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Cook, L. M. and Soltis, P. S.. Mating systems of diploid and allotetraploid populations of Tragopogon (Asteraceae). I. Natural populations. Heredity. 82: 237-244

Department of Botany, PO Box 644238, Washington State University, Pullman, WA 99164-4238, USA.
Heredity (Impact Factor: 3.81). 05/1999; 82(3). DOI: 10.1038/sj.hdy.6884620
Source: OAI

ABSTRACT

Although polyploidy is a significant force in the diversification of plants, the evolutionary consequences of polyploidization are not thoroughly understood. One possible consequence of polyploidy predicted by most population genetic theories is that the newly synthesized polyploid will self-fertilize at a greater rate than its diploid progenitors. To test for increased selfing rates in a polyploid, the mating systems of the allotetraploid Tragopogon mirus and one of its diploid progenitors, T. dubius, were compared. Tragopogon mirus is a recently derived species that arose sometime in the last 80 years and thus provides an opportunity to probe how quickly a shift in outcrossing rates might occur. Based on analyses of variation in maternal plants and their progeny arrays, the two tetraploid populations surveyed have higher outcrossing rates than the two diploid populations. This result is the opposite of that predicted by population genetic theory. This discrepancy between theoretical and empirical results may result from bias in the genetic sample, traits in the natural histories of the taxa involved or a lack of sufficient time since the formation of the polyploid (80 years or 40-80 generations) for a shift towards increased selfing to have occurred. Alternatively, the partial dominance model of inbreeding depression typically applied to polyploids may not be appropriate; the overdominance model predicts outcrossing rates in diploids and their tetraploid derivatives that are consistent with those observed in T. dubius and T. mirus.

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    • "Most studies on polyploidization have been focused on establishing the frequencies or patterns of homeologous gene expression in the context of polyploidization (Tate et al. 2004; Wendel and Doyle 2005; Adams 2007). Moreover, most of them employed the synthesized haploids and polyploids, while the natural polyploids were seldom used (Peng et al. 2008), except some recent polyploids such as Spartina (Baumel et al. 2001), Tragopogon (Cook and Soltis 1999) and Senecio (Abbott and Lowe 2004; Hegarty et al. 2006). As we know, both inducing treatment and tissue culture conditions have the potential to modify the DNA structure, influence gene expression, and eventually interference the accuracy of study on ploidy effects. "
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    • "This sort of heterozygosity would be evident if there were a very low-copy array and a very high-copy array in parents. However, FISH analysis revealed no indication of rDNA heterozygosity in the diploid Tragopogon individuals investigated, a situation which might be expected for species that are largely selfing [58,59], and in plants that were derived from inbred lines propagated in a greenhouse (at least one generation). In estimating rDNA locus sizes, and hence relative copy numbers at individual loci, FISH may be influenced by the condensation state of the chromatin. "
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    • "An estimated 45–70% of angiosperm species are polyploid descendents of taxa with lower ploidy levels (Grant 1981, Masterson 1994), and the process of polyploidization can alter morphology, physiology, phenology, rates of genetic drift, ecological tolerances, and population dynamics (Stebbins 1971, Eagles and Othman 1978, Burdon and Marshall 1981, Grant 1981, Levin 1983, Warner and Edwards 1989, Moody et al. 1993, Dhawan and Lavania 1996, Segraves and Thompson 1999, Otto and Whitton 2000, Bretagnolle and Thompson 2001, Mu¨nzbergova´2007). Polyploids also often differ from diploids in mating systems, thereby altering patterns of gene flow within and among populations that differ in cytotype (Brochmann et al. 1993, Jacquemart and Thompson 1996, Cook and Soltis 1999, Lichtenzveig et al. 2000, Quarin et al. 2001). "
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