There is also correspondence in the position of sites under positive directional selection in the stick insects and those identified as either under positive selection, associated with fitness differences or segregating between other arthropod species ([ 18, 38, 54]; Figure 3).
Rapid evolution of these proteins appears to proceed through the action of positive (directional) selection, increasing the proportion of nonsynonymous substitutions (those that cause amino acid changes) relative to synonymous substitutions (the dn/ds ratio) [ 25].
In short, an optimum sperm length in birds might reflect a (temporary) resolution of the evolutionary arms-race with female sperm storage tubule length, which is the major force behind the interspecific pattern of positive directional selection in sperm length in birds [e.g. 9], [11].
Altogether, our results strongly support age-1 as the focal point of positive directional selection and a global selective sweep.
However, no investigation before now has aimed to test rigorously using population genetic and phylogenetic tests the occurrence of natural positive directional or balancing selection on a sandfly salivary peptide.
Sequence analysis of nine genes involved in the OXPHOS pathway revealed signatures of both purifying and positive (directional) selection in the mitochondrial genome of the Atlantic salmon, a non-model organism that has been widely used in studies of local adaptation [ 39].
The logic value of a positive directional fault is 1, and that of the negative directional fault is equal to −1, and 0 means there is no fault.
Contrary to simple predictions, we found evidence for strong stabilizing selection on the ontogeny of unfed hatchery fry, with weaker evidence for positive directional selection on the ontogeny of fed fry.
Additionally, in the intron 3 of the OXTR gene, the SNP rs59190448 appears to be under positive directional selection.
In this process, the mutant will in general remain under positive directional selection and will displace the first strain in a selective sweep, as observed in the actual process of influenza (Plotkin et al. 2002).
