Fróðskaparrit - 01.01.2001, Side 89

TARAR í FØROYSKUM ØKI
93
lands, Simmons (1897) about 125, Børge-
sen (1902) 216 and Irvine (1982) 223
species. In comparing the numbers it is im-
portant to realise that the delimitations of
species have changed over the years, some
were in the past considered independent
species and later changed the status, others
were found to be different phases in the life
history of a single species. Other algae,
considered taxa of lower rank have now
been elevated to species or referred to dif-
ferent species.
The number of species partly reflects the
intensity of studies and only a few are like-
ly newcomers within the period of pub-
lished records.
Many small species, especially micro-
scopic epiphytes, crustose algae and
Cyanophyceae may have been overlooked
in previous investigations. The same con-
cerns the heteromorphic brown algae,
Acrothrix gracilis and Striaria attenuata,
these can be present as unrecognizable
microthalli and only develop macrothalli
under suitable conditions at unpredictable
intervals. Acrothrix gracilis is widely dis-
tributed in the North Atlantic, but not re-
ported from Iceland (Forward and South,
1985) ; Striaria attenuata is widely distrib-
uted in the eastem part of the North At-
lantic, but not reported from the Shetland
Islands and Iceland (South and Tittley,
1986) .
Justified as candidates for newcomers
are therefore only the relatively large
species. Callithamnion tetragonum is
widely distributed in the North Atlantic, in-
cluding Iceland (South and Tittley, 1986).
Ceramium diaphanum has a southern dis-
tribution in the northeastern North Atlantic
(South and Tittley, 1986 as C. tenuissimun
(Roth) J.Agardh). A surprising discovery
was Ophiocladus simpliciusculus since this
species is known from the warm temperate
Atlantic Ocean and also the Seychelles
(Wynne, 1995) and South Africa (Stegenga
et al., 1997). Dilsea carnosa is an example
of a successful newcomer, first reported by
Rex (1970, unpubl. report). In our material
D. carnosa was very common often well
developed with fronds up to 80 cm long.
Another example may be Fucus serratus,
the old report by Landt (1800) was neither
documented nor confirmed by succeeding
investigations; therefore both Børgesen
(1902) and Irvine (1982) thought it was a
mistake. The species was collected at a
single locality in the Trongisvágsfjord in
1997 (Bruntse et al., 1999a; 1999b), while
well developed stands were observed at
several places along the same fjord in 2000
(K. Gunnarsson, pers. obs.).
In sheltered localities a non digitate
Laminaria with a long hollow stipe occurs,
it was described as L. longicruris var.
faeroensis by Børgesen (1896) and later el-
evated to species (Børgesen, 1902) based
on the absence of mucilage ducts in the
stipe.
Laminaria longicruris is common along
the east coast of North America, from Arc-
tic Canada to Connecticut (Egan and
Yarish, 1988). Transplantexperiments have
shown that both the presence of mucilage
ducts and hollow stipe are influenced by
environmental conditions (Chapman, 1973;
1974). In a series of crossing experiments
nearly complete interfertility was found be-