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The origin and evolutionary significance of triploid hybrids in diploid-tetraploid contact zone in Tripleurospermum inodorum
Ryšavá, Hana ; Čertner, Martin (advisor) ; Chrtek, Jindřich (referee)
The presence of triploid individuals, whether hybrids arising from crosses of diploid and tetraploid plants, or spontaneously generated triploid hybrids diploid populations, is increasingly important in plant populations. However, the possible evolutionary role of the triploid hybrids is closely connected to the frequency of their occurrence, to their relative fitness (compared to parental cytotype) and fertility. As a model plant I choosed Tripleurospermum inodorum, in which a relatively frequent occurrence of triploid hybrids was documented in mixed populations of tetraploids and diploids. This annual plant achieves realy quick its reproductive maturity and is easily cultivated, making it an ideal model for cultivation and pollinating experiments. Compared to parental cytotypes, the triploid hybrids of T. inodorum take approximately the same (mostly mediated) fitness values. In vitro conditions were cultivated to measure of germination rates. Germination rate of triploid seeds was comparable to diploid parental cytotype. In the subsequent comparative cultivation, nearly 150 plant individuals (2x, 3x, 4x, and aneuploid cytotype) in the greenhouse showed that the triploids had intermedial values of their parental cytotypes or close to one of the parents. Thus, the vitality of the triploid plants is...
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The role of triploid hybrids in mixed-ploidy populations of Tripleurospermum inodorum (Asteraceae)
Jirsáková, Hana ; Čertner, Martin (advisor) ; Kolář, Filip (referee)
The doubling of the nuclear genome is considered to be one of the main ways in which new sympatry plant species can arise. Polyploidy is also generally a significant source of new evolutionarily advantageous abilities. However, it is not always that way, polyploids with an odd number of chromosome sets have often limited viability and fertility. In cytotype mixed populations of diploids and tetraploids, or in diploid populations alone with the contribution of high rate of unreduced gametes formation may produce triploid hybrids. In some cases, their vitality is even comparable with parental cytotypes but they produce only a small number of offsprings and in addition of different ploidy levels. Although it has been recently thought that they have no evolutionary significance, now based on many experimental works it is known with confidence that they can significantly participate in the new polyploid formation. If triploids occur in the population with sufficient frequency, they may play a role in stabilizing of the common coexistence of diploid and tetraploid cytotypes. Triploid hybrids may despite their limited fertility contribute to the bi-directional gene flow between their parents, and thus overcome the barrier of their different ploidy levels. A suitable model to study the role which can the triploid...
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The origin and evolutionary significance of triploid hybrids in diploid-tetraploid contact zone in Tripleurospermum inodorum
Ryšavá, Hana ; Čertner, Martin (advisor) ; Chrtek, Jindřich (referee)
The presence of triploid individuals, whether hybrids arising from crosses of diploid and tetraploid plants, or spontaneously generated triploid hybrids diploid populations, is increasingly important in plant populations. However, the possible evolutionary role of the triploid hybrids is closely connected to the frequency of their occurrence, to their relative fitness (compared to parental cytotype) and fertility. As a model plant I choosed Tripleurospermum inodorum, in which a relatively frequent occurrence of triploid hybrids was documented in mixed populations of tetraploids and diploids. This annual plant achieves realy quick its reproductive maturity and is easily cultivated, making it an ideal model for cultivation and pollinating experiments. Compared to parental cytotypes, the triploid hybrids of T. inodorum take approximately the same (mostly mediated) fitness values. In vitro conditions were cultivated to measure of germination rates. Germination rate of triploid seeds was comparable to diploid parental cytotype. In the subsequent comparative cultivation, nearly 150 plant individuals (2x, 3x, 4x, and aneuploid cytotype) in the greenhouse showed that the triploids had intermedial values of their parental cytotypes or close to one of the parents. Thus, the vitality of the triploid plants is...
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The role of triploid hybrids in mixed-ploidy populations of Tripleurospermum inodorum (Asteraceae)
Jirsáková, Hana ; Čertner, Martin (advisor) ; Kolář, Filip (referee)
The doubling of the nuclear genome is considered to be one of the main ways in which new sympatry plant species can arise. Polyploidy is also generally a significant source of new evolutionarily advantageous abilities. However, it is not always that way, polyploids with an odd number of chromosome sets have often limited viability and fertility. In cytotype mixed populations of diploids and tetraploids, or in diploid populations alone with the contribution of high rate of unreduced gametes formation may produce triploid hybrids. In some cases, their vitality is even comparable with parental cytotypes but they produce only a small number of offsprings and in addition of different ploidy levels. Although it has been recently thought that they have no evolutionary significance, now based on many experimental works it is known with confidence that they can significantly participate in the new polyploid formation. If triploids occur in the population with sufficient frequency, they may play a role in stabilizing of the common coexistence of diploid and tetraploid cytotypes. Triploid hybrids may despite their limited fertility contribute to the bi-directional gene flow between their parents, and thus overcome the barrier of their different ploidy levels. A suitable model to study the role which can the triploid...
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