Fróðskaparrit - 01.01.1998, Side 22

28
A BIOGEOGRAPHIC ANALYSIS OF THE PLANTS IN THE FAROEISLANDS
10
11 12 13
14
15 16 17 lí
1: Suðuroy fiBM
2: Stóra Dímun -0.6 i m
3: Skúvoy 0.4 1.5 9
4: Sandoy -1.7 0.6
5: Mykines -0.5 3.1*
6: Vágar -1.8 -0.8
7: Hestur 0.5 1.7
8: Koltur 1.1 2.3*
9: Nólsoy -1.7 1.4
10: Streymoy -1.8 -1.3
11: Eysturoy -4.9* -1.5
12: Kalsoy -1.4 -0.4
13: Kunoy -7.1* -1.7
14: Borðoy -4.4* -0.5
15: Viðoy -2.2* -0.2
16: Svínoy 0.7 1.4
17: Fugloy 0.0 1.5
18: Lftla Dímun 0.2 2.5*
0.2
-0.B
-3.8"
0.8 -2.6* 0.0 I
1.0 -0.7 1.7 -0.2 1
1.4 -0.4 4.4* 0.6 3.5*1
0.3 -0.9 -2.0* -1.6 0.3 -0.1 1
1.1 -5.0* -0.6 1.6 -0.8 0.2 -1.0 i ■Hl
-0.8 -5.3* -1.6 -1.7 0.1 -2.2* -3.9* -0.1 1
-0.4 -4.5* -2.5* 0.4 0.0 -0.9 -3.2* 0.8 1.7 1
-2.9* -7.8* -2.3* -3.9* -1.9 0.4 -4.2* -3.2* -1.1 2.5* i
-1.2 -6.0* -2.1* -1.8 -1.8 0.0 -3.0* -0.7 -0.9 1.9 o.3 ððaøc
-0.7 -4.2* -0.6 -1.3 0.8 1.0 -2.2* 0.1 1.0 3.6* 1.7 3.0* JNHB
0.1 -3.7* -0.2 -0.8 2.0 1.3 0.5 0.9 1.1 2.8* 1.0 0.7 3.2*1 wm
1.5 -1.4 -0.3 -0.3 2.3* 1.6 1.3 1.5 1.5 2.1* -0.6 0.1 1.9 4.6*1
0.6 0.2 0.7 0.4 1.3 0.1 0.8 0.4 0.4 0.0 -1.4 0.7 0.1 0.3
0.3
Table 3: Similarity index of the florae in the 18 Faroe Islands. The index describes the number of common species
ofthe two islands minus the calculated number ofcommon species, divided by a variance, which depends on the
number of common species. An asterisk (*) indicates that theflorae ofthe islands are significantly different.
Positive values indicate that theflorae of the two islands are more alike than anticipated on the basis ofthe null
hypothesis.
Talva 3. Líkleikayvirlit yvir floruna í teimum 18 oyggjunum í Føroyum. Yvirlitið lýsir talið á sløgum, báðar
oyggjarnar hava í felag, minus tað útroknaða talið á sløgum, tær hava í felag, býtt við einum fráviki, sum er
treytað av talinum á felags sløgum. Ein stjørna (*) vísir, at munurin á floruni í oyggjunum er signifikantur. Positiv
virði vísa, at floran í báðum oyggjunum er líkari enn væntað, um null-hypotesan verður løgd sum grund.
pairs of islands. If the difference of flora on
the two islands is statistically significant,
the number is marked by an asterisk.
Treatment of the comparisons
In order to have a clearer picture of Table 3,
we have conducted a cluster analysis, see
Figure 4. The technique applied is that you
focus on the two islands displaying the
largest similarity indexes; subsequently
these two islands are combined into one,
just as if they were in fact one island. The
index between this ‘new’ island and the
others are then calculated. Subsequently
you focus on the islands which now have
the largest index. You combine them, cal-
culate new indexes, and the calculations are
continued until all islands have been relat-
ed to each other.
A group of northern islands is distinctly
separated, i.e. Kalsoy, Kunoy, Viðoy,
Borðoy, and Svínoy-Fugloy, islands which
are most like each other of all islands but
which as a group distinguish themselves
slightly from the other, northerly islands.
Eysturoy is clearly different from the
southerly islands, but rather indifferent in
relation to the northerly islands.
The southerly islands from Streymoy
and southwards constitute another large
group of islands; it is not as homogenous as
the northerly group. Streymoy does not de-