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.

Cytogeography of the genus Eremophila

1971 ◽  
Vol 19 (3) ◽  
pp. 295 ◽  
Author(s):  
BA Barlow
Keyword(s):  
Western Australia ◽  
Frequent Occurrence ◽  
Cell Physiology ◽  
Genetic Isolation ◽  
Ploidy Levels ◽  
Chromosome Races ◽  
Geographical Expansion ◽  
Land Surfaces ◽  
Diploid Populations

Polyploidy is of relatively frequent occurrence in Eremophila (x = 18). In 27 species examined karyologically from four or more localities, 13 were uniformly diploid, one was uniformly tetraploid, and 13 showed infraspecific polyploidy, diploid and/or tetraploid and/or hexaploid races being recorded. In most cases the chromosome races within a species have a pattern of geographical replacement. It is suggested that the formation of polyploid biotypes may lead to geographical expansion into new territory. Polyploidy may be effective in fixing adaptive recombinants near the margins of the diploid area, or may have direct adaptive effects on cell physiology. The ancient land surfaces of Western Australia appear to be a reservoir for relic diploid populations. In a few cases closely related entities which occur sympatrically have been found to be at different ploidy levels in the area of overlap. It is suggested that polyploidy in Eremophila has also facilitated the establishment of genetic isolation between differentiating biotypes.

Polyploidy in Sporobolus virginicus (L.) Kunth

1979 ◽  
Vol 27 (4) ◽  
pp. 429 ◽  
Author(s):  
AR Smith-White
Keyword(s):  
Salt Marsh ◽  
Chromosome Number ◽  
Meiotic Division ◽  
Distribution Patterns ◽  
Meiotic Behaviour ◽  
Polyploid Complex ◽  
South Eastern ◽  
Sporobolus Virginicus ◽  
Eastern Australia ◽  
Tetraploid Cytotypes

Chromosome number and meiotic behaviour was examined in Sporobolus virginicus Kunth from south-eastern Australia. Var. minor Bail. forms a polyploid complex with diploid (2n = 20), triploid and tetraploid cytotypes. Meiosis in tetraploid plants of this variety is substantially normal, which indicates an alloploid origin. Var. virginicus, which has been found only in the tetraploid state, has irregular meiotic division, which suggests autoploidy. Most cytotypes were collected from sandy and well-drained situations along the coast. However, tetraploid var. minor plants were generally found in poorly aerated salt marsh swamps. This apparent edaphic adaption of tetraploid cytotypes may be important in explaining distribution patterns.

The taxonomy of the Viola nuttallii complex

1987 ◽  
Vol 65 (12) ◽  
pp. 2562-2580 ◽  
Author(s):  
D. M. Fabijan ◽  
J. G. Packer ◽  
K. E. Denford
Keyword(s):  
Chromosome Number ◽  
Phylogenetic Relationships ◽  
Basic Chromosome Number ◽  
Chemical Diversity ◽  
Statistical Analyses ◽  
Polyploid Complex ◽  
Basic Chromosome ◽  
Wide Range ◽  
Flavonoid Chemistry

Morphological, cytological, and phytochemical data were incorporated into numerical and statistical analyses to produce a revision of Viola subsection Nuttallianae. A basic chromosome number of x = 6 was confirmed for this polyploid complex, which includes five species: V. vallicola, 2n = 12; V. tomentosa, 2n = 12; V. nuttallii, 2n = 24; V. praemorsa, 2n = 36 and 48; and V. bakeri, 2n = 48. Departures from recent authors include the recognition of two varieties in V. vallicola, vallicola and major (Hook.) Fabijan, based on flavonoid chemistry and distribution. Viola praemorsa is envisaged as embracing a wide range of morphological and chemical diversity, the extremes of which are recognized as the subspecies praemorsa, flavovirens (Pollard) Fabijan, and linguaefolia. In the absence of significant morphological or distributional differences between the V. linguaefolia and V. praemorsa subspecies major (sensu Baker and Clausen) and oregona, these three previously recognized taxa are included in subspecies linguaefolia. Based on cytological, morphological, and flavonoid data presented here, possible phylogenetic relationships are discussed.

The mitotic chromosomes of Marsupials and their bearing on taxonomy and phylogeny.

1961 ◽  
Vol 9 (1) ◽  
pp. 38 ◽  
Author(s):  
GB Sharman
Keyword(s):  
Chromosome Number ◽  
Chromosome Numbers ◽  
Parallel Evolution ◽  
Mitotic Chromosomes ◽  
Cytological Evidence ◽  
Separate Genus ◽  
Y Chromosomes ◽  
Related Group ◽  
Living Species ◽  
Potorous Tridactylus

Chromosome numbers of marsupials vary between 2n = 11 B 10 @ and 2n =24. Most species have 14 or 22 chromosomes. There is no evidence that polyploidy has occurred in marsupial evolution. The Dasyuridae have 12 metacentric autosomes, a small metacentric X-chromosome and a very small Y-chromosome (20% of living species have been studied) and the chromosomes of Myrmecobius fasciatus are typically like those of other Dasyuridae. The Peramelidae (30% of species have been studied) have chromosomes like the Dasyuridae except that X- and Y-chromosomes are much larger. The occurrence of similar chromosome numbers in Dasyuridae and Peramelidae is not necessarily evidence of affinity. The chromosomes of the Phascolomidae are similar in number and morphology to those of the Peramelidae and the resemblances are, almost certainly, due to parallel evolution. The chromosomes of Phascolarctos are unlike those of any of the Phalangeridae and this genus might be just as easily grouped with the Phascolomidae. The Phalangeridae have considerable chromosomal heterogeneity but less than 20% of species have been studied. Two species of Cercaertus have 12 metacentric autosomes and small sex chromosomes like all members of the Dasyuridae. This suggests that the primitive phalangers may have retained the chromosome number and morphology of possible dasyurid ancestors but the resemblances may be due to parallel evolution of similar chromosome number and morphology in separate groups. The chromosomes have been studied in more than 50% of Macropodinae. Cytological evidence suggests that Thylogale (3 species studied), Petrogale (2 species studied), and probably Lagorchestes (1 species studied), all with 22 chromosomes, are a related group. Onychogalea unguifer, with 20 chromosomes, may be derived from this group. There is no justification for the placing of Thylogale billardierii in the genus Protemnodon. Lagostrophus fasciatus has 2n = 24 and its placement in a monotypic genus is justified. Macropus major and all species of Protentnodon, except P. bicolor, are a related group with 16 chromosomes. M. robustus is possibly included in this group. M. rufus has 20 chromosomes and should perhaps be placed in the separate genus Megaleia. P. bicolor, with 11 chromosomes in the male and 10 in the female, differs from all other species of Protemnodon and this genus, as at present constituted, may be diphyletic. The relationships of P. bicolor are unknown. Setonix brachyurus has 22, mostly metacentric, chromosomes and its affinities are at present unknown. Three species of Bettongia (Potoroinae) have 22 chromosomes which are mostly metacentric. Hypsiprymnodon moschatus has 22 chromosomes which are mostly acrocentric. Both genera are very different cytologically from Potorous tridactylus.

Quantification of the susceptibility of the native flora of the South-West Botanical Province, Western Australia, to Phytophthora cinnamomi

2004 ◽  
Vol 52 (4) ◽  
pp. 435 ◽  
Author(s):  
B. L. Shearer ◽  
C. E. Crane ◽  
A. Cochrane
Keyword(s):  
Western Australia ◽  
National Park ◽  
Phytophthora Cinnamomi ◽  
Natural Environments ◽  
The South ◽  
Irreversible Damage ◽  
Eucalyptus Marginata ◽  
Native Flora ◽  
South West ◽  
Wide Range

This study compares, for the first time, variation in estimates of susceptibility of native flora to Phytophthora cinnamomi Rands among four databases and proposes an estimate of the proportion of the flora of the South-West Botanical Province of Western Australia that is susceptible to the pathogen. Estimates of the susceptibility of south-western native flora to P. cinnamomi infection were obtained from databases for Banksia woodland of the Swan Coastal Plain, jarrah (Eucalyptus marginata Donn. ex Smith) forest, the Stirling Range National Park and Rare and Threatened Flora of Western Australia. For the woodland, forest and national park databases, hosts were naturally infected in uncontrolled diverse natural environments. In contrast, threatened flora were artificially inoculated in a shadehouse environment. Considerable variation occurred within taxonomic units, making occurrence within family and genus poor predictors of species susceptibility. Identification of intra-specific resistance suggests that P. cinnamomi could be having a strong selection pressure on some threatened flora at infested sites and the populations could shift to more resistant types. Similar estimates of the proportion of species susceptible to P. cinnamomi among the databases from the wide range of environments suggests that a realistic estimate of species susceptibility to P. cinnamomi infection in the south-western region has been obtained. The mean of 40% susceptible and 14% highly susceptible equates to 2284 and 800 species of the 5710 described plant species in the South-West Botanical Province susceptible and highly susceptible to P. cinnamomi, respectively. Such estimates are important for determining the cost of disease to conservation values and for prioritising disease importance and research priorities. P. cinnamomi in south-western Australia is an unparalleled example of an introduced pathogen with a wide host range causing immense irreversible damage to unique, diverse but mainly susceptible plant communities.

The Antennaria frieseana (Asteraceae: Inuleae) polyploid complex: morphological variation in sexual and agamospermous taxa

1994 ◽  
Vol 72 (7) ◽  
pp. 1018-1026 ◽  
Author(s):  
Jerry G. Chmielewski
Keyword(s):  
Chromosome Number ◽  
Key Words ◽  
Reproductive Biology ◽  
Morphological Variation ◽  
Polyploid Complex ◽  
Corolla Length

The Antennaria frieseana (Trautv.) Ekman polyploid complex has been evaluated on numerous occasions without concensus to either the taxa that should be included or their proper ranks. The purpose of this phenetic study was to present a taxonomy for the polyploid complex that is not only independent of a knowledge of chromosome number and reproductive biology but that concurrently reflects morphological variation associated with each. The rank of subspecies (A. frieseana ssp. frieseana and A. frieseana ssp. alaskana (Malte) Hultén) was accepted as the most appropriate level of circumscription that satisfied the purpose of the phenetic study and was supported by the analysis. These subspecies differ with respect to the length of the involucre, inner phyllary length, pappus length, corolla length (the latter subspecies being typically smaller than the former), chromosome number, reproductive biology, and (in part) provenance. Antennaria frieseana ssp frieseana is an agamospermous polyploid, represented by pentaploid (2n = 70) and hexaploid (2n = 84) cytotypes. Antennaria frieseana ssp. alaskana is sexual, probably partially agamospermous (tetraploid cytotype), and either diploid (2n = 28) or tetraploid (2n = 56). Key words: Antennaria frieseana, morphological variation, apomicts, sexual, agamospermy.

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.

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.

Reproductive Isolation Between Isozyme Groups of Glycine tomentella (Leguminosae), and Spontaneous Doubling in Their Hybrids

1986 ◽  
Vol 34 (5) ◽  
pp. 523 ◽  
Author(s):  
MJ Doyle ◽  
JE Grant ◽  
AHD Brown
Keyword(s):  
Chromosome Number ◽  
Reproductive Isolation ◽  
Hybrid Sterility ◽  
Gene Pools ◽  
Single Chromosome ◽  
Glycine Tomentella ◽  
Hybrid Plants ◽  
Genomic Divergence ◽  
Close Relationship ◽  
Mother Cells

Previous studies of infraspecific isozyme variation in Glycine tornentella have recognised five tetraploid (TI, T2, ... T5) and seven diploid (Dl, D2, ... D7) subspecific groups. This report analyses the meiosis in pollen mother cells of 31 new tetraploid hybrids, 10 diploid hybrids and three diploid by tetraploid combinations. A close relationship, over the range of diversity, was observed between isozyme similarity of the parents of hybrids and chromosome pairing at meiosis. In general, hybrids between parents belonging to the same isozyme group were fertile whereas hybrids between groups were sterile. In the tetraploids, the fertility of interregional hybrids when the accessions belonged to the same group confirmed the widespread distribution of groups T1 and T4. Alternatively, the sterility of intraregional hybrids between groups showed that groups can coexist and remain as separate gene pools. Each isozyme group apparently had a single chromosome number (TI and T5 had 2n = 78; T2, T3 and T4 had 2n = 80). Some otherwise sterile hybrid plants produced rare progeny with elevated chromosome num- ber, probably from the functioning of unreduced male and female gametes. Considerable genomic divergence was apparent from the hybrids between diploid groups, comparable with that found between recognised Glycine species. Again isozyme groups had a characteristic chromosome number (Dl and D2 had 2n = 38, the remainder had 2n = 40). Thus reproductive isolation through reduced formation of bivalents at meiosis operated both between and within cytotypes (2n = 38, 40, 78, 80) of G. tornentella. The pattern of hybrid sterility was as predicted from the analysis of isozyme similarity, confirming the grouping as a meaningful classification within this diverse species.

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