Banded karyotypes of mole rats (Spalax, Spalacidae, Rodentia) from Turkey: a comparative analysis

Chromosome banding (G-, C- and Ag-NOR) analysis was carried out on 27 specimens of Sphalax ehrenbergi from seven localities and two specimens of S. leucodon from one locality, all from Turkey. No chromosomal variation was detected in S. ehrenbergi populations from Elazig, Siverek, Diyarbakir and Birecik having the same diploid numbers (2n = 52) and morphology of chromosomes (NFa = 72). The karyotypes of mole rats from Tarsus and Gaziantep possessed the identical diploid number (2n = 56) but different numbers of autosomal arms: NFa = 68 in the Tarsus and NFa = 78 in the Gaziantep populations. Chromosomes of S. leucodon from Malaty (2n = 60, NFa = 74) differed distinctly in the C-banding pattern from all S. ehrenbergi cytotypes by the almost entire absence of heterochromatin in acrocentric autosomes and the presence of heterochromatin arms iin subtelocentric autosomes. Nucleolar organizing regions were found mainly on three pairs of chromosomes, but some differences in their localization were revealed. Comparison of G-banded chromosomes showed, that most chromosomes have a similar pattern. The types of chromosomal rearrangemetns were revealed due to the banding methods.     

Cytogenetics of the genus Arvicanthis (Rodentia,Muridae). 3. Comparative cytogenetics of A. neumanni and A. nairobae from Tanzania

The African rats of the genus Arvicanthis have been widely studied during recent years to clarify species boundaries and phylogenetic relationships. The wide chromosomal variability of the genus has been highlighted in several studies, with each accepted species characterised by its individual karyotypes and others being revealed as cryptic species. In the present paper we report the karyotype and the C- and G-banding patterns of the two species A. nairobae and A. neumanni from seven localities of Tanzania, an area of the range poorly studied. The two karyotypes were compared to that of A. niloticus, which is considered to be primitive. The karyotype of A. neumanni is characterised by 2n = 53–54 and NFa = 62. This karyotypic variability depends on a widespread Robertsonian polymorphism. The karyotype of A. nairobae shows 2n = 62 and NFa = 78; it diverges from that of A. niloticus through one reciprocal translocation, five inversions and three heterochromatic additions. The comparison with the karyotypes of other species of the genus showed that A. neumanni belongs to the east African lineage (with A. abyssinicus, A. blicki, A. niloticus), while A. nairobae is closer to the central and the west African representatives which were all previously under the name of A. niloticus (ANI-2, ANI-3, ANI-4). The distribution of A. nairobae in east Africa opens new scenarios in the biogeographical pattern of evolution of the genus.     

Meiosis in gray voles of the subgenus <Emphasis Type="Italic">Microtus</Emphasis> (Rodentia,Arvicolinae) and in their hybrids

The results of light and electron microscopic (EM) studies of meiosis in Microtus arvalis males of the karyoform “arvalis” (2n = 46, NFa = 80), in hybrids between the chromosomal forms arvalis and obscurus (2n = 46, NFa = 68), in M. rossiaemeridionalis voles (2n = 54, NFa = 54), and in a hybrid between the species M. rossiaemeridionalis and kermanensis (2n = 54, NFa = 54) are presented. SC (synaptonemal complex) karyotypes of the parental forms and the hybrids were constructed on the basis of measurements of the length of autosomal SCs revealed by the EM analysis in spermatocytes at the stage of middle pachytene. The SC karyotypes of M. arvalis and the hybrids ♀ obscurus × ♂ arvalis consist of 22 synaptonemal complexes of autosomal bivalents and the axial elements of the synaptonemal complexes of the sex chromosomes X and Y. The SC karyotypes of M. rossiaemeridionalis and the hybrid M. rossiaemeridionalis × M. kermanensis consist of 26 synaptonemal complexes of autosomal bivalents and a sex bivalent; they differ only in the length of the Y chromosome axis (Y chromosome in the hybrid was inherited from M. kermanensis). Asynaptic configurations of the autosomal SCs were not observed in the hybrids. The SC axial elements of the X and Y chromosomes in the parental forms and in the hybrids were located close to each other throughout pachytene, but they did not form a synaptic region. The normal synapsis in sterile hybrids (M. rossiaemeridionalis × M. kermanensis) and the behavior of the sex chromosomes in meiosis in fertile and sterile hybrids are discussed in the context of specific features of meiosis and reproductive isolation.     

New data on the evolution of the Cretan spiny mouse,Acomys minous (Rodentia: Murinae), shed light on the phylogenetic relationships in the cahirinus group

The karyotype of the Cretan spiny mouse Acomys minous was examined with chromosome banding techniques in 53 individuals from 12 localities of Crete, aiming to gain a more detailed knowledge on the chromosomal constitution and variability of its natural populations. We found that it consists of three Robertsonian (Rb) populations with 2n = 38, 2n = 40 and 2n = 42, respectively, the last one being reported for the first time, and with stable fundamental number (FNa = 66, FN = 68). The G‐banding pattern proves that the Rb populations are closely linked phylogenetically by the many common Rb fusions and the lack of monobrachial homologies. In addition, they appear to freely mate at their contact areas, producing viable and fertile hybrids. No other type of chromosomal rearrangement appears to have played part in the chromosomal evolution of this species, at least in the recent past, as indicated also by the study of the telomeric sequences. Heterochromatin appears to be restricted to the pericentromeric position of all acrocentric and most biarmed autosomes, as well as of the X chromosome, whereas the Y chromosome is uniformly, yet faintly heterochromatic. Chromosome banding comparison of the karyotypes in A. minous with those of the other species in the cahirinus group (i.e. Acomys cahirinus, Acomys cilicicus, and Acomys nesiotes) proves their very close phylogenetic relationship, further reinforced by the study of the cytochrome b sequences, and that A. minous possesses the ancestral karyotype of the group. It is suggested that at least two of the karyotypes that characterize A. minous today, pre‐existed in North Africa before it colonized Crete and that the specific status of the four members in the cahirinus group may need to be revisited. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 498–509.     

Effects of climate and local aridity on the latitudinal and habitat distribution of Arvicanthis niloticus and Arvicanthis ansorgei (Rodentia, Murinae) in Mali

Introduction The genus Arvicanthis (Lesson 1842) (Rodentia: Murinae), usually referred to as the unstriped grass rat, is mainly distributed in savanna and grassland habitats of Sub-Saharan Africa. Among the four chromosomal forms of Arvicanthis recently differentiated in Western and Central Africa, the one with a diploid chromosomal number (2n) of 62 and an autosomal fundamental number (NFa) of 62 or 64 is ascribed to Arvicanthis niloticus (Demarest 1822), while the one with 2n = 62 and a NFa between 74 and 76 is referred to A. ansorgei (Thomas 1910). Despite the broad area of sympatry recently uncovered along the inner delta of the Niger river in Mali [details in Volobouev et al. (2002) Cytogenetics and Genome Research, 96, 250–260], the distribution of the two species is largely parapatric and follows the latitudinal patterns of the West-African biogeographical domains, which are related to the latitudinal patterns of annual rainfall in this region. Here, we analyse the suggestion that the two species show specific adaptations to differences in climate aridity. Methods Karyologically screened animals were sampled in 19 localities in seasonally flooded regions located along the ‘Niger’ river in Mali and extending from 1100 to 200 mm of mean annual rainfall. The analysis of trapping success (TS) data allowed us to investigate the respective effects of climate (i.e. annual rainfall) and local (i.e. duration of the green herbaceous vegetation) aridity on the latitudinal and habitat distribution of the two species. Conclusions The broad zone of sympatry was found to correspond to a northward expansion of the recognized distribution area of A. ansorgei. TS values indicated that the two species responded very differently to climatic and local conditions of aridity. Arvicanthis ansorgei decreased in TS as regional conditions became more arid; a similar trend was also observed within regions where habitat occupancy decreased with local aridity. The higher TS observed in the most humid habitat relative to the others persisted throughout the latitudinal rainfall gradient. In contrast, TS of A. niloticus increased with latitudinal aridity. This species was present in more arid habitats than A. ansorgei from 1000 mm down to 400 mm of mean annual rainfall where a shift to the most humid habitat occurred. These opposite trends in TS distribution between species suggest that A. ansorgei is less adapted than A. niloticus to arid environments at both a regional and habitat level; thus, A. ansorgei would be able to invade dry regions only along the extensive floodplains bordering the inner delta of the ‘Niger’ river. Several biological traits that may be involved in limiting the southward distribution of A. niloticus are discussed.     

The banded karyotype ofCercopithecus mitis maesi compared with the karyotypes ofC. albogularis samango andC. nictitans stampflii

The karyotypes ofCercopithecus alcogularis andC. mitis, both with 72 chromosomes, are similar but differ in a numer of rearrangements.C. nicitans (2n=70) andC. mitis karyotypes, even though differing in diploid number, appear to be closely related to each other because of several banding features and especially because they may be linked by a derived complex inversion polymorphism. The results show that chromosomal inversion variants can survive speciation. These results do not support recent chromosomal phylogenetic interpretations which were based on the finding of a diploid number of 2n=70 forC. mitis. The results described here emphasize the use of chromosomal characters in the study of the phylogeny and taxonomy ofCercopithecus.     

Comparative cytogenetics of six Indo‐Pacific moray eels (Anguilliformes: Muraenidae) by chromosomal banding and fluorescence in situ hybridization

A comparative cytogenetic analysis, using both conventional staining techniques and fluorescence in situ hybridization, of six Indo‐Pacific moray eels from three different genera (Gymnothorax fimbriatus, Gymnothorax flavimarginatus, Gymnothorax javanicus, Gymnothorax undulatus, Echidna nebulosa and Gymnomuraena zebra), was carried out to investigate the chromosomal differentiation in the family Muraenidae. Four species displayed a diploid chromosome number 2n = 42, which is common among the Muraenidae. Two other species, G. javanicus and G. flavimarginatus, were characterized by different chromosome numbers (2n = 40 and 2n = 36). For most species, a large amount of constitutive heterochromatin was detected in the chromosomes, with species‐specific C‐banding patterns that enabled pairing of the homologous chromosomes. In all species, the major ribosomal genes were localized in the guanine‐cytosine‐rich region of one chromosome pair, but in different chromosomal locations. The (TTAGGG)_n telomeric sequences were mapped onto chromosomal ends in all muraenid species studied. The comparison of the results derived from this study with those available in the literature confirms a substantial conservation of the diploid chromosome number in the Muraenidae and supports the hypothesis that rearrangements have occurred that have diversified their karyotypes. Furthermore, the finding of two species with different diploid chromosome numbers suggests that additional chromosomal rearrangements, such as Robertsonian fusions, have occurred in the karyotype evolution of the Muraenidae.     

Karyology of the genus Epidendrum (Orchidaceae: Laeliinae) with emphasis on subgenus Amphiglottium and chromosome number variability in Epidendrum secundum

Epidendrum is one of the largest Neotropical genera of Orchidaceae and comprises approximately 1500 species. Only 2.8% of these species have been studied cytologically, demonstrating chromosome numbers ranging from n = 12 in E. fulgens to n = 120 in E. cinnabarinum. The present work evaluated the evolution of the karyotypes of Epidendrum spp. based on data gathered from the literature and from analyses of the karyotypes of 16 Brazilian species (nine previously unpublished). The appearance of one karyotype with n = 12 with one larger chromosome pair in subgenus Amphiglottium appears to have occurred at the beginning of the divergence of this lineage, and x = 12 probably represents the basic number of this subgenus. Epidendrum secundum exhibits wide variation in chromosome numbers, with ten different cytotypes found in 22 Brazilian populations, seven of which were new counts: 2n = 30, 42, 50, 54, 56, 58 and 84. Most lineages of Epidendrum seem to have been secondarily derived from one ancestral stock with x = 20, as is seen in the majority of the present‐day representatives of the genus. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 172 , 329–344.     

Chromosomal characterization of three species of the genus Mastomys in Senegal

Mastomys rats are present as three distinct karyomorphs in Senegal. Specific assignations were accorded to each form on the basis of chromosomal, reproductive and distribution characteristics. Mastomys erythroleucus (2n = 38 , NFa = 52) is ecologically a generalist, M. huberti (2n = 32 , NFa = 44) is restricted to humid biotopes and M. cf natalensrs (2n = 32 , NFa = 54) is strictly commensal and found in Southeastern Senegal.     

Genetic and morphological variability in South American rodent Oecomys (Sigmodontinae, Rodentia): evidence for a complex of species

The rodent genus Oecomys (Sigmodontinae) comprises ~16 species that inhabit tropical and subtropical forests in Central America and South America. In this study specimens of Oecomys paricola Thomas, 1904 from Belém and Marajó island, northern Brazil, were investigated using cytogenetic, molecular and morphological analyses. Three karyotypes were found, two from Belém (2n = 68, fundamental number (FN) = 72 and 2n = 70, FN = 76) and a third from Marajó island (2n = 70, FN = 72). No molecular or morphological differences were found between the individuals with differing cytotypes from Belém, but differences were evident between the individuals from Belém and Marajó island. Specimens from Belém city region may represent two cryptic species because two different karyotypes are present in the absence of significant differences in morphology and molecular characteristics. The Marajó island and Belém populations may represent distinct species that have been separated for some time, and are in the process of morphological and molecular differentiation as a consequence of reproductive isolation at the geographic and chromosomal levels. Thus, the results suggest that O. paricola may be a complex of species.     

Cytogenetics, geographical distribution, and pollen fertility of diploid and tetraploid cytotypes of Santolina pectinata Lag. (Asteraceae: Anthemideae)

A cytogenetic study of 62 populations of Santolina pectinata in Spain shows the existence of two ploidy levels. The diploid cytotypes with 2 n  = 18 occupy the eastern Betic mountains, and the tetraploid cytotypes with 2 n  = 36 are located on the spurs of the Iberian System. The former show a much wider ecological spectrum than the latter. Mixed cytotypes were observed in two diploid populations, with one tetraploid in each, showing different karyotypes. Three trisomic individuals were detected, one in a diploid population and the other two in a tetraploid population. Also, three hypotetraploid individuals were detected in a tetraploid population. Polyploidy is shown to be spontaneous and recurrent, promoting partial sterility in the pollen. Structural chromosomal changes, principally translocations, and local speciation through autopolyploidy are the principal factors in the evolution and diversification of this species.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 657–667.     

Cytogenetic studies in the speciesCercopithecus pogonias (Bennet 1833) andCercopithecus nictitans (Linnaeus 1966)

We describe the banding patterns of the chromosomes of Cercopithecus pogonias(2n = 72) and Cercopithecus nictitans nictitans(2n = 70), the two species which exhibit the highest diploid numbers among the Cercopithecidae, using G-banding, C-banding, and nucleolar organizing region (NOR)-staining techniques. The karyotypes of these two species show a large number of morphological homologies, but several chromosome pairs cannot be matched. It is suggested that translocations and insertions may have been important in the chromosomal evolution of this group.     

KARYOTYPIC VARIATION OF EASTERN NORTH AMERICAN CLAYTONIA CHEMICAL RACES

Considerable karyotypic differentiation has occurred within the group of taxa comprising the eastern North American members of the genus Claytonia. Patterns of karyotypic differentiation are congruent with evolutionary groupings based on flavonoid chemistry, particularly at the diploid level. The 2n = 16 diploid chemotype found in both C. caroliniana and C. virginica possesses a karyotype composed entirely of metacentric chromosomes, while acrocentric chromosomes predominate in the karyotypes of the 2n = 12 and 2n = 14 diploid chemotypes of C. virginica. The 2n = 16 diploid also has a karyotype significantly larger than those of the other diploid cytotypes. Polyploid karyotypes of both species show varying degrees of divergence from their presumed diploid progenitors.     

CYTOGENETIC ANALYSIS OF CHROMOSOMAL INTERMEDIATES FROM A HYBRID ZONE BETWEEN TWO CHROMOSOME RACES OF THE SCELOPORUS GRAMMICUS COMPLEX (SAURIA,PHRYNOSOMATIDAE)

Underdominance for chromosomal rearrangements is the central assumption of several models of chromosomally based speciation including the cascade model, proposed for the Sceloporus grammicus complex. Several cytotypes of the S. grammicus complex hybridize at localities in central México. A hybrid zone between two of the most chromosomally divergent races (= cytotypes) of S. grammicus (F5, 2n = 34 and FM2, 2n = 44–46) was examined to assess the meiotic effects of heterozygosity at multiple chromosomes. Meiosis was examined in males heterozygous for “simple” Robertsonian fissions at chromosomes 1, 3, 4, and 6 and/or a pericentric inversion at chromosome 4. Analysis of synaptonemal complexes and chromosomal configurations at diakinesis showed trivalent formation in fission heterozygotes and heterosynapsis (lack of reverse-loop formation) in an inversion heterozygote. Analysis of metaphase II configurations revealed primarily balanced segregation and low levels of nondisjunction regardless of chromosomal background. The lack of underdominance associated with “simple” fission heterozygosity in this narrow hybrid zone contradicts the key premise of most chromosomally based models of speciation.     

Comparative chromosome painting in hummingbirds (Trochilidae)

Hummingbirds (Trochilidae) are one of the most enigmatic avian groups, and also among the most diverse, with approximately 360 recognized species in 106 genera, of which 43 are monotypic. This fact has generated considerable interest in the evolutionary biology of the hummingbirds, which is reflected in a number of DNA-based studies. However, only a few of them explored chromosomal data. Given this, the present study provides an analysis of the karyotypes of three species of Neotropical hummingbirds, Anthracothorax nigricollis (ANI), Campylopterus largipennis (CLA), and Hylocharis chrysura (HCH), in order to analyze the chromosomal processes associated with the evolution of the Trochilidae. The diploid number of ANI is 2n=80 chromosomes, while CLA and HCH have identical karyotypes, with 2n=78. Chromosome painting with Gallus gallus probes (GGA1-12) shows that the hummingbirds have a karyotype close to the proposed ancestral bird karyotype. Despite this, an informative rearrangement was detected: an in-tandem fusion between GGA7 and GGA9 found in CLA and HCH, but absent in ANI. A comparative analysis with the tree of life of the hummingbirds indicated that this fusion must have arisen following the divergence of a number of hummingbird species.     

A pericentric-inversion polymorphism and s ZZ/ZW sex-chromosome system in Varanus acanthurus Boulenger analyzed by G- and C-banding and Ag staining

A chromosomal analysis of the monitor Varanus acanthurus Boulenger has been made using G- and C-banding and silver-staining techniques. This species has two cytotypes, one of which has a pericentric-inversion polymorphism, whereas the other is chromosomally monomorphic. A ZZ/ZW sex-chromosome system is also present in both cytotypes of this species. The banding patterns of these mechanisms are described and their evolution is discussed.     

Phylogenomics of several deer species revealed by comparative chromosome painting with Chinese muntjac paints

A set of Chinese muntjac (Muntiacus reevesi) chromosome-specific paints has been hybridized onto the metaphases of sika deer (Cervus nippon, CNI, 2n = 66), red deer (Cervus elaphus, CEL, 2n = 62) and tufted deer (Elaphodus cephalophus, ECE, 2n = 47). Thirty-three homologous autosomal segments were detected in genomes of sika deer and red deer, while 31 autosomal homologous segments were delineated in genome of tufted deer. The Chinese muntjac chromosome X probe painted to the whole X chromosome, and the chromosome Y probe gave signals on the Y chromosome as well as distal region of the X chromosome of each species. Our results confirmed that exclusive Robertsonian translocations have contributed to the karyotypic evolution of sika deer and red deer. In addition to Robertsonian translocation, tandem fusions have played a more important role in the karyotypic evolution of tufted deer. Different types of chromosomal rearrangements have led to great differences in the genome organization between cervinae and muntiacinae species. Our analysis testified that six chromosomal fissions in the proposed 2n = 58 ancestral pecoran karyotype led to the formation of 2n = 70 ancestral cervid karyotype and the deer karyotypes is more derived compare with those of bovid species. Combining previous cytogenetic and molecular systematic studies, we analyzed the genome phylogeny for 11 cervid species.     

CHROMOSOMAL EVOLUTION IN RHOGEESSA (CHIROPTERA: VESPERTILIONIDAE): POSSIBLE SPECIATION BY CENTRIC FUSIONS

Within the Rhogeessa tumida-parvula complex, there are seven cytotypes involving diploid numbers of 30, 32, 34, 42, 44, and 52. Based on G-band analysis, the 30, 32, 34, and 44 forms differ from each other by centric fusions (13 different fusions were identified). Two 2n = 32 samples (one from Belize and one from Nicaragua) having essentially identical standard karyotypes differed from each other by eight fusion events. Cytotypes are allozymically distinct; however, other studies indicate that the cytotypes are morphologically very similar if not indistinguishable (LaVal, 1973; Baker, 1984). G-band chromosomal data are best interpreted as indicating that, within this complex, several species exist which should be maintained by a post-mating isolating mechanism resulting from meiotic problems in F₁ individuals. Mus musculus (Capanna et al., 1977; Capanna, 1982; White, 1978) and the Rhogeessa tumida-parvula complex are unusual among mammalian species thus far studied in their pattern of chromosomal variation and presumptive mode of speciation. Strong evidence exists suggesting that in both groups populations differing by multiple centric fusions are biological species. It appears that the population and reproductive biology of Mus and Rhogeessa are quite different and any model that attempts to explain the mode of speciation in these two diverse taxa, must be compatible with their different biological characteristics.     

Does <Emphasis Type="Italic">Alexandromys evoronensis</Emphasis> Inhabit the Northeastern Part of Verkhnezeiskaya Plain?

Gray voles of the “maximowiczii” group of the genus Alexandromys were found in the Argi River of the Amur region (northeastern part of Verkhnezeiskaya Plain). Analysis of mtDNA showed its similarity to A. evoronensis. The karyotype was 2n = 36, and NFa = 51–52. The karyotypes of these individuals did not contain the marker chromosome typical for Alexandromys maximowiczii.