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

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10.11 SUMMARY
(1) Four DurviZZaea species are recognised: D. potatorum (Labill.)
Areschoug, D. antarctica (Chamisso) Hariot., D. IlYillana Lindauer and i:~
net·! species D. chathamica. The:r::e is insufficient eV'idence to tet:cd11.
D. caepestipes (Mont.) Skottsbg. or D, harveyi as separate species.
The three species with non buoyant blades are endenic either to
Aus·tralia, New Zealand or the Chatharn and Antipodes Islands. D.
antarctica, which is the only buoyant species, and capable of drifting
vast distances, is circumpolar in its distribution.
(2) A variety of physical and biological factors appears to
dictate the ",orld distribution of Dul'villaea spp. Locally, wave force
and a stable substratum are the most impo~tant factors limiting
distribution laterallyo Vertically, intolerance of desiccation,
grazing by limpets and the quality and quantity of light are the most
important limiting factors.
(3) The zonation of DurviZZaea spp. does not fit naturally into
the universal zonation scheme proposed by Stephenson and Stephenson
(1949j, but fits better into an amendment of their scheme proposed by
Womersley and Edmonds (1952).
(4) The morphology of three species studied is extre.mely
plastic / and is 'co a large extent determined by wave force. In some
areas fish grazing exerts a profound influence on the morphology of
plantso Many species described in the literature are just phenotypic
f.orms.
(5) There is no localised meristem in D. antarctica and no
apical or intercalary meristems in any Du~villaea 6PP, Growth of D.
anta~otiaa
increases distally along the blade.
(6) There is some evidence of latitudinal vari,d::ion in the
morphology of D. antarotica and D. wiUana 0
In general, size of
plants increases southwards. D. anta:rotioa from'l'Jidely separated
popula.tions exhibits light morphological differences.
(7) Individual D. antarct~ca and D. wiZlana plants produce one
crop of conceptacles each year more or less simul taneously over th(~
la.mina surface. Up to four concepi::.ac:le layers can be det.ected in the
outer cortex of old plants, each layer representing one year's crop.
Dark ba.nds are also formed annually in the outer cortex: and these,
together t ... i th the conceptacle layers, may be used to obtaLn the