Náttúrufræðingurinn - 2009, Blaðsíða 11

75
Tímarit Hins íslenska náttúrufræðifélags
Summary
Betula pollen in Iceland
Icelandic downy-birch (Betula pubescens)
is often shrub-like and polycormic com-
pared to the same species in Europe.
This type of birch is relatively common
in the subarctic and mountainous re-
gions of Europe and hence has been
called mountain-birch (B. pubescens ssp.
tortuosa). The morphological character-
istics of mountain-birch are thought to
reflect past hybridization between
downy-birch and dwarf-birch (B. nana).
These species have different chromo-
some numbers: downy-birch is a tetra-
ploid species with 56 chromosomes,
whereas dwarf-birch is diploid with 28
chromosomes. Triploid hybrids of the
two species, bearing 42 chromosomes,
have been found in a relatively high
frequency in natural woodlands in
Iceland. Birch is wind-pollinated and
produces large quantities of pollen.
Pollen grains are well preserved in wet
and damp places and therefore pollen in
lake sediments and peat is widely used
to reveal history of vegetation and cli-
mate. Differentiation of downy-birch
and dwarf-birch pollen is difficult but
important in the interpretation of past
ecology. We measured pollen from 39
downy-birch, 31 dwarf-birch and 22 tri-
ploid plants in order to determine its
relative size and shape. The difference in
pollen size between the two birch spe-
cies has turned out to be less than those
published elsewhere, probably because
the effects of introgressive hybridization
between the two species become clearer
when species identification is based on
cytotaxonomy rather than morphology.
We also found distinctive characteristics
linked to hybrid pollen, which was of-
ten damaged or malformed. The results
can be used to track the history and ori-
gin of birch in Iceland.
Þakkir
Bestu þakkir færum við Aðalsteini Sigurgeirssyni og Þresti Eysteinssyni hjá
Skógrækt ríkisins, sem tóku virkan þátt í skipulagningu og þróun rann-
sóknarinnar sem hér er sagt frá, og Magnúsi Jóhannssyni hjá Landgræðslu
ríkisins sem miðlaði af reynslu sinni við vinnu með birkifrjókorn. Þorsteini
Tómassyni er þökkuð hvatning til rannsókna á erfðablöndun birkis og fjall-
drapa. Rannsóknin var styrkt af Rannís, styrknúmer 040238021.
Heim ild ir
Ægir Þór Þórsson 2008. Genecology, introgressive hybridisation and 1.
phylogeography of Betula species in Iceland. Thesis for the degree of
doctor of philosophy, Department of biology, Faculty of science,
University of Iceland, Reykjavík.
Elkington, T.T. 1968. Introgressive hybridization between 2. Betula nana L. and
B. pubescens Ehrh. in North-West Iceland. New Phytologist 67. 109–118.
Fægri, K. & Iversen, J. 1989. Textbook of pollen analysis. (4th edition). 3.
Revised edition by Fægri, K., Kaland, P.E., Krzywinski, K.J. Wiley &
Sons. Chichester, New York, Brisbane, Toronto, Singapore.
Mäkelä, E.M. 1999. The Holocene history of birch in northeastern 4.
Fennoscandia – an interpretation based on fossil birch pollen measure-
ments. Ph.D. dissertation, University of Helsinki. 28 bls.
Kesara Anamthawat-Jónsson 2003. Preparation of chromosomes from 5.
plant leaf meristems for karyotype analysis and in situ hybridisation.
Methods in Cell Science 25. 91–95.
Lilja Karlsdóttir, Ægir Þór Þórsson, Margrét Hallsdóttir, Aðalsteinn Sigur-6.
geirsson, Þröstur Eysteinsson & Kesara Anamthawat-Jónsson 2007. Dif-
ferentiating pollen of Betula species from Iceland. Grana 46. 78–84.
Lilja Karlsdóttir, Margrét Hallsdóttir, Ægir Þór Þórsson & Kesara 7.
Anamthawat-Jónsson 2008. Characteristics of pollen from natural trip-
loid Betula hybrids. Grana 47. 52–59.
Ægir Þór Þórsson, Snæbjörn Pálsson, Aðalsteinn Sigurgeirsson & Kesara 8.
Anamthawat-Jónsson 2007. Morphological variation among Betula nana
(diploid), B. pubescens (tetraploid) and their triploid hybrids in Iceland.
Annals of Botany 99. 1183–1193.
Birks, H.J.B. 1968. The identification of 9. Betula nana pollen. New
Phytologist 67. 309–314.
Caseldine, C. 2001. Changes in 10. Betula in the Holocene record from Ice-
land – a palaeoclimatic record or evidence for early Holocene hybridisa-
tion? Review of Palaeobotany and Palynology 117. 139–152.
Ægir Þór Þórsson, Salmela, E. & Kesara Anamthawat-Jónsson 2001. 11.
Morphological, cytogenetic, and molecular evidence for introgressive
hybridization in birch. Journal of heredity 92. 404–408.
Ramsey, J. & Schemske, D.W. 1998. Pathways, mechanisms and rates of 12.
polyploid formation in flowering plants. Annual Review of Ecology
and Systematics 29. 467–501.
Um höfundana
Lilja Karlsdóttir (f. 1952) lauk BS-prófi í líffræði frá HÍ
2001 og MS-prófi 2004. Hún starfar við rannsóknir á Líf-
og umhverfisvísindadeild Háskóla Íslands.
Margrét Hallsdóttir (f. 1949) lauk BS-prófi í jarðfræði
við HÍ 1973 og doktorsgráðu í ísaldarjarðfræði frá
Háskólanum í Lundi 1987. Hún hefur starfað við
kennslu og rannsóknir bæði í Svíþjóð og á Íslandi. Frá
1997 hefur Margrét starfað við frjókornarannsóknir á
Náttúrufræðistofnun Íslands.
Ægir Þór Þórsson (f. 1970) lauk BS-prófi í líffræði frá
HÍ 1998 og doktorsgráðu 2008. Hann starfar við rann-
sóknir á Líf- og umhverfisvísindadeild Háskóla Íslands.
Kesara Anamthawat-Jónsson (f. 1951) lauk BS-námi í
grasafræði frá Chulalongkornháskóla í Taílandi árið
1973, meistaraprófi í grasafræði frá Kansasháskóla Í
Bandaríkjunum árið 1979 og doktorsprófi í plöntuerfða-
fræði frá Cambridgeháskóla í Bretlandi 1992. Kesara er
prófessor við Háskóla Íslands.
Póst- og netföng höfunda/Authors’ addresses
Lilja Karlsdóttir Margrét Hallsdóttir
Líf- og umhverfisvísindadeild Náttúrufræðistofnun Íslands
Sturlugötu 7 Hlemmi 3
IS-101 Reykjavík IS-105 Reykjavík
liljaka@hi.is mh@ni.is
Ægir Þór Þórsson Kesara Anamthawat-Jónsson
Líf- og umhverfisvísindadeild Líf- og umhverfisvísindadeild
Háskóla Íslands Háskóla Íslands
Sturlugötu 7 Sturlugötu 7
IS-101 Reykjavík IS-101 Reykjavík
aethth@hi.is kesara@hi.is