Glossary of "Evolution (4th ed.)" by Futuyma & Kirkpatrick (2017)
- The allele frequency, or combination of allele frequencies at two or more loci, at which the mean fitness of a population has a (local) maximum. Also, the mean phenotype (for one or more characters) that maximizes mean fitness. An adaptive valley is a set of allele frequencies at which mean fitness has a minimum.
- Futuyma, D. J. & Kirkpatrick, M. 2017. Evolution, 4th ed. -xviii + 602 pp. Sinauer Associates, Inc., Sunderland.