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Degradation of sexual reproduction in Veronica filiformis after introduction to Europe.

Scalone R, Albach DC - BMC Evol. Biol. (2012)

Bottom Line: These results were similar to intrapopulation crossings, but this depended on the populations used for crossings.Results from AFLP fingerprinting confirmed a lack of genetic diversity in the area of introduction, which is best explained by the dispersal of clones.This came at the cost of an accumulation of phenotypically observable mutations in reproductive characters, i.e. Muller's ratchet.

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Affiliation: Institut für Spezielle Botanik und Botanischer Garten, Johannes Gutenberg-Universität Mainz, Bentzelweg 9, Mainz 55099, Germany.

ABSTRACT

Background: Baker's law predicts that self-incompatible plant species are generally poor colonizers because their mating system requires a high diversity of genetically differentiated individuals and thus self-compatibility should develop after long-distance dispersal. However, cases like the introduction of the self-incompatible Veronica filiformis (Plantaginaceae) to Europe constitute an often overlooked alternative to this rule. This species was introduced from subalpine areas of the Pontic-Caucasian Mountains and colonized many parts of Central and Western Europe in the last century, apparently without producing seeds. To investigate the consequences of the absence of sexual reproduction in this obligate outcrosser since its introduction, AFLP fingerprints, flower morphology, pollen and ovule production and seed vitality were studied in introduced and native populations.

Results: Interpopulation crossings of 19 introduced German populations performed in the greenhouse demonstrated that introduced populations are often unable to reproduce sexually. These results were similar to intrapopulation crossings, but this depended on the populations used for crossings. Results from AFLP fingerprinting confirmed a lack of genetic diversity in the area of introduction, which is best explained by the dispersal of clones. Flower morphology revealed the frequent presence of mutations affecting the androecium of the flower and decreasing pollen production in introduced populations. The seeds produced in our experiments were smaller, had a lower germination rate and had lower viability than seeds from the native area.

Conclusions: Taken together, our results demonstrate that V. filiformis was able to spread by vegetative means in the absence of sexual reproduction. This came at the cost of an accumulation of phenotypically observable mutations in reproductive characters, i.e. Muller's ratchet.

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Crossing polygon indicating results from interpopulation crossings. The color of the circles corresponds to the crossing groups inferred by the crossing experiment. Names of the populations correspond to the codes in Table1. A double line indicates that the crossings were done in both directions (♀ pop. X with ♂ pop. Y as well as ♂ pop X with ♀pop. Y), whereas unique single line means that only one direction of the cross was conducted. The width of the lines is proportional to the number of flowers tested for this crossing. The dashed lines refer to incompatible crossings, whereas solid lines indicate compatible crossings leading to the formation of seeds.
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Figure 2: Crossing polygon indicating results from interpopulation crossings. The color of the circles corresponds to the crossing groups inferred by the crossing experiment. Names of the populations correspond to the codes in Table1. A double line indicates that the crossings were done in both directions (♀ pop. X with ♂ pop. Y as well as ♂ pop X with ♀pop. Y), whereas unique single line means that only one direction of the cross was conducted. The width of the lines is proportional to the number of flowers tested for this crossing. The dashed lines refer to incompatible crossings, whereas solid lines indicate compatible crossings leading to the formation of seeds.

Mentions: Populations were assigned to crossing groups when crossings between populations did not produce seeds (dashed lines; Figure2) but did so when crossed with populations from other crossing groups (solid line; Figure2). By this method, 19 populations were assigned to five different crossing groups represented by different colors (with non-capitalized color names) in Figure2.


Degradation of sexual reproduction in Veronica filiformis after introduction to Europe.

Scalone R, Albach DC - BMC Evol. Biol. (2012)

Crossing polygon indicating results from interpopulation crossings. The color of the circles corresponds to the crossing groups inferred by the crossing experiment. Names of the populations correspond to the codes in Table1. A double line indicates that the crossings were done in both directions (♀ pop. X with ♂ pop. Y as well as ♂ pop X with ♀pop. Y), whereas unique single line means that only one direction of the cross was conducted. The width of the lines is proportional to the number of flowers tested for this crossing. The dashed lines refer to incompatible crossings, whereas solid lines indicate compatible crossings leading to the formation of seeds.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3539859&req=5

Figure 2: Crossing polygon indicating results from interpopulation crossings. The color of the circles corresponds to the crossing groups inferred by the crossing experiment. Names of the populations correspond to the codes in Table1. A double line indicates that the crossings were done in both directions (♀ pop. X with ♂ pop. Y as well as ♂ pop X with ♀pop. Y), whereas unique single line means that only one direction of the cross was conducted. The width of the lines is proportional to the number of flowers tested for this crossing. The dashed lines refer to incompatible crossings, whereas solid lines indicate compatible crossings leading to the formation of seeds.
Mentions: Populations were assigned to crossing groups when crossings between populations did not produce seeds (dashed lines; Figure2) but did so when crossed with populations from other crossing groups (solid line; Figure2). By this method, 19 populations were assigned to five different crossing groups represented by different colors (with non-capitalized color names) in Figure2.

Bottom Line: These results were similar to intrapopulation crossings, but this depended on the populations used for crossings.Results from AFLP fingerprinting confirmed a lack of genetic diversity in the area of introduction, which is best explained by the dispersal of clones.This came at the cost of an accumulation of phenotypically observable mutations in reproductive characters, i.e. Muller's ratchet.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut für Spezielle Botanik und Botanischer Garten, Johannes Gutenberg-Universität Mainz, Bentzelweg 9, Mainz 55099, Germany.

ABSTRACT

Background: Baker's law predicts that self-incompatible plant species are generally poor colonizers because their mating system requires a high diversity of genetically differentiated individuals and thus self-compatibility should develop after long-distance dispersal. However, cases like the introduction of the self-incompatible Veronica filiformis (Plantaginaceae) to Europe constitute an often overlooked alternative to this rule. This species was introduced from subalpine areas of the Pontic-Caucasian Mountains and colonized many parts of Central and Western Europe in the last century, apparently without producing seeds. To investigate the consequences of the absence of sexual reproduction in this obligate outcrosser since its introduction, AFLP fingerprints, flower morphology, pollen and ovule production and seed vitality were studied in introduced and native populations.

Results: Interpopulation crossings of 19 introduced German populations performed in the greenhouse demonstrated that introduced populations are often unable to reproduce sexually. These results were similar to intrapopulation crossings, but this depended on the populations used for crossings. Results from AFLP fingerprinting confirmed a lack of genetic diversity in the area of introduction, which is best explained by the dispersal of clones. Flower morphology revealed the frequent presence of mutations affecting the androecium of the flower and decreasing pollen production in introduced populations. The seeds produced in our experiments were smaller, had a lower germination rate and had lower viability than seeds from the native area.

Conclusions: Taken together, our results demonstrate that V. filiformis was able to spread by vegetative means in the absence of sexual reproduction. This came at the cost of an accumulation of phenotypically observable mutations in reproductive characters, i.e. Muller's ratchet.

Show MeSH
Related in: MedlinePlus