Fróðskaparrit - 01.01.1998, Side 11

17
An Island Biogeographical Analysis
of the Flora in the Faroe Islands
Ein oyggjalívlandafrøðilig greining av floruni í Føroyum
Hans Guldager Christiansen1 and Erik Hansen2
1: Kalundborg Gymnasium, J. Hagemann-Petersens Alle 4,4400 Kalundborg, Denmark
2: Odsherreds Gymnasium, Ástoftevej 34,4550 Asnæs, Denmark
Úrtak
Útbreiðslan av teimum føroysku leggstreingjagróplant-
unum varð nágreiniliga kannað í 1960’árunum. Við hes-
um tilfarinum sum grundarlag hava vit talt, hvussu nógv
sløg eru í teimum 18 oyggjunum.
Tað ber til at vísa á, at talið á plantusløgum í Føroy-
um er treytað av víddini á teimum einstøku oyggjunum,
soleiðis at í eini oyggj, sum er tíggju ferðir størri, eru
tvær ferðir so nógv plantusløg. Ella fyri at vera neyvari:
Talið á sløgum (S) er í lutfalli til víddina á oyggjunum
(A), sum víst í líkningini S = 73,8A°.20.
Við teirri treyt, at útbreiðslan av plantusløgum í
oyggjunum er tilvildarlig, hava vit gjørt eina støddfrøði-
liga lýsing, sum er grundað á títtleikan av sløgum, eina
sing, sum samanumtikið fer at greiða betur frá, hvussu
nógv sløg eru í oyggjunum. Tað kunnu vera aðrar
grundir til frávik frá hesi null-hypotesu enn bert tað, at
útbreiðslan er treytað av vídd. Eitt nú vísir kanningin, at
tað eru fá sløg í teimum norðaru oyggjunum, meðan tað
arafturímóti eru sera nógv sløg í Koltri.
Tann støddfrøðiliga null-hypotesan er eisini grund-
arlag undir einum samanburði av floruni í oyggjunum.
rslitið er nógvar upplýsingar um floruna í teimum ein-
støku oyggjunum, t.d. at Skúvoy er ‘føroyskari’ enn hin-
31 oyggjarnar, tá talan er um floru.
Abstract
I he distribution of the Faroese vascular plants was tho-
roughly examined in the 1960s. We have used this ma-
tøial and conducted an enumeration of the number of
species found on each of the 18 largest islands.
The number of plant species found on the Faroe Is-
lands may be demonstrated to depend on the area of the
island in question, in such a way that an island ten times
bigger will contain approximately twice as many spe-
cies of plants. Or to be more exact: The number of
species (S) is proportional to the area of the islands (A)
as indicated in the equation S = 73.8 A0-20.
By assuming that the distribution of plant species in
the Islands is random, we have made a mathematical de-
scription based on the frequency of the species, a de-
scription which will by and large provide a better expla-
nation for the number of species in the Islands. Devia-
tions from this ‘null hypothesis’ may be attributed to
other causes than mere dependence on area. The model
illustrates for example that the northern islands contain
few species whereas Koltur is extremely rich on species.
The mathematical null hypothesis also forms the ba-
sis for a comparison of the Islands’ flora. The result is
much information on the florae of the individual islands,
for example that Skúvoy floristicly is the most ‘Faroese’
of all the islands.
Introduction
Ever since Charles Darwin’s voyage to the
Galapagos Islands in 1835, remote islands
have exerted a magnetic attraction on biol-
ogists world-wide. As a rule, animal and
plant life on islands is poorer than in areas
on corresponding mainlands. Consequent-
ly, it is often easier to fmd biological corre-
lations and pattems on islands than on con-
tinents where the biological diversity may
seem infmite.
Fróðskaparrit 46. bók 1998: 17-32