Polyploidy and other changes at chromosomal level and in genome size: Its role in systematics and evolution exemplified by some genera of Anthemideae and Cardueae (Asteraceae)

Abstract

Polyploidy is one of the major evolutionary forces in plants and in particular in the largest angiosperm family, the Asteraceae. This chromosome set multiplication directly impacts the nuclear DNA contents, in terms of variation at holoploid and monoploid levels. Other karyological changes such as aneuploidy or dysploidy might produce genome size alterations as well, therefore playing also a relevant role as evolutionary forces. All these factors may promote speciation, thus having systematic implications. In this paper we review the mechanisms associated with genome size variation, as well as their evolutionary consequences at phylogenetic, systematic and even taxonomic levels. To do so, C–values and chromosome numbers have been compiled and complemented with other molecular cytogenetic data to be discussed within their respective molecular phylogenetic frameworks. The case studies come from several genera of the Asteraceae belonging to tribes Anthemideae (Artemisia) and Cardueae (Cheirolophus, Echinops and members of Rhaponticum group), which cover a wide range of life strategies (e.g., life cycles, ecology, geographical distribution).

The explosive radiation of Cheirolophus (Asteraceae, Cardueae) in Macaronesia

“…Self-compatibility potential in Cheirolophus [ 17 ] may also have favoured the success of these colonization events, as dispersal of one single seed to a new habitat could establish a sexually reproducing population [ 85 ]. Finally, the basic chromosome number in Cheirolophus is x = 15, implying that the genus is originally polyploid [ 86 , 87 ]. This palaeopolyploidy could result in single fruits carrying higher genetic diversity – due to duplications – than what is expected in a diploid species, thus ameliorating the problem of severe genetic bottlenecks in the founding populations.…”

Chromosome counts and karyotype analysis of some representatives of genusCirsiumMill. (Asteraceae) in Turkey

“…Cirsium displays frequent polyploidy levels ranging from 4x to 7x (2n=112-114 in Cirsium quercetorum Jeps.) (Vallès et al 2012). According to Yüksel et al (2013), the polyploidy level derived from a mechanism of abnormal cell division.…”

Ploidy Level, Karyotype, and DNA Content in the Genus Lonicera

“…The multiplication of chromosome set impacts genome size or the nuclear DNA contents. Nuclear DNA amount variation has strong relationships with many biological factors and implications in plant differentiation and evolution (Bennett and Leitch, 2011;Vall es et al, 2012). Previously reported nuclear DNA contents in seven taxa varied 6-fold, from 1C value = 0.65 pg for Lonicera nigra (Olszewska and Osiecka, 1984) to 3.88 pg for Lonicera vesicarria Komar.…”