The BSBI Viola handbook covers the problems and attempts to provide a practical approach based on morphological features but concludes 'more work needs to be undertaken on the taxonomy of this group'.
I found a paper on the internet (abstract only unfortunately ) that has an interesting claim that in Europe there is no evidence of hybridisation, or that's what I understand it means. Whether this result would apply to plants in the UK is not known. The paper was written in Eastern Europe and the UK appears not to have been one of the four countries sampled. (I have not been able to review the full paper and would not have the knowledge to understand it anyway. )
It was published in the July 2017 edition of Plant Biology. The abstract is below the following photos of Viola reichenbachiana variation. These plants had quite pale spurs and remarkably sharp ends to the purple veins but within the limits of variation. Short sepal appendages well within normal range of V. reichenbachiana. Just an example of variation in Early Dog Violet.
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| Viola reichenbachiana with quite pale spur , Brinkley, Cambridgeshire, 6th April 2019 |
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| Viola reichenbachiana with clear ends to dark veins. Brinkley, Cambridgeshire, 6th April 2019 |
Plant Biol (Stuttg). 2017 Jul;19(4):542-551. doi: 10.1111/plb.12571. Epub 2017 May 17.No evidence of contemporary interploidy gene flow
between the closely related European woodland violets
Viola reichenbachiana and V. riviniana (sect. Viola,
Violaceae).
Migdałek G1, Nowak J2, Saługa M2, Cieślak E2, Szczepaniak M2, Ronikier M2, Marcussen T3, Słomka A4, Kuta E4.Author information
Abstract
Viola reichenbachiana (2n = 4x = 20) and V. riviniana (2n = 8x = 40) are closely related species widely distributed in Europe, often sharing the same habitat throughout their overlapping ranges. It has been suggested in numerous studies that their high intraspecific morphological variability and plasticity might have been further increased by interspecific hybridisation in contact zones, given the sympatry of the species and the incomplete sterility of their hybrid. The aims of this study were to: (i) confirm that V. reichenbachiana and V. riviniana have one 4x genome in common, and (ii) determine the impact of hybridisation and introgression on genetic variation of these two species in selected European populations. For our study, we used 31 Viola populations from four European countries, which were analysed using AFLP and sequencing of a variable plastid intergenic spacer, trnH-psbA. Our analysis revealed that V. reichenbachiana exhibited larger haplotype diversity, having three species-specific haplotypes versus one in V. riviniana. The relationships among haplotypes suggest transfer of common haplotypes into V. riviniana from both V. reichenbachiana and hypothetically the other, now extinct, parental species. AFLP analysis showed low overall genetic diversity of both species, with V. riviniana showing higher among-population diversity. None of the morphologically designated hybrid populations had additive AFLP polymorphisms that would have indicated recent hybridisation. Also, kinship coefficients between both species did not indicate gene flow. V. riviniana showed significant population subdivision and significant isolation by distance, in contrast to V. reichenbachiana. The results indicate lack of gene flow between species, high influence of selfing on genetic variability, as well as probably only localised introgression toward V. riviniana.
An interesting abstract for fans of Violets.
Peter Leonard
Rampton, Cambridgeshire.
7th April 2019
Update 7th May 2020. The full paper was sourced and the headline is not quite what the results showed. (The sample did include the UK with about 20 plants involved from two sites. A small sample.)
Although plants taken from what were considered hybrid populations, they did not show an sign of hybridisation. Three plants out of several hundred were regarded as hybrids.
A toxic site in Poland also did not show hybridisation unlike a toxic site in Germany which had been previously studied and did show hybridisation.
The conclusion has to be that very occasionally hybrids can occur and this is not really surprising as this study suggests that the V. reichenbachiana is a parent of V. riviniana. The other parent being unknown, probably extinct.
between the closely related European woodland violets
Viola reichenbachiana and V. riviniana (sect. Viola,
Violaceae).
Migdałek G1, Nowak J2, Saługa M2, Cieślak E2, Szczepaniak M2, Ronikier M2, Marcussen T3, Słomka A4, Kuta E4.Author information
Abstract
Viola reichenbachiana (2n = 4x = 20) and V. riviniana (2n = 8x = 40) are closely related species widely distributed in Europe, often sharing the same habitat throughout their overlapping ranges. It has been suggested in numerous studies that their high intraspecific morphological variability and plasticity might have been further increased by interspecific hybridisation in contact zones, given the sympatry of the species and the incomplete sterility of their hybrid. The aims of this study were to: (i) confirm that V. reichenbachiana and V. riviniana have one 4x genome in common, and (ii) determine the impact of hybridisation and introgression on genetic variation of these two species in selected European populations. For our study, we used 31 Viola populations from four European countries, which were analysed using AFLP and sequencing of a variable plastid intergenic spacer, trnH-psbA. Our analysis revealed that V. reichenbachiana exhibited larger haplotype diversity, having three species-specific haplotypes versus one in V. riviniana. The relationships among haplotypes suggest transfer of common haplotypes into V. riviniana from both V. reichenbachiana and hypothetically the other, now extinct, parental species. AFLP analysis showed low overall genetic diversity of both species, with V. riviniana showing higher among-population diversity. None of the morphologically designated hybrid populations had additive AFLP polymorphisms that would have indicated recent hybridisation. Also, kinship coefficients between both species did not indicate gene flow. V. riviniana showed significant population subdivision and significant isolation by distance, in contrast to V. reichenbachiana. The results indicate lack of gene flow between species, high influence of selfing on genetic variability, as well as probably only localised introgression toward V. riviniana.
An interesting abstract for fans of Violets.
Peter Leonard
Rampton, Cambridgeshire.
7th April 2019
Update 7th May 2020. The full paper was sourced and the headline is not quite what the results showed. (The sample did include the UK with about 20 plants involved from two sites. A small sample.)
Although plants taken from what were considered hybrid populations, they did not show an sign of hybridisation. Three plants out of several hundred were regarded as hybrids.
A toxic site in Poland also did not show hybridisation unlike a toxic site in Germany which had been previously studied and did show hybridisation.
The conclusion has to be that very occasionally hybrids can occur and this is not really surprising as this study suggests that the V. reichenbachiana is a parent of V. riviniana. The other parent being unknown, probably extinct.
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