Another alternative is that RGE reflects loss of genomic sequences that are no longer efficiently maintained by selection ("relaxed-selective" pressure).
Though the interactions are entirely mechanistic when considered at the molecular level of description, a fully adequate explanation of why such properties would be selected and maintained by selection requires, in addition, the semiotic level of description.
Thus, if the duplication has been maintained by selection, control of replication may not be the singular or primary selective driving force.
Despite the widespread occurrence of multiple ornaments, and the theoretical interest in how they are maintained by selection, there have been few experimental studies of the phenomenon.
The dearth of pseudogenes suggests that sequence clusters are maintained by selection for high gene-copy number, perhaps due to selection for high expression rates.
These genes show substantially higher values of Tajima's D statistic24 than random genes (Supplementary Fig. 8), as expected for ancestral polymorphisms, regardless of whether they are maintained by selection.
In the actual data we observed 599, and we conclude that either there was gene flow more recently than what is implied by the high divergence under the simple model of splitting or polymorphisms were maintained by selection.
Local adaptation might result from antagonistic pleiotropy, where alternate alleles are favoured in distinct habitats, and polymorphism is maintained by selection.
Two, multiple copies may prove to be beneficial such that their repetition is maintained by selection thereafter ("isofunctionalization"; Oakley et al. 2006).
Stable cell lines were maintained by selection with 5 µg/ml G418.
It is therefore reasonable to conclude that the property is maintained by selection pressure.
