Plant Population Genetics and Evolution

Hamrick, J. L.

doi:10.1002/j.1537-2197.1982.tb13421.x

Cited by 160 publications

(112 citation statements)

References 40 publications

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“…This absence of association was reported by Moura (2003b) in diversity studies applying ecogeographic descriptors. There are several factors that affect species variability distribution over their occurrence areas, including the form of reproduction, mating, migration, natural selection, genetic drift, genetic flow, (Hamrick, 1982). Therefore identifying the genotypic similarity in these geographically diverse accessions would require studies on molecular level.…”

Section: Resultsmentioning

confidence: 99%

Phenotypic variability among pumpkin accessions in the Brazilian semiarid

Borges¹,

Resende²,

Lima³

et al. 2011

Hortic. Bras.

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The aim of this study was to estimate the phenotypic divergence among fourteen pumpkins accessions of the cucurbits Germplasm Active Bank of Embrapa Semiárido, in order to support breeding program to these species. Nine morphoagronomic descriptors were analyzed by the principal components and by UPGMA techniques. In the analysis of principal components, the formation of three contrasting clusters was observed, each one composed of two accessions. There occurred also the formation of one core group composed of five accessions, being the accessions called 683 and 684 collected in Bahia and the other in Maranhão. The most divergent accessions were 620, 624 and 748. The variables of the greatest contribution to the genetic divergence were diameter, weight and average length of the fruit. In the UPGMA analysis, obtained from the symmetric matrices generated by the Mahalanobis distance for the nine descriptors, there was the formation of one core group, composed of ten accessions, whose similarity was 45.71%, with geographically divergent accessions presenting the greatest similarity. Three accessions were not clustered with others. The study identified phenotypic variability for the analyzed characters and the absence of relationship between place of collection and phenotypic diversity.

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Section: Resultsmentioning

confidence: 99%

Phenotypic variability among pumpkin accessions in the Brazilian semiarid

Borges¹,

Resende²,

Lima³

et al. 2011

Hortic. Bras.

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“…Gene flow plays a major role in shaping the spatial distribution of genes in a population. In plant populations, gene flow is mediated through both pollen and seed dispersal, and a prevailing view is that gene flow is quite restricted (Levin, 1981;Hamrick, 1982). Dispersal of pollen and/or seed usually follows a leptokurtotic distribution, with most dispersal occurring within a few metres of the parent plant (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, inbreeding populations are expected to exhibit genetic structure, existing as small clusters or patches of genetically related individuals (Hamrick et at., 1979). Until recently, however, there have been relatively few studies on microgeographic differentiation of populations for which the mating system is known (Hamrick, 1982), and so these predictions have only rarely been tested for plant populations (but see; Ennos, 1985;Soltis & Soltis, 1988;Abbott & Gomes, 1989), Indeed, some of the species studied do not appear to conform to this general view. Spatial structuring of genotypes has been observed in some apparently outcrossing species (Linhart et at., 1981;Silander, 1984;Wendel & Parks, 1985), while inbreed- ing species sometimes show spatial genetic patterns more consistent with panmictic expectations (Brown, 1979).…”

Section: Introductionmentioning

confidence: 99%

Population genetic structure of Banksia spinulosa

Carthew

1993

Heredity

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This study investigated the genetic structure of a population of the highly outcrossed perennial shrub, Banksia spinutosa. Three variable loci were detected; Pgm1, Adh1 and Pgi2. Some genetic differentiation was detected in the population, and as a whole it deviated from a panmictic unit.This primarily resulted from the behaviour of Pgi2. This locus exhibited a large deficit of heterozygotes, possibly in association with a Wahiund effect. However, deviations from panmixia were small compared with species which are predominantly self-fertilizing, and estimates of gene flow indicated that the movement of genes occurs over a fairly wide area. This study provides the first description of spatial genetic variability within a population of Banksia spinutosa.

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“…Estimates of realized pollen dispersal show that this assumption is violated in P. mo//is populations where 70 per cent of all pollen dispersal from one plant is on average to its immediate neighbour (Table 6). Deviation from the mixed-mating model assumption of uniform pollen frequency over maternal genotypes can also be caused by subpopulation structure (Shaw et at., 1981;Ennos & Clegg, 1982;Hamrick, 1982;Ellstrand & Foster, 1983). Some contrived types of subpopulation structure, such as over-dispersed plantations of genotypes, have led to upward biases in estimates of t (e.g.…”

Section: Mating System Parametersmentioning

confidence: 99%

Restricted gene flow within the morphologically complex species Persoonia mollis (Proteaceae): contrasting evidence from the mating system and pollen dispersal

Krauss

1994

Heredity

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Severely restricted gene flow may be a factor contributing to the remarkable amount of morphological variation within the complex species Persoonia mollis, in which nine subspecies are recognized. The mating system and realized pollen dispersal were studied to assess their effect on gene flow. Mating system parameters were estimated in seven natural populations over two seasons using allozyme electrophoresis. Realized pollen dispersal was measured in two natural populations over two seasons by monitoring the dispersion of a rare allozyme from a known source plant in each population. Single-and multilocus estimates of outcrossing rate (t) were consistently equal to or greater than one (i.e. complete outcrossing). Realized pollen dispersal distances showed that 99 per cent of the pollen received by given females was donated by males on average within 33 m. However, 70 per cent of all pollen dispersal was on average to the paternal plant's immediate neighbour. Genetic neighbourhood sizes due to pollen dispersal alone ranged from one to five plants and paternity pool sizes ranged from four to 22 plants. These population sizes are small enough to allow genetic differentiation in the absence of selection. However, in contrast to the expectation that small population size leads to biparental inbreeding and reduced heterozygosity compared with Hardy-Weinberg expectations, the mean fixation index (F) of -0.035 indicated a slight excess of heterozygotes in the seed cohort. This apparent paradox could be the result of selection for heterozygous seeds, disassortative mating or more likely because gene flow through seed dispersal substantially increases the neighbourhood sizes estimated here through pollen dispersal alone.

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Plant Population Genetics and Evolution

Cited by 160 publications

References 40 publications

Phenotypic variability among pumpkin accessions in the Brazilian semiarid

Phenotypic variability among pumpkin accessions in the Brazilian semiarid

Population genetic structure of Banksia spinulosa

Restricted gene flow within the morphologically complex species Persoonia mollis (Proteaceae): contrasting evidence from the mating system and pollen dispersal

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