Relationship of Indian Ocean Epiplanktonic Calanoids to the World Ocean
347
ionally broad (extensive) warm water distribution and concurs with our noting an absence
from such species of appreciable morphological variation between oceans. In contrast,
epiplanktonic copepods occurring mostly in the lower equatorial latitudes, i.e. with
northern and southern limits falling roughly between the 20th and 30th parallels, tend to
show regional provincialisms. Moreover, geographical patterns of species succession
within a species group appear to be more similar among the copepods than among
bathypelagic fish, although this may reflect a more restricted depth range represented
by the copepod groups discussed above. Thus the tropical (equatorial) copepods tend
to be restricted to either 1) the Atlantic Ocean, 2) the Indian Ocean and western portion,
or more, of the Pacific Ocean, or 3) the eastern tropical (equatorial) Pacific Ocean. The
existence of oceanic species of copepods apparently restricted in distribution to the
eastern tropical Pacific is in accord with similar endemics in other pelagic organisms,
e.g. melamphaid fishes (EBELING, 1962) and euphausiids (BRINTON, 1962).
The distributions noted among the 5 calanoid genera suggest 2 generalities of biogeographical significance to the epiplankton of the Indian Ocean:
a) warm water species that breed regularly up to mid-latitudes tend to be circumglobal
in distribution and probably maintain gene flow around South Africa;
b) warm water species that breed regularly only in low latitudes are provincial and
may have one or more tropical cognates elsewhere in the other oceans.
347
ionally broad (extensive) warm water distribution and concurs with our noting an absence
from such species of appreciable morphological variation between oceans. In contrast,
epiplanktonic copepods occurring mostly in the lower equatorial latitudes, i.e. with
northern and southern limits falling roughly between the 20th and 30th parallels, tend to
show regional provincialisms. Moreover, geographical patterns of species succession
within a species group appear to be more similar among the copepods than among
bathypelagic fish, although this may reflect a more restricted depth range represented
by the copepod groups discussed above. Thus the tropical (equatorial) copepods tend
to be restricted to either 1) the Atlantic Ocean, 2) the Indian Ocean and western portion,
or more, of the Pacific Ocean, or 3) the eastern tropical (equatorial) Pacific Ocean. The
existence of oceanic species of copepods apparently restricted in distribution to the
eastern tropical Pacific is in accord with similar endemics in other pelagic organisms,
e.g. melamphaid fishes (EBELING, 1962) and euphausiids (BRINTON, 1962).
The distributions noted among the 5 calanoid genera suggest 2 generalities of biogeographical significance to the epiplankton of the Indian Ocean:
a) warm water species that breed regularly up to mid-latitudes tend to be circumglobal
in distribution and probably maintain gene flow around South Africa;
b) warm water species that breed regularly only in low latitudes are provincial and
may have one or more tropical cognates elsewhere in the other oceans.