Low genetic divergence obscures phylogeny among populations of Sphenodon,remnant of an ancient reptile lineage

Tuatara (two species of Sphenodon) are the last representatives of a branch of an ancient reptilian lineage, Sphenodontia, that have been isolated on the New Zealand landmass for 82 million years. We present analyses of geographic variation in allozymes, mitochondrial DNA, nuclear DNA sequences, and one-way albumin immunological comparisons. These all confirm a surprisingly low level of genetic diversity within Sphenodon for such an ancient lineage. We hypothesise a recent extended population bottleneck, probably during the Pliocene/Pleistocene glaciation cycles, to explain the current paucity of variation. All data sets reveal clear genetic differentiation between the northern populations and those in Cook Strait, but offer conflicting views of the history and taxonomic relationships of the Cook Strait population on North Brother Island, currently recognised as Sphenodon guntheri. Allozymes show this population to be the most divergent of all tuatara populations, but preliminary mitochondrial DNA data indicate few differences between S. guntheri and Cook Strait Sphenodon punctatus. Interpretation of the trees is confounded by the lack of a suitable outgroup. As in other cases of conflicting nuclear and mitochondrial data sets, the different data sets likely reveal different aspects of the animals' evolutionary history, and introgression is not uncommon between species pairs.     

Morphological, functional and evolutionary aspects of tail autotomy and regeneration in the 'living fossil'Sphenodon (Reptilia: Rhynchocephalia)

Tail autotomy and regeneration are less known in Sphenodon ('Reptilia': Rhynchocephalia) than in Squamata. We examined museum specimens, Sphenodon guntheri ( N  = 8) and Sphenodon punctatus ( N  = 172), wild Sphenodon punctatus ( N  = 19) and Sphenodon sp. skeletons ( N  = 8). In S. punctatus , unlike in typical Squamata, sexes had similar relative (intact) tail lengths, and regeneration frequencies; tail and body growth was isometric. Tail breakage was usually intravertebral, usually followed by ablation of a variably sized terminal vertebral piece, partly deviating from lizards. Hypothetically, imperfect autotomy results from sphenodon's primitiveness. As in squamates, tail-losers were morphologically more left-side dominant than tail-retainers. Individual directional asymmetries in digit morphology and in digit injury were correlated (in lizards observed only at population level); tail-losers had more fluctuating asymmetry but their exclusion did not facilitate morphological taxonomic distinctions (no 'Seligmann effect'). In S. punctatus , extents and directions of sexual dimorphism paralleled differences between tail-retainers and tail-losers, females resembling tail-losers, also accounting for character interdependence (developmental constraints; employing a method similar to phylogenetic contrasts). The variation in the location of tail injury was correlated with the continuum of variation between injured and intact (pholidotic) morphotypes. These last two phenomena remain to be explored in Squamates.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 721–743.     

Karyology and karyotype analysis of diploid freshwater planarian populations of the Dugesia gonocephala group (Platyhelminthes,Tricladida) found in Sardinia

Karyology and karyotype analysis were carried out on freshwater planarian populations of the Dugesia gonocephala group. The strains studied were all diploid with chromosomic number 2n = 16; n = 8. They came from 12 sites mainly localized on the west of the island of Sardinia. Three karyotypes indicated with the letters A, B and C were found in which eight homomorphic pairs of chromosomes were easily identified. In karyotype A all chromosomes are metacentric. Ten populations of the twelve examined showed this karyotype which appears to be the most common. In karyotype B the seventh pair of chromosomes is submetacentric. This karyotype is quite common having been previously found in another eight Sardinian localities. Karyotype C differs from the others in having submetacentric third and seventh pairs of the chromosome complement. It was found in only one locality. The differences observed between these three karyotypes could be interpreted either as sign of differentiation at species level, or as an intraspecific variation due to chromosome mutations (pericentric inversions). This revised version was published online in July 2006 with corrections to the Cover Date.     

尼罗罗非鱼和萨罗罗非鱼遗传生殖隔离的初步证据(英文)

罗非鱼类(Tilapiini)含3个属70余种,种间和属间颇易人工杂交,但尼罗罗非鱼(Oreochromis niloticus)和萨罗罗非鱼(Sarotherodon melanotheron)人工杂交难度大,产苗概率甚低,要获得数量足够的可用于生产的杂交子代相当困难。该文对这两种鱼及其正交(O.niloticus♀×S.melanotheron♂)和反交(S.melanotheron♀×O.niloticus♂)子代的头肾细胞的核型进行了比较。此外,采用同工酶电泳方法检测肾、肝、眼、肌肉、心中乳酸脱氢酶等4种同工酶的表型差异。4种遗传型罗非鱼具有相同的染色体二倍数(2n=44)和总臂数(NF=50),但各具不同的染色体类型,尼罗罗非鱼为3对近中着丝点染色体(sm)、12对近端着丝点染色体(st)和7对端着丝点染色体(t);萨罗罗非鱼为1对中间着丝点染色体(m)、2对sm、12对st和7对t;正反杂交子代表现为介于双亲之间的混合类型,为0.5对m、2.5对sm、12对st和7对t。在同工酶中,仅见肾脏乳酸脱氢酶电泳结果有清晰差异,尼罗罗非鱼出现5条谱带,萨罗罗非鱼3条,而杂交子代6条,且所有谱带的迁移率和活性均表现出多态性。据此初步认为,核型和同工酶方面的差异可能是导致这两种不同属罗非鱼生殖隔离的遗传原因,这些差异也可能为这两种(属)鱼的分类学提供新的遗传背景资料。     

Nucleolar Organizing Regions, 18S and 5S rDNA in Astyanax Scabripinnis (Pisces, Characidae): Populations Distribution and Functional Diversity

Astyanax scabripinnis specimens from four distinct populations in Brazil were studied with respect to their karyotype macrostructure, nucleolar organizer regions, and 18S and 5S rRNA genes. The four populations showed a 2n = 50 chromosomes (3 M + 11 SM + 5 ST + 6 A pairs) and 1–2 B chromosomes. No chromosomal differentiations were observed between sexes. Although a karyotypic diversity has been characterized in this fish group, the populations now analyzed presented the same macrokaryotypic pattern. Chromosome mapping of 5S rDNA showed a total of eight sites located in four distinct chromosomal pairs, with no apparent differences among populations. A comparative study on 18S rDNA locations and Ag-NORs showed some secondary NOR sites that are not usually expressed in karyotypes and a probable differential NOR activity among populations. Correlations between these data, environmental conditions and B chromosomes are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Archolaemus janeae (Gymnotiformes,Teleostei): First insights into karyotype and repetitive DNA distribution in two populations of the Amazon

Archolaemus, one of the five genera of Neotropical freshwater fish of the family Sternopygidae (Gymnotiformes), was long considered a monotypic genus represented by Archolaemus blax. Currently, it consists of six species, most of them occurring in the Amazon region. There are no cytogenetic data for species of this genus. In the present study, we used classical cytogenetics (conventional staining and C‐banding) and molecular cytogenetics (probes of telomeric sequences and multigenic families 18S rDNA, 5S rDNA, and U2 snDNA) to study the karyotype of Archolaemus janeae from Xingu and Tapajós rivers in the state of Pará (Brazil). The results showed that the two populations have identical karyotypes with 46 chromosomes: four submetacentric and 42 acrocentric (2n = 46; 4m/sm + 42a). Constitutive heterochromatin occurs in the centromeric region of all chromosomes, in addition to small bands in the interstitial and distal regions of some pairs. The 18S rDNA occurs in the distal region of the short arm of pair 2; the 5S rDNA occurs in five chromosome pairs; and the U2 snDNA sequence occurs in chromosome pairs 3, 6, and 13. No interstitial telomeric sequence was observed. These results show karyotypic similarity between the studied populations suggesting the existence of a single species and are of great importance as a reference for future cytotaxonomic studies of the genus.     

Chromosome banding study of the golden loach,Sabanejewia aurata balcanica from Slovakia (Cobitidae)

The karyotype of a subspecies of the golden loach,Sabanejewia aurata balcanica from eastern Slovakia was studied by conventional Giemsa staining, Ag-NOR staining, and C-banding. The diploid chromosome number was 2n = 50. The karyotype comprised 2 pairs of metacentric, 6 pairs of submetacentric and 17 pairs of subtelocentric to acrocentric chromosomes. Both metacentric pairs and 2 large subtelocentric pairs had massive pericentromeric blocks, while all other elements had only weak blocks of heterochromatin. The NORs were localized on the short arms of one middle-sized subtelocentric pair. The karyotype ofS. a. balcanica differs from that ofS. aurata kubanica, suggesting chromosomal polymorphism of this widely distributed, polytypic cobitid species. The polymorphic karyotypes of the golden loach may thus demonstrate transient stages, linking primitive and advanced cobitid karyotypes.     

Cytogenetic characterization and description of an XX/XY1Y2 sex chromosome system in catfish Harttia carvalhoi (Siluriformes, Loricariidae)

Karyotypic and cytogenetic characteristics of catfish Harttia carvalhoi (Paraíba do Sul River basin, S?o Paulo State, Brazil) were investigated using differential staining techniques (C-banding, Ag-staining) and fluorescent in situ hybridization (FISH) with 18S and 5S rDNA probes. The diploid chromosome number of females was 2n = 52 and their karyotype was composed of nine pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric and four pairs of acrocentric chromosomes. The diploid chromosome number of males was invariably 2n = 53 and their karyotype consisted of one large unpaired metacentric, eight pairs of metacentric, nine pairs of submetacentric, four pairs of subtelocentric, four pairs of acrocentric plus two middle-sized acrocentric chromosomes. The differences between female and male karyotypes indicated the presence of a sex chromosome system of XX/XY1Y2 type, where the X is the largest metacentric and Y1 and Y2 are the two additional middle-sized acrocentric chromosomes of the male karyotype. The major rDNA sites as revealed by FISH with an 18S rDNA probe were located in the pericentromeric region of the largest pair of acrocentric chromosomes. FISH with a 5S rDNA probe revealed two sites: an interstitial site located in the largest pair of acrocentric chromosomes, and a pericentromeric site in a smaller metacentric pair of chromosomes. Translocations or centric fusions in the ancestral 2n = 54 karyotype is hypothesized for the origin of such multiple sex chromosome systems where females are fixed translocation homozygotes whereas males are fixed translocation heterozygotes. The available cytogenetic data for representatives of the genus Harttia examined so far indicate large kayotype diversity.     

The discovery of triploid Lycoris sprengeri Comes ex Baker from Anhui,China

Lycoris sprengeri Comes ex Baker is endemic to China. Reported in the present paper are the chromosomes number and karyotypes for two wild populations of the species from Anhui. ( 1 )Caishi population has a karyotype 2n=33=9st+21t+3T. The length of chromosomes ranges from 5.58～9.15μm. The karyotype belongs to Stebbin’s (1971) “4A”. (2)Longyashan populations have two karyotypes. The karyotype formula of the type I is 2n=22=8st+14t, with chromosomes ranging from 6.88～9.15μm. The karyotype belongs to “4A”. The karyotype formula of the type Ⅱ is 2n＝22＝1m+1sm+14st+6t, with chromosomes ranging from 7.20～15.80μm. The karyotype belongs to “3B”. The triploid type of L. sprengeri was discovered in Anhui for the first time. The karyotype 2n=22 =1m+1sm+14st+6t in diploid type of this species is here reported for the first time.The Robertsonian change plays a key role in karyotype evolution of Lycoris.     

The karyotype of Clivia mirabilis analyzed by differential banding and fluorescence in-situ hybridization

The karyotype of the recently described species Clivia mirabilis was analyzed by differential chromosome staining with Giemsa, chromomycin, and DAPI and by fluorescence in-situ hybridization with 5S and 45S rDNA probes. Like the other five Clivia species it was shown to have a unique karyotype, although its karyotype was similar in several respects to that of C. gardenii, differing in having only one pair of chromosomes with CMA bands compared with two pairs in C. gardenii and lacking any DAPI-positive bands. The evolutionary relationships of the species and their karyotypes are discussed.     

The karyotype of Adenomera diptyx (Boettger 1885) (Anura, Leptodactylidae) from northeastern Argentina

In this work we analyzed the karyotype of five populations of Adenomera diptyx from Argentina after conventional staining, Ag-NOR and C-banding. All specimens presented 2n = 26 and FN = 34. The karyotype was formed by three submetacentric, one metacentric and nine telocentric pairs. Silver staining revealed that the NOR was located on a secondary constriction in pair 7. C- banding evidenced constitutive heterochromatin at the pericentromeric region of all chromosomes. The karyotype of A. diptyx was similar to that of A. hylaedactyla (2n = 26, FN = 34) and different from that of A. andreae (2n = 26, FN = 40) in the fundamental number and secondary constriction position. It also differed from the karyotypes of A. marmorata (2n = 24, FN = 34 and 36) and of A. aff. bokermanni (2n = 23, FN = 34) in diploid number. Until a comprehensive cytogenetic analysis of all the species of the genus is performed, their chromosome evolution will remain poorly understood.     

Chromosomes of the liver fluke, Clonorchis sinensis

A karyological study was carried out in order to compared the chromosome numbers, chromosome morphologies and karyotypes of the oriental liver fluke, Clonorchis sinensis (Trematoda: Opisthorchiidae), collected from Korea and China. Chromosome preparations were made by means of air-drying method. The chromosome number was 2n = 56 in both Korean and Chinese flukes, and chromosomes were divided into two groups based on this size; consisting of 8 pairs of large and 20 pairs of small chromosomes. However, the karyotypes showed some differences between Korean and Chinese flukes. The karyotype of liver flukes from Korea consisted of three metacentric pairs, one meta-/submetacentric pair, 16 submetacentric pairs and eight subtelocentric pairs of chromosomes. On the other hand, liver flukes from China consisted of two metacentric pairs, two meta-/submetacentric pairs, 16 submetacentric pairs and eight subtelocentric pairs of chromosomes.     

Comparative analysis of karyotypes in European shrew species. I. The sibling species Sorex araneus and S. gemellus: Q-bands, G-bands, and position of NORs

The karyotypes of two closely related species of the genus Sorex (Mammalia, Insectivora) were compared with each other by G- and Q-banding techniques and by Ag-AS staining (GOODPASTURE and BLOOM, 1975). By comparing the G-banded karyotypes, it could be ascertained that the basic differences in karyotype between the two species lie in three pericentric inversions, three paracentric inversions, and one reciprocal translocation. This is in near agreement with FORD and HAMERTON (1970), who assumed that both species differ by three pericentric inversions and one tandem translocation. Furthermore, the karyotype of S. araneus (race C) presented by HALKKA et al. (1974) has been compared with the S. araneus of the present report. Considering the species with respect to karyotypic evolution, it is supposed that S. araneus and S. gemellus derive from a common ancestor.     

风毛菊属5种植物的核型分析

采用常规压片法,对风毛菊属(Saussurea)5种植物的染色体数目和核型类型进行分析。结果表明:大耳叶风毛菊(S.macrota)核型公式为2n=2x=26=10m+12sm+4st,属2A型;长梗风毛菊(S.dolichopoda)核型公式为2n=2x=26=14m+8sm+4st,属2A型;川陕风毛菊(S.licentiana)核型公式为2n=2x=28=12m+16sm,属2B型;杨叶风毛菊(S.populifolia)核型公式为2n=2x=28=6m+18sm+4st,属2B型;尾叶风毛菊(S.caudata)核型公式为2n=2x=30=14m+14sm+2st,属2A型。这5种风毛菊属植物中,除大耳叶风毛菊染色体数目和核型类型与前人报道的一致外,其余4种植物的染色体数目和核型类型均为首次报道,并在川陕风毛菊中发现1对B染色体。     

A cytogenetic analysis of the genus Neodendrocoelum (Triclada,paludicola) from Lake Ohrid

Nine species of the genus Neodendrocoelum from Lake Ohrid, five from sublittoral and four from littoral regions, have a diploid chromosome complement 2n=32 and show a marked resemblance in their karyotypes, comprising four large pairs (group L), seven medium pairs (group M) and five small pairs (group S). Polymorphism has only been found in groups S. Variations in chiasma frequency in the species of this genus indicate that their meiotic systems are different. In these species the number of quadrivalent were found to be different in metaphase I. The process of speciation of this genus was manifested in the diploidization of autotetraploid species.     

Chromosome studies on capsicum (Solanaceae) I. Karyotype analysis in C. Chacoënse

The somatic chromosomes and karyotypes of two Argentine populations of Capsicum chacoënse A. T. Hunz. have been studied, both of which have 2n=24. The karyotypes are symmetrical, being composed of 11 m paris + one st pair; two pairs of chromosomes are satellied: pairs 1 and 12 in one population and pairs 11 and 12 in the other one. A heteromorphic pair of satellited chromosomes in one individual suggests a spontaneous reciprocal translocation. Results are compared with previous reports for the species and genus. Data show an intraspecific karyotype variation.     

A Chromosomal Study on 7 Species of Smilax L.

The chromosome numbers and karyotypes of 7 species of Smilax L. in Liliaceae (s. 1.) are cytotaxonomically studied in this work. Their karyotypic characters, distinction between the species and the chromosomal basis of sexual differentiation are discussed. The karyotypes of most species are first reported. The results are shown as follows (see Tables 1-4 for the chromosome parameters and the karyotype constitution; Fig. 1 for their idiograms): 1. Smilax nipponica Miq. The species is one of the herbaceous species distributed in East Asia. Two karyotypes, 2n = 26(type A) and 2n = 32 (type B), are found in the species (Plate 1: 1-7). The karyotype of No. 88032 (uncertain of -L--M--S- sexuality) is 2n = 26 = 2m + 6st + 6m + 4sm + 6sm + 2st. The karyotype has 4 pairs of L chromosomes, of which the first three pairs are subterminal, and the 4th is median. The karyotype belongs to 3B. No. 88045 (the male) and No. 88046 (the female) have 2n = 32. Their karyotypes are basically uniform, and both are -L--M-- S 2n=32= 2m+4sm+ 2st+ 2m+4sm+ 6m+ 10sm + 2st, also with 4 pairs of L chromosomes, but the 2nd pair is median, and thus different from the type A. The karyotype belongs to 3B. The first pair of chromosomes of the male are distinctly unequal in length, with the D. V. (0.93) of relative length between them obviously greater than that of the female (0.1). The pair seems to be of sex-chromosomes. Sixteen bivalents (n= 16) were observed at PMCs MI of No. 88045 (Plate 1: 4). The major difference between the karyotypes A and B are greater relative length of L chromosomes in the type A than in the type B, and the increase of chromosome number in the karyotype B mainly due to the increase of st chromosomes. Nakajima (1937)reports 2n= 30 for S. hederacea var. nipponica (=S. nipponica, Wang and Tang, 1980). 2. S. riparia A. DC. This species is also herbaceous, distributed in East Asia. Thirty chromosomes were found in root-tip cells (uncertain of sexuality). The kar -L--M--S-yotype is 2n = 30 = 8st + 6sm + 2st + 6m + 6sm + 2st (Plate 3: 1, 5), consisting mainly of sm and st chromosomes. There are 4 pairs of L chromosomes which are all subterminal and the m chromosomes appear to fall all into S category. Though the karyotype belongs to 3B, it is less symmetrical than that of S. nipponica. The species is karyologically rather different from S. nipponica, therefore. The first pair of chromosomes of this material are unequal in length, and it may be a male. The karyotype of this species is first reported. 3. S. sieboldii Miq. The species is a thorny climbing shrub, distributed in East Asia. At PMCs All, 16 chromosomes (n= 16) were found (Plate 2: 6), in accordance with Nakajima's (1933) report for a Japanese material. 4. S. china L. This species, a thorny climbing shrub, is of a wide distribution range mainly in East Asia and Southeast Asia. Two karyotypes were observed in different populations. (1) The population from Xikou has 2n = 96(6x) = 20st+L- -M- 6t + 6sm + 12st + 52(S) (Plate 3:7), of which the first three pairs of chromosomes are terminal, different from those in the other species. The arm ratios of both L and M chromosomes are larger than 2.0, which resembles those of S. davidiana. (2) PMCs MI of the population from Shangyu shew 15 chromosomes (n 15). The hexaploid of the species is recorded for the first time. Hsu (1967,1971) reported 2n = 30 from Taiwai and Nakajima (1937) recorded n = 30 from Japan, which indicates that the karyotype of the species varies not only in ploidy, but also in number. 5. S. davidiana A. DC. The somatic cells were found to have 32 chromosomes, and PMCs MI shew 16 bivalents (Plate 2: 1-5). The karyotype is 2n = 32=-L- -M- -S 8st + 4sm + 4st + 8sm + 8st. The karyotype belongs to 3B, and is less symmetrical than those in herbaceous species. The D. V. (0.20) of relative length between the two homologues of the first pair is slightly larger in the male than in the female (0.14), and it is thus difficult to determine whether they are sexual chromosomes or not. 6. S. glabra Roxb. The species is a non-thorny climbing shrub, distributed in East Asia and Southeast Asia. 32 chromosomes were found in somatic cells. The -L- -M- - Skaryotype is 2n= 32= 8st + 10st+6sm+8st (Plate 3: 2, 6),with only 3 pairs of sm chromosomes (12, 13 and 16th). The karyotype is more asymmetric than that of S. davidiana, although it is also of 3B (Table 1). The karyotype is first reported for the species. 7. S. nervo-marginata Hay. var. liukiuensis (Hay.) Wang et Tang The variety has a relatively narrow distribution range, mainly occurring in eastern China. The chromosomal number of somatic cells is 2n= 32 (Plate 3: 3-4). The karyotype is -L- -M- -S 2n = 32 = 2sm + 6st + 2sm + 2st + 2m + 6sm + 12st, evidently different from that of S. glabra. The first pair of chromosomes are submedian, and much longer than the 2nd to 4th pairs. The ratio in length of the largest chromosome to the smallest one is 4.3. The symmetric degree is of 3C, a unique type. The karyotype of the species is reported for the first time. In Smilax, the known basic numbers are 13, 15, 16 and 17. The two herbaceous species distributed in East Asia have three basic numbers: 13, 15 and 16, while the woody species studied mainly have 16, with no 13 recorded. Mangaly (1968) studied 8 herbaceous species in North America and reported 2n=26 for them except S. pseudo-china with 2n=30. Mangaly considered that a probably ancestral home of Smilax, both the herbaceous and woody, is in Southeast Asia and the eastern Himalayas, and speculated that the ancestral type of Sect. Coprosmanthus is possibly an Asian species, S. riparia. The karyotypes of the two herbaceous species in East Asia consist mostly of sm and m chromosomes, whereas those for the North American species are all of st chromosomes. Based on the general rule of karyotypic evolution, i.e. from symmetry to asymmetry, his speculation seems reasonable. Researches on sex-chromosomes of Smilax have been carried out since 1930 (Lindsay, 1930; Jensen, 1937; Nakajima, 1937; Mangaly, 1968), and they are generally considered to be the largest pair, but there is still no adequate evidence. The result of our observation on S. nipponica may confirm that the first pair of chromosomes of this species is XY type of sex-chromosomes. Chromosomes of the genus are small and medium-sized, varying between 1-6 μm, slightly larger in herbaceous species than in woody ones, larger in the karyotype of 2n=26 than in that of 2n=32. Based on karyotype constitution of the above 5 species, the karyotype in the genus is characterized by 4 pairs of L chromosomes and 2-5 pairs of M chromosomes, and mostly st and sm chromosomes, and by rather asymmetrical 3B type. The degree of symmetry in the above 5 species is from Sect. Coprosmanthus to Sect. Coilanthus, and herbaceous species towoody ones.     

Karyotypes of Cerastoderma glaucum (Bivalvia) from Baltic and Mediterranean populations

Chromosomes of C. glaucum from Baltic (Gdansk Bay) and Mediterranean (Thau lagoon, Sète) populations were studied using karyometric analysis and silver-staining. The karyotype of the Gdansk population consists of three metacentric, ten submetacentric and six subtelocentric chromosome pairs. The karyotype of the Thau population shows four metacentric, nine submetacentric and six subtelocentric pairs. Nucleolus organizer regions were found terminally on the second largest submetacentric chromosome pair of the Gdansk population and on the second largest metacentric chromosome pair of the Thau population. This suggests a cytotaxomomic difference between these two geographically isolated populations. Striking differences exist between C. glaucum and C. edule karyotypes, probably resulting from a long divergence time.     

A Cytological Study of Six Populations of Disporum cantoniense (Liliaceae)

Disporum cantoniense (Lour.) Merr. is widely distributed in the area from the Himalayas to Indonesia, via south China, Indo-China and Taiwan, especially in the various parts of Yunnan Province. In this paper, the karyotype variation of six populations of the apecies from southeastern, middle and northwestern part of Yunnan are studied. The result shows that the chromosome number of all the populations are 2n= 14. The species was reported to have 2n= 16, 30 (Hasegawa 1932, Mehra and Pathamia 1960, Kurosawa 1966, 1971, Tang et al. 1984) and 2n= 14 (Kurosawa 1971, Mehra and Sachdeva 1976a). 2n= 14, 2n= 16 and 2n=32 were observed in the material from Taiwan (Chuang, et al. 1962, Chao, 1963, Hsu, 1971, 1972, Chang, 1974). Based on the cytological study of D. megalanthum Wang et Tang and seven other species in this genus reported by other authors, Hong and Zhu (1990) consider that the basic number of this genus is x= 8, because species with 2n= 16 was more than those with 2n= 14, despite some number variation of chromosomes in this genus. Based on the results of the present paper, we consider that x= 7 might be one of the basic numbers of this genus. In the karyotypes studied here, the relative chromosome lengths and the ratio of the longest/the shortest chromosomes of the six populations are rather approximate. Moreover, all the karyotypes belong to Stebbins’3B type. However, karyotype variation was detected in these populations. The homologues of the 2nd, 3rd and 6th pair of chromosomes are different from each other, the numbers and popsition of satellites are found very different, among the populations except for the Lijiang population, the 1st, 2nd, 3rd or 4th pair of all the populations exhibited heterozygosity. Although all the karyotypes belong to Stebbins ‘3B type, the homologues were more regular in the Lijiang population than in the other populations, and the most irregular in the Wenshan population, because it hadfour pairs of heterozygous chromosomes.