Karyotype diversification and evolution in diploid and polyploidy South American Hypochaeris (Asteraceae) inferred from rDNA localization and genetic fingerprint data.

Hanna Weiss-Schneeweiss (Corresponding author), Karin Tremetsberger, Gerald Schneeweiss, J Parker, Tod Stuessy

    Publications: Contribution to journalArticlePeer Reviewed

    Abstract

    ¿ Background and Aims Changes in chromosome structure and number play an important role in plant evolution. A system well-suited to studying different modes of chromosome evolution is the genus Hypochaeris (Asteraceae) with its centre of species diversity in South America. All South American species uniformly have a chromosome base number of x = 4 combined with variation in rDNA number and distribution, and a high frequency of polyploidy. The aim of this paper is to assess directions and mechanisms of karyotype evolution in South American species by interpreting both newly obtained and previous data concerning rDNA localisation in a phylogenetic context. ¿ Methods Eleven Hypochaeris species from 18 populations were studied using fluorescence in situ hybridisation (FISH) with 35S and 5S rDNA probes. A phylogenetic framework was established from neighbour-net analysis of amplified fragment length polymorphism (AFLP) fingerprint data. ¿ Key Results A single 5S rDNA locus is invariably found on the short arm of chromosome 2. Using 35S rDNA loci, based on number (one or two) and localisation (interstitial on the long arm of chromosome 2, but sometimes lacking, and terminal or interstitial on the short arm of chromosome 3, only very rarely lacking) seven karyotype groups can be distinguished; five of these include polyploids. Karyotype groups with more than one species do not form monophyletic groups. ¿ Conclusions Early evolution of Hypochaeris in South America was characterised by considerable karyotype differentiation resulting from independent derivations from an ancestral karyotype. There was marked diversification with respect to the position and evolution of the 35S rDNA locus on chromosome 3, probably involving inversions and/or transpositions. Among these different karyotype assemblages, the apargioides group and its derivatives constitute by far the majority of species.
    Original languageEnglish
    Pages (from-to)909-918
    Number of pages10
    JournalAnnals of Botany
    Volume101
    Issue number7
    Publication statusPublished - 2008

    Austrian Fields of Science 2012

    • 106052 Cell biology
    • 106012 Evolutionary research
    • 106008 Botany

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