Patterns of cytotype distribution and genome size variation in the genusSesleria Scop. (Poaceae)

Abstract

Polyploidization has played an important role in the diversification of the genus Sesleria (Poaceae), which comprises c. 48 species and subspecies mostly distributed in Europe. The genus' centre of diversity clearly is the Balkan Peninsula, harbouring about 80% of the species, half of which are endemic to this area. We employed chromosome counts, measurements of absolute genome size and determination of relative DNA-content for 460 populations belonging to 43 species of Sesleria. Our main aim was to provide essential baseline data for future molecular genetic reconstructions of the genus' evolutionary history. Relative genome size allowed for a mostly clear separation of four ploidy levels. The most frequent and widespread cytotypes are tetraploids followed by octoploids, while di-and dodecaploids were only found in a few species. We present first chromosome numbers for the tetraploid species S. doerfleri, S. phleoides, S. skipetarum and S. tuzsonii as well as for diploid S. ovata. Based on relative and partly also on absolute genome size measurements, ploidy level was determined in tetraploid S. rhodopaea and S. voronovii for the first time, and new cytotypes were identified in S. interrupta, S. kalnikensis and S. wettsteinii (tetraploids), S. caerulea, S. klasterskyi, S. latifolia, S. tenerrima, S. ujhelyii and S. vaginalis (octoploids), and S. albanica and S. vaginalis (dodecaploids). While most Sesleria species are ploidy-uniform, several comprise two or even, in the case of S. vaginalis, three ploidy levels. Genome downsizing after polyploidization was confirmed by significant negative correlation between ploidy level and monoploid genome size. Finally, we found a significant increase in monoploid relative genome size towards the margin of the genus' distribution area, which may be triggered by increased activity of transposable element in populations exposed to environmental or genomic stress.

Phylogenetic relationships in Seslerieae (Poaceae) including resurrection of Psilathera and Sesleriella, two monotypic genera endemic to the Alps

“…"Calcariae" Deyl; the correct name of the latter is, however, S. sect. Sesleria as noted by Lazarević & al. (2015).…”

“…The taxonomic intricacy of Sesleria likely relates to the frequent occurrence of hybridisation and polyploidy within the genus (Deyl, 1946). Tetraploids (2n = 4x = 28) are most frequent, followed by octoploids (2n = 8x = 56, e.g., Strgar, 1979;Lysak & Doležel, 1998;Petrova, 2000;Budžakova & al., 2014;Lazarević & al., 2015), whereas dodecaploids (2n = 12x = 84) are rare and have been reported for only three species from southern Italy and Albania (Di Pietro & al., 2005;Lazarević & al., 2015). Deyl (1946) hypothesized a hybrid origin of many species, for instance S. kalnikensis Jáv.…”

Polyphyletic Alyssum cuneifolium (Brassicaceae) revisited: Morphological and genome size differentiation of recently recognized allopatric taxa

“…The prevalent trend towards genome downsizing correlated with increasing ploidy level in polyploid series of closely related species (or within species) has been repeatedly confirmed in many plant genera, most recently, for example, in Aloe L. (Rao et al, ), Avena L. (Yan et al, ), Calligonum L. (Gouja et al, ), Chrysanthemum L. (Luo et al, ), Festuca L. (Ezquerro‐López et al, ), Fragaria L. (Nosrati, ), Knautia L. (Frajman et al, ), Sesleria Scop. (Lazarević et al, ) and Veronica L. (Meudt et al, ). Considering this general trend, the opposite patterns observed in the Alyssum species under study could be attributed to the fact that they are not each others' closest relatives (Zozomová‐Lihová et al, ; Španiel et al, ); however, there are also other possible explanations.…”

“…Species with smaller genomes are believed to be more successful under stressful conditions, for instance at higher elevations or in cold and dry climates (Šmarda & Bureš, ; Olšavská et al, ); in particular cases, however, it is for the most part difficult to separate the influence of the environment from that of the phylogenetic framework. Several studies have found a significant increase in monoploid relative genome size towards the margins of distribution areas, where populations are exposed to environmental or genomic stress (Frajman et al, ; Lazarević et al, ). A larger sample of taxa and populations of Alyssum from various habitat types is needed to critically assess the adaptive nature of genome size differences between the Alyssum species under study.…”

Which changes are needed to render all genera of the German flora monophyletic?

“…Preliminary data from Ampliied Fragment Length Polymorphisms (AFLPs) and plastid DNA (trnLndhF) sequences support the recognition of Oreochloa Link as a separate genus (with only O. disticha (Wulfen) Link represented in the German lora) and underline that Psilathera ovata (Hoppe) Deyl diverges from the remainder of Sesleria (Lakušić 2013). Further study including a more comprehensive taxon sampling is needed to clarify whether the monospeciic Psilathera Link (only P. ovata (Hoppe) Deyl in the German lora) can be maintained or should be merged with Sesleria as was done in Jäger (2011) and by Lazarević & al. (2015).…”