Diversity and Geographic Distribution of Pelagic Copepoda > Cosmopolitanism and endemism
 
   


Abstract | Introduction | Presentation | Diversity | Main marine currents | The different oceanic zones : Summary of the species - Marine currents and other maps | Cosmopolitanism and endemism | Species indicative of continental drift | Species whose localization is difficult to explain | Anthropic mechanisms | Conclusion

 

Cosmopolitanism and endemism :

Of the 2643 recorded forms taking all orders together, the number of cosmopolitan and endemic species has been established. A total of 1225 species, i.e. 46.3 %, are known in only one of the 25 zones, and 77 (2.9 %) are cosmopolitan with the occasional exception of regions where they have not been identified (polar or other) and are present in at least 20 zones. One species, Oithona similis, has been reported in all zones;3 in 24 zones: Aetideus armatus, Pleuromamma xiphias, Rhincalanus nasutus; 10 in 23 zones: Euchirella rostrata, Gaetanus tenuispinus, Haloptilus longicornis, Megacalanus princeps, Nannocalanus minor, Oithona atlantica, Oncaea venusta, Paracalanus parvus, Pleuromamma robusta, Undeuchaeta major; and 19 in 22 zones: Calocalanus pavo, Gaetanus brevispinus, Haloptilus acutifrons, Heterorhabdus papilliger, Heterorhabdus spinifrons, Heterostylites longicornis, Mecynocera clausi, Mesocalanus tenuicornis, Metridia brevicauda, Metridia lucens, Neocalanus gracilis, Oithona plumifera, Paraeuchaeta barbata, Pleuromamma abdominalis, Pleuromamma gracilis, Pseudoamallothrix ovata, Scaphocalanus magnus, Scolecithricella minor, Undeuchaeta plumosa.


So contrary to general ideas about ancient forms, tributary to the exchange mechanisms between the various oceans, the number of cosmopolitan species seems relatively low. It is true that the distribution of many meso- and bathypelagic forms, often poorly represented in catches, is still badly documented, as is that of many podopleans because of their small size and the fact that they are not taken into consideration when samples are analysed. Hyperbenthic species are underestimated because sampling techniques are not adapted to their way of life.


The table below presents in two columns the numbers of endemic and cosmopolitan species (present in at least 20 zones) for each of the 25 zones (with the access to the lists of species with hyperlink under each number) :

Number of endemic species
Number of cosmopolitan species
Sub-Antarctic (zone 3)
Antarctic (zone 4)
South Africa (E & W), Namibia (zone 5)
Gulf of Guinea (sensu lato): Angola-Liberia (zone 6)
Venezuela, Caribbean Sea, Gulf of Mexico, Caribbean, Florida, Sargasso Sea (zone 7)
Cape Verde Is., Canary Is., Madeira Is., Azores, Bay of Biscay, Ibero-Moroccan Bay (zone 8)
Ireland, English Channel, Faroe, Norway, North Sea, Baltic Sea (zone 9)
Southern Iceland, southern Greenland (E & W), Strait of Davis, Labrador Sea (zone 10)
Cape Cod, Nova Scotia, Island of Newfoundland (zone 11)
Central South-Atlantic (Tristan da Cunha-Trinidad-St Helena-N Ascension) (zone 12)
Brazil-Argentina (zone 13)
Mediterranean Sea, Black Sea (zone 14)
Red Sea (zone 15)
Indian Ocean (zone 16)
Gulf of Thailand, Malaysia-Indonesia-Philippines (zone 17)
Australia (E), Great Barrier Reef, Tasman Sea, New Zealand, New Caledonia (zone 18)
Central Tropical Pacific (zone 19)
Eastern Tropical Pacific (Central America, Galapagos, Northern Peru) (zone 20)
China Seas, Vietnam (zone 21)
Japan Sea, Japan (zone 22)
North West Pacific (Sea of Okhotsk-Kuril Islands-Kamtchatka-Sea of Bering) (zone 23)
North East Pacific (Gulf of Alaska, "P" station, British Columbia) (zone 24)
California-Gulf of California (zone 25)
Chile (sensu lato) (zone 26)
Arctic Ocean (zone 27)

It may be noted that the zone 7 includes a large number of endemic species (145). A wide area as Indian Ocean (zone 16), has a high number of endemic species (164). However, the zone 19, as wide but little explored, includes a small number of endemic species (27).

Polar areas are those where the presence of cosmopolitan species is among the least important (40 for the zone 4 and 26 for the zone 27). A small zone rather close as the Red Sea (zone 15), and recently opened to the Mediterranean through the Suez Canal, has a relatively small number of cosmopolitan species (43).



Fig. C1B : Distribution of the number of species of pelagic Copepoda depending on their number of quotations (N)The graph opposite shows the distribution of the number of species of pelagic Copepoda with the factor N (numbers of quotations of the concerned species in the consulted publications).
870 species have been only once quoted (logically close to 1225 known species in only one of the 25 zones). And only 744 species (28.1 %) have more than 10 quotations.
Some species of the Heterorhabdus genus (belonging to the "Abyssalis" Group established by Park, 2000) show a wide distribution for only one quotation.

Below is the table of 20 most often quoted species :

 Species Number of quotations Number of zones
 Oithona similis 621 (??: see in remarks) 25
 Paracalanus parvus 590 ? 23
 Pareucalanus sewelli 504 ? 14
 Acartia (Acartiura) clausi 492 ? 16
 Calanus finmarchicus 452 6
 Oithona plumifera 397 22
 Acartia (Acanthacartia) tonsa 390 16
 Nannocalanus minor 388 23
 Temora stylifera 377 ? 14
 Pleuromamma gracilis 367 22
 Euterpina acutifrons 359 17
 Oncaea venusta 355 ? (probably less because inadequacy précision with O. venella, if it is maintened) 23
 Rhincalanus nasutus 350 24
 Clausocalanus furcatus 348 20
 Lucicutia flavicornis 344 ? 21
 Calocalanus pavo 338 22
 Centropages typicus 333 (SE Pacif.: 1, S Atlant.: 3; N Atlant.: 173; Arct.: 1; Medit.: 148; Black Sea: 2) 8
 Oithona nana 326 21
 Temora longicornis 319 (SE Pacif.: 1, S Atlant.: 3; Arctic: 24; N Atlant.: 160; Medit.: 139; Black Sea: 2) 8
 Pleuromamma abdominalis 311 ? 21

The numbers of quotations followeb by the ? character indicate serious doubts about the concerned species (possible confusion with other species).
The number of quotations is strongly linked to fishing effort in each zone. However, in most cases, it changes proportionally with the number of distribution zones of the species .

   

 Toute utilisation de ce site pour une publication sera mentionnée avec la référence suivante :

Razouls C., de Bovée F., Kouwenberg J. et Desreumaux N., 2005-2017. - Diversité et répartition géographique chez les Copépodes planctoniques marins. Disponible sur http://copepodes.obs-banyuls.fr 
[Accédé le 18 décembre 2017]

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