Genome and Chromatin: Organization, Evolution, Function

Volume 2 of the series Plant Systematics and Evolution pp 41-66

Genome Size and Phenotypic Evolution in Microseris (Asteraceae, Cichorieae)

  • Konrad BachmannAffiliated withPremedical Biology Program, University of Heidelberg
  • , Kenton L. ChambersAffiliated withPremedical Biology Program, University of Heidelberg
  • , H. James PriceAffiliated withPremedical Biology Program, University of Heidelberg

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Reduction of the nuclear DNA amount in a constant number of n = 9 chromosomes characterizes the evolutionary genetics of the genus Microseris. Correlated with this reduction are physiological, ecological and morphological changes. The morphological changes are of two kinds: (1) nucleotypic, i.e. changes in the dimensions correlated with DNA amount changes; (2) qualitative, specifically concerning an increase in the degree of developmental canalization with a decrease in genome size. The latter changes are amenable to formal genetic analysis, and two polygenic systems are described in some detail. As far as preliminary estimates indicate, the complexity of these polygenic systems is independent of genome size. They are probabely influenced by genome size via nucleotypic limitations on gene expression.

Key Words

Angiosperms Asteraceae = Compositae Cichorieae Microseris. — Evolutionary genetics genome size developmental canalization polymorphism heterocarpy