Cytotaxonomy and evolution in Cryptocoryne (Araceae)
J. W. F. Reumer
Institute for Earth Sciences, Budapestlaan 4, Utrecht, The Netherlands
Present address: Station de Zoologic expbrimentale, 154, route de Malagnou, 1224 CH,
ChOne-Bougeries, Genbve, Switzerland
Abstract
A hypothetical phylogeny is presented for the genus Cryptocoryne (Araceae, Cryptocoryninae). This
scheme is based on both geographical and cytological data. Therefore the geography of S. E. Asia, the
distribution of the various base numbers and the possible relationships between the base numbers are
discussed.
In the resulting phylogeny the various base numbers of Crvptocorvne (and the one of Lagenandra) are
thought to have been derived from a hypothetical primary base number x I = 9. As a consequence of the
scheme, Cryptocoryne is assumed to have a diphyletic character.
Introduction
Many chromosome numbers are known within
the Asiatic monocotyledon genus Crvptocorvne. In
the literature the following diploid numbers have
been mentioned: 20, 22, 28, 30, 33, 34, 36, 42, 54, 60,
66, 68, 72, 85, 88, 90, 102 and 132 (Jacobsen, 1976,
1977a, 1979, 1980; Arends et al., 1982; De Wit,
1983). Some of these numbers (viz. 60 and 90, see
below) are questionable; on the other hand not all
species of Cryptoeoryne have been studied yet.
The chromosome numbers mentioned above can
be related to six different base numbers, viz. x = 10,
11, 14, 15, 17 and 18 (Jacobsen, 1977a; Arends et
al., 1982; see Table 1). It has been proposed (Arends
et al., 1982) that this series of base numbers originated as an aneuploid series, starting at x = 18 and
decreasing to x = 10. This suggestion is based on the
assumption that x = 18 is the most primitive
c h r o m o s o m e condition, which seems to be confirmed by the fact that the closely related genus
Lagenandra has 2n = 36, x --- 18 in all known species
(Arends & Van der Laan, 1978).
However, when this suggestion is considered toGenetica 65. 149-158 (1984).
© Dr W. Junk Publishers. Dordrecht. Printed in the Netherlands.
gether with biogeographical facts, it appears that
the situation is rather more complicated. This article attempts to combine cytological and biogeographical data into a hypothetical phylogeny of the
genus Cryptocoryne.
Geography
The distribution area of the genus Co'ptocoryne
includes continental S. Asia from W. India to S.
China, and comprises Bangladesh, Burma, Thailand, lndochina and Malaysia, as well as the islands
of Sri Lanka (Ceylon), Sumatra, Borneo, Java,
Sulawesi (Celebes), the Philippines and I r i a n / P a pua (New Guinea). The distributions of the six base
numbers are more restricted, in many cases quite
considerably (Figs. 1-6).
The area under consideration is geographically
rather incoherent, different parts having a different
paleogeographical origin. In Figure 7 the area is
shown divided into four sectors:
(A) The mainland sector. This sector comprises
continental Asia, including the islands of Sri Lan-
150
Table 1. List of Cryptocoryne species of which the chromosome number is known. Compiled atter Jacobsen, 1977a, 1980; Arends et al.,
1982; De Wit, 1983.
Base number
Species
Chromosome number
Area
x = 10
striolata Engler
keei Jacobsen
20
20
Borneo
Borneo
x = 11
eiliata (Roxb.) Schott
spiralis (Retz.) Wydler
22, 33
33, 66, 88, 132
entire SE Asia
India
x = 14
wendtii De Wit
beckettii Thwaites ex Trimen
undulata Wendt
walkeri Schott
(incl. lutea Alston)
x willisii Reitz
(incl. lucens De Wit)
parva De Wit
nevillii Trimen ex Hooker f.
28,
28,
28,
28,
Sri
Sri
Sri
Sri
42
42
42
42
Lanka
Lanka
Lanka
Lanka
28
Sri Lanka
28
28
Sri Lanka
Sri Lanka
x = 15
pontederiifolia Schott
moehlmannii De Wit
villosa Jacobsen
longicauda Beccari ex Engler
(incl. johorensis En~ler
30
30
30
30
Sumatra
Sumatra
Sumatra
Borneo, Johore
x = 17
amicorum De Wit et Jacobsen
gasseri Jacobsen
scurrilis De Wit
griffithii Schott
zewaldiae De Wit
minima Ridley
purpurea Ridley
jacobsenii De Wit
zukalii Rataj
diderici De Wit
schulzei De Wit
nurii Furtado
affinis Brown ex Hooker f.
cordata Griffith
(incl. blassii De Wit,
siamensis Gagnepain)
edithiae De Wit
grabowskii Engler
zonata De Wit
versteegii Engler
ferruginea Engler
(incl. sarawacensis (Rat.) Jac.)
fusca De Wit
tortilis De Wit
auriculata Engler
bullosa Engler
pallidinervia Engler
usteriana Engler
pygmaea Merrill
34
34
68
34
34
34
34
34
34
34
34
34
34
34, 68, 85, 102
Sumatra
Sumatra
Sumatra
Malay Peninsula
Malay Peninsula
Malay Peninsula
Malay Peninsula
Malay Peninsula
Malay Peninsula
Malay Peninsula
Malay Peninsula
Malay Peninsula
Malay Peninsula
Malay Peninsula
68
68
68
34
34
Borneo
Borneo
Borneo
New Guinea
Borneo
34
34
34
34
34
34
34
Borneo
Borneo
Borneo
Borneo
Borneo
Philippines
Philippines
36
36, 54
Thailand, Birma
India to SE China
36, 72
36
36
36
36
India
Sri Lanka
Sri Lanka
Sri Lanka
Borneo
x = 18
albida Parker
crispatula Engler
(incl. balansae Gagnepain)
retrospiralis (Roxb.) K u n t h
thwaitesii Schott
bogneri Rataj
alba De Wit
lingua Beccari ex Engler
151
Fig. l.
D i s t r i b u t i o n o f t h e b a s e n u m b e r x = 10.
q
Fig. 2.
D i s t r i b u t i o n o f t h e b a s e n u m b e r x = ! 1.
ka, Hainan and Taiwan (Formosa), but without the
Malay Peninsula. This area has always been continental and underwent only minor changes in its
geographical structure during the Quaternary
(Pleistocene and Holocene; Dunn & Dunn, 1977).
(B) The Sunda sector. This sector consists of the
Malay Peninsula, Sumatra, Palawan (not according to Dunn & Dunn (1977), but according to
Hooijer (1967), whose opinion is followed here),
Borneo, Java, Bali and the many smaller islands in
between these larger ones. The influence of fluctuations in the sea level has been large in this sector
during the Quaternary. At certain times the area
consisted of one big land mass (Sundaland) attached to the mainland; at other moments it became
separated and was split into many different islands,
as is the case today (Dunn & Dunn, 1977).
(C) The island sector, comprising the Philip-
152
Fig. 3. Distribution of the base number x = 14.
Fig. 4. Distribution of the base number x = 15.
pines (without Palawan), Sulawesi, the Moluccan
Islands, the Lombok-Timor range, the Tanimbar
Islands and the Kai Islands. In contrast to the
straits between the islands of the Sunda sector (B),
the straits between the islands in this sector are
relatively deep. Throughout the Pleistocene the islands must have always been islands, which were
not connected either to each other or to a continental shelf (Dunn & Dunn, 1977).
(D) The Sahul sector. This sector comprises
New Guinea, the Aru Islands and Australia, which
are all situated on one continental shelf (Hooijer,
1967).
It is worth noting that the boundary between
sectors B and C coincides with the zoogeographical
Wallace's line, and the C / D boundary coincides
with Weber's line.
Returning to C r y p t o c o r y n e , the following pie-
153
Fig. 5.
Distribution of the base n u m b e r x = 17.
Fig. 6.
Distribution of the base n u m b e r x = 18.
ture can be d r a w n of the distribution of the six base
numbers (see Jacobsen, 1977a, 1980; Arends et al.,
1982).
x = 10 is f o u n d exclusively in one island, Borneo
(Fig. 1).
x = 11 is f o u n d in sectors A, B, C and D. It should
be noted that in sectors B, C and D only one
species is found: C. ciliata (Fig. 2).
x = 14 is f o u n d exclusively in one island, Sri Lan'ka
(Fig. 3).
x = 15 is found in sector B only: in Sumatra, Borneo and J o h o r e on the Malay Peninsula (Fig. 4).
x = 17 is f o u n d in sectors B, C and D; it is missing
from sector A (Fig. 5).
x = 18 is found exclusively in sector A, with one
exception: C. lingua in Borneo in sector B
(Fig. 6).
It needs to be mentioned that the groups of base
154
I
\
\\
J
/
Fig. 7. Sectoral subdivision of SE Asia, A: Mainland Sector, B: Sunda Sector, C: Island Sector, D: Sahul Sector. For further explanation
see text.
Fig. 8. Distribution of the genus Lagenandra.
n u m b e r s are here considered to be coherent groups
of m o r e or less related species.
A d d i t i o n a l l y , the genus L a g e n a n d r a (which together with C r y p t o c o r y n e constitutes the subtribe
C r y p t o c o r y n i n a e ) is f o u n d on the I n d i a n subcontinent and in Sri L a n k a (sector A, Fig. 8).
The base numbers
The x = 18 g r o u p
A r e n d s et al. (1982) suggest that the different
base n u m b e r s originate f r o m x = 18. It is generally
a c c e p t e d t h a t the diversification of the C r y p t o c o r y ninae o r i g i n a t e d on the I n d i a n subcontinent. R a t a j
155
(1975) a d o p t s this view too, except with r e g a r d to
his s u b g e n u s S u b m e r s i n a (op. cir., figs. 2 - 5 , pp.
118-119).
T h e most i m p o r t a n t a r g u m e n t s s u p p o r t i n g this
view are:
the d i s t r i b u t i o n of Lagenandra in I n d i a and Sri
Lanka;
- the occurrence of several Cryptocorvne-species
with primitive c h a r a c t e r s in I n d i a o r B a n g l a d e s h
( C. spiral&, C. huegelii, C. gomezii);
-
the d i s t r i b u t i o n of the x = 18 g r o u p of Cryptocoryne, which occurs a l m o s t exclusively in s e c t o r
A.
T h e present a u t h o r agrees that the C r y p t o c o r y ninae o r i g i n a t e d in the m a i n l a n d sector, but, as will
be discussed below, he does n o t agree that there was
simply an a n e u p l o i d series f r o m x = 18 to x = 10.
T h e presence of C. lingua in B o r n e o must be
e x p l a i n e d as the e a s t e r n m o s t occurrence o f the x =
18 group; there is an a p p a r e n t e a s t w a r d m i g r a t o r y
t r e n d in this g r o u p (e.g. the presence of C. crispatula in S. E. China; J a c o b s e n , 1980). T h e x = 18 g r o u p
m u s t have reached B o r n e o at a time when the S u n d a sector (B) was a t t a c h e d to the m a i n l a n d (A), i.e.
d u r i n g a period of sea-level lowering c o r r e s p o n d i n g
to a glaciation at higher latitudes.
b e t w e e n the areas of the x = 14 and of the x = 15
g r o u p s and the fact that the Sri L a n k a n species have
a y o u n g a n d e n d e m i c c h a r a c t e r m a k e the step x =
15 ~ x = 14 r a t h e r unlikely.
The x = 11 group
In a d d i t i o n to the x = 18 a n d x = 14 g r o u p s , x =
11 is the third one present in sector A. It is r a t h e r
unclear how x = 11 could have originated f r o m x =
18, as one i n t e r m e d i a t e n u m b e r (x = 14) is k n o w n
o n l y as a n island endemic, a n d three i n t e r m e d i a t e s
(16, 13 a n d 12) are not k n o w n at all (which does not
imply that these n u m b e r s c a n n o t exist or c a n n o t
have existed). In o r d e r to e x p l a i n the existence of
x = 11 (and x = 10, see below) we need a scheme
o t h e r t h a n simply an a n e u p l o i d series f r o m x = 18
d o w n to x --- 10.
A c c o r d i n g to A n d r e a s (1972; using G r a n t , 1963)
plant t a x a are c h a r a c t e r i z e d on a d i p l o i d level by
p r i m a r y base n u m b e r s Xl = 2 t h r o u g h Xl -~ 13. Base
n u m b e r s a b o v e 13 are s e c o n d a r y base n u m b e r s (x2),
which have evolved from c o m b i n a t i o n s of groups
with lower ( p r i m a r y ) base n u m b e r s . T h e e v o l u t i o n a r y scheme to be presented here (Fig. 9) has the
p r i m a r y base n u m b e r Xl = 9 as its starting point.
F r o m this base n u m b e r x~ = 9 the s e c o n d a r y base
The x = 14 group
T h e g r o u p with x = 14 is restricted to Sri L a n k a
a n d in this p a p e r it is a s s u m e d that it o r i g i n a t e d
there after Sri L a n k a b e c a m e isolated f r o m the
m a i n l a n d at the end of the Pleistocene. This w o u l d
i m p l y t h a t the x = 14 g r o u p is r a t h e r a y o u n g one.
T h i s is c o n f i r m e d by the instability of the g r o u p .
T h e r e are quite a n u m b e r of hybrids, a n d the t a x o n o m i c status o f several species is s o m e w h a t u n c l e a r
(Bastmeijer, 1981); this suggests t h a t we are d e a l i n g
with a y o u n g a n d d e v e l o p i n g group.
T h e only o t h e r g r o u p present in Sri L a n k a is the
x = 18 g r o u p . It is t h e r e f o r e suggested that the
x - - 14 g r o u p o r i g i n a t e d f r o m the x = 18 g r o u p ,
a l t h o u g h it r e m a i n s u n c l e a r how this h a p p e n e d . In
the o p i n i o n of A r e n d s et al. (1982) x = 14 o r i g i n a t e d
f r o m the x = 15 g r o u p (one of the steps in their
a n e u p l o i d series). R a t a j (1975) is of the same o p i n ion, as can be d e d u c e d f r o m his figure 5 (op cit., p.
119).
T h e g r o u p with x = 15 is k n o w n f r o m S u m a t r a ,
B o r n e o and J o h o r e . H o w e v e r , the vast d i s t a n c e
/f
-'~\
@
Fig. 9. Hypothetical phylogeny of the subtribe Cryptocoryninae,
Araceae, showing the relations between the different base
numbers. Above broken line: evolutionary steps taken place in
the Indian subcontinent; below broken line: steps taken place in
other areas and/or in islands.
156
n u m b e r x 2 = 18 originated by means of a simple
euploid doubling; on the other hand the primary
base n u m b e r xl = 11 developed as an aneuploidy
(9 + 2). Whether or not this last step took place with
x = 10 as an intermediate will be discussed below.
The most likely mechanism for such aneuploid
steps is c h r o m o s o m e fusion/fission.
The distribution of C. spiralis (India to Bangladesh) more or less coincides with the supposed area
of origin of the Cryptocoryninae; this finding supports the hypothesis stated above. Also, C. spiralis
and the closely related C. huegelii have some noteworthy morphological characters of the inflorescence in c o m m o n with Lagenandra: the absence of
a tube, the presence of a perforated wall closing off
the kettle and a wrinkled surface of the limb.
S a r k a r et al. (1976) report 2n = 90 for C. spiralis.
We think this is a slight mistake and should have
been 2n = 88.
The other species belonging to the x = 11 group,
C. ciliata, is the most widely distributed species of
Crvptocoryne: it is found from India to P a p u a and
it is the only species present in Sulawesi, J a v a (with
the possible exception of C. cordata, see Rataj,
1975) and the Moluccan Islands.
One obtains the impression that C. ciliata has the
ability to cross considerable stretches of sea. This is
explained as follows.
The generative proliferation of Cryptocoryne
species is restricted by the fact that the seed has no
resting period prior to germination (Hermsen &
Van Hasselt, 1982), but vegetative reproduction by
means of runners is c o m m o n . C. ciliata is found in
tidal-influenced rivers, and according to Rataj
(1975) even in mangrove areas; the species has a
tolerance for salt judging by its occurrence in brackish waters (op. cit.).
A rather c o m m o n feature in river-mouths is the
detachment of large pieces of vegetation, which
f o r m floating islands. These are carried out to the
open sea and can be transported over vast distances
by currents and winds. In this way plants and animals can be distributed to distant islands (this form
of distribution is known for e.g. mammals; Sondaar,
1977). It is tempting to suppose that the large
distribution of C. ciliata came about in a similar
way.
The x = 10 group
It is supposed here that the x = 10 group (comprising C. striolata and C. keei from Borneo) originated as an endemic group, c o m p a r a b l e to the x =
14 g r o u p f r o m Sri Lanka. It is likely to have the x =
11 g r o u p as ancestor, as this involves the least complicated step (x- 1). It is however a problem that the
only representative of the x = 11 g r o u p in Borneo is
C. ciliata; there are great morphological differences
between C. ciliata on the one hand and C. striolata
and C. keei on the other.
Alternatively, it could be argued that the x = 10
g r o u p can be seen as an intermediate step in the
x = 9 ~ x = 11 transition. There are two arguments
against this idea. Firstly, there is a geographical
argument. If we suppose that the x = 11 group
originated from xz = 9 on the Indian subcontinent
(see above), then the x = 10 group in Borneo should
be a relict, far away f r o m the area of origin, from
which it apparently disappeared. Such large-scale
extinctions are rather unlikely as the genus is quite
successful. Secondly, the x = 11 group contains the
primitive C. spiralis which should be morphologically and hence also phylogenetically close to the
c o m m o n ancestor of Cryptocoryne and Lagenandra, i.e. the hypothetical xl = 9.
At present we prefer to adhere to the idea that the
x = t0 g r o u p originated in Borneo as an endemic
development, even t h o u g h this cannot be satisfactorily explained.
The x = 17 group
The g r o u p with x = 17 has a large distribution;
species are k n o w n f r o m sector B (Malay Peninsula,
S u m a t r a and Borneo), f r o m sector C (the Philippines) and from sector D (New Guinea). It is reasonable to assume that x = 17 originated f r o m x = 18;
this implies only a simple step ( x - l ) .
In general, the area of distribution of x = 17 is
more easterly than that of x = 18, and apparently
the x = 17 g r o u p continued the eastward migratory
trend of the x = 18 group. The areas of both groups
overlap in parts of the Malay Peninsula and in
Borneo. A p a r t f r o m C. ciliata, the x = 17 group is
the only taxon that has been able to cross the seastraits of sector C. Probably, the same mechanism
as described above for C. eiliata operated here. The
157
enormous morphological differences between the
various species (compare e.g.C, usteriana from the
Philippines and C. versteegii from Papua) suggest
that this process took place a long time ago.
Some remarks should be made here. C. gasseri
has 2n = 34; Jacobsen (1979) however mentioned
2n = 30 for this species. Arends et al. (1982) note
that this was erroneous. De Wit (1983, in a section
written by Arends) mentions the erroneous 2n -- 30.
The same applies to C. scurrilis with 2n = 68
(Arends et al., 1982). Jacobsen (1979) as well as De
Wit (1983) erroneously mention 2n -- 60 for this
species.
The great morphological resemblance between
C. lingua (Borneo, 2n = 36, x = 18)and C. versteegii
(New Guinea, 2n = 34, x = 17) should be interpreted
as a parallel development and does not indicate any
phylogenetic proximity. Rataj (1975) places both
species together in one section (Linguae); his view is
disputed here (see also Jacobsen, 1977a). Crusio
(1982) and Arends et al. (1982) place C. versteegii in
a separate group.
On the basis of resemblances in the seedling,
M iihlberg (1979) concludes that there is a relationship between C. versteegii and C. ciliata (x = 11,
also on New Guinea). We consider this to be yet
another parallel development.
It would be interesting to know the chromosome
number of the third Cryptocoryne in New Guinea
(next to C. ciliata and C. versteegii): C. dewitii. This
species is known from herbarium sheets only (Jacobsen, 1977b). Attempts should be made to relocate this species in order to verify whether or not C.
dewitii belongs to the x = 17 group. It is likely that it
does belong to this group on geographical grounds
(Arends et al., 1982, are of the same view).
The x = 15 group
The x = 15 group is found in sector B only, where
it shares its area with the x -- 17 group. It is likely
that the x = 15 group originated from the x = 17
stock and that it spread over Johore, Sumatra and
Borneo at a moment when this area formed one
single land mass (Sundaland).
The greatest polymorphism of the x = 15 group is
found in Sumatra (three species). It will be clear
that the suggestion of Crusio (1982) that C. villosa
belongs to the C. scurrilis-group cannot be upheld.
His suggestion is probably based on the erroneous
publication of 2n = 60 for C. scurrilis. The C.
scurrilis-group has the base number x = 17 and not
x=15.
One might have the impression that the four
species of the x = 15 group, which all have the
somatic chromosome number 2n = 30, belong to
the x = 10 group (in which case they would be
triploids). However, since all four species are fertile,
this possibility can be virtually ruled out; triploids
are nearly always sterile.
Conclusions
These discussions about the relationships between the various base numbers, together with the
data from the geographical distribution of the base
numbers, lead us to the hypothetical phylogeny
shown in Figure 9. As stated above, the basis of this
phylogeny is the hypothetical primary base number
x~ = 9. From this base number it is thought that the
following are derived:
(a) xl = 11, possibly with or without x I = 10 as an
intermediate step. The currently existing x = 10
group from Borneo however is here considered to
have descended from x = 11. It will be evident that
in the nomenclature of Andreas (1972) both groups
(x = I0 and 11) have primary base numbers.
(b) x2 = 18 by means of doubling. From this
secondary base number it is thought that x = 14 (in
Sri Lanka), x = 17 and from x = 17 again x = 15 are
derived. In contrast to the former two groups, these
four groups (I 8, 17, 15 and 14) have secondary base
numbers.
(c) the genus Lagenandra, also having x 2 = 18.
The existence of two more or less separate parts
(a and b) means that in its present form the genus
Cryptocoryne is diphyletic. The origin of the Cryptocoryninae is supposedly on the Indian subcontinent; this is where the first evolutionary steps took
place (the part of Figure 9 above the broken line).
Further steps occurred in other areas a n d / o r on
islands (the part of Figure 9 below the broken line).
The phylogeny presented here gives a good explanation for the absence of the base numbers x =
12 and x = 13. Neither part of the phylogeny (the
above-mentioned a and b) has x = 12 or x = 13 as
(imaginary) intermediate steps.
Several problems and questions are still to be
solved or answered:
158
l) The explanation of the large step x = 18 -- x = 14
in Sri Lanka.
2) The relationship between x = 10 and x = 11.
3) The suggested diphyletic character of the genus.
4) Can the presented phylogeny be supported by
other characters, such as the morphology of the
inflorescence?
5) Many species have not been studied cytogenetically yet. Do their numbers fit in with the phylogeny presented here?
6) Hybrid studies should be undertaken in order to
test chromosome homologies and relationships
between different karyotypes.
Acknowledgements
The author is indebted to J. D. Bastmeijer, J. M.
van Brink and J. de Vos for critically reading the
original Dutch version of this article; S. M. McNab
improved the English text.
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Received 9 . 1 2 . 8 3
Accepted 13.7.84.