Insectes Sociaux, Paris
9
M a s s o n , P a r i s , 1983
1983, V o l u m e 30, n ~ 2, p p . 14%164
ANT CHROMOSOMES
II, KARYOTYPES OF WESTERN
PALEARCTIC
SPECIES
*
E. HAUSCHTECK-JUNGEN (1) and H. JUNGEN (2)**
t l ) Zootogisches Institut der UniversiRit Ziirich, Winterthurerstr. 190, CH - 8057 Ziirich,
Switzerland
(2) Zoologisches Museum der Universitlit Zi'trich, Winterthurerstr, 190, CH - 8057 Zi~rich,
Switzerland
Regu le 6 d6eembre 1980.
Accept6 le 23 avril 1982.
S UMMARY
The c h r o m o s o m e n u m b e r s of 40 a n t species are reported. For 22 species t h e karyot y p e s as ~r
as the c h r o m o s o m e n u m b e r s are presented. The c h r o m o s o m e n u m b e r s
range between n = 8 and n = 26. R e m a r k a b l e karyotypes are those of the germs LaMas
in exhibiting mainly acrocentric chromosomes. In all o t h e r ?~aryotypes t h e majori:ty of
c h r o m o s o m e s show medio- o r s u b m e d i o c e n t r i c c e n t r o m e r e position.
Differences in c h r o m o s o m e n u m b e r s in the genus Camponotus reflect t h e grouping
in subgenera 'with the e x c e p t i o n of Taneemyrmex. This p a t t e r n is n o t true f o r the
genera Aphaenoeaster a n d Leptothorax, w h e r e a variety of c h r o m o s o m e n u m b e r s ~r
found in the different subgenera.
ZUSAMMENFASSUNG
Ameisenchromosomen:- IL Karyotypen westpal~arktischer Arten
Die C h r o m o s o m e n z a h l e n yon 40 Ameisenarten ,~verden mitgeieilt. Ffir 22 Arten w i r d
zus~tztich der Karyotyp vorgelegt. Die haploiden Chrornosomenzahlen bewegen sich
zwischen n = 8 u n d n = 26. B e m e r k e n s w e r t sind die Karyotypen d e r G a t t t m g Lasius.
Diese Karyotypen besitzen, abgesehen yon einern oder zwei m e d i o z e n t r i s c h e n Paaren.
ausscbliesslich acrozentrische Chromosornen. ARe fibrigen Karyotypen b e s t e h e n iiberwiegend aus rnedio- bzvr s u b m e d i o z e n t r i s c h e n Chrornosornen.
In d e r G a t t u n g Carnponorus e m s p r i c h t die G r u p p i e r u n g in U n t e r g a t t u n g e n auch
einer Gruppierung yon u n t e r s c h i e d l i c h e n Chrornosomenzahlen. Fi.ir die G a t t u n g e n Aphceno.
gaster u n d Leptothorax gilt diese E n t s p r e c h u n g nicht.
(*) S u p p o r t e d b y : Karl HESCHELER-STIFrur~G, Georg u n d Antoine CLARAz-ScFIENKUNG,
a n d b y grants of the Schweizerischer Nationalfonds zur F,S r d e r u n g w i s s e n s c h a f t t i c h e r
F o r s c h n n g Nr. 4326, 4847, 3.187.69,
(**) T h e f o r m e r s t u d e n t s Peter DUELLI. Hans HOSBACH, a n d O t h m a r KUHN took p a r t
in the c h r o m o s o m e studies,
150
E. H A U S C H T E C K - J U N G E N and H. ] U N G E N
INTRODUCTION
T h e o r i g i n o f t h e F o r m i c i d ~ is in t h e M e s o z o i c e r a (WILSON et al., 1967),
so t h e m o r p h o l o g i c a l a n d b e h a v i o u r a l c h a r a c t e r i s t i c s a s w e l l a s t h e c h r o m o some sets could develop over a long time span. In fact, the haploid chrom o s o m e n u m b e r s o f F o r m i c i d ~ e c o v e r the r a n g e b e t w e e n 4 (HAuSCHTECK,
1962 ; IMAI a n d KuBora, 1972) a n d 42 (IMAI et al., 1977), e v e n t u a l l y e v e n m o r e
t h a n 45 (TAYLOR, 1978). T h e c h r o m o s o m e d i v e r s i f i c a t i o n a r o s e i n d e p e n d e n t l y
in different subfamilies. Mechanisms of karyotype evolution, such as centric
fission and fusion, chromosome polymorphism, B chromosomes, translocations, pericentric and paracentric inversions and DNA amplification have
b e e n d i s c u s s e d b y Cg0zIER (1975) a n d L ~ I et al. (1977).
B e s i d e s i n s i g h t s i n t o g e n e r a l m e c h a n i s m s of k a r y o t y p e e v o l u t i o n , w h i c h
a r e s u m m a r i z e d f o r i n s t a n c e b y JOHN a n d L E w i s (1968) o r WHITE (1973), t h e
k a r y o t y p e a n a l y s i s s h o u l d c l a r i f y t a x o n o m y . T h e k a r y o t y p i c a l v a r i a b i l i t y in
s o m e g e n e r a , e.g. Camponotus o r Aphcenogaster, c a n b e q u i t e l a r g e . Of
c o u r s e , m o r p h o l o g i c a l o r e c o l o g i c a l v a r i a b i l i t y o f a t a x o n d o e s n o t h a v e to
be paralleled by karyological variability.
CROZIER (1975) s u m m a r i z e d all c h r o m o s o m a l d a t a on a n t s u p to 1975.
S i n c e t h e n , a d d i t i o n a l r e s u l t s w e r e p r e s e n t e d o n t h e g e n u s Formica
(HAuscHTECK-JUNCEN a n d JvNcz~q, 1976) o n A u s t r a l i a n s p e c i e s (IMAI eL at..
1977). I n s p i t e o f a r e l a t i v e l y l a r g e n u m b e r o f s p e c i e s i n v e s t i g a t e d u p to
n o w , c y t o t a x o n o m i e i n f o r m a t i o n o n t h e w e s t e r n p a t e a r c t i c a n t s p e c i e s is
still fragmentary. With two exceptions, this paper presents karyotypes of
European and North African species of Formicidze. Most of the chromosome
n u m b e r s a r e a l r e a d y p r e v i o u s l y m e n t i o n e d in CROZIER (1975).
MATERIAL
AND METHOD
As in other insects, the suitable material to find mitosis are the cerebral ganglia
of preputree. D i s s e c t e d ganglia from a t l castes available ~vere kept in" sterile ringer
solution to which Colcemid ~vas added to a final concentration of 0,004 %. After one
to three hours incubation the organs were transferred to a t g's sodium citrate solution
for 20 to 40 re.in. They ~vere then fixed in 50 % acetic acid and stained in acetic orcein,
The cells ~vere squashed under a siliconized coverslip, ~vhich was removed after being
frozen on dry ice. Permanent preparations ~vere made by mounting in Euparal. For
determination of the chromosome number ten mitoses with the same mammal chromosome number were thought to be enough to determine the diploid or haploid chromosome number of the species.
RESULTS
AND DISCUSSION
B o t h r i o m y r m e x : T h e k a r y o t y p e o f B. gibbus ( n o t f i g u r e d , table D is
characterized by one long subtelocentric chromosome, twice as long as the
ANT CHROMOSOMES
next one, which is submediocentfic.
Pair three is mediocentric,
pairs
and six are submediocentric.
The smaller chromosomes
are acrocentric.
151
five
T a p i n o m a ([ig: I a, I b, table I ) : T h e k a r y o t y p e o f T. e r r a t i c u m l o o k s
similar to one of the karyotypes
known
from the American
T. sessile.
CROZIER (1970 b ) d e s c r i b e s f o r t h i s s p e c i e s a c h r o m o s o m a l
potymorphism,
the karyotypes differing by pericentric inversions.
One of the karyotypes
Fig. 1. - - Karyotypes a n d m e t a p h a s e plate. 2 000 •
a) Tapinoma erraticum, diploid set, 2 n = 16.
b ) T. nigerrimum, haploid metaphase, n -- 9.
c) Plagiotepis pygmaea, diploid set. 2 n --- 18.
d) P. barbara, haploid set, n = 9.
e) Lasius (Lasius) atienus, diploid set, 2 n = 30.
f) L. (Cautolasius) flavus, diploid set, 2 n = 30.
g) L. (DendroIasius) fuliginosus, haploid set, n --- 14.
Abb. 1. - - Karyotypen u n d Metaphaseptatten. 2 000 x.
a) Tapinoma erraticum, diplolder Satz, 2 n = 16.
b ) T. nigerrimum, haptoide Metaphase, n = 9.
c) Plagiolepis pygmaea, diploider Satz. n = 18.
d) P. barbara, haploider Satz, n = 9.
e) Lasius (Lasius) alienus, diploider Satz. 2 rt = 30.
f) L. (Cautolasius) flavz~s, diploider Satz, 2 n = 30.
g) L. (Dendrotasius) fuIiginosus, haploider Satz, n = 14.
E. H A U S C H T E C K . J U N G E N
152
a n d H. J U N G E N
Table I. - - Haploid c h r o m o s o m e n u m b e r s of E u r o p e a n a n d N o r t h African a n t species.
Metaphases f r o m queens a n d w o r k e r s ~ e r e diploid, t h o s e f r o m m a l e s haploid.
At least one nest f r o m each collection site 'was analysed. Nests ~ i t h c ~ r o m o s o m a l
a b e r r a t i o n s are o m i t t e d here.
C H : S'witzerland, D : Federal Republic of Germany, E : Spain, F : France, G R :
Greece, I : Italy, T N : Tunisia, USA: United States of America, Y U : Yugoslavia.
n : haploid c h r o m o s o m e n u m b e r .
Tabelle I. - - Haptoide C h r o m o s o m e n z a h l e n europ4iischer u n d n o r d a f r i k a n i s c h e r Ameisenarten. M e t a p h a s e n yon K.~Sniginnen u n d Arbeiterirmen ,waren diploid, solche yon
Mfirmchen haploid. Von j e d e m F t m d o r t wurde m i n d e s t e n s ein Nest u n t e r s u c h t .
Nester, in denen Tiere m i t c h r o m o s o m a l e r A b e r r a t i o n gefunden ~ u r d e n , sind bier
nicht a u f g e ~ h r t .
C H : Sch~ceiz, D : B u n d e s r e p u b l i k Deutschland, E : Spanien, F : F r a n k r e i c h . G R :
Griechenland, I : Italien. T N : Tunesien, USA: Vereinig~e S t a a t e n yon Amerika,
YU : Jugosla~viem.
n : haploide C h r o m o s o m e n z a h L
Species
Collection site
n
Genova (I)
Pfin',vald (CH)
Dietsdorf (CFI)
Boppelsen (CH)
Pr~les (CH)
Locarno (CH)
Tunis (TN)
T a b a r k a (TN)
Tunis (TN)
Jefna (TN)
Malaga (E)
11
8
Caste
Number
analysed of nuclei
analysed
Dolichoderin~e
Tapinomini
Bothriorn yrmex gibbus
Tapinoma erraticum
T. nigerrimum
T, simrothi
~
~ g ~
> 10
> 10
9
4
> 10
9
9 ~
> 10
T u n i s (TN)
T o r r e m o l i n o s (E)
Malaga ( E )
Loja (E)
Tessin (CH)
Wallis (CH)
Podgara (YU)
9
9
~ 6
9 ~ c~
> 10
> t0
Ziirich (CH)
Ziirich (CH)
Pavia (I)
K a i s e r s t u h l (D)
S u r E n (CH)
Celoni G e r o n a (E)
Fiirstenau (CH)
15
14
9 ~
~
> 10
> 10
15
r g
> 10
14
18
9~
> I0
7
Formicin~e
Plagiolepidini
Plagiolepis barbara
P. pygmaea
Formicini
Lasius ( Cautolasius ) flavus
L. (Dendrolasius) fuliginOsus
L. ( Lasius ) alienus
Camponotini
Camponotus (Camponotus) ligniperda
Wallis (CH)
Camponotus (Myrmosericus) cruentatus Diezma (E)
ANT CHROMOSOMES
Species
C. (M.) rufoglaucus
Camponotus (Tana~myrmex) azthiops
C. (T.) alii
C. (T.) compressus
C. (T.) foreli
C. (T.) pilieornis
C, (T.) sytyaticus
CataglypI~is albicans
C. bicolor
153
Collection site
Sedjenane (TN)
Tabarka (TN)
Granada (E)
St-Giles (F)
Yugoslavia
Alcoy (E)
Tabarka (TN)
Tunis (TN)
Malaga (E)
Ordal (E)
Rhodos (GR)
Hospitalet (E)
Ordal (E)
Hospitalet (TN)
Israel
Tabarka (TN)
Caste Number
analysed of nuclei
analysed
I8
~8
> I0
21 9 ~
> 10
21
20 ~
6
> 10
> 10
25
6
20 ~ 6
> 10
26
> 10
> 10
2698
Ponerin~
Ponerini
Ponera pennsylvanica
USA
> 10
Myrmicinze
Myrmieini (broad sense)
Aphcenogaster (Aphcenogas ter ) depitis
Tunis (TN)
Sedjenane (TN)
A. (AJ sardoa
Sedjenane (TN)
A. (A.) testaceopilosa
Malaga (E)
Tunis (TN)
Sibenik (YU)
Aph~enogaster (Attomyrma) subterranea Pfirrwatd (CH)
TesSin (CH)
Pr~les (CH)
Kaiserstuhl (D)
Harpagoxenus subl~vis
Niirenberg (CH)
Leptothorax (Leptothorax) acervorum
Bonn (D)
Sur En (CH)
Wallis (CH)
MaILx (CH)
Wiirzburg (D)
Leptothorax (Myralant) interruptus
Boppelsen (CH)
L, (M,) nylanderl
L. (M.) schaumi
Ithaka (USA)
L, (M.) tuberum
Graub~ndcn (CH)
Waltis (CH)
Braurtwatd (CH)
Sur En (CH)
2
17
17
17 ~ $
2
> 10
11 ~ .
> 10
20 ~ 8
13 g 8
> 10
> I0
12
> I0
3
2
> 10
9
9
9~6
154
E. H A U S C H T E C K . J U N G E N and H. J U N G E N
Species
L. (M,) unffasciatus
Manica rubida
Myrmica &evinodis
M. ruginodis
M. sabuteti
M. schencki
M. suIcinodis
PheidoIe palIidula
Collection site
n Caste
analysed
Bonn (D)
Pr~les (CH)
Dielsdorf (CH)
Graubfinden (CH)
Biirglen (CH)
Greifensee (CH)
Ziirich (CH)
Fiirstenau (CH)
Rodets (CH)
Switzerland
Povil Muogl (CH)
Tessin (CH)
Gordemo (CH)
Malaga (E)
Rhodos (GR)
Gab~s (TN)
9
~
Number
of nuclei
analysed
> I0
22 ~
24 9 ~
> 10
> 10
24~
23
23
24
10
>
>
>
>
>
9
~
~ /~
9 ~ $
10
10
I0
10
I0
h a s a s i n g l e a c r o c e n t r i c c h r o m o s o m e p a i r l i k e T. erraticum.
T. meIano.
cephalum d i f f e r s f r o m a l l o t h e r s p e c i e s in h a v i n g o n l y n = 5 c h r o m o s o m e s
(CRoZIeR, 1970 b).
Plagiolepis : T h e k a r y o t y p e s of P. pygmeea a n d
s i m i l a r (fig. 1 c, 1 d, and table I).
P. barbara
look very
Lasius : C h r o m o s o m e n u m b e r s o f L. alienus, L. flavus a n d L. /uliginosus
w e r e a l r e a d y r e p o r t e d b y HACSCHTECK (t962) (table I). I n t h i s w o r k t h e
k a r y o t y p e s o f t h e s e s p e c i e s a r e s h o w n (fig. I e-g). O u r r e s u l t s a r e c o n f i r m e d
For L. atienus f r o m E n g l a n d (PEARSON, p e t s . c o m m . ) . H o w e v e r , i n t h e d r a w i n g
o f H:VSC~TEC~ (1962) t h e d i p l o i d m e t a p h a s e p l a t e d i s p l a y s o n l y 28 c h r o m o s o m e s i n s t e a d o f 30 a s in this p a p e r . I n t h e c a s e o f t h e n = 14 c h r o m o s o m e s
o n e l a r g e s u b m e d i o c e n t r i c c h r o m o s o m e w a s f o u n d w h i c h is a b s e n t in all
n = 15 Lasius k a r y o t y p e s .
O t h e r s p e c i e s w i t h n = 14 c h r o m o s o n e s a r e L. pallitarsis f r o m t h e USA,
r e p o r t e d b y HuNG (1969), a n d L. fuIiginosus (fig. 1 g, table D. T h e k a r y o t y p e
of this latter species includes two mediocentric chromosomes in contrast
to t h e n = 15 s p e c i e s w h i c h e x h i b i t o n l y one.
F o r L. niger w e c o n f i r m t h e k a r y o t y p e a s p u b l i s h e d b y IMAI (1969) a n d
IMAI a n d KUBOTA (1972) f r o m J a p a n . I t r e s e m b l e s t h o s e o f t h e Lasius s p e c i e s
w i t h t5 c h r o m o s o n e s , as f o r i n s t a n c e L. alienus, L. flavus o r L. nearcticus
(CRozIER, 1970 a).
J u d g i n g f r o m t h e r e p r e s e n t a t i o n of t h e Lasius p h y l o g e n y g i v e n b y
WlLSO~ (1955), o n e m a y a s s u m e t h a t n = 15 w a s t h e b a s i c n u m b e r o f t h e g e n u s .
ANT CHROMOSOMES
155
Fig. 2. ~ K a r Y 0 t y p c s a n d m i t o s e s .
a) Camponotus
(Tanaemyrmex)
compressus, h a p l o i d set, n = 20.
2400 x ,
b) C. (T.) aethiops, d i p l o i d set,
2 n = 42. 2400 •
c) Ponera. pemzsylvanica, a n a p h a se o f t h e 8 t h c l e a v a g e d i v i s i o n ,
2 n --- 12.2200 •
d) Harpagoxenus
subl~vis,
p l o i d m e t a p h a s e , 2 n = 40.
2400 x .
di-
Abb. 2 . Karyotypen und Mitosen.
a) Camponotus (Tanaemyrmex) compressus, h a p l o i d e r Satz, n = 20. 2400 •
b) C. (T) aethiops, d i p l o i d e r S a t z , 2 n --- 42. 2 400 •
r Ponera pennsylvanica, A n a p h a s e d e r a c h t e n F u r c h u n g s t e i l u n g , 2 n = 12. 2 200 •
d) Harpagoxenus subtaevis, d i p t o i d e M e t a p h a s e , 2 n = 40. 2 400 x .
E. HAUSCHTECK-JUNGEN and H. JUNGEN
156
_=
0
~4
r~
r
t~
~
o3
o3
ANT CHROMOSOMES
157
Ca,.nponotus : K a r y o t y p e s are presented f r o m C. (Tancemyrmex) r
and C. (T.) c o m p r e s s u s (fig. 2 a, 2 b).
This genus includes as many as 1 500 species, subspecies, and varieties,
n o w subdivided into a b o u t 45 subgenera.
In this group, c h r o m o s o m e
n u m b e r s ( f r o m n = 9 to n = 25) and m o r p h o l o g y of c h r o m o s o m e s are highly
variable (I.~lAI, 1966 and 1969; IMAX and KUBOTA, 1972; CROZ~R, t970,
KUUBtCARNI, 1965; IMAI et aI., 1977). Therefore it seems attractive to took
at the c h r o m o s o m e n u m b e r s in the subgenera (table II). I n spite of the
fact that taxonomists as for instance EMERY (1925) were a w a r e that some
groups are r a t h e r artificially defined, the different subgenera seem to be
characterized by different c h r o m o s o m e numbers. The u n i f o r m look of taxa
like M y r m a m b I i s o r Myrrnosericus m a y partially be induced b y the small
n u m b e r s of species investigated. So, C a m p o n o t u s s. str. seems to be characterized by n = 14, M y r m a m b l i s b y n = 9, M y r m o s e r i c u s by n = 18. I n Tance.
m y r m e x , species are assembled with r a t h e r high c h r o m o s o m e n u m b e r s . The
only exception here w o u l d be C. compressus, described b y KUMBKARNI (1965),
f r o m India. Unfortunately, in his p a p e r convincing p h o t o g r a p h s are missing.
However, o u r Tunisian specimens fit well the general trend. No c o r r e l a t i o n is
visible as yet between the species groups and c h r o m o s o m e n u m b e r s within
Tancemyrmex.
Cataglyphis : I n C. aIbicans and C. bicolor (not figured, table I), the three
largest c h r o m o s o m e s are submediocentric. The smallest c h r o m o s o m e s are
at the limit of being recognized by the light m i c r o s c o p e and m a y be of the
smallest ones f o u n d in ants.
Ponera : Figure 2 c shows an anaphase f r o m an egg. Alt c h r o m o s o m e s are
obviously long which on one h a n d is due to the early stage of development
f r o m which the nucleus was taken. On the o t h e r hand species with low
c h r o m o s o m e n u m b e r s as also k n o w n f r o m P. scabra (n = 7) (IuAI and KUBOTA,
1972) a n d S t e n a m m a brevicorne (n = 4) (HAuscHTECK, 1962) have larger chrom o s o m e s than species with high c h r o m o s o m e n u m b e r s .
Aphaenogaster : I n o u r material we f o u n d two groups of karyotypes, one
with n = 11 and the o t h e r with n --- 17. A. subterranea. (fig. 3 a) belongs to
the first g r o u p and all of its c h r o m o s o m e s are longer than those of the n = 17
k a r y o w p e s . With the exception of one acrocentric c h r o m o s o m e all are
mediocentric. F r o m the n = 17 group the k a r y o t y p e of A. testaceopiIosa
(fig. 3 b) was c o m p a r e d to A. subterranea. I n the first g r o u p of six chrom o s o m e s all are submedio- or mediocentric, the remaining c h r o m o s o m e s are
submedio- or acrocentric.
A. subterranea inhabits central and southern Europe, spreading to the
Caucasus. In contrast, the three remaining species w i t h h i g h e r c h r o m o s o m e
n u m b e r s are restricted to the Mediterranean area. This situation ~ different
climatic regions inhabited by species with different c h r o m o s o m e n u m b e r s
is paralleled in Japan where A. s m v t h i e s i (table l l I ) is of t e m p e r a t e origin
,'Fig. 3. ~ K a r y o t y p e s , 2 0(30 •
a) Aphaenogaster subterranea, diploid set, 2 n = 22.
b ) A. testaceopitosa, diploid set, 2 n = 34,
c) Leptothorax (Myra[ant)tuberum h a p l o i d szt, n = 9.
d) L, (M.) unifasciatus, diploid set, 2 n = 18.
e) L. (M.) interruptus, diploid set, 2 n = 24~
f) L. (M.)acervorum, diploid set, 2 n = 26.
g) Pheidotr pallidula,, diploid set, 2 n = 20.
Abb. 3. - - K a r y o t y p e n . 2 000 x
a) Apheenogaster subterranea, diploider Satz, 2 n = 22.
b ) A. testaceopiIosa, d i p l o i d e r Satz, 2 n = 34.
c) Leptothorax (Myrafant) tuberum, h a p l o i d e r Satz, n -- 9
d) L. (M.) unifasciatus, d i p l o i d e r Satz, 2 n = 18.
e) L. (M.) interruptus, diploider Satz, 2 n = 24.
f) L. (M.) acervorum, d i p l o i d e r Sa~z, 2 n -- 26.
g) Pheiclole pallidula, diploider Satz, 2 n -- 20.
ANTCHROMOSOMES
0
0
0
v
p~
~J
p~
r~
8
0
bO
r~
0
~N
0
C~
0
r~
~t
0
r~
159
160
E. HAUSCHTECK-JUNGEN and H. JUNGEN
w h e r e a s A. osimensis and A. famelica w i t h h i g h e r c h r o m o s o m e n u m b e r s a r e
a s s u m e d to be of t r o p i c a l o r i g i n (IMAI, 1971). H o w e v e r , a d e t a i l e d a n a l y s i s
of E u r o p e a n a n d J a p a n e s e species w i t h t h e s a m e c h r o m o s o m e n u m b e r s r e v e a l s
m a n y d i f f e r e n c e s in c h r o m o s o m e sizes a n d c e n t r o m e r e p o s i t i o n s . So o n e
h a s to c o n c l u d e t h a t e i t h e r t h e s a m e c h r o m o s o m e n u m b e r s a r e d e r i v e d
i n d e p e n d e n t l y or, if A. subterranea a n d A. smythiesi are close r e l a t i v e s , the
karyotypes, although from a common ancestor, have differentiated themselves
by p e r i e e n t r i c i n v e r s i o n s a n d t r a n s l o c a t i o n s .
Evidence that pericentric
i n v e r s i o n s have p l a y e d a role in t h e e v o l u t i o n of Aphcenogaster m a y b e d r a w n
f r o m k a r y o t y p e s w i t h even h i g h e r c h r o m o s o m e n u m b e r s b u t o n l y a few
a c r o c e n t r i c c h r o m o s o m e s , as f o r i n s t a n c e in t h e A u s t r a l i a n s p e c i e s A. longiceps
w i t h n = 23 (IMAI et al., 1977) o r s o m e A m e r i c a n species (CRozIER, 1977). In
A. rudis k a r y o t y p e s w i t h n = 21 c h r o m o s o m e s two o r t h r e e a d d i t i o n a l acroc e n t r i c s w e r e found" b u t t h o s e a r e m u c h s m a l l e r and p e r h a p s r e l i c t s of c e n t r i c
fission. I t is t e m p t i n g to a s s u m e t h a t s u c h m e d i u m sized a c r o c e n t r i e chromosomes are protected from being changed by pericentric inversions.
Table I t I gives the s u b d i v i s i o n of t h e i n v e s t i g a t e d species i n t o s u b g e n e r a .
In Aphcenogaster s. str. t h e r e a r e only s p e c i e s w i t h n = 17. They are p r o b a b l y
closely r e l a t e d to each o t h e r . The p a l e a r c t i c species g r o u p of A t t om yrm a is
m a r k e d by the o c c u r r e n c e of n = t 1 k a r y o t y p e s , w h e r e a s the A m e r i c a n species
s h o w h i g h e r c h r o m o s o m e n u m b e r s f r o m n = 17 to n = 22. We guess t h a t a
n u m b e r like n = 17 o r n e a r was p r e s e n t in t h e c o m m o n a n c e s t o r of Aphcenogaster s. str. a n d Attomyrma. However, IMm (1971) p r o p o s e d a h y p o t h e t i c a l
b a s i c k a r y o t y p e with n = 8 c h r o m o s o m e s , all medio- or s u b m e d i o c e n t r i c , f o r
t h e J a p a n e s e Aphcenogaster species.
Harpagoxenus (fig. 2 d, table I) : H. sublcevis is a d u l o t i c s p e c i e s a n d a
p a r a s i t e m a i n l y of Leptothorax acervom~m.
Both genera are commonly
r e g a r d e d as closely r e l a t e d . BUSCHINGER(1971) s t a t e d t h a t H. sublcevis t o g e t h e r
w i t h o t h e r p a r a s i t i c species a r e c l o s e r to the Leptothorax s u b g e n u s Mychothorax t h a n to Leptothorax s. str. KUTTER (1977) calls Harpagoxenus like
s o m e o t h e r social p a r a s i t i c g e n e r a a " s a t e l l i t e g e n u s " of Leptothorax in t h e
s e n s e t h a t these social p a r a s i t e s a r e alt d e r i v e d f r o m Leptothorax s p e c i e s a n d
a r e still p a r a s i t i n g on t h e i r a n c e s t r M f o r m s or a t l e a s t on a r e l a t e d species.
H o w e v e r , the k a r y o t y p e of H. sublcevis d i f f e r s r e m a r k a b l y f r o m t h a t o f
L. acervomtm as well as f r o m t h e k a r y o t y p e s of o t h e r Leptothorax species.
So we t h i n k t h a t H. subtcevis is r a t h e r d i s t a n t f r o m the genus Leptothorcc~,
Leptothorax (fig. 3 c-f, table I) : The k a r y o t y p e s o f L. (M.) interruptus a n d
L. (L.) acervorum r e s e m b l e each o t h e r in s p i t e of t h e species b e l o n g to
d i f f e r e n t subgenera, and t h e r e is no e v i d e n c e f o r a close r e l a t i o n s h i p .
IMAI a n d KtJBOTA (1972) d e s c r i b e d t h e k a r y o t y p e of the J a p a n e s e species
L. congruus with n = 9 c h r o m o s o m e s w h i c h s e e m s to be i d e n t i c a l w i t h the
n = 9 k a r y o t y p e s given in this p a p e r , b e c a u s e the s u b m e d i o c e n t r i c c h r o m o -
ANT CHROMOSOMES
161
Fig. 4, - - Metaphase plates. 2 000 x .
a) Myrmica schencki, diploid metaphase, 2 n = 46.
b) M. ruginodis, haploid metaphase, n = 24.
c) M. laevinodis, diploid metaphase, 2 n = 48.
d) Manica rubida, diploid metaphase, 2 n = 44.
Abb; 4. - - M e t a p h a s e n p l a t t e n . 2 000 x.
a) Myrmica schencki, d i p i o i d e Metaphase, 2 n = 46.
b) M. ruginodis, haploide Metaphase, n = 24.
c) M. laevinodis, diploide Metaphase, 2 n = 48i
d) Manica rubida, diploide Metaphase, 2 n = 44.
some may be placed at the fifth position as well as at the sixth. But also the
morphological
s i m i l a r i t y o f t h e n = 12 k a r y o t y p e s s e e m s q u i t e h i g h . S o
L. spinosior f r o m J a p a n (IMAI, 1966), L. longispinosus f r o m t h e U S A a s w e l l
162
E. H A U S C H T E C K - J U N G E N and H. J U N G E N
as L. interruptus f r o m Switzerland seem to contain one subtelocentric chrom o s o m e besides medio- and s u b m e d i o c e n t r i c elements.
Manica : Manica rubida (fig. 4 d, table I).
Myrmica : (fig. 4 a-c, table I).
BERr~ARD (1968) divided the E u r o p e a n Myrmica species into two groups.
The scabrinodis g r o u p shares a s h o r t scapus in the male and a p r e f e r e n c e for
w a r m and dry habitats whereas the rubra group assembles species with a
long scapus in the males and a p r e f e r e n c e for cooler and m o i s t e r nesting
sites. Of o u r investigated species, M. sabuleti and M. schencki belong to the
first group, M. tcevinodis, M. ruginodis, and M. sulcinodis to the second.
Moreover, M. lobicornis which shows n = 24 c h r o m o s o m e s (unpublished)
belongs also to the second group. So it seems that, in addition to morphological characters, .the scabrinodis g r o u p is characterised b y n = 23 chromos o m e s and the rubra group by n = 24. IMAI (1969) listed M. rubra, w h i c h may
be M. ruginodis o r M. laevinodis, with n = 23.
Pheidole (fig. 3, table t ) : HAUSCHrECK (1961) drew f r o m P. paUidula a set
of 2 n = 24 instead of 2 n = 20 c h r o m o s o m e s with at least one c h r o m o s o m e
pair obviously smaller than the others, thus differing f r o m the k a r y o t y p e in
this paper. A reinspection of the slides c o n f i r m e d the n u m b e r . So this
species is p r o b a b l y p o l y m o r p h i c for the c h r o m o s o m e number. P. pallidula
is not the only p o l y m o r p h i c species of this genus. IMAI and KUBOTA (1972,
1975) observed a series of different c h r o m o s o m e n u m b e r s in P. nodus, a
Japanese species, which p o l y m o r p h i s m is b r o u g h t a b o u t by R o b e r t s o n i a n
r e a r r a n g e m e n t s . In three American species the k a r y o t y p e s are similar as
in P. pallidula, also with n = 10 c h r o m o s o m e s (CRozIER, 1970 a).
CONCLUDING REMARKS
The c h r o m o s o m e n u m b e r s p r e s e n t e d in this p a p e r fit the raflge of those
already k n o w n and reviewed b y CROZIER (1975). B-chrorfiosomes as o c c u r r i n g
in Japanese ants (IMAI, 1974) were not observed.
The cytotaxonomic results in the family Formicidae are, in spite of the
investigation of a large n u m b e r of species, r a t h e r , p o o r w h a t c o n c e r n s
insights into phylogenic relationships a m o n g the subfamilies,
The main
reason m a y be the r e m a r k a b l e k a r y o t y p e evolution in the different taxa. This
fact i s not surprising if one considers that the evolution of the Formicid~e
m u s t have begun not later than during the cretaceous p e r i o d o r 100 million
years ago. I n the Baltic a m b e r s we find m a n y still existing genera, o r at
least near relatives. So it w o u l d be unwise to speculate a b o u t p h y l o g e n y on
the level of subfamilies, on the contrary, we think that the s t u d y of ant cytot a x o n o m y m a y be promising between the level of tribes a n d the level of
ANT CHROMOSOMES
163
s p e c i e s g r o u p s a n d in s o m e c a s e s e v e n o n t h e l ev el o f s p e c i e s . I n g e n e r a l ,
we obtained satisfying concordance between the karyological findings and
groupings established by taxonomists on m o r p h o l o g i c a l traits.
T h e g e n e r a T a p i n o m a , Ptagio!epis, L a s i u s , a n d M y r m i c a e x h i b i t m o r e o r
less s t a b l e c h r o m o s o m e n u m b e r s . A s t a b l e k a r y o t y p e c a n c o n s i s t o f a c r o c e n t r i c c h r o m o s o m e s as in L a s i u s s. str. N o p e r i c e n t r i c i n v e r s i o n h a s c h a n g e d
t h e c e n t r o m e r i c p o s i t i o n in a n y o f t h e s e s p e c i e s .
But stable karyotypes
m a y a l s o c a r r y m a i n l y m e d i o - a n d s u b m e d i o c e n t r i c c h r o m o s o m e s , as i n
M y r m i c a o r F o r m i c a (HAUSEHTECK-JUNGEN a n d JUNGEN, t976). I t s e e m s t h a t
in al l o f t h e s e c a s e s s p e c i a t i o n is n o t o b v i o u s l y c o r r e l a t e d w i t h k a r y o t y p e
e v o l u t i o n . O n t h e o t h e r h a n d s p e c i e s w i t h i n t h e g e n e r a C a m p o n o t u s , Aphcenogaster and Leptothorax differ greatly in t h e i r c h r o m o s o m e n u m b e r s .
ACrd~OWLEIX;EMENTS.~ We thank Miss Doris ~BELT for technical assistance. Dr. H. KtrrrrR,
Dr. W.L. BROWN, Prof. Dr. A. BUSCHINGERand Dr. C. BARONI-URI3ANIgenerously helped us
by determining the species and discussing taxonomical problems. Dr. H. KUrrEl~, Dr. U.
PRmroRIUS, Prof. Dr. A. Buscm,~c~R, Dr. E.T.E. ELTON, Dr. W.L. BROWS, Dr. J. OFER and
P. MiiLLER-MEYREprovided us with material for this investigation.
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