Occurrence of tetraploid and hexaploid cytotypes between and within populations in Dianthus sect. Plumaria (Caryophyllaceae)

Abstract

Summary• The occurrence of both tetraploid and hexaploid cytotypes within and between populations of several species of Dianthus section Plumaria was analysed.• Chromosome numbers for 13 populations of eight taxa are presented together with a thorough compilation of previously published data.• Most of the taxa are polyploids (tetraploids and hexaploids). Three groups can be distinguished: (1) only one ploidy level within a taxon; (2) more than one ploidy level, but only single cytotypes within a population; and (3) populations with a cytotype mixture. From some populations, reported earlier to contain tetraploids, we found only hexaploid individuals. Hexaploids occur over the whole range of polyploid taxa, revealing no geographical pattern.• Polyploidy is very likely the result of autopolyploidization, at least for the hexaploid cytotypes, which formed many times independently and occur sympatrically with tetraploids. Most of the populations with mixed cytotypes represent primary hybrid zones. It is not yet possible to decide whether directional (one cytotype will become extinct in the longer term) or balanced selection (both cytotypes can coexist) is acting in those populations.

Unparalleled rates of species diversification in Europe

“…It is tempting to hypothesize that the possession of such an unusual phenology in a context of predictable summer drought may have influenced diversification processes by triggering strong local divergence of floral characters in response to pollinators, which are rare in the summer. An additional force that may have promoted rapid reproductive isolation is the occurrence of polyploidization events, given that genome duplications seem to occur readily in the genus (Carolin 1957;Weiss et al 2002). However, both these hypotheses raise the question as to why Dianthus has diversified so extensively in Europe but not in the summer-dry Cape of South Africa, despite the fact that African carnations share similar phenology and climate, and should be as prone to polyploidization as their Northern Hemisphere relatives.…”

Cytotaxonomy of two species of genus Chrysolaena H. Robinson, 1988 (Vernonieae, Asteraceae) from Northeast Paraguay

“…Since the taxonomic treatment realized by Robinson (1988), where the author segregates Chrysolaena from Vernonia Schreb., 1791, most of the studies have been focused in nomenclature, anatomy, cytology and palynology (Martins and Oliveira 2007, Oliveira et al 2007b, Mendonça et al 2007, Dematteis 2009, Galastri et al 2010, Via do Pico and Dematteis 2012a, 2012b, 2013, Appezzato-da-Glória et al 2012). Despite these contributions, the chromosome information is still scarce.…”

Allozyme Variation in Diploid, Polyploid and Mixed-Ploidy Populations of the Pilosella alpicola Group (Asteraceae): Relation to Morphology, Origin of Polyploids and Breeding System

“…Independent autopolyploid origin of polyploids within diploid populations is supported also by previously established commonness of mixed ploidy populations (75%) and absence of morphological and ITS differentiation (Šingliarová et al 2011). While there are numerous examples of secondary contact zones of previously allopatric cytotypes (e.g., Thompson and Lumaret 1992;Hardy et al 2000;Husband and Sabara 2004;Schlaepfer et al 2008;Kolář et al 2009), evidence for primary contact zones is still quite sparse (Soltis and Soltis 1989;Weiss et al 2002;Kolář et al 2009;Trávníček et al 2011).…”