Limits...
Evolutionary and Taxonomic Implications of Variation in Nuclear Genome Size: Lesson from the Grass Genus Anthoxanthum (Poaceae).

Chumová Z, Krejčíková J, Mandáková T, Suda J, Trávníček P - PLoS ONE (2015)

Bottom Line: In addition to diploids, we found two low (rare 3x and common 4x) and one high (~16x-18x) polyploid levels.Intraspecific variation in genome size was observed in all recognized species, the most striking example being the A. aristatum/ovatum complex.Altogether, our study showed that genome size can be a useful taxonomic marker in Anthoxathum to not only guide taxonomic decisions but also help resolve evolutionary relationships in this challenging grass genus.

View Article: PubMed Central - PubMed

Affiliation: Department of Botany, Faculty of Science, Charles University in Prague, Prague, Czech Republic.

ABSTRACT
The genus Anthoxanthum (sweet vernal grass, Poaceae) represents a taxonomically intricate polyploid complex with large phenotypic variation and its evolutionary relationships still poorly resolved. In order to get insight into the geographic distribution of ploidy levels and assess the taxonomic value of genome size data, we determined C- and Cx-values in 628 plants representing all currently recognized European species collected from 197 populations in 29 European countries. The flow cytometric estimates were supplemented by conventional chromosome counts. In addition to diploids, we found two low (rare 3x and common 4x) and one high (~16x-18x) polyploid levels. Mean holoploid genome sizes ranged from 5.52 pg in diploid A. alpinum to 44.75 pg in highly polyploid A. amarum, while the size of monoploid genomes ranged from 2.75 pg in tetraploid A. alpinum to 9.19 pg in diploid A. gracile. In contrast to Central and Northern Europe, which harboured only limited cytological variation, a much more complex pattern of genome sizes was revealed in the Mediterranean, particularly in Corsica. Eight taxonomic groups that partly corresponded to traditionally recognized species were delimited based on genome size values and phenotypic variation. Whereas our data supported the merger of A. aristatum and A. ovatum, eastern Mediterranean populations traditionally referred to as diploid A. odoratum were shown to be cytologically distinct, and may represent a new taxon. Autopolyploid origin was suggested for 4x A. alpinum. In contrast, 4x A. odoratum seems to be an allopolyploid, based on the amounts of nuclear DNA. Intraspecific variation in genome size was observed in all recognized species, the most striking example being the A. aristatum/ovatum complex. Altogether, our study showed that genome size can be a useful taxonomic marker in Anthoxathum to not only guide taxonomic decisions but also help resolve evolutionary relationships in this challenging grass genus.

No MeSH data available.


Flow cytometric histograms demonstrating genuine intraspecific variation in holoploid genome size (simultaneous analysis of individuals with distinct DNA C-values).(A) 4x A. odoratum – pops. CZ03 + HR03 (difference 8.0%); (B) ‘Mediterranean diploid’ – pops. ME05 + IT03 (difference 3.5%); (C) A. amarum – intrapopulation variation in pop. PT13 (difference 8.2%); (D) A. aristatum/ovatum – intrapopulation variation in pop. ES09 (difference 10.7%, both individuals with 2n = 10).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4514812&req=5

pone.0133748.g004: Flow cytometric histograms demonstrating genuine intraspecific variation in holoploid genome size (simultaneous analysis of individuals with distinct DNA C-values).(A) 4x A. odoratum – pops. CZ03 + HR03 (difference 8.0%); (B) ‘Mediterranean diploid’ – pops. ME05 + IT03 (difference 3.5%); (C) A. amarum – intrapopulation variation in pop. PT13 (difference 8.2%); (D) A. aristatum/ovatum – intrapopulation variation in pop. ES09 (difference 10.7%, both individuals with 2n = 10).

Mentions: Intraspecific variation in genome size was observed in all analysed taxa (Table 1). 2C-values varied from 5.5% in A. gracile up to 64.8% in the polymorphic complex of A. aristatum/ovatum (Figs 3 and 4). In species collected from sufficiently large geographic areas, the intraspecific variation was non-randomly distributed and showed highly significant negative correlation with latitude (in 2x A. alpinum and 4x A. odoratum) and a less pronounced but still significant association with altitude (positive in 2x A. alpinum and negative both in the “Mediterranean diploid” and 4x A. odoratum) (Table 2, S1 Fig). Narrow geographic distribution precluded performing the same analyses for 4x A. alpinum, A. gracile, or A. maderense. Anthoxanthum aristatum/ovatum showed not only intraspecific but also considerable intrapopulation variation in genome size (up to 37% in pop. ES09; S1 Table, Table 1).


Evolutionary and Taxonomic Implications of Variation in Nuclear Genome Size: Lesson from the Grass Genus Anthoxanthum (Poaceae).

Chumová Z, Krejčíková J, Mandáková T, Suda J, Trávníček P - PLoS ONE (2015)

Flow cytometric histograms demonstrating genuine intraspecific variation in holoploid genome size (simultaneous analysis of individuals with distinct DNA C-values).(A) 4x A. odoratum – pops. CZ03 + HR03 (difference 8.0%); (B) ‘Mediterranean diploid’ – pops. ME05 + IT03 (difference 3.5%); (C) A. amarum – intrapopulation variation in pop. PT13 (difference 8.2%); (D) A. aristatum/ovatum – intrapopulation variation in pop. ES09 (difference 10.7%, both individuals with 2n = 10).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4514812&req=5

pone.0133748.g004: Flow cytometric histograms demonstrating genuine intraspecific variation in holoploid genome size (simultaneous analysis of individuals with distinct DNA C-values).(A) 4x A. odoratum – pops. CZ03 + HR03 (difference 8.0%); (B) ‘Mediterranean diploid’ – pops. ME05 + IT03 (difference 3.5%); (C) A. amarum – intrapopulation variation in pop. PT13 (difference 8.2%); (D) A. aristatum/ovatum – intrapopulation variation in pop. ES09 (difference 10.7%, both individuals with 2n = 10).
Mentions: Intraspecific variation in genome size was observed in all analysed taxa (Table 1). 2C-values varied from 5.5% in A. gracile up to 64.8% in the polymorphic complex of A. aristatum/ovatum (Figs 3 and 4). In species collected from sufficiently large geographic areas, the intraspecific variation was non-randomly distributed and showed highly significant negative correlation with latitude (in 2x A. alpinum and 4x A. odoratum) and a less pronounced but still significant association with altitude (positive in 2x A. alpinum and negative both in the “Mediterranean diploid” and 4x A. odoratum) (Table 2, S1 Fig). Narrow geographic distribution precluded performing the same analyses for 4x A. alpinum, A. gracile, or A. maderense. Anthoxanthum aristatum/ovatum showed not only intraspecific but also considerable intrapopulation variation in genome size (up to 37% in pop. ES09; S1 Table, Table 1).

Bottom Line: In addition to diploids, we found two low (rare 3x and common 4x) and one high (~16x-18x) polyploid levels.Intraspecific variation in genome size was observed in all recognized species, the most striking example being the A. aristatum/ovatum complex.Altogether, our study showed that genome size can be a useful taxonomic marker in Anthoxathum to not only guide taxonomic decisions but also help resolve evolutionary relationships in this challenging grass genus.

View Article: PubMed Central - PubMed

Affiliation: Department of Botany, Faculty of Science, Charles University in Prague, Prague, Czech Republic.

ABSTRACT
The genus Anthoxanthum (sweet vernal grass, Poaceae) represents a taxonomically intricate polyploid complex with large phenotypic variation and its evolutionary relationships still poorly resolved. In order to get insight into the geographic distribution of ploidy levels and assess the taxonomic value of genome size data, we determined C- and Cx-values in 628 plants representing all currently recognized European species collected from 197 populations in 29 European countries. The flow cytometric estimates were supplemented by conventional chromosome counts. In addition to diploids, we found two low (rare 3x and common 4x) and one high (~16x-18x) polyploid levels. Mean holoploid genome sizes ranged from 5.52 pg in diploid A. alpinum to 44.75 pg in highly polyploid A. amarum, while the size of monoploid genomes ranged from 2.75 pg in tetraploid A. alpinum to 9.19 pg in diploid A. gracile. In contrast to Central and Northern Europe, which harboured only limited cytological variation, a much more complex pattern of genome sizes was revealed in the Mediterranean, particularly in Corsica. Eight taxonomic groups that partly corresponded to traditionally recognized species were delimited based on genome size values and phenotypic variation. Whereas our data supported the merger of A. aristatum and A. ovatum, eastern Mediterranean populations traditionally referred to as diploid A. odoratum were shown to be cytologically distinct, and may represent a new taxon. Autopolyploid origin was suggested for 4x A. alpinum. In contrast, 4x A. odoratum seems to be an allopolyploid, based on the amounts of nuclear DNA. Intraspecific variation in genome size was observed in all recognized species, the most striking example being the A. aristatum/ovatum complex. Altogether, our study showed that genome size can be a useful taxonomic marker in Anthoxathum to not only guide taxonomic decisions but also help resolve evolutionary relationships in this challenging grass genus.

No MeSH data available.