in which many species from both regions overlap. The region of overlap is called a vegetation tension zone .

In traditional schemes, areas in phytogeography are classified hierarchically, according to the presence of endemic families, genera or species, e.g., in floral (or floristic, phytogeographic) zones and regions, ^[1] or also in kingdoms, regions and provinces, ^[2] sometimes including the categories empire and domain. However, some authors prefer not to rank areas, referring to them simply as "areas", "regions" (in a non hierarchical sense) or "phytochoria". ^[3]

Systems used to classify vegetation can be divided in two major groups: those that use physiognomic-environmental parameters and characteristics and those that are based on floristic (i.e. shared genera and species) relationships. ^[4] Phytochoria are defined by their plant taxonomic composition, while other schemes of regionalization (e.g., vegetation type, physiognomy, plant formations, biomes) may variably take in account, depending on the author, the apparent characteristics of a community (the dominant life-form), environment characteristics, the fauna associated, anthropic factors or political-conservationist issues. ^[5]

Explanation

Several systems of classifying geographic areas where plants grow have been devised. Most systems are organized hierarchically, with the largest units subdivided into smaller geographic areas, which are made up of smaller floristic communities, and so on. Phytochoria are defined as areas possessing a large number of endemic taxa. Floristic kingdoms are characterized by a high degree of family endemism, floristic regions by a high degree of generic endemism, and floristic provinces by a high degree of species endemism. Systems of phytochoria have both significant similarities and differences with zoogeographic provinces, which follow the composition of mammal families, and with biogeographical provinces or terrestrial ecoregions, which take into account both plant and animal species.

The term "phytochorion" (Werger & van Gils, 1976) ^[6] is especially associated with the classifications according to the methodology of Josias Braun-Blanquet, which is tied to the presence or absence of particular species, ^[7] mainly in Africa. ^[8]

Taxonomic databases tend to be organized in ways which approximate floristic provinces, but which are more closely aligned to political boundaries, for example according to the World Geographical Scheme for Recording Plant Distributions.

Early schemes

In the late 19th century, Adolf Engler (1844-1930) was the first to make a world map with the limits of distribution of floras, with four major floral regions (realms). ^{[9] [10]} His Syllabus der Pflanzenfamilien , from the third edition (1903) onwards, also included a sketch of the division of the earth into floral regions. ^[11]

Other important early works on floristics includes Augustin de Candolle (1820), ^[12] Schouw (1823), ^[13] Alphonse de Candolle (1855), ^[14] Drude (1890), ^[1] Diels (1908), ^[15] and Rikli (1913). ^[16]

Good (1947) regionalization

Good (1947) floristic kingdoms

Botanist Ronald Good (1947) identified six floristic kingdoms (Boreal or Holarctic, Neotropical, Paleotropical, South African, Australian, and Antarctic), the largest natural units he determined for flowering plants. Good's six kingdoms are subdivided into smaller units, called regions and provinces. The Paleotropical kingdom is divided into three subkingdoms, which are each subdivided into floristic regions. Each of the other five kingdoms are subdivided directly into regions. There are a total of 37 floristic regions. Almost all regions are further subdivided into floristic provinces. ^[17]

Takhtajan (1978, 1986) regionalization

Armen Takhtajan (1978, 1986), in a widely used scheme that builds on Good's work, identified thirty-five floristic regions, each of which is subdivided into floristic provinces, of which there are 152 in all. ^{[18] [19] [20] [21]}

Holarctic Kingdom

I. Circumboreal region

1 Arctic province

2 Atlantic Europe province

3 Central Europe province

4 Illyria or Balkan province

5 Pontus Euxinus province

6 Caucasus province

7 Eastern Europe province

8 Northern Europe province

9 Western Siberia province

10 Altai-Sayan province

11 Central Siberia province

12 Transbaikalia province

13 Northeastern Siberia province

14 Okhotsk-Kamchatka province

15 Canada incl. Great Lakes province

II. Eastern Asiatic region

16 Manchuria province

17 Sakhalin-Hokkaidō province

18 Japan-Korea province

19 Volcano-Bonin province

20 Ryūkyū or Tokara-Okinawa province

21 Taiwan province

22 Northern China province

23 Central China province

24 Southeastern China province

25 Sikang-Yuennan province

26 Northern Burma province

27 Eastern Himalaya province

28 Khasi-Manipur province

III. North American Atlantic region

29 Appalachian province (forested areas extending east to include the piedmont and west to the start of the prairies)

30 Atlantic and Gulf Coastal Plain province

31 North American Prairies province

IV. Rocky Mountain region

32 Vancouverian province

33 Rocky Mountains province

V. Macaronesian region

34 Azores province

35 Madeira province

36 Canaries province

37 Cape Verde province

VI. Mediterranean region

38 Southern Morocco province

39 Southwestern Mediterranean province

40 South Mediterranean province

41 Iberia province

42 Baleares province

43 Liguria-Tyrrhenia province

44 Adriatic province

45 East Mediterranean province

46 Crimea-Novorossijsk province

VII. Saharo-Arabian region

47 Sahara province

48 Egypt-Arabia province

VIII. Irano-Turanian region

8A. Western Asiatic subregion

49 Mesopotamia province

50 Central Anatolia province

51 Armenia-Iran province

52 Hyrcania province

53 Turania or Aralo-Caspia province

54 Turkestan province

55 Northern Baluchistan province

56 Western Himalaya province

8B. Central Asiatic subregion

57 Central Tien Shan province

58 Dzungaria-Tien Shan province

59 Mongolia province

60 Tibet province

IX. Madrean Region

61 Great Basin province

62 Californian province

63 Sonoran province

64 Mexican Highlands province

Paleotropical Kingdom

X. Guineo-Congolian region

65 Upper Guinean forests province

66 Nigeria-Cameroon province

67 Congo province

XI. Usambara-Zululand region

68 Zanzibar-Inhambane province

69 Tongoland-Pondoland province

XII. Sudano-Zambezian region

12A. Zambezian subregion

70 Zambezi province

12B. Sahelo–Sudanian subregion

71 Sahel province

72 Sudan province

12C. Eritreo–Arabian subregion

73 Somalia-Ethiopia province

74 South Arabia province

75 Socotra province

12C. Omano-Sindian subregion

76 Oman province

77 South Iran province

78 Sindia province

XIII. Karoo-Namib region

79 Namibia province

80 Namaland province

81 Western Cape province

82 Karoo province

XIV. St. Helena and Ascension region

83 St. Helena and Ascension province

XV. Madagascan region

84 Eastern Madagascar province

85 Western Madagascar province

86 Southern and Southwestern Madagascar province

87 Comoro province

88 Mascarenes province

89 Seychelles province

XVI. Indian region

90 Ceylon (Sri Lanka) province

91 Malabar province

92 Deccan province

93 Upper Gangetic Plain province

94 Bengal province

XVII. Indochinese region

95 South Burma province

96 Andamans province

97 South China province

98 Thailand province

99 North Indochina province

100 Annam province

101 South Indochina province

XVIII. Malesian region

18A. Malesian subregion

102 Malaya province

103 Borneo province

104 Philippines province

105 Sumatra province

106 Java province

18B. Papuan subregion

107 Celebes province

108 Moluccas and West New Guinea province

109 Papua province

110 Bismarck Archipelago province

XIX. Fijian region

111 New Hebrides province

112 Fiji province

XX. Polynesian region

113 Micronesia province

114 Polynesia province

XXI. Hawaiian region

115 Hawaii province

XXII. Neocaledonian region

116 New Caledonia province

Neotropical Kingdom

XXIII. Caribbean region

117 Central America province

118 West Indies province

119 Galápagos Islands province

XXIV. region of the Guayana Highlands

120 The Guianas province

XXV. Amazon region

121 Amazonia province

122 Llanos province

XXVI. Brazilian region

123 Caatinga province

124 Central Brazilian Uplands province

125 Chaco province

126 Atlantic province

127 Paraná province

XXVII. Andean region

128 Northern Andes province

129 Central Andes province

South African Kingdom

XXVIII. Cape region

130 Cape province

Australian Kingdom

XXIX. Northeast Australian region

131 North Australia province

132 Queensland province

133 Southeast Australia province

134 Tasmania province

XXX. Southwest Australian region

135 Southwest Australia province

XXXI. Central Australian or Eremaean region

136 Eremaea province

Antarctic Kingdom

XXXII. Fernandezian region

137 Juan Fernández province

XXXIII. Chile-Patagonian region

138 Northern Chile province

139 Central Chile province

140 Pampas province

141 Patagonia province

142 Tierra del Fuego province

XXXIV. region of the South Subantarctic Islands

143 Tristan-Gough province

144 Kerguelen province

XXXV. Neozeylandic region

145 Lord Howe province

146 Norfolk province

147 Kermadec province

148 Northern New Zealand province

149 Central New Zealand province

150 Southern New Zealand province

151 Chatham province

152 New Zealand Subantarctic Islands province

Regionalization according to Wolfgang Frey and Rainer Lösch (2004, 2010)

Flora regions in Europe

Notes

(with focus on Europe, matching the image on the right) ^{[22] [23]}

• The central European region and the central Russian region are sister regions.
• The border between them is similar to the Fagus sylvatica limit (January, day-time temperature average: above -2 °C).
• The border between the central Russian region and the boreal region is similar to the Quercus spp. limit (Day-time temperature average: above 10 °C, 4 months per year).
• The border between the boreal region and the arctic region is similar to the tree line, taiga/arctic tundra limit (July, day-time temperature average: above 10 °C).
• The border of the Atlantic region is the limit of no frost (average), Gulf Stream influence.
• The warm islands in the Atlantic Ocean are in the Macaronesia region: isolated populations in a more humid environment.
• The Mediterranean region is similar to the occurrence of wild Olea europea and wild Cistus salviifolius (Olea europea is grown very North in Italy).
• The border between the submediterranean region and the central European region is similar to the alpine arc (upper Rhone, upper Rhine, lower Danube), a weather barrier.
• The Pontic region border is similar to the tree line/ steppe limit (less than 450 mm precipitation per year).
• The Turanian region has a semi-arid climate.

Liu et al. (2023, 2024) Regionalization

Critiquing previous attempts for their lack of phylogenetic relationships in the construction of their regions, Liu et al. incorporated distribution data alongside phylogenetic relationships to configure their realms. This led to the classification of eight realms organized into two super-realms and each composed of a number of sub-realms. ^[24]

• Gondwanan Super-Realm

1 African

2 Indo-Malesian

3 Australian

4 Novozealandic

5 Neotropical

6 Chile-Patagonian

• Laurasian Super-Realm

7 Holarctic

8 Saharo-Arabian

Differences from Takhtajan's floristic kingdoms mainly focus on emphasizing the uniqueness of certain realms that he had as subdivisions within kingdoms. Two examples are separating some kingdoms into two separate realms, as happened to the Paleotropical and Antarctic kingdoms, reasoning that they have been separated form each other for long enough time to constitute a different phylogenetic trajectory. The merging of the Cape floristic kingdom with the African realm was based by the low endemism of higher taxonomic ranks, which could be found outside the cape region in the rest of Africa. The final major change is the separation of the Saharo-Arabian realm from the Holarctic kingdom, though they admit the northern boundary is not clear, with flora from the Holarctic being found within this area.

After publishing their regions, Dr. Hong Qian criticized Liu et al. for the inclusion of nonnative distributions in their analyses. ^[25] In response to this, the group cleaned their data to remove nonnative ranges and reassessed their regions. They suggest that the previous inclusion of exotic species did not significantly affect their mapping and found that the cleaned data revealed the same floristic realms. ^[26]

References

1. Drude, O. (1890). Handbuch der Pflanzengeographie. Stuttgart: Engelhorn, , . French translation: Manuel de géographie botanique. Paris: P. Klincksieck, 1897. 552 p., .
2. Braun-Blanquet, J. (1932). Plant sociology; the study of plant communities. New York and London, McGraw-Hill, .
3. Linder, Lovett, Mutke, et al. (2005): A numerical re-evaluation of the sub-Saharan phytochoria. Biologiske Skrifter 55: 229-252.
4. JOLY, C.A., AIDAR, M.P.M., KLINK, C.A., McGRATH, D.G., MOREIRA, A.G., MOUTINHO, P., NEPSTAD, D.C., OLIVEIRA, A.A.; POTT, A.; RODAL, M.J.N. & SAMPAIO, E.V.S.B. 1999. Evolution of the Brazilian phytogeography classification systems: implications for biodiversity conservation. Ci. e Cult. 51: 331-348.
5. Magno Coutinho, L. (2006) O conceito de bioma. Acta bot. bras. 20(1): 13-23.
6. Werger, M. J. A. & H. van Gils. 1976. Phytosociological classification problems in chorological border line areas. J. Biogeogr. 3: 49–54, .
7. glossary Archived 2008-04-11 at the Wayback Machine from Bredenkamp, George J.; Granger, J. Ed; Hoffman, M. Timm; Lubke, Roy A.; Mckenzie, Bruce; Rebelo, A. (Tony) & Noel, van Rooyen (February 1998). Low, A. Barrie & Rebelo, A. (Tony) G. (eds.). Vegetation of South Africa, Lesotho and Swaziland: A companion to the Vegetation Map of South Africa, Lesotho and Swaziland. Department of Environmental Affairs and Tourism, Pretoria.
8. Prance, G. T. (1989). American Tropical forests, in Ecosystems of the World, Vol. 14B. Tropical Rain Forest Ecosystems, (eds H. Lieth and M. J. A. Werger), Elsevier, Amsterdam, pp. 99–132, .
9. Engler, A. (1879-1882). Versuch einer Entwicklungsgeschichte der Pflanzenwelt. 2 vols., Leipzig.
10. Cox, C. B., Moore, P.D. & Ladle, R. J. 2016. Biogeography: an ecological and evolutionary approach. 9th edition. John Wiley & Sons: Hoboken, p. 10, .
11. Engler, Adolf (1903). Syllabus der Pflanzenfamilien: eine Übersicht über das gesamte Pflanzensystem mit Berücksichtigung der Medicinal- und Nutzpflanzen nebst einer Übersicht über die Florenreiche und Florengebiete der Erde zum Gebrauch bei Vorlesungen und Studien über specielle und medicinisch-pharmaceutische Botanik (3rd ed.). Berlin: Gebrüder Borntraeger Verlag. p. 233. Retrieved 31 January 2014.
12. de Candolle, Augustin (1820). Essai Élémentaire de Géographie Botanique. In: Dictionnaire des sciences naturelles, Vol. 18. Flevrault, Strasbourg, .
13. Schouw, J. F. (1822). Grundtræk til en almindelig Plantegeographie. Copenhagen, Gyldendalske Boghandels Forlag. German translation: Grundzüge einer allgemeinen Pflanzengeographie, Berlin, 1823, .
14. de Candolle, Alphonse (1855). Géographie botanique raisonnée. Paris: V. Masson, .
15. Diels, L. (1908). Pflanzengeographie. Göschen, Leipzig, ; 5th ed. rev. 1958 (F. Mattick), De Gruyter, Berlin.
16. Rikli, M. (1913). "Geographie der Pflanzen (Die Florenreiche)". In: Handwörterbuch der Naturwissenschaften 4:776–857, .
17. Good, R. (1947). The Geography of Flowering Plants. Longmans, Green and Co, New York, . 2nd ed., 1953, .
18. Takhtajan, A. 1969. Flowering plants: origin and dispersal. Transl. by C. Jeffrey. Oliver &. Boyd, Edinburgh. 310 pp. .
19. Тахтаджян А. Л. Флористические области Земли / Академия наук СССР. Ботанический институт им. В. Л. Комарова. — Л.: Наука, Ленинградское отделение, 1978. — 247 с. — 4000 экз. DjVu, Google Books.
20. Takhtajan, A. (1986). Floristic Regions of the World. (translated by T.J. Crovello & A. Cronquist). University of California Press, Berkeley, PDF, DjVu.
21. Cox, C. B. (2001). The biogeographic regions reconsidered. Journal of Biogeography, 28: 511-523, .
22. Frey, Wolfgang; Lösch, Rainer (2004). Lehrbuch der Geobotanik. München, Heidelberg: Elsevier, Spektrum. ISBN   3-8274-1193-9.
23. Frey, Wolfgang; Lösch, Rainer (2010). Geobotanik: Pflanzen und Vegetation in Raum und Zeit (3 ed.). Heidelberg: Spektrum. ISBN   978-3-8274-2335-1.
24. Liu, Y., Xu, X., Dimitrov, D., Pellissier, L., Borregaard, M. K., Shrestha, N., Su, X., Luo, A., Zimmermann, N. E., Rahbek, C., & Wang, Z. (2023). An updated floristic map of the world. Nature Communications, 14(1). https://doi.org/10.1038/s41467-023-38375-y
25. Qian, H. (2024). Reassessing data quality underlying the recently updated floristic map of the world. Nature Communications, 15(1). https://doi.org/10.1038/s41467-024-47543-7
26. Liu, Y., Xu, X., Dimitrov, D., Rahbek, C., & Wang, Z. (2024). Reply to: Reassessing data quality underlying the recently updated floristic map of the world. Nature Communications, 15(1). https://doi.org/10.1038/s41467-024-47544-6

Bibliography

• Frodin, D.G. (2001). Guide to Standard Floras of the World. An annotated, geographically arranged systematic bibliography of the principal floras, enumerations, checklists and chorological atlases of different areas. 2nd ed. (1st edn 1984), pp. xxiv, 1100, .Cambridge University Press, Cambridge, .