Article

Shrinking genomes? Evidence from genome size variation in Crepis (Compositae).

Botanic Garden and Botanical Museum Berlin-Dahlem, Freie Universität Berlin, Berlin, Germany.
Plant Biology (Impact Factor: 2.32). 01/2011; 13(1):185-93. DOI: 10.1111/j.1438-8677.2010.00341.x
Source: PubMed

ABSTRACT Large-scale surveys of genome size evolution in angiosperms show that the ancestral genome was most likely small, with a tendency towards an increase in DNA content during evolution. Due to polyploidisation and self-replicating DNA elements, angiosperm genomes were considered to have a 'one-way ticket to obesity' (Bennetzen & Kellogg 1997). New findings on how organisms can lose DNA challenged the hypotheses of unidirectional evolution of genome size. The present study is based on the classical work of Babcock (1947a) on karyotype evolution within Crepis and analyses karyotypic diversification within the genus in a phylogenetic context. Genome size of 21 Crepis species was estimated using flow cytometry. Additional data of 17 further species were taken from the literature. Within 30 diploid Crepis species there is a striking trend towards genome contraction. The direction of genome size evolution was analysed by reconstructing ancestral character states on a molecular phylogeny based on ITS sequence data. DNA content is correlated to distributional aspects as well as life form. Genome size is significantly higher in perennials than in annuals. Within sampled species, very small genomes are only present in Mediterranean or European species, whereas their Central and East Asian relatives have larger 1C values.

0 Bookmarks
 · 
134 Views
  • Organisms Diversity & Evolution 03/2012; 12(1):1-16. · 3.37 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The effects of chromosome rearrangement on genome size are poorly understood. While chromosome duplications and deletions have predictable effects on genome size, chromosome fusion, fission, and translocation do not. In this study, we investigate genome size and chromosome number evolution in 87 species of Carex, one of the most species-rich genera of flowering plants and one that has undergone an exceptionally high rate of chromosome rearrangement. Using phylogenetic generalized least-squares regression, we find that the correlation between chromosome number and genome size in the genus grades from flat or weakly positive at fine phylogenetic scales to weakly negative at deeper phylogenetic scales. The rate of chromosome evolution exhibits a significant increase within a species-rich clade that arose approximately 5 million years ago. Genome size evolution, however, demonstrates a nearly constant rate across the entire tree. We hypothesize that this decoupling of genome size from chromosome number helps explain the high lability of chromosome number in the genus, as it reduces indirect selection on chromosome number.
    Evolution 09/2012; 66(9):2708-22. · 4.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Studies in experimental grasslands have shown variation in plant individual performance in response to neighbourhood diversity. To which extent these responses are due to phenotypic plasticity or genetic variation is largely unknown. We collected seed families of five herbaceous species (Cirsium oleraceum, Crepis biennis, Plantago lanceolata, Plantago media and Rumex acetosa) in monocultures and 60-species mixtures five years after establishment and replanted or transplanted the offspring into the same monocultures and 60-species mixtures. In all five species the actual environment significantly affected plant survival, growth and performance in terms of shoot biomass and investment into reproduction, indicating stronger competition for light and different levels of herbivory in mixtures as compared with monocultures. Effects of the original environment were smaller and less consistent, but indicated differential selection in monocultures vs. mixtures. The interaction between actual and original environment, corresponding to the “home” vs. “away” comparison, was rarely significant, yet this was providing a first sign of local adaptation. We conclude that, for the investigated plant species, more than five growing seasons in monocultures or mixtures would be needed to better demonstrate the selection of genotypes specifically adapted to monocultures or mixtures. A faster local adaptation may have been prevented by the ability of these species to respond to variation in neighbourhood diversity to a large degree via phenotypic plasticity and other factors.
    Basic and Applied Ecology 06/2011; 12(4):360-371. · 2.39 Impact Factor

Full-text (2 Sources)

Download
16 Downloads
Available from
Oct 7, 2014