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

Abstract

Alyssum cuneifolium has been recognized as a perennial alpine species growing in five isolated European mountain ranges: the Pyrenees, Western Alps, Apennines, Pirin Mts and Mt Smolikas. Recent molecular systematic studies revealed that the disjunct populations from distant mountains are not closely related and belong to five independent species: A. cacuminum (Spain, Pyrenees), A. cuneifolium (Italy, Apennines), A. flexicaule (France, Western Alps), A. pirinicum (Bulgaria, Pirin Mts), and A. spruneri (Greece, Mt Smolikas). The present study brings the thorough morphometric analysis of the segregated taxa. We found minor morphological differences between them. Whereas A. pirinicum can be clearly distinguished, the other taxa are recognizable only at the level of population means of investigated characters. The morphological similarity of these distantly related species is obviously the result of adaptation to similar high‐alpine scree habitats. It is not clear, however, whether this adaptation is environmentally controlled or whether it is also genetically fixed and whether it reflects parallel evolution towards similar morphotypes. The observed morphological patterns and their assumed correlation with environmental factors are discussed using examples from other Alyssum taxa. Three different ploidy levels have been reported for the species under study. In the present article, we examine variation in relative nuclear genome size. The Alpine and Pyrenean species have larger relative monoploid genome sizes than the Apennine and Balkan ones, probably reflecting the evolutionary history of the group. A nomenclatural account of the study species is presented, and lectotypes of A. cuneifolium and of two other names are selected.

Diversification and independent polyploid origins in the disjunct species Alyssum repens from the Southeastern Alps and the Carpathians

“…Monoploid relative genome size (relative C x value) was calculated as the relative 2C DNA value divided by the number of chromosome sets x . Our recent studies of Brassicaceae genera have shown that the correlation between absolute and relative DNA content values is almost perfect (Marhold et al., ) and that silica gel‐dried leaf material can be used to identify genuine differences in relative genome size (Šlenker et al., ; Španiel et al., , ). Differences in monoploid relative genome size between the genetic groups of A. repens were tested with Kruskal‐Wallis tests followed by Mann‐Whitney pairwise comparisons with Bonferroni correction of P‐values using PAST 3 (Hammer et al., ).…”

“…The Alyssum montanum – A. repens group (Brassicaceae) is a polyploid species complex that displays high species and genetic diversity in the Mediterranean and adjacent regions, as well as in mountainous areas (Ball and Dudley, ; Jalas et al., ; Španiel et al., 2011b, , b; Zozomová‐Lihová et al., 2014b). Most species show fairly restricted, allopatric distribution ranges, several are local endemics whereas only a few are more widespread, and even those show geographically structured genetic variation (Zozomová‐Lihová et al., 2014b; Španiel et al., 2017b, ). In fact, several mountain ranges in Europe (the Pyrenees, Alps, Apennines, Carpathians, and Dinarides) harbor at least one endemic taxon from this species complex (Španiel et al., 2011b, , 2017b, , ; Magauer et al., ; Zozomová‐Lihová et al., 2014b).…”

“…Most species show fairly restricted, allopatric distribution ranges, several are local endemics whereas only a few are more widespread, and even those show geographically structured genetic variation (Zozomová‐Lihová et al., 2014b; Španiel et al., 2017b, ). In fact, several mountain ranges in Europe (the Pyrenees, Alps, Apennines, Carpathians, and Dinarides) harbor at least one endemic taxon from this species complex (Španiel et al., 2011b, , 2017b, , ; Magauer et al., ; Zozomová‐Lihová et al., 2014b). It has been suggested that restricted seed dispersal along with recent diversification (late Pliocene/early Pleistocene) and possibly also ecological differentiation are responsible for the present, geographically structured patterns in this species complex (Zozomová‐Lihová et al., 2014b).…”

So Closely Related and Yet So Different: Strong Contrasts Between the Evolutionary Histories of Species of the Cardamine pratensis Polyploid Complex in Central Europe

“…Similar scenarios of independent colonization of alpine habitats by several distinct genetic lineages from foothill areas were recently inferred also in Arabidopsis arenosa (Kolář et al, 2017) and in the formerly broadly conceived species Alyssum cuneifolium (Španiel et al, 2019). In both these cases, the overall phenotypic similarity of alpine populations contrasting with their genetic heterogeneity has been caused by a similar (alpine) environment (Kolář et al, 2017;Monnahan et al, 2019;Španiel et al, 2019;Wos et al, 2019).…”

Sympatric genome size variation and hybridization of four oak species as determined by flow cytometry genome size variation and hybridization

“…Flow cytometry (FCM), which is a fast and effective tool to estimate GS, has been successfully applied to ploidy identification, cell cycle analysis, and species identification, including hybrids, rarely occurring cytotypes, and aneuploids (Francis et al., 2008; Hanusova et al., 2014; Vit et al., 2014; Zhang et al., 2019). It has been used successfully in plant genetic variation studies, genetic analyses, and breeding, as well as in studies of reproductive ecology, evolution, and plant system classification (Bilinski et al., 2018; Galbraith, 2004; Sharma et al, 2019; Spaniel et al., 2019). In the 1980s, Galbraith et al.…”