Linking genome size variation to population phenotypic variation within the rotifer, Brachionus asplanchnoidis

Eukaryotic organisms usually contain much more genomic DNA than expected from their biological complexity. In explaining this pattern, selection-based hypotheses suggest that genome size evolves through selection acting on correlated life history traits, implicitly assuming the existence of phenotypic effects of (extra) genomic DNA that are independent of its information content. Here, we present conclusive evidence of such phenotypic effects within a well-mixed natural population that shows heritable variation in genome size. We found that genome size is positively correlated with body size, egg size, and embryonic development time in a population of the monogonont rotifer Brachionus asplanchnoidis. The effect on embryonic development time was mediated partly by an indirect effect (via egg size), and a direct effect, the latter indicating an increased replication cost of the larger amounts of DNA during mitosis. Our results suggest that selection-based change of genome size can operate in this population, provided it is strong enough to overcome drift or mutational change of genome size. Claus-Peter Stelzer et al. take advantage of genome size variation within a natural population of the rotifer, Brachionus asplanchnoidis, to investigate the effects of genome size on phenotypic correlates, such as cell size and development time. Their results suggest a positive correlation between genome size and female adult body size, egg size, and development time.

Automated summary

The study found a positive correlation between genome size and body size, egg size, and embryonic development time in a natural population, indicating genetic variation influences the relationship between these traits.