Isozyme Variation within and among Australian Populations of Emex spinosa (L.) Campd.

Маршалл, .; Pw, Weiss

doi:10.1071/bi9820327

Cited by 17 publications

(9 citation statements)

References 10 publications

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“…In contrast, some colonizing allopolyploid plant species with low levels ofallozymic variability maintain considerable genetic variation and biochemical diversity as a result of fixed heterozygosity (Roose and Gottlieb, 1976). For instance, fixed heterozygosity, as indicated by a nonsegregating "heterozygous" banding pattern, was observed in the widespread allopolyploid colonizers Avena fatua and A. barbata (Marshall and Allard, 1970), Hordeum jubatum (Babbel and Wain, 1977), and Hordeum murinum (Giles, 1984).…”

Section: Discussionmentioning

confidence: 99%

“…Other aspects of the genetic structure of B. tectorum in North America contrast with results for other predominantly selfing introduced plant species. Both A. fatua and A. barbata (Marshall and Jain, 1969;Marshall and Allard, 1970;Singh and Jain, 1971;Clegg and Allard, 1972;Jain and Rai, 1974) possess considerable intrapopulation genetic variation in California (% P = 31. 9 and 26.1, respectively).…”

Section: ) Striga Asiaticamentioning

confidence: 99%

“…Allard (1965) and Jain (1976) indicate that occasional outcrossing events are sufficient to maintain genetic variability within populations of predominantly selfing species. Outcrossing rates for the A vena species in their introduced range vary from 2% to 5% (Marshall and Allard, 1970) to a high of 10% or more (Allard, 1965). Because no heterozygous individuals were detected in our analysis, the outcrossing rate among B. tectorum populations in North America is 0.0%.…”

Section: ) Striga Asiaticamentioning

confidence: 99%

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Genetic Variation in Bromus tectorum (Poaceae): Population Differentiation in Its North American Range

Novak¹,

Soltis²

1991

American Journal of Botany

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Allelic variation in seedlings from 60 North American populations of the alien annual grass Bromus tectorum was determined at 25 loci using starch gel electrophoresis. Populations were collected from four regions; east of the Rocky Mountains, Nevada and California, the Intermountain West, and British Columbia. Compared to other diploid seed plants, genetic variation within these populations of B. tectorum is low: 4.60% of loci are polymorphic per population, with an average of 1.05 alleles per locus and a mean expected heterozygosity of 0.012. Although 2,141 individuals were analyzed, no heterozygous individuals were detected, and consequently, mean observed heterozygosity is 0.000. Extensive deviations from Hardy‐Weinberg expectations were observed at every polymorphic locus due to heterozygote deficiencies. The mean genetic identity (Nei's I) between population pairs was 0.980 and indicates a high level of overall genetic similarity among populations. The among‐population component of the total gene diversity is high (GST = 0.478), indicating substantial genetic differentiation among populations. These results are consistent with previous reports for highly self‐pollinating plants of low genetic variation and substantial genetic differentiation among populations. Despite the lack of genetic variation as measured by enzyme electrophoresis, this weedy grass has become exceedingly abundant in a diverse array of arid environments throughout much of western North America, perhaps due to phenotypic plasticity.

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Section: Discussionmentioning

confidence: 99%

Section: ) Striga Asiaticamentioning

confidence: 99%

Section: ) Striga Asiaticamentioning

confidence: 99%

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Genetic Variation in Bromus tectorum (Poaceae): Population Differentiation in Its North American Range

Novak¹,

Soltis²

1991

American Journal of Botany

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“…The genetic consequences of founder events have been documented for populations known to have originated in historical times by long-distance dispersal ofrelatively few individuals. These populations have decreased levels ofgenetic variation, caused by the loss ofalleles following long-distance dispersal (Schwaegerle and Schaal, 1979;Marshall and Weiss, 1982;Cleggand Brown, 1983;Levin, 1984). This is also illustrated by several populations ofthe Hawaiian Madiinae on younger islands that have lost alleles present in polymorphic populations on older islands (e.g., D. laxa [Tpi-l and Tpi-2], D. linearis served in island ecosystems.…”

Section: Genetic Variation In Island Taxamentioning

confidence: 99%

Adaptive Radiation and Genetic Differentiation in the Hawaiian Silversword Alliance (Compositae: Madiinae)

1988

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Abstract. -The Hawaiian silversword alliance consists of the three genera Dubautia, Argyroxiphium, and Wilkesia, and is a classic example ofadaptive radiation in an insular setting. Genetic variation and interspecific genetic differentiation based on ten enzyme loci are described for Dubautia and Wilkesia. Genetic identities among species span the range of values expected from interpopulation comparisons within a single species (l = 0.90-1.00) to those typical of interspecific comparisons (1 = 0.67). Genetic-identity values correspond to biogeographic distribution and morphological distinctiveness, supporting a correlation of increasing genetic distance associated with the time of separation among lineages. It may be inferred that the high genetic identities observed within the Hawaiian Madiinae and other island plant groups are due to limited time spans available for taxa to accumulate new genetic variation through mutation. It appears that species may remain genetically similar (l > 0.90) even after time spans on the order of magnitude of 1,000,000 years.

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“…The presence of monomorphic populations or subpopulations in the sites on roadsides suggests that this is what has happened. Colonizing populations of some other species have been shown to be very limited genetically (Schwaegerle & Schaal, 1979;Marshall & Weiss, 1982), though this is not always true and must depend on the breeding system, and other factors Wain & Martins, 1979;Brown & Marshall, 1981).…”

Section: Roadside and Sand Dune ~O~u~a T I~n Smentioning

confidence: 99%

Allele frequencies, genetic relationships and heterozygosity in Polygala vulgaris populations from contrasting habitats in southern Britain

Lack

Kay

1988

Biological Journal of the Linnean Society

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Poolygala uulgaris is a widespread perennial plant species of basic to neutral grassland throughoutBritain. It is variable in flower colour and some vegetative characters in most populations. Gene flow is restricted in all populations since the plants are normally self-pollinating (up to 200/;;, outcrossing, calculated from figures of heterozygosity) and seeds are normally dispersed only up to 2 m from the parent plant. Examination of several enzyme systems, using starch gel electrophoresis, showed that all enzyme loci appeared to have been duplicated, probably owing to the fact that P. vulgaris is a tctraploid in a genus which has primarily diploid members in Europe.Polymorphisms were found at both of the duplicated loci in four enzyme systems and at one locus in each of two further systems.Fifty-one populations from a diversity of habitats were sampled in southern Britain. In most populations from the typical habitat of lowland calcareous grassland, polymorphisms occurred at five or more loci, and the alleles were distributed throughout the populations. In all these sites there was a diversity of microhabitat and, in one area, marked differences in microhabitat distribution between different cnzymc rnorphs. It is likely that differential selection is an important factor in the maintenance of the polymorphisms in all these areas. These populations were divided, genetically, into two main groups, those from the Gower peninsula, South Wales, and those from the English chalk. Within each group the populations were quite closely related genetically, though some large differences at particular loci occurred even between adjacent populations. Diffuse clumps of alleles occurred within all these populations, and it is likely that limited gene flow has affected the genetic structure of the populations, particularly since cycles of local extinction and recolonization are likely to be recurring. 'L'he genetic structure of each population, at the allozyme loci examined, is likely to be the consequence of a balance between differential selection and restricted gene flow. The number of heterozygotrs was small, though higher than expected from an analysis of experiinental progeny, suggesting a hcterozygotc advantage. Few strong multilocus associations were found despite the predominance of self-pollination.In the populations from sand dunes, roadsides, submontarie grassland and water meadows there was, in general, much lcss polymorphism than in those from lowland calcareous grassland and some populations were entirely monomorphic; in most others there wrre large, entirely monomorphic groups of plants. Genetic distances between these populations were variable, even within one habitat and area, and they did not appear to show any particular relationship to each other. It is likely that thr gcnetic structure of these populations, at the loci studied, has arisen largely through chance colonizations and genetic drift. I19 0024-4066/88/060119 +29 $03.00/0 0 1988 The Linnean Society of London 120 A. J. LACK AND Q. 0. N. KAY KEY WORDS...

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Isozyme Variation within and among Australian Populations of Emex spinosa (L.) Campd.

Cited by 17 publications

References 10 publications

Genetic Variation in Bromus tectorum (Poaceae): Population Differentiation in Its North American Range

Genetic Variation in Bromus tectorum (Poaceae): Population Differentiation in Its North American Range

Adaptive Radiation and Genetic Differentiation in the Hawaiian Silversword Alliance (Compositae: Madiinae)

Allele frequencies, genetic relationships and heterozygosity in Polygala vulgaris populations from contrasting habitats in southern Britain

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