CYTOLOGICAL STUDIES IN SAMBUCUS

1968 ◽  
Vol 10 (2) ◽  
pp. 235-247 ◽  
Author(s):  
Robert W. Hounsell
Keyword(s):  
Chromosome Number ◽  
Environmental Conditions ◽  
Chromosome Races ◽  
Somatic Number ◽  
Gamete Production

Karyotypes were determined for six taxa in the genus Sambucus, family Caprifoliaceae. Chromosome number determinations of 2n = 36 agreed with previous findings for S. canadensis and S. nigra of section Eusambucus and for S. ebulus of section Ebulus. Three taxa from the section Botryosambucus were found to have diploid numbers of 38: S. sieboidiana, S. racemosa var. arborescens and S. racemosa var. pubens. A Quebec population of the latter variety had a somatic number of 42. It is suggested that chromosome races in var. pubens came about through aneuploid gamete production in 2n = 36 ancestors and that their persistence may be related to their newly acquired ability to adapt to varying environmental conditions in the formerly glaciated areas.Differences in karotype within sections were small while between sections they were a little greater and rested mainly on variation in chromosome number, presence of satellites and number of telocentrics.

The cytology of Brachycome. I. The subgenus Eubrachycome: A general survey

1970 ◽  
Vol 18 (1) ◽  
pp. 99 ◽  
Author(s):  
S Smith-White ◽  
CR Carter ◽  
HM Stace
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Base Number ◽  
Undescribed Species ◽  
General Survey ◽  
Chromosome Races ◽  
Chromosomal Change ◽  
Cytological Data ◽  
Wide Range ◽  
Annual Habit

Chromosome number determinations and cytological observations are reported for 37 recognized taxonomic species and varieties, and for a number of undescribed species and chromosome races in Eubrachycome. Additionally, chromosome numbers are reported for six species of Metabrachycome and two species of related genera. A wide range of numbers has been found. It is inferred that x = 9 is the primitive base number in the group. Eubrachycome has used various modes of chromosomal change, including polyploidy, amphidiploidy, decrease in base number, and the establishment of B. chromosomes. The present taxonomy of the group requires revision, taking into account cytological data. Primitive Eubrachycome was probably a mesic perennial. The evolution of desert species has involved reduction in chromosome number and the adoption of the annual habit, but other methods of desert adaptation have been available. Many species are chromosomally unstable, and may have been subject to catastrophic selection.

Taxonomy of Rock Wallabies, Petrogale (Marsupialia, Macropodidae) .1. A Revision of the Eastern Petrogale With the Description of 3 New Species

1992 ◽  
Vol 40 (6) ◽  
pp. 605 ◽  
Author(s):  
MDB Eldridge ◽  
RL Close
Keyword(s):  
New Species ◽  
Gene Flow ◽  
Chromosome Number ◽  
Cryptic Species ◽  
Genetic Identity ◽  
Separate Species ◽  
Species Definition ◽  
Chromosome Races ◽  
Primary Means ◽  
Cape York

The taxonomy of Petrogale has been in a state of flux for many years. The eight chromosome races of the eastern Petrogale radiation are currently placed in four species. However, several of these 'species' contain chromosomally unrelated taxa. In this paper a species definition for Petrogale is proposed that allows for some gene flow between species but requires a species to maintain a substantial and distinct genetic identity. When this definition was applied to the eastern Petrogale eight 'good' species were identified. Thus we now consider the eastern Petrogale complex to consist of P. penicillata, P. herberti (formerly P. penicillata herberti), P. inornata, P. assimilis, P. sharmani, sp. nov. (formerly the Mt Claro race), P. mareeba, sp. nov. (formerly the Mareeba race), P. godmani and P. coenensis, sp. nov. (formerly the Cape York race). Several of these taxa are cryptic species and the primary means of identification used was chromosome number and morphology. However, genic data were useful in establishing whether each taxon should be regarded as a separate species.

CYTOTAXONOMIC OBSERVATIONS IN THE GENUS AESCHYNANTHUS(GESNERIACEAE)

2001 ◽  
Vol 58 (1) ◽  
pp. 31-43 ◽  
Author(s):  
M. H. RASHID ◽  
K. JONG ◽  
M. MENDUM
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Seed Morphology ◽  
Basic Number ◽  
Somatic Number ◽  
Basic Numbers

This study is a contribution to the further understanding of cytological patterns in Aeschynanthus(Gesneriacaeae). Chromosome numbers are reported for 12 species from six sections; nine of these are new counts. Two basic numbers, x=16 and x=15, are generally encountered. Aeschynanthus gracilis proved to be of exceptional interest, as its rare somatic number, 2n=28, confirms the occurrence of a third basic number, x=14, in the genus. Variation in chromosome number in relation to seed morphology is examined.

The taxonomy and distribution in eastern Canada of Polygonum arenastrum (4x = 40) and P. monspeliense (6x = 60), introduced members of the P. aviculare complex

1981 ◽  
Vol 59 (12) ◽  
pp. 2744-2751 ◽  
Author(s):  
J. McNeill
Keyword(s):  
Chromosome Number ◽  
Single Species ◽  
Sensu Stricto ◽  
The Other ◽  
Eastern Canada ◽  
Uniform Size ◽  
Chromosome Races ◽  
Morphological Studies ◽  
Distinguishing Features ◽  
Polygonum Arenastrum

The introduced nonmaritime knotweeds have generally been regarded in North America as comprising a single species called P. aviculare L. In recent years cytological and morphological studies have suggested that at least two chromosome races are present and that certain morphological features are correlated with chromosome number. There have been, however, discrepancies in the reports of the distribution and relative abundance of the two races. Studies of the morphology and cytology of introduced knotweeds in eastern Canada confirm the existence of two groups that are recognizable at species rank, and establish that the most common knotweeds in open habitats, e. g., along roadsides and sidewalks, are tetraploid plants distinguishable from their hexaploid relatives by the relatively uniform size of their leaves, the short and narrow free portion of the perianth segments, and by one side of the fruit being very much narrower than the other two. These plants are referable to P. arenastrum Boreau. This species is compared with the heterophyllous hexaploid, usually called P. aviculare sensu stricto, or, if that is considered a nomen ambiguum, P. monspeliense Pers. A table of distinguishing features, illustrations of the two species, and maps of their distribution in eastern Canada are provided.

CYTOGENETIC, ECOLOGIC AND MORPHOLOGIC STUDIES IN BRAZILIAN FORMS OF PASPALUM NOTATUM

1973 ◽  
Vol 15 (3) ◽  
pp. 523-531 ◽  
Author(s):  
M. Irene B. De Moraes Fernandes ◽  
I. L. Barreto ◽  
F. M. Salzano
Keyword(s):  
Chromosome Number ◽  
Meiotic Chromosome ◽  
The Other ◽  
Paspalum Notatum ◽  
Meiotic Behavior ◽  
Ecological Data ◽  
Somatic Number ◽  
The Difference ◽  
Different Strains ◽  
Fair Degree

The somatic number, meiotic behavior, morphology and ecology of five forms of Paspalum notatum are reported. All of them showed a chromosome number of 2n = 40. There is a fair degree of variation in the frequencies of meiotic chromosome configurations in different strains of a given form, but for four of the five we could characterize them as showing about 2-3 IV and 14-16 II. The type Capivari presents distinct differences in relation to all others, with about 1 IV and 18 II. The prevalence of I and III is very low (about 0.1) in all forms investigated. The morphological and ecological data, in a general way, confirm the difference between Capivari and the other taxons.

Variation in chromosome number in the Manuleae (Scrophulariaceae) and its cytotaxonomic implications

1993 ◽  
Vol 50 (3) ◽  
pp. 365-379
Author(s):  
K. Jong
Keyword(s):  
Chromosome Number ◽  
South African ◽  
Chromosome Numbers ◽  
Somatic Number ◽  
Basic Numbers

Chromosome numbers for 11 genera and 36 species in the predominantly South African tribe Manuleae (Scrophulariaceae) are presented, the majority being first reports. The basic numbers of the genera form a dysploid series, x = 6, 7, 8, 9. The somatic number of most of the species is diploid, ranging from 2n = 12 to 2n = 18; that of Jamesbrittenia, 2n = 24, is probably of polyploid derivation. The highest somatic number encountered in this survey is that in Camptoloma lyperiiflorum, with 2n = c.56, which, taken in conjunction with a published count of 2n = 28 for another species of Camptoloma, is octoploid based on x = 7. This is the only example, so far, of intrageneric polyploidy in the Manuleae. The somatic number in certain genera appears to be constant over some subgeneric divisions (e.g. Jamesbrittenia, 2n = 24), but variable in others (e.g. Sutera, 2n = 12, 14). The variation in chromosome number observed in this study parallels and corroborates the redefinition of generic boundaries proposed by O. M. Hilliard. One species of Selago (in the tribe Selagineae) was also included in this survey for cytological comparison with Tetraselago (Manuleae).

scholarly journals Genomic behavior of hybrid combinations between elephant grass and pearl millet

2011 ◽  
Vol 46 (7) ◽  
pp. 712-719 ◽  
Author(s):  
Fernando Ferreira Leão ◽  
Lisete Chamma Davide ◽  
José Marcello Salabert de Campos ◽  
Antonio Vander Pereira ◽  
Fernanda de Oliveira Bustamante
Keyword(s):  
Chromosome Number ◽  
Pearl Millet ◽  
Somatic Chromosome ◽  
Pennisetum Purpureum ◽  
Chromosomal Race ◽  
Elephant Grass ◽  
Chromosome Races ◽  
Number Variation ◽  
Chromosome Number Variation ◽  
High Level

The objective of this work was to evaluate the genomic behavior of hybrid combinations between elephant grass (Pennisetum purpureum) and pearl millet (P. glaucum). Tetraploid (AAA'B) and pentaploid (AA'A'BB) chromosome races resulting from the backcross of the hexaploid hybrid to its parents elephant grass (A'A'BB) and pearl millet (AA) were analyzed as to chromosome number and DNA content. Genotypes of elephant grass, millet, and triploid and hexaploid induced hybrids were compared. Pentaploid and tetraploid genomic combinations showed high level of mixoploidy, in discordance with the expected somatic chromosome set. The pentaploid chromosome number ranged from 20 to 34, and the tetraploid chromosome number from 16 to 28. Chromosome number variation was higher in pentaploid genomic combinations than in tetraploid, and mixoploidy was observed among hexaploids. Genomic combinations 4x and 5x are mixoploid, and the variation of chromosome number within chromosomal race 5x is greater than in 4x.

The distribution and cytology of the chromosome races of Themeda australis in southern Australia

1960 ◽  
Vol 8 (1) ◽  
pp. 58 ◽  
Author(s):  
DL Hayman
Keyword(s):  
Chromosome Number ◽  
Western Australia ◽  
Polyploid Complex ◽  
Clear Pattern ◽  
Cytological Evidence ◽  
Native Flora ◽  
Chromosome Races ◽  
Close Relationship ◽  
Eastern Highlands ◽  
Diploid Populations

Thermeda australis (R.Br.) Stapf is a polyploid complex based on n = 10, and diploid, triploid, tetraploid, pentaploid, and hexaploid individuals have been found. Over 98 per cent. of more than 800 individuals examined were either diploid or tetraploid. Some 300 populations, from localities on the Australian mainland below the Tropic of Capricorn, were characterized by their chromosome number and a very clear pattern of distribution was found. Diploid populations occur exclusively on the Eastern Highlands and slopes in southern Victoria and in Tasmania; elsewhere tetraploid populations occur across to Western Australia. Triploid, pentaploid, and hexaploid plants are found as individuals in populations of another chromosome number. The cytological evidence shows a very close relationship to exist between the constituent genomes of the polyploids. The significance of the distribution of the chromosome races, the effects of polyploidy, and the implications of this pattern for further studies on the native flora are discussed.

Chromosomal diversity in the Australian Phasmatodea

1972 ◽  
Vol 20 (4) ◽  
pp. 445 ◽  
Author(s):  
E Craddock
Keyword(s):  
Chromosome Number ◽  
Sex Chromosome ◽  
Australian Species ◽  
Chromosome Races ◽  
Karyotypic Diversity ◽  
Chromosomal Differentiation ◽  
History Of ◽  
Karyotypic Variation ◽  
Numerical Variation ◽  
Population Structure And Dynamics

A cytological survey of the Australian Phasmatodea, involving 24 species from the five major subfamilies present in Australia, has confirmed earlier indications of the karyotypic diversity of this Order of insects. Male diploid chromosome numbers range from 26 to 45, and XO and XY sex-chromosome mechanisms occur. Whilst being within the overall range of cytological variation already established for the Order, with respect to level of variability, the diversity shown by Australian species exceeds that of previous observations. Numerical variation is present within some species, as well as within subfamilies and genera. The five Australian species which show a geographic pattern of chromosomal differentiation are the first such examples known amongst phasmatids. Didymuria violescens, the most variable, has at least 10 chromosome races, a range in chromosome number from 26 to 39 (2n), and three forms of the sex-chromosome system. Ctenomovpha chronus has at least three chromosome races. It is suggested that the cytological and biological characteristics of this group of insects, including features of their population structure and dynamics, predispose phasmatids to high levels of variability for otherwise conservative chromosome characters. Newly arisen structural rearrangements have been fixed repeatedly in the evolutionary history of the Order. Many of these have resulted in a change in chromosome number; some few have been responsible for XY types of sex mechanism, by incorporation of autosomal material into the primitive XO system. In view of the amount of karyotypic variation present, cytological characters are effectively useless as indicators of broad phylogenetic relationships within the Phasmatodea. Only chromosome size shows some possible correlation with established interrelationships at the subfamily level. The incidence of intraspecific chromosomal differentiation, together with the usual concurrence of chromosomal differences with intrageneric species differences, further suggests that karyotypic differentiation at a racial level may be involved as a normal stage in the speciation pattern of many phasmatids.

An investigation of chromosome numbers in the genus Brachiaria (Poaceae: Paniceae) in relation to morphology and taxonomy

1987 ◽  
Vol 65 (11) ◽  
pp. 2297-2309 ◽  
Author(s):  
G. P. Basappa ◽  
M. Muniyamma ◽  
C. C. Chinnappa
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Indian Subcontinent ◽  
Base Number ◽  
Chromosome Races ◽  
Morphological Studies

Determinations of chromosome number and morphological studies of 260 populations, belonging to 32 taxa, of the genus Brachiaria from the Indian subcontinent reveal that all sexually reproducing taxa have no chromosome races. Six agamic taxa, viz., B. brizantha var. brizantha (n = 27), B. brizantha var. ciliata (n = 18), B. decumbens (n = 18), B. hybrida (n = 27), B. mutica (n = 18), and B. setigera var. albistyla (n = 14), have consistently shown uniformity in chromosome numbers, based on x = 7, 8, and 9. Brachiaria setigera var. setigera, a genetically unstable apomict, is the only taxon that tends to have a heteroploid series (n = 16, 17, 18, 21, and 32). The population of B. setigera var. setigera with n = 17 is based on a secondary base number of x = 17. There are 6 diploids, 20 tetraploids, 5 hexaploids, and 3 octoploids in the genus. Aneuploidy and triploidy are characteristically absent in the genus, although their plausible existence in the B. setigera complex cannot be ruled out. In several species certain previously reported chromosome numbers that deviate from the present study are found to be the result of erroneous identifications or the result of taxonomically complex situations such as those found in B. brizantha, the B. distachya complex, and the B. ramosa complex.

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