Jökull - 01.01.2004, Side 13

Theories on migration and history of the North-Atlantic flora: a review
að úr suðri eftir síðasta kuldaskeið (ördeyðukenning-
in). Í lok 19. aldar var ördeyðukenningunni andmælt
og hugmyndin um miðsvæðakenninguna kom fram,
þ.e. að plöntutegundir hafi lifað af á íslausum svæð-
um sem stóðu upp úr meginísbreiðunni. Miðsvæða-
kenningin átti marga fylgjendur allt til seinni hluta
síðustu aldar enda var hún talin geta skýrt útbreiðslu
ákveðinna plöntutegunda við N-Atlantshaf, einlend-
ar tegundir í háfjallaflóru Skandinavíu og tiltekin út-
breiðslumynstur í flóru Íslands og Skandinavíu. Síðar
voru þessi rök gagnrýnd og t.a.m. sýnt fram á fleiri
mögulegar skýringar á útbreiðslu þessara tegunda. Á
síðasta áratug hafa verið notaðar nýjar rannsóknar-
aðferðir s.s. sameindafræðilegar aðferðir, ískjarnabor-
anir og frjókornagreining til að reyna að svara sömu
spurningum og vísindamenn í byrjun 20. aldar höfðu
varpað fram. Þessar nýju rannsóknir hafa gefið mikil-
vægar niðurstöður en gátan um uppruna og sögu flór-
unnar við N-Atlantshaf er þó enn óleyst.
Glossary
Apomictic groups reproduce asexually without meio-
sis or formation of gametes but nevertheless produce
seeds that are indistinguishable from normal sexually
produced seeds.
Chloroplast DNA (cpDNA) is a very useful marker
for the analysis of the late Quaternary history of an-
giosperms because in most angiosperms, cpDNA is
transmitted through the ovules, not pollen. This may
lead to less swamping through interpopulational gene
flow of the initial genetic structure, established during
refugial survival and/or at colonization.
Endemic species is one that evolved in and has re-
mained restricted to a particular area. In a sense, all
plant species are endemic since none has a global dis-
tribution but the term is usually reserved for species
with a small distributional range.
Polyploidy is a mutation like effect that duplicates
whole sets of chromosomes in plants. Polyploidy can
be divided into autopolyploids, which are composed
of multiple sets from within one species, and allopoly-
ploids, which are composed of sets from different but
related species.
Random Amplified Polymorphic DNA (RAPD) is a
molecular method, used to examine phylogeography
and genetic diversity within and among populations.
Self-compatibility refers to plants that are capable of
self-fertilization.
REFERENCES
Abbot, R. J., H. M. Chapman, R. M. M. Crawford and D.
G. Forbes 1995. Molecular diversity and derivations
of populations of Silene acaulis and Saxifraga opposi-
tifolia from the high Arctic and more southerly lati-
tudes. Molecular Ecology 4, 199–207.
Abbot, R. J., L. C. Smith, R. I. Milne, R. M. M. Crawford,
K. Wolff and J. Balfour 2000. Molecular analysis of
plant migration and refugia in the Arctic. Science 289,
1343–1346.
Anderson, G. 1906. Die Entwicklungsgeschichte der skan-
dinavischen Flora: Resultat scientifique du Congrès
international de Botanique, Wien, pp. 45–97.
Bennike, O. 1999. Colonisation of Greenland by plants
and animals after the last ice age: a review. Polar
Record 35, 323–336.
Bennike, O., S. Björck, J. Böcher, L. Hansen. J. Heine-
meier and B. Wohlfarth 1999. Early Holocene plant
and animal remains from North-east Greenland. Jour-
nal of Biogeography 260, 667–677.
Birks, H. J. B. 1993. Is the hypothesis of survival on glacial
nunataks necessary to explain the present-day distribu-
tions of Norwegian mountain plants? Phytocoenolo-
gia 23, 399–426.
Birks, H. J. B. 1996. Statistical approaches to interpreting
diversity patterns in the Norwegian mountain flora.
Ecography 19, 332–340.
Blytt, A. 1882. Die Theorie der wechselnden konti-
nentalen und insularen Klimate. Englers Botanische
Jahrbücher 2, 1–50.
Blytt, A. 1893. Zur Geschichte der nordeuropäischen
Flora: Englers Botanische Jahrbücher 17, Beiblatt 41,
1–30.
Brochmann, C. and S. W. Steen 1999. Sex and genes in
the flora of Svalbard – implications for conservation
biology and climate change. Det Norske Videnskaps
Akademi, I. Matematisk Naturvitenskapelig Klasse,
Skrifter, Ny serie 38, 33–72.
Brochmann, C., T. M. Gabrielsen, I. Nordal, J. Y. Land-
vik and R. Elven 2003. Glacial survival or tabula rasa?
The history of North Atlantic biota revisited. Taxon
52, 417–450.
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