Exercising the most influence or control. Most prominent, as in position; ascendant. Genetics Of, relating to, or being an allele that produces the same phenotypic effect whether inherited with a homozygous or heterozygous allele. Ecology Of, relating to, or being a species that is most characteristic of an ecological community and usually determines the presence, abundance, and type of other species. Music Relating to or based on the fifth tone of a diatonic scale. Genetics A dominant allele or trait. Ecology A dominant species. Music The fifth tone of a diatonic scale.