Functional and ecological significance of rDNA intergenic spacer variation in a clonal organism under divergent selection for production rate
- 22 November 2002
- journal article
- Published by The Royal Society in Proceedings Of The Royal Society B-Biological Sciences
- Vol. 269 (1507), 2373-2379
- https://doi.org/10.1098/rspb.2002.2145
Abstract
It has recently been hypothesized that variation in the intergenic spacer (IGS) of rDNA has considerable developmental, evolutionary and ecological significance through effects on growth rate and body C : N : P stoichiometry resulting from the role of the IGS in production of rRNA. To test these ideas, we assessed changes in size and structure of the repetitive region of the IGS, juvenile growth rate (JGR), RNA and phosphorus (P) contents in clonal lineages of Daphnia pulex derived from a single female and subjected to divergent selection on weight–specific fecundity (WSF). As a result of selection, WSF diverged rapidly, with significant reductions within two generations. Other significant changes accompanying shifts in WSF were that juveniles produced by low–WSF females grew more rapidly and had higher RNA and P contents. An increased predominance of long IGS variants was observed in lineages with elevated JGRs and low WSF. The observed variations in IGS length were related to the number of subrepeat units carrying a promoter sequence in the repetitive region. These results strongly support the hypothesized relationships, indicate a genetic mechanism for the evolution of such associations and demonstrate that Daphnia (and perhaps other parthenogens) possess considerable potential for rapid adaptive change in major life–history traits.Keywords
This publication has 42 references indexed in Scilit:
- Copepod development rates in relation to genome size and 18S rDNA copy numberGenome, 2000
- Molecular characterization of ribosomal gene variation within and among NORs segregating in specialized populations of chickenGenome, 1999
- Genetic variation within a parthenogenetic lineageInsect Molecular Biology, 1998
- A study of variation in rDNA ITS regions shows that two haplotypes coexist within a single aphid genomeGenome, 1998
- Evolution of mitotic cell-lineages in multicellular organismsTrends in Ecology & Evolution, 1998
- Rapid response to intraclonal selection in the pea aphid (Acyrthosiphon pisum)Evolutionary Ecology, 1995
- Mutational divergence of life-history traits in an obligate parthenogenGenome, 1994
- rRNA synthesis in the nucleolusTrends in Genetics, 1990
- Variation in structure and expression of ribosomal DNA loci in wheatGenome, 1989
- Estimating cladoceran birth rates: The importance of egg mortality and the egg age distribution1Limnology and Oceanography, 1979