Selection favouring phenotypes that are either common or rare is called:

1. Sometimes how common a phenotype is decides its fitness. 2. Frequency-dependent selection is another type of selection. 3. It favors phenotypes that are either common or rare. 4. Favouring the common form is positive, and favouring the rare form is negative. _Source: OpenStax Biology 2e (CC BY 4.0), Ch 19 'The Evolution of Populations', sections 19.1-19.3_