Ecological, morphological and allozymic differentiation between diploid and tetraploid knapweeds (Centaurea jacea) from a contact zone in the Belgian Ardennes

Abstract

In the northeastern part of Belgium, the Centaurea jacea complex shows extensive morphological variation and is represented by a diploid (2n l 22) and a tetraploid (2n l 44) cytotype. Polysomic inheritance of allozyme markers in the tetraploids, suggesting autopolyploidy, is here demonstrated for the first time. In order to test whether the two cytotypes occupy distinct habitats and possess different gene pools, patterns of allozymic and morphological variation were investigated in relation to ploidy level and site characteristics in 26 populations from the Belgian Ardennes. The two cytotypes showed a parapatric distribution, the diploids occurring at higher elevations (mostly above 500 m) than the tetraploids (mostly below 500 m). Three mixed populations were found near the contact zone of the two cytotypes. Within the mixed populations no triploid plant and no evidence for gene flow between cytotypes were found, despite widely overlapping flowering periods. The two cytotypes can be distinguished on the basis of morphological traits and enzymatic gene pools. The congruence of morphological and allozymic variation with chromosome numbers suggests a secondary contact between the two cytotypes with limited gene flow between them. The origin and persistence of the parapatric distribution are discussed.

Phenomenon of Cytomixis and Intraspecific Polyploidy (2<i>x</i>, 4<i>x</i>) in <i>Spergularia diandra</i> (Guss.) Heldr. & Sart. in the Cold Desert Regions of Kinnaur District (Himachal Pradesh)

“…The tetraploid plants were observed to be much taller and possessed large fleshy leaves in a smaller quantity. It is thus apparent that morphological characters in both the cytotypes of the species are directly correlated with the increase in ploidy level which has also been reported in Andropogon gerardii Vitman (Keeler and Davis 1999), Centaurea jacea L. (Hardy et al 2000), Parasenecio auriculata (DC.) J.R. Grant (Nakagawa 2006), Dactylis L. (Amirouche and Misset 2007), Centaurea phrygia L. (Koutecký 2007), Rorippa amphibia L. (Luttikhuizen et al 2007), Centaurea stoebe L. (Španiel et al 2008(Španiel et al , Mráz et al 2011 and Ranunculus hirtellus (Kumar and Singhal 2011).…”

Diploid and Tetraploid Cytotypes of Centaurea stoebe (Asteraceae) in Central Europe: Morphological Differentiation and Cytotype Distribution Patterns

“…These include the Centaurea phrygia group (Koutecký 2007), C. jacea group (Hardy et al 2000(Hardy et al , 2001Vanderhoeven et al 2002;Koutecký 2008), and also C. stoebe (Hufbauer and Sforza 2008;current study;Mráz et al in prep.). Results based on a wide spectrum of applied methods, including morphometric, karyological and molecular analyses, will give the possibility of deeper insights into speciation patterns in this genus, into auto-vs allopolyploidy, and morphological differentiation among ploidy levels.…”

Plant polyploidy and non-uniform effects on insect herbivores

“…This previous work allowed us to establish marked pairs of diploid and tetraploid individuals within each of the 4 years of this study from 1997 to 2000. The ability to pair plants of di¡erent ploidy levels is ideal for studying the e¡ects of polyploidy on patterns of insect herbivory, because it minimizes the potential in£uence of microhabitat di¡erentiation between the ploidy levels (Hancock & Bringhurst 1981;Lumaret et al 1987;Hardy et al 2000;Husband 2000) We used the interactions between H. grossulariifolia and three species of phytophagous insects to investigate whether the evolution of plant polyploidy has had a signi¢cant e¡ect on the pattern of insect attack within local populations. The insects included two closely related Greya species, Greya politella and Greya piperella in the family Prodoxidae and a more distantly related moth species, Eupithecia misturata in the family Geometridae.…”