The 'common vole' in Svalbard identified as Microtus epiroticus by chromosome analysis

Abstract

The chromosomes were studied in six individuals from a population of Microtus from Grumantbyen, Svalbard, and in six Microtur arualis (Pallas 1778) from Lauwersee, Holland. It was shown that the voles from Svalbard did not belong, as earlier supposed, to the species M. arualis (2n = 46) but to M . epiroticus (Ondrias, 1966) (2n = 54). We suggest that the Svalbard voles were introduced by man between 1920 and 1960 together with hay on Russian ships from the vicinity of Leningrad, USSR.

Full text

The
'common vole' in Svalbard identified as
Microtus
epiroticus
by chromosome analysis
KARL FREDGA, MAARIT JAAROLA.
ROLF
ANKER IMS, HARALD STEEN AND NlGEL G. YOCCOZ
Fredga, K., Jaarola, M., Ims, R. A,, Steen,
FI.
&
Yoccoz. N.
G.
1990:
The 'common vole' in Svalbard
identified
as
Microtus epiruticur
by chromosome analysis.
Polar Research
8,
283-2Y0.
The chromosomes were studied in six individuals from
a
population of
Microtus
from Grumantbyen,
Svalbard, and
in
six
Microtur arualis
(Pallas
1778)
from Lauwersee, Holland. It was shown that the voles
from Svalbard did not belong, as earlier supposed, to the species
M. arualis
(2n
=
46)
but to
M.
epiroticus
(Ondrias,
1966)
(2n
=
54).
We
suggest that the Svalbard voles were introduced by man between
1920
and
1960
together with hay on Russian ships from the vicinity
of
Leningrad, USSR.
Karl Fredga
and
Maarit Jaarola, Department
of
Genetics,
Uppsala University,
P.O.
Box 7003. S-750 07
Uppsala.
Sweden:
Rolf
Anker
Ims
and
Harald
Steen,
Department
of
Biology, Division
of
Zoology,
University
of
Oslo,
P.O.
Box
1050
Blindern, N-0316
Oslo
3, Norway; Nigel
G.
Yoccoz,
Deparrment
of
Biology, Division
of
Zoology, Uniuersify
of
Oslo.
P.O.
Box
I050
Blindern, N-0316
Oslo
3, Norway.
or:
Laboratoire de Biometrie, Unioersitk Claude Bernard Lyon
1.
69622 Villeurhanne Cedex. France; February
1990 (revised July
1990).
'
In
1960
a member of the Finnish zoological
expedition to Svalbard found the first vole in
Svalbard at Longyearbyen. In
1964
and
1965
voles were abundant in the Longyearbyen village
and district and several specimens were collected
(Nyholm
1966).
In
1975
voles were trapped at
Hotellneset, Longyearbyen, and in
1976
at
Fuglefjellet, Grumantbyen,
W
Adventfjorden,
by Alendal
(1977).
The voles collected in the
1960s
and
1970s
were identified as
Microtus
aruulis
(Pallas
1778)
on morphological grounds.
A more recent report describes voles collected at
Coles Bay and Barentsburg as
M. arualis
(Bolshakov
&
Shubnikova
1988).
The present
study is part of a comparative ecological
investigation aimed at revealing which cir-
cumstances make it possible for a southern vole
species to establish itself in arctic conditions. In
order
to
find a relevant reference population it
was important to find out, if possible, the origin
of the ancestors.
Microtus
must have been brought to Svalbard
by man and according to Alendal
(1977),
the
voles might have been introduced by whale and
walrus hunters from Holland in the 17th
or
18th
century. This conclusion was based on the
identification of the specimens captured
in
Svalbard as
Microtus arvalis.
In
1972
a new
Microtus
species was described
by Meyer et al. It was called
M. subarvalis,
but
since this name is an absolute homonym of a
fossil
species,
Microtus subarualis
Heller
1933,
the name was changed to
M.
epiroticus
Ondrias
1966
(see Honacki et al.
1982).*
It is a sibling
*Recently.
the namc
Microtus rossiaemeridionrrlis
Ognev
1924
was applied
to
this species (Malygin
1983:
Malygin
&
Yatscnko
1986).
Fifteen spccimens of the 'common volc' were collcctcd
in the type locality (Aninsk region. Voronej district) of the
taxon
M. arualis rossiaemeridionalis
Ognev
1924.
All fiftccn
had
2n
=
54
and since, according to Malygin
&
Yatscnko
(1986).
M. arualis
(2n
=
46)
docs not cxist
in
this
area
they
conclude that thc animals described by Ogiicv
also
must have
had
54
chromosomes. Consequcntly, the sibling spccies with
54
chromosomes should be called
M. russiaemeridiorralls
Ognev
1924
and not
M. epiroticus
Ondrias
1966.
Howevcr, we arc not
willing
to
accept their conclusion
for
the following reasons:
I.
We can not
kriow
which taxon Ogncv described in
1924
since the two sibling spccies
of
'common voles' can not he
distinguished by their external morphology. He did not study
the characters that distinguish the two (chromosomes.
blood
proteins
or
sperm).
2.
M. arualis 'arualis'
and
M. arualis 'ohvcurus'
occur west
and east
of
Voroncj, respectivelv. 1s it possiblc to excludc the
present occurrence
of
either of these at the type locality
of
M.
a.
rossiaemeridiormlisis"
Only
15
specimens were invcstigatcd.
Also.
the distribution
of
thc two sihling spccics may have
changcd since
1924
('?)when the holotypc
of
ro.\iormrridionali.~
was collected.
3.
Wc recommend that this question bc considcred by the
Intcrnational Commission
on
Zoological Nomenclature.
According to Article
80,
Status
of
casc under consideration (a)
(International Code
of
Zoological Nomenclature
1985),
existing
usage is to
he
maintained until
a
ruling of the Commission is
published, Prcscntly, the twoauthoritative taxonomic references
(Niethammcr
&
Krapp
1982;
Honacki et al.
1982)
usc
the name
M. epiroticus
Ondrias
1966.
For
thcse reasons we prefer to use the name
M.
epiroticus
in the present article.

284
K.
Fredga
et
al.
FIR.
I
Didhution
of
M.
uruulk
(solid
linc)
and
M.
rpirulicus
(\hudowcd)
in
Europc
and
western
USSR
(haacd
on
Matygin
S:
Orlov
1974;
Kril
CI
al.
1980:
Nicthammcr
8:
Krapp 1982:
Vorontsov
el
al.
1984).
species
of
M.
arualis,
and
is
found within the
central part of the vast distribution area
of
M.
arualis
(Fig.
1).
The new species cannot be
distinguished from
M.
arvalis
by external
morphology, but the two species have charac-
teristic karyotypes:
M.
epiroticus
has
2n
=
54
and
M.
arvalis
has
2n
=
46.
There is also a difference
between the two species
in
the size and shape
of
the spermatozoa and with regard to several
proteins (Mejer et al. 1972, 1973: Sakiyan et al.
1984).
Since both
M.
arvalis
and
M.
epiroticus
potentially could have been introduced from
Russia with supply ships to some of the permanent
Russian settlements in Svalbard, it was important
to
study the chromosomes
of
the Svalbard voles.

The
‘common
vole’
in
Svalbard
285
Furthermore, the comparison
of
the chromosomes
and the mitochondria1 DNA of voles from
Svalbard with voles
from
Holland and other parts
of northern Europe might solve the problem
of
origin and perhaps
also
tell something about the
number of specimens introduced.
We here show that the
Microtus,
belonging to
a
viable population living in natural habitats in
the surroundings of Grumantbyen, Isfjorden, are
M.
epiroticus
and not
M.
arvalis
as
believed
earlier (Alendal 1977).
Material
and methods
During a two-week period in late August 1989,
three of
us
visited localities
in
the Isfjorden area
where
Micrntus
either had been captured
or
‘seen’
according to Alendal(1977). Coles Bay and some
other localities were also checked (Fig.
2).
lOkm
Fig.
2.
Map
of
the Isfjorden area. Circle:
Voles
caught during
the prcsent study. Stars: Voles reported
to
be present by
Nyholni
(1966).
Alendal
(1977)
or
Bolshakov
&
Shubnikova
(1988).
hut nor found by
us
examining thc loealitics
in
August
1989. Trianglcs: Localities with no earlier reports about vole
occurrence, but examined by
us
in August
1989
with negative
results.
Squares: Localities previously reported to contain voles
(Alendal
1977;
Bolshakov
&
Shubnikova 1988) but not
cxarnined by
us.
1
=
Grurnantbyen,
2
=
Longyearbyen,
3
=
ColesBay,
4
=
Kapp
Laila.5
=
Bjondhavna.Ternpelfjellet,
6
=
Alkhornet,
7
=
Knpp Lime. 8
=
Sassendalen.
9
=
Pyramiden,
10
=
Barentshurg.
11
=
Bellsund.
Each locality was first examined for signs
of
small rodents (grazing, runways
or
faeces) in
grassy vegetation. Such signs
of
Microtus
activity
are conspicuous
even
at low densities. At places
where signs were found multiple-capture live-
traps (type: Ugglan) were set.
Only the area between Bjarndalen,
2
km W
Longyearbyen, and Coles Bay (Fig.
2)
was
found
to be inhabited by
Microtus.
Signs of
Microtus-
activity were, however, most pronounced
in
the
grassy slopes under Fuglefjella and the animals
seemed to prefer places on peat soil with lush
vegetation of grass and herbs, interspersed with
patches of boulders. Generally, these preferred
areas were on stable well-drained ground.
Approximately
100
live-traps were set for
2‘12 days in the surroundings of Grumantbyen. A
total of
46
individuals were caught, indicating
a
dense population. The animals were brought alive
to the Department of Biology, University of
Oslo,
where
a
breeding colony was established.
Fifty
M. urvalis
were live trapped in October
1989 at Lauwersee, NE Holland. All specimens
were brought alive to the Department
of
Biology,
University of
Oslo,
where
a
breeding colony was
established.
Six
of
the voles from Svalbard and six from
Holland, 4males and2femalesof eachpopulation,
were karyotyped. Chromosome preparations
were made from bone marrow by the direct
method
of
Fredga (1987).
For
G-
and C-banding
the techniques of Wang
&
Fedoroff (1972) and
Sumner (1972) were used, respectively.
Results
M. epiroticus
The six voles studied from Svalbard had identical
autosomal karyotypes and males were
XY,
females
XX.
The chromosome number was 2n
=
54 and
all
chromosomes but the smallest pair
of
autosomes were telocentric (Fig.
3.4).
The
X
chromosome
was
the largest of the complement
and the
Y
the next largest, but close
in
size to
the largest autosome. This autosome was the only
telocentric that could be identified without
G-
banding.
The
rest
of
the single-armed autosomes
decreased continuously
in
size.
A
G-banded
karyotype is shown
in
Fig.
3B.
After C-staining,
all
autosomes showed centromeric C-bands (Fig.
3C).
The distal half of the
X
stained
as
a positive
C-block and the entire
Y
appeared dark after

286
K.
Fredga
et
al.
Fig.
3.
Karyotypes
of
male
Microtus epiroticur
from Grumantbyen, Svalbard.
A)
unbanded,
B)
G-banded,
C)
C-banded. Boxed:
sex chromosomes from
a
female with
one
normal and one deleted X chromosome (Xd). Arrows indicate the position of the
centromeres in the sex chromosomes. Preparations from bone marrow. Bar
=
10
pm. Same magnification in
A.
B
and
C.

The
‘common vole’
in
Svalbard
287
Fig.
4.
Karyotypes
of
Microtus
arualis
from Lauwersee, Holland.
A)
male, unbanded,
B)
female, G-banded, C) male, C-banded
Preparations
from
bone
marrow. Bar
=
10
pm,
Same magnification
in
A.
B and
C.

288
K. Fredga et al.
C-staining.
One
of
the females studied had one
normal and
one
deleted
X;
a little more than half
of the heterochromatic distal part was missing
(Fig.
3C).
The karyotypes of the voles from Svalbard are
in perfect agreement with those
of
M.
epiroticus
from Finland (Fredga et al. unpublished) and
from different parts
of
the USSR (Vorontsov et
al. 1984; Mejer et al. 1985).
M.
arvalis
The six voles from Holland had identical
karyotypes (males
XY,
females
XX).
The
chromosome number was2n
=
46. The autosomes
may be divided into two size groups:
5
large and
17 small pairs.
All
the large chromosomes and
13
of the small were bi-armed. Four
of
the
small chromosomes were acrocentric. The
X
Chromosome was of intermediate size and
metacentric, the
Y
was the smallest of the
complement and acrocentric (Fig. 4A).
A C-banded karyotype is shown in Fig.
4B.
After C-staining, centromeric blocks of
heterochromatin were present in 10 of the small
pairs,
h
bi-armed and 4 acrocentric (Fig.
4C).
The NF value was
84
(female).
Different populations
of
M.
arvalis
may be
distinguished by their karyotypes
(Kral
&
Lyapunova 1975; Zima
&
Kril 1984). They all
have 2n
=
46
and
5
large, bi-armed chromosomes,
but the number of small single-armed pairs varies,
as well
as
the number
of
chromosomes with
centromeric C-blocks. The karyotype of voles
from this Dutch population is similar (but not
identical) to that
of
voles from Osnabruck in
Germany (Camper1 1982). They both have 10
pairs with C-blocks and no acrocentric without.
However, the number of acrocentric pairs in the
Dutch population is 4 compared to
3
in the
German one.
Discussion
The present chromosome study has shown that
the voles collected in 1989 at Fuglefjella,
Grumantbyen, belongto the species
M.
epiroticus.
Five individuals caught in 1976 in the same area
by Alendal (1977) were identified as
M. arvalis,
according to guidelines from literature that did
not distinguish
arvalis
from
epiroticus.
We were
not able to find voles anywhere else, although
attempts were made at another seven sites (Fig.
2).
This means that we cannot exclude the
possibility that the voles caught by earlier
investigators at Longyearbyen and its vicinities
(Nyholm 1966; Alendal 1977), Coles Bay and
Barentsburg (Bolshakov
&
Shubnikova 1988)
really were
M.
arualis.
Bolshakov
&
Shubnikova
(1988) pointed
out,
however, that
Microtus
in
Svalbard needs to be karyotyped to confirm the
identification of the species.
The distribution
of
M.
aroalis
and
M.
epiroticus
is shown in Fig. 1.
M.
arvalis
is present in western
Europe, from the Atlantic coast and eastwards
to about longitude 90"E in western Siberia.
M.
epiroticus
has a more limited distribution in the
approximate middle third
of
this vast area. In
Europe
M. epiroticus
has its northernmost
populations in Finland and the southernmost
on
the Balkan peninsula. These are
also
the two
westernmost areas of its distribution. The type
locality of
M.
epiroticus
is
in the Epiros mountains
in northwestern Greece (Kuzic et al.
1Y75).
The two species exist sympatrically in many
areas but appear to occupy different habitats in
the breeding season. In the winter
M.
epiroticus
seems to have the habit
of
living in association
with human settlements, in hay barns etc. In the
vicinity
of
Saratov on the east bank
of
the
Vulga
River both species were caught in two haystacks
in early spring (Belanin ct al. 1973, quoted by
Kril
et
al.
1980). In both haystacks
M.
epiroticus
was by far the most common species, the
proportions
of
epiroticus
and
arvalis
being
38
:
3
and
56:2,
respectively. However, the exact
ecological requirements of either species and the
differences between the species have not yet been
fully elucidated
(Kral
et al. 1980).
The close association af the Svalbard voles
to
human buildings has been pointed out by several
authors (Nyholm 1966; Alendal 1977; Bolshakov
&
Shubnikova 1988). The apparent association
of
M.
epiroticus
with humans may have been
important during the species' colonization and
establishment in Svalbard. However, it is clear
that the highly viable population in the Fuglefjella
area occurs in natural habitats independent of
human settlements.
Svalbard is located 657 km north
of
Nordkapp,
midway between Norway and the North
Pole,
and has never been connected by a landbridge
with Fennoscandia or any other part
of
the
Eurasian continent. Voles cannot possibly have
survived a fortuitous transport on ice
or
on a

The
‘common
vole’
in
Svalbard
289
floating log because
of
the long distances involved.
Thus, the voles must have been brought to
Svalbard by man. (We also exclude the possibility
that voles were introduced secretly to Svalbard
by scientists as part
of
an ecological experiment.)
Both
arualis
and
epiroticus
exist in the
Leningrad region (Pavlovsk, Volosovo and
Volchov districts), but in the areas closest to the
coast (Leningrad and the Lomonosov district)
only
epiroticus
was found (Mejer et al. 1972;
Malygin
&
Orlov 1974; Kril et al. 1980).
However, the recent discovery of
M.
arualis
in
southeastern Finland (Fredga et al. unpublished)
indicatesthat bothspeciesrnay occursyrnpatrically
along the easternmost coasts of the Gulf
of
Finland.
However,
M.
epiroricus
is by far the
most
common species in Finland an3 adjacent
parts
of
the USSR.
Hence, Fixiand, western
USSR
and Balkan are
the only
areas
where
M.
epiroticus
exists near
water and harbours. We are not aware
of
any
transportations from the eastern Mediterranean
(Yugoslavia or Greece)
or
from the Black Sea
(USSR, Rumania
or
Bulgaria) to Svalbard.
Finland has not been involved in any industrial
or agricultural activities in Svalbard. Thus, we
find it unlikely that the voles in Svalbard originate
from the Balkan Peninsula
or
Finland but from
the western parts
of
the USSR, bordering the
Gulf
of
Finland.
The Russians have exploited coal mines in
Grumantbyen since 1920 (Hoe1 1966) and at
Coles Bay since
1938
(Bolshakov
&
Shubnikova
1988). Horses were used for transportation and
hay must have been brought there for their winter
survival. We conclude that the voies were
introduced together with hay by Russian ships
from Leningrad
(or
nearby harbours) in the
period 1920-1960, and thus originate from the
vicinity of Leningrad. Prof. Charles Elton visited
Svalbard in 1921, 1923 and 1924 as a member
of
the Oxford expeditions
to
Svalbard.
‘I
feel certain
they [the voles] were not introduced by 1924
-
the last time
I
went there!
I
would have been
told’ (Charles Elton, in a letter to K.F.).
Further studies
of
DNA
may tell
us
whether
voles were introduced to Svalbard more than
once, and may also support the hypothesis about
their origin put forward here. We cannot exclude
the possibility that
M.
arvalis
also
has
been
introduced. But
so
far, the only vole species that
has been proven to exist in Svalbard is
M.
epiroticus.
Acknowledgements.
-
This study was supported
financially
by
the Swedish Natural Science Research Council, the Norwcgian
Polar
Research Institute, the ‘Fondation Franco-Norvegiennc
pour
la
recherche scicntifique
et
techniquc
ct
le
d&Aoppcmcnt
industriel’
(FFN)
and the Norwcgian Research Council for
Scicnce and thc Humanities (NAVF).
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