A biological study of Durvillaea antarctica (Chamisso) Hariot and D ...

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several thousand miles. It is likely that drifting D. anta~~tiaa
have been responsible for the colonisa.tion of shores far removed from
those where the kelp is abundant. Several plants are normally
attached to a composite holdfast, it. is probable that. both sexes will
wa,sh ashore at the same time. If this supposition is correct, ahd
the pattern of ocean currents has remained much the same in recent
millennia, then on the basis of the origin and direction of currents
it should be possible to predict. j~e presence or absence of D.
antarctica at various localities. In general this is found
on shores that are directly influenced by the Wes,t Wind Drift, and
associated currents. Ho",ever, the kelp does not grow on some
shores where, on the basis of current patt.erns, it would predictably
groN,
(d)
Biological competition:
On some shores other algae or animals may be better suited than
DurvilZaea to conditions in the lower littoral or upper sublittoral 0
Competition could account for the absence of DurvilZaea in some of
those areas that otherwise appear to be a sui'cable habitat, In such
areas it is important to check on the species living at levels
normally occupied by Du:rviUaea, and to find ...out i-£ the distribut.ions
of these species anrlofDurviZlaea are mutually exclusive"
4,6 UNUSUAL FEATURES IN THE DrS'I'RIBUTION OF Dl/RVILLAEA
In the light of what is knotom about the growth requirements of
D. antar>CJtiaa, there are several regions which appear to be suitable
habitat, that are uninhabited by the kelp.
A closey. study of these
regions is likely to yield clues as to \'Ihich factors determine the
world dis tr ibution of species.
(a) Why, when the cool Peru Current extends much f~rrther north of
at that
latitude? :
When the West Wind Drift approaches the South American ce;ast it
divides into the Cape Horn Current which flows easblards south of
Cape Horn I and the narrm'l Peru Current which is deflected norlli'Y/ards
along the Chilean and Peruvian coasts. According to Schott (1935)