Chromosomal rearrangements in rock wallabies, Petrogale (Marsupialia: Macropodidae). VII. G-banding analysis of Petrogale brachyotis and P. concinna: species with dramatically altered karyotypes.

G-banded metaphase preparations of cultured fibroblasts were used to construct the karyotypes of Petrogale brachyotis (2n = 18) and P. concinna (2n = 16). The two karyotypes differ significantly from the plesiomorphic karyotype of the genus and from those of all other Petrogale species examined. Petrogale brachyotis and P. concinna are characterised by three synapomorphies: a 1-10 centric fusion, a 3a-6 centric fusion, and a submetacentric chromosome 2 (2s). Both species also possess autapomorphies. Petrogale brachyotis is characterised by submetacentric chromosomes 5 (5s) and 4 (4sm), whereas P. concinna is characterised by a 5-9 centric fusion and a submetacentric chromosome 8 (8m). The 2s, 5s, 4sm, and 8m chromosomes all appear to be derived from their plesiomorphic homologs by centromeric transpositions. Although the rate of chromosome evolution varies considerably in Petrogale, the genus clearly exhibits karyotypic orthoselection, with all the autosomal rearrangements identified being either centric fusions or centromeric transpositions. This study also illustrates the potential for convergent evolution in chromosomally diverse groups and demonstrates the importance of G-banding studies for accurate identification of chromosome rearrangements.     

Chromosomal rearrangements in rock wallabies, Petrogale (Marsupialia: Macropodidae). II. G-banding analysis of Petrogale godmani

Chromosomal rearrangements in the two currently recognised races of Petrogale godmani were examined using C- and G-banding. The nominate race P. godmani godmani (2n = 20) was found to possess an inverted chromosome 5 and an acrocentric 6-10 fusion, which can be derived from a 6-10 centric fusion by a centromeric transposition. The Cape York race (2n = 22) was found to retain the ancestral submetacentric chromosome 4 and the ancestral chromosome 5. Thus despite their genic similarity, the two races clearly have major chromosomal differences and should be regarded as separate species. Petrogale g. godmani shares two derived chromosomes with another Queensland taxon, the assimilis race of P. assimilis, indicating recent common ancestry. The Cape York race retains characteristics of an ancestral stock of Petrogale and its genic similarity with P. g. godmani could therefore be the result of extensive introgression.     

Mapping the distribution of the telomeric sequence (T(2)AG(3))(n) in rock wallabies,Petrogale (Marsupialia: Macropodidae), by fluorescence in situ hybridization. ii. the lateralis complex

The distribution of the conserved vertebrate telomeric sequence (T(2)AG(3))(n) was examined by fluorescence in situ hybridization in the six Petrogale (rock wallabies) taxa of the lateralis complex. As expected, the (T(2)AG(3))(n) sequence was located at the termini of all chromosomes in all taxa. However, the sequence was also present at several nontelomeric (viz., interstitial and centromeric) sites. The signals identified were associated with either ancient rearrangements involved with the formation of the 2n = 22 plesiomorphic macropodine karyotype or more recent rearrangements associated with karyotypes derived from the 2n = 22 karyotype. Interstitial (T(2)AG(3))(n) signals identified on chromosomes 3 and 4 in all six species of the lateralis complex and a large centromeric signal identified on chromosome 7 in the five subspecies/races of P. lateralis appear to be related to the more ancient rearrangements. Subsequent chromosome evolution has seen these signals retained, lost, or amplified in different Petrogale lineages. Within the lateralis complex, in two submetacentric chromosome derived by recent centric fusions, the telomeric sequence was identified at or near the centromere, indicating its retention during the fusion process. In the two taxa where chromosome 3 was rearranged via a recent centromeric transposition to become an acrocentric chromosome, the telomeric signal was located interstitially.     

Chromosome evolution in kangaroos (Marsupialia: Macropodidae): cross species chromosome painting between the tammar wallaby and rock wallaby spp. with the 2n = 22 ancestral macropodid karyotype.

Marsupial mammals show extraordinary karyotype stability, with 2n = 14 considered ancestral. However, macropodid marsupials (kangaroos and wallabies) exhibit a considerable variety of karyotypes, with a hypothesised ancestral karyotype of 2n = 22. Speciation and karyotypic diversity in rock wallabies (Petrogale) is exceptional. We used cross species chromosome painting to examine the chromosome evolution between the tammar wallaby (2n = 16) and three 2n = 22 rock wallaby species groups with the putative ancestral karyotype. Hybridization of chromosome paints prepared from flow sorted chromosomes of the tammar wallaby to Petrogale spp., showed that this ancestral karyotype is largely conserved among 2n = 22 rock wallaby species, and confirmed the identity of ancestral chromosomes which fused to produce the bi-armed chromosomes of the 2n = 16 tammar wallaby. These results illustrate the fission-fusion process of karyotype evolution characteristic of the kangaroo group.     

G-banding evidence for a conserved complement in the Marsupialia

G-banding data are presented for a wide range of Australian marsupial species and one South American species, all of which have 2n = 14. The chromosome banding pattern in each of these species is very similar. Variations between species can be explained by structural changes internal to individual chromosomes. This evidence favors the hypothesis of a conserved complement common to both Australian and American marsupials and underlies the dominant role of chromosome fission in the evolution of this group.     

Phylogenetic relationships of rock-wallabies, Petrogale (Marsupialia: Macropodidae) and their biogeographic history within Australia

The rock-wallaby genus Petrogale comprises a group of habitat-specialist macropodids endemic to Australia. Their restriction to rocky outcrops, with infrequent interpopulation dispersal, has been suggested as the cause of their recent and rapid diversification. Molecular phylogenetic relationships within and among species of Petrogale were analysed using mitochondrial (cytochrome oxidase c subunit 1, cytochrome b, NADH dehydrogenase subunit 2) and nuclear (omega-globin intron, breast and ovarian cancer susceptibility gene) sequence data with representatives that encompassed the morphological and chromosomal variation within the genus, including for the first time both Petrogale concinna and Petrogale purpureicollis. Four distinct lineages were identified, (1) the brachyotis group, (2) Petrogale persephone, (3) Petrogalexanthopus and (4) the lateralis-penicillata group. Three of these lineages include taxa with the ancestral karyotype (2n=22). Paraphyletic relationships within the brachyotis group indicate the need for a focused phylogeographic study. There was support for P. purpureicollis being reinstated as a full species and P. concinna being placed within Petrogale rather than in the monotypic genus Peradorcas. Bayesian analyses of divergence times suggest that episodes of diversification commenced in the late Miocene-Pliocene and continued throughout the Pleistocene. Ancestral state reconstructions suggest that Petrogale originated in a mesic environment and dispersed into more arid environments, events that correlate with the timing of radiations in other arid zone vertebrate taxa across Australia.     

Chromosome homology and heterochromatin in goat,sheep and ox studied by banding techniques

Peripheral blood lymphocyte metaphase chromosomes of three Bovoidean species have been studied using Quinacrine fluorescence and Giemsa banding techniques to give Q-, G-, and C-banding patterns. Q- and G-banding characteristics, coupled with chromosome length, enabled all of the chromosomes in each of the chromosome complements to be clearly distinguished, although some difficulties were encountered with the very smallest chromosomes. A comparison of G-banding patterns between the species revealed a remarkable degree of homology of banding patterns. Each of the 23 different acrocentric autosomes of the domestic sheep (2n=54) was represented by an identical chromosome in the goat (2n=60) and the arms of the 3 pairs of sheep metacentric autosomes were identical matches with the remaining 6 goat acrocentrics. A similar interspecies homology was evident for all but two of the autosomes in the ox (2n=60). This homology between sheep metacentric and goat acrocentric elements confirms a previously suggested Robertsonian variation. The close homology in G-banding patterns between these related species indicates that the banding patterns are evolutionarily conservative and may be a useful guide in assessing interspecific relationships. —The centromeric heterochromatin in the autosomes of the three species was found to show little or no Q-or G-staining, in contrast to the sex chromosomes. This lack of centromeric staining with the G-technique (ASG) contrasts markedly with results obtained with other mammalian species. However, with the C-banding technique these regions show a normal intense Giemsa stain and the C-bands in the sex chromosomes are inconspicuous. The amount of centromeric heterochromatin in the sheep metacentric chromosomes is considerable less than in the acrocentric autosomes or in a newly derived metacentric element discovered in a goat. It is suggested that the pale G-staining of the centromeric heterochromatin in these species might be related to the presence of G-Crich satellite DNA.     

Karyometrical analysis of 10 species of the subfamily Monocelidinae (Proseriata,Platyhelminthes) with remarks on the karyological evolution of the Monocelididae

Ten species of the Monocelidinae have been examined. All were found to be regularly diploid. Four of them show the chromosome number n=3 and remarkably similar karyotypes (one pair of large metacentrics, one pair of medium sized metacentrics and one pair of small heterobrachial chromosomes). This set is considered as basic (plesiomorphic) for the family Monocelididae. Three species present n=4 and three species n=5, with an increase of heterobrachial chromosomes. Based on karyometrical data, it is suggested that these complements are derived from the basic complement through fission of one or both metacentric chromosomes, respectively. Further minor chromosome rearrangements, involving centromere position, were observed.     

Metaphase karyotypes and G-banding in sandflies of the Lutzomyia longipalpis complex

Mitotic metaphase chromosomes (2n = 8) from brain cells of fourth instar sandfly larvae of four geographical strains of the Lutzomyia longipaplis complex were examined microscopically, with bright-field illumination, after staining by a new G-banding technique involving exposure of air-dried chromosome preparations to quinacrine and ultraviolet light. Differences of G-banding and/or position of the centromere on chromosome 4 (the smallest chromosome pair) distinguished four putative sibling species from Costa Rica, Colombia and Brazil (distinctive populations from Jacobina and Lapinha Caves). The karyotype of the population from Jacobina, Brazil, showed an apparently plesiomorphic pattern of G-banding. On the basis of their recognizably different mitotic karyotypes, cytogenetic identification of separate taxa in the L. longipalpis complex should be useful for specific female vector competence and ecology studies.     

Cytogenetic analysis of the neotropical spider Nephilengys cruentata (Araneomorphae, Tetragnathidae): standard staining nors, C-bands and base-specific fluorochromes.

The aim of this work is to characterize Nephilengys cruentata in relation to the diploid number, chromosome morphology, type of sex determination chromosome system, chromosomes bearing the Nucleolar Organizer Regions (NORs), C-banding pattern, and AT or GC repetitive sequences. The chromosome preparations were submitted to standard staining (Giemsa), NOR silver impregnation, C-banding technique, and base-specific fluorochrome staining. The analysis of the cells showed 2n = 24 and 2n = 26 chromosomes in the embryos, and 2n = 26 in the ovarian cells, being all the chromosomes acrocentric. The long arm of the pairs 1, 2 and 3 showed an extensive negative heteropycnotic area when the mitotic metaphases were stained with Giemsa. The sexual chromosomes did not show differential characteristics that allowed to distinguish them from the other chromosomes of the complement. Considering the diploid numbers found in N. cruentata and the prevalence of X1X2 sex determination chromosome system in Tetragnathidae, N. cruentata seems to possess 2n = 24 = 22 + X1X2 in the males, and 2n = 26 = 22 + X1X1X2X2 in the females. The pairs 1, 2 and 3 showed NORs which are coincident with the negative heteropycnotic patterns. Using the C-banding technique, the pericentromeric region of the chromosomes revealed small quantity or even absence of constitutive heterochromatin, differing of the C-banding pattern described in other species of spiders. In N. cruentata the fluorochromes DAPI/DA, DAPI/MM and CMA3/DA revealed that the constitutive heterochromatin is rich in AT bases and the NORs possess repetitive sequences of GC bases.     

Chromosome banding in three species of <Emphasis Type="Italic">Hypsiboas</Emphasis> (Hylidae,Hylinae), with special reference to a new case of B-chromosome in anuran frogs and to the reduction of the diploid number of 2n = 24 to 2n = 22 in the genus

The chromosomes of hylids Hypsiboas albopunctatus, H. raniceps, and H. crepitans from Brazil were analyzed with standard and differential staining techniques. The former species presented 2n = 22 and 2n = 23 karyotypes, the odd diploid number is due to the presence of an extra element interpreted as B chromosome. Although morphologically very similar to the small-sized chromosomes of the A complement, the B was promptly recognized, even under standard staining, on the basis of some characteristics that are usually attributed to this particular class of chromosomes. The two other species have 2n = 24, which is the chromosome number usually found in the species of Hypsiboas karyotyped so far. This means that 2n = 22 is a deviant diploid number, resulted from a structural rearrangement, altering the chromosome number of 2n = 24 to 2n = 22. Based on new chromosome data, some possibilities were evaluated for the origin of B chromosome in Hypsiboas albopunctatus, as well as the karyotypic evolution in the genus, leading to the reduction in the diploid number of 2n = 24 to 2n = 22.     

Phylogenetic Reconstruction by Cross-Species Chromosome Painting and G-Banding in Four Species of Phyllostomini Tribe (Chiroptera,Phyllostomidae) in the Brazilian Amazon: An Independent Evidence for Monophyly

The subfamily Phyllostominae comprises taxa with a variety of feeding strategies. From the cytogenetic point of view, Phyllostominae shows different rates of chromosomal evolution between genera, with Phyllostomus hastatus probably retaining the ancestral karyotype for the subfamily. Since chromosomal rearrangements occur rarely in the genome and have great value as phylogenetic markers and in taxonomic characterization, we analyzed three species: Lophostoma silvicola (LSI), Phyllostomus discolor (PDI) and Tonatia saurophila (TSA), representing the tribe Phyllostomini, collected in the Amazon region, by classic and molecular cytogenetic techniques in order to reconstruct the phylogenetic relationships within this tribe. LSA has a karyotype of 2n=34 and FN=60, PDI has 2n=32 and FN=60 and TSA has 2n=16 and FN=20. Comparative analysis using G-banding and chromosome painting show that the karyotypic complement of TSA is highly rearranged relative to LSI and PHA, while LSI, PHA and PDI have similar karyotypes, differing by only three chromosome pairs. Nearly all chromosomes of PDI and PHA were conserved in toto, except for chromosome 15 that was changed by a pericentric inversion. A strongly supported phylogeny (bootstrap=100 and Bremer=10 steps), confirms the monophyly of Phyllostomini. In agreement with molecular topologies, TSA was in the basal position, while PHA and LSI formed sister taxa. A few ancestral syntenies are conserved without rearrangements and most associations are autapomorphic traits for Tonatia or plesiomorphic for the three genera analyzed here. The karyotype of TSA is highly derived in relation to that of other phyllostomid bats, differing from the supposed ancestral karyotype of Phyllostomidae by multiple rearrangements. Phylogenies based on chromosomal data are independent evidence for the monophyly of tribe Phyllostomini as determined by molecular topologies and provide additional support for the paraphyly of the genus Tonatia by the exclusion of the genus Lophostoma.     

四十五种叶蝉的染色体研究（同翅目：叶蝉总科）

研究观察了45种中国雄性叶蝉的减数分裂,其中44种的核型为首次报道,染色体数目变化在2n=12～26之间,性别决定均为XO型。从叶蝉总科的组型图来看,该科染色体数目变化在2n=8～28之间,峰值为2n=18(16+XO),另外几种类型2n=16,20,22也有较高的出现频率。科内染色体数目的进化不具有明显的方向性,2n=22(20+XO)是该科的原始核型,易位导致的不均等互换可能是染色体数目进化的主要机制。从精子发生来看叶蝉总科与角蝉总科的关系较为密切,两者的共同特点是：①精母细胞体积较大,显著不同于沫蝉和蝉科;②减数分裂行为及精子变态过程相似;③染色体数目较少,染色体体积较大;④减数分裂前期具有典型的花束期,没有弥散期,因而不同于蜡蝉。但是由于叶蝉总科的染色体变异范围明显大于角蝉总科,而角蝉总科的核型相对较为保守,从核型上来说角蝉总科是比叶蝉总科较为原始的类群。     

Unique multiple sex chromosomes of the tree mouse Vandeleuria o. oleracea: identification of X1 and X2.

The tree mouse Vandeleuria o. oleracea has an odd diploid chromosome complement (2n = 29 female/male) accompanied by a unique multiple sex-chromosome mechanism (X1X2Ymale/X1X1X2female). In the present paper the sex chromosomes have been identified unequivocally with the help of G-banding and DNA replication patterns which confirm our earlier suggestion that the X1 is smaller in size than the simple mammalian X, and also that the combined sizes of the X1 and X2 (3-8 and 1-7 per cent respectively) approximate to the size of the conservative mammalian X (5 per cent). It is proposed that the mammalian X has attained a minimum functional size so that further reduction is not tolerated.     

Cytotaxonomical Studies on Liliaceae (s.l.): (2) Report on Chromosome Numbers and Karyotypes of 8 Species of 8 Genera from Zhejiang,China

Eight species in eight genera of Liliaceae from Zhejiang were cytotaxonomically studied in this work. The karyotypes of Chinese materials of these species are mostly reported for the first time. The results are shown as follows (see Table 2-4 for chromosome parameters of them): 1. Disporum sessile D. Don Sixteen chromosomes are counted at metaphase of roottip cells.The Karyotype formula is 2n=16=2lm+2sm+4st+2sm+3sm+ 1sm(SAT)+2st (Plate 1: 2-3, see Fig. 1:1 for its idiogram). The Karyotype belongs to 3B in Stebbins’ (1971) karyotype classification, and consists of four pairs of larger chromosomes (1-4) and four pairs of smaller chromosomes (5-8). One SAT-chromosome is situated at the sixth pair. The chromosomes range between 4.85-16.63μm. The karyotypic constitution is similar to that of Japanese material reported by Noguchi (1974). Chang and Hsu (1974) reported 2n=14=13st+1sm and 2n= 16=2m + 13st + 1sm for the material from Taiwan under the name of D. shimadai Hay. (=D. sessile D. Don). Compared with our result of D. sessile, the differences are obvious. 2. Polygonatum odoratum (Mill.) Druce PMCs diakinesis shows eleven bivalents, n = 11, 5 large and 6 small (Plate 2:5). The meiosis is normal. The majority of reports of this species are 2n=20, with a few 2n=22 and 30 (see Table 1). The materials from southen Siberia and the Far East in USSR are all of 2n= 20. Our result is the same as recorded by Jinno (1966) in the Japanese material and by Li (1980) from Beijing. Ge (1987) reported 2n=20 in the cultivated individuals of Shandong, China, showing that both 2n=20 and 22 exist in China. 3. Scilla scilloides (Lindl.) Druce This species has the somatic chromosome number 2n=18 (Plate 1: 4-6, see Fig. 1:2 for its idiogram), of which two groups of chromosomes can be recognized, i.e. the 1 st -5 th pairs of large and the 6 th-9th pairs of small chromosomes. A distinct character of the karyotype is that two satellites are attached to the short arms of the 1st pair of chromosomes. The degree of asymmetry is of 3C. The karyotype formula is 2n = 18 = 2sm (SAT) + 6st + 2t+ 6m + 2sm. The chromosomes range from 2.02 to 11.93 μm. The Previous counts on the species are 2n = 16, 18, 26, 34, 35, 36 and 43 (see Table 1). The present investigation confirms Noda’s and Haga’s results. The species is considered to be of two genomes, namely A(x = 8) and B(x = 9). Our result shows a genome composition of BB, having a pair of large SAT-chromosomes. Chang and Hsu (1974) reported 2n = 34 from a population of Taiwan, an amphidiploid (AABB), Karyotypes of other Chinese populations are worth further researches. 4. Tricyrtis macropoda Miq. The chromosome number of somatic cells is 2n= 26, and PMCs MII shows 13 bivalents (n= 13) (Plate 3:1-3, see Fig. 1:3 for its idiogram). The karyotype formula is 2n= 26= 6m + 10sm + 6st + 4st (or t), which is composed of chromosomes: 4L + 22S in size. The degree of asymmetry is of 3B. No centromeres of the 12th and 13th pairs of chromosomes were observed at metaphase, and the chromosomes may be of st or t. Nakamura (1968) reported 2n= 26(4L+ 22S)= 2sm+ 2sm-st+ 14st-sm+ 8st for T. macropoda Miq. and 2n= 26(4L+ 22S)= 8m+ 2sm+2sm-st+ 2st-sm+ 12st for its ssp. affinis, both from Japan. It is clear that the major character of their karyotypes, i. e. 4L + 22S, is consistent with that reported here. Based on the previous and present reports, all Tricyrtis species studied are remarkably uniform in the basic karyotype, i. e. 4L + 22S. 5. Allium macrostemon Bunge. The present observation on the root-tip cells of the species shows 2n = 32 (Plate 3: 4-5, see Fig. 1:4 for its idiogram). The karyotype formula is 2n (4x)= 32= 26m + 6sm, which belongs to 2B, being of high symmetry. Except the 6th, 10th and 13th pairs of chromosomes all the are metacentric. Chromosomes of this species are large, ranging from 5.94 to 18.06 μm. Our result agrees with Kawano’s (1975) report under the name of A. grayi Regel ( = A. macrostemon, Wang and Tang 1980). 6. Asparagus cochinchinensis (Lour.) Merr. Ten bivalents were observed in PMCs MI, n=10 (Plate 1: 1). The present result confirms the number of a population of Taiwan recorded by Hsu (1971). 7. Ophiopogon japonicus (L. f.) Ker-Gawl. The species from Mt. Taogui, Hangzhou, is found to have 2n (2x)=36=22m + 14sm (Plate 2: 1,5, see Fig. 1:5 for its idiogram) which belongs to 2B. The karyotype is composed of 2 medium-sized chromosomes with metacentric centromeres and 34 small chromosomes, ranging from 1.34 to 4.92 μm. The populations from Mt. Tianzhu and Mt. Yuling, Zhejiang, are found to be aneuploids at tetraploid level (2n=64-70). It is interesting that Nagamatsu (1971) found the karyotypes of Japanese materials to be 2n= 67 and 68, also showing unsteady 4x karyotypes of this species. In the previous. reports (see Table 1), the chromosome numbers of this species are mainly 2n = 72, besides 2n = 36 recorded by Sato (1942) from Japan. 8. Liriope platyphylla Wang et Tang The somatic complement of the species collected from Mt. Tianzhu, Hangzhou, is 2n = 36 (Plate 2: 3-4, see Fig. 1:6 for its idiogram). The karyotype is 2n(2x) = 36 = 16m + 20sm, belonging to 2B type. The chromosomes are small except the medium-sized, 1st pair and the range is from 1.27 to 5.19μm. The material from Mt. Yuling, Zhejiang, is found to have a variety of chromosome numbers (2n= 60-71), as observed in Ophiopogon japonicus. Hasegawa (1968) reported the karyotype of 2n = 72 (4x) from Japan The 2x karyotype is first recorded. This genus is closely related to Ophiopogon. Based on the Hasegawa’s and present studies, all the species in these two genera are remarkably uniform in karyo-type. Therefore, the taxonomy of the two genera is worth further researches.     

Constitutive heterochromatin variation in two species of rattus with apparently similar karyotypes

Rattus blanfordi and R. cutchicus medius both have a chromosome complement of 2n=36 and all chromosomes except the submetacentric Y of R. blanfordi are acrocentric. The apparently similar karyotypes of the two species, however, show variations in the nature and quantity of C-band-positive constitutive heterochromatin (C-heterochromatin) as revealed by C- and G-banding and Hoechst 33258 fluorescence. R. blanfordi with large-sized X and Y chromosomes and conspicuously larger centromeric heterochromatin in all the autosomes as compared to that of R. cutchicus medius has much more C-heterochromatin in its genome than the latter. The variation in the quantity of C-heterochromatin has been accomplished without altering the morphology of the acrocentric chromosomes unlike other mammals in which variations have been reported to result generally in the addition or deletion of a totally heterochromatic second arm.     

Trisomy 9q-. a variant of the 9p trisomy syndrome.

A low-birth-weight near-term male infant was found to have a non-familial 47,XY chromosome complement with an extra medium-sized metacentric chromosome slightly larger than a number 16. By Giemsa-trypsin (G-banding) this extra chromosome was determined to be a number 9 with deletion of approximately half of the long arm at region q 22. Chromosome studies on the clinically normal 38-year-old mother showed a balanced translocation with the deleted portion attached onto the distal end of a number 8 short arm, i.e. 46,XX,t(8;9)(p23;q22). Nondisjunction during meiosis of this woman's normal and deleted number 9 chromosomes is the basis of the child's abnormalities. One half-sibling of the child has a balanced translocation similar to that in the mother. Chromosome analyses on 4 others of the child's maternal half-siblings and on the maternal grandmother all showed normal patterns.     

New chromosome numbers for plant taxa endemic to the Balearic Islands

Mitotic chromosome numbers are reported from 25 vascular plant taxa, endemic to the Balearic Islands that are poorly known cytogenetically. The chromosome numbers ofAnthyllis vulneraria subsp.balearica (2n=12),Cymbalaria fragilis (2n=56), andPolygonum romanum subsp.balearicum (2n=40) were determined for the first time. A new chromosome number was found in several populations ofAnthyllis hystrix (2n=70) suggesting that this species is decaploid, in contrast to an earlier work reporting a higher ploidy level (2n=12x=84). The new chromosome number 2n=32 was reported inHypericum hircinum subsp.cambessedesii. It is suggested that the previous count (2n=40) could be explained by the presence of anomalous pentaploid cells in some tissues, contrating with the presence of a regular tetraploid complement (2n=32). Cytogenetic observations suggest thatSibthorpia africana has a diploid chromosome complement of 2n=18, with 0–2 accessory chromosomes. Accessory chromosomes are also reported forPhlomis italica, being the first record of B chromosomes in this genus. Chromosomal instability was found inGalium crespianum andG. friedichii species, with three numbers 2n=44, 55 and 66. Two cytotypes differing in ploidy level were documented within single plants. It is suggested that both species share a regular complement of 2n=44 and that the past hybridization events and formation of regenerating roots from the typical rootstock ofG. crespianum andG. friedrichii could be involved in the genesis of chromosome variants through partial endopolyploidy and concomitant somatic segregation.     

三种姬鼠的染色体比较研究

本文采用染色体分带技术（Ｇ－,Ｃ－带和银染色）,对中华姬鼠（Ａｐｏｄｅｍｕｓｄｒａｃｏ）、大林姬鼠（Ａ．ｐｅｎｉｎｓｕｌａｅ）和大耳姬鼠（Ａ．ｌａｔｒｏｎｕｍ）的核型进行了观察分析。结果表明：３种姬鼠的２ｎ均为４８。中华姬鼠的染色体均为端着丝点染色体。大林姬鼠的常规核型中,除１对中着丝点染色体（Ｎｏ．２３）外,其余均为端着丝点染色体。大耳姬鼠的核型中,有１３对端着丝点染色体,２对亚端着丝点染色体,１对亚中着丝点染色体和７对中着丝点染色体。中华姬鼠Ｃ－带核型中,所有染色体着丝点Ｃ－带都呈强阳性,异染色质非常丰富,Ｙ染色体整条深染。在大林姬鼠Ｃ－带核型中,Ｎｏｓ．７,１１,１５,２１,２２着丝点Ｃ－带弱化甚至近阴性,其余染色体着丝点异染色质Ｃ－带都呈现程度不同的阳性。且Ｎｏｓ．２,４,７有强弱不同的端位异染色质带。Ｘ染色体着丝点区有大块的异染色质斑带出现,Ｙ染色体整条深染。大耳姬鼠除Ｎｏｓ．３,４,１０,１２,１３染色体着丝点Ｃ－带很弱外,其余染色体着丝点Ｃ－带均呈阳性,并有８对（Ｎｏｓ．１６－２３）染色体出现异染色质短臂。从总体上看,大林姬鼠和大耳姬鼠的着丝点异染色质明显比中华姬鼠的少。中华姬鼠的Ａｇ－ＮＯＲ