GRAPHIS ScnIPTA

GRAPHTS SCRTPTA 12 (2000)
supralittoral zone and 16 on shaded rock
faces. At Ll, the gneiss hosted 25 ta:ra (10
supralittoral and 17 tenestrial), while the diabase
hosted 30 taxa (13 supralittoral and 23
terrestrial). One species is new for Blekinge,
viz. Lecanora rimicola.
Less than 50% of the taxa occurred on
both gneiss and diabase. However, these differences
may partly be due to differences in
the abundance of the substrates in different
habitats. Pavements with gneiss were more
conrmon than pavements with diabase, both
within and above the supralittoral zone, and
prevailed therefore in the study. On the other
hand, the best developed lichen flora in
shaded situations was found on diabase. However,
some of the differences found may be
related to the properties of the substrates.
At Ll, the slope and exposition of the
gneiss and diabase pavements seem to be
similar (Figure 2), making this locality suitable
for a comparison of the lichen vegetation.
The diabase pavement host slightly more
species than the gneiss pavement, both in the
supralittoral and terrestrial zones (Table I ).
However, more studies are required for any
conclusions on the species richness of the two
substrates.
Lecanora achariana, L. campestris and
Phaeophyscia sciastra were abundant to
rather abundant at Ll on diabase, while
Acarospora fuscata and Lecanora achariana
were abundant at IA on diabffie, but they all
lacked on gneiss (Table I ). These species
probably prefer a high pH value (Hallingbiick
1995, Nimis 1999). L. achariana dominated
on the upper parts of the diabase pavement at
Ll as well as parts of the horizontal pavement
at I-4. Although it prefers acid substrates in
the Mediterranean according to Nimis (1999),
the species has been found on rock surfaces
with trickled water on Hallands V6derci (Arup
& Ekman l99l) and on Skaftri (Degelius
1939), two islands on the Swedish west coast.
The increased supply of nutrients due to the
running water might create similar conditions
as those on the diabase pavement. In the study
of the lichen flora of Hallands Vtiderci, SW
Lichens on Tcirnd 5
Sweden (Arup & Ekman 1991), an amphibolite
ridge was investigated. Five of the lichen
species on the ridge also occur on Ttirnri on
diabase, viz. Caloplaca atroflava, Candelariella
aurella, Diploschistes scruposus, Lecanora
campestris and Lecidella scabra. All of
these species except C. atroflava are absent on
gneiss on Ttirn0. Both amphibolite and diabase
consist of hard rock with a high pH
value, which may be suitable for these lichen
species.
Miriquidica deusta was rather abundant
on gneiss at Ll and L2, and Arctoparmelia
incurva was rather abundant on gneiss at L5,
while they were absent on diabase (Table l).
Both species probably prefer acid substrates
according to Nimis (1999) and Wirth (1995).
In the supralittoral zone, Caloplaca
scopularis was abundant to rather abundant
on gneiss at Ll and LL while C. thallincola
was rather abundant at Ll on diabase instead
(Table 1). In an investigation of the lichen
flora of the Karlsci islands, SW of Gotland in
the Baltic Sea (Johansson et al. 2000), C.
thallincola was cornmon in the supralittoral
zone on mainly calcareous rock, while C.
scopulans was found only on siliceous rock at
a few localities. The latter species presumably
prefers acidic substrates, and was probably
rare on the Karlsri islands because of the scarcity
of siliceous rock here.
Considerations of nature preservation
Although no red-listed or other rare species
have been found in this investigation, the
lichen vegetation on the exposed bedrock on
TArnO may warrant some kind of protection.
Diabase which is sunexposed and have a rich
lichen flora is rare in the region. Ll on the NE
coast of the island, which has the unique combination
of gneiss and diabase pavements
beside each other, is situated outside the present
area of the nature reserve and should be
protected. The knowledge of the differences
between the lichen vegetation on these substrates
is presently very little.