The new mutation theory of phenotypic evolution
Masatoshi Nei *
Author Affiliations
Institute of Molecular Evolutionary Genetics and Department of Biology, Pennsylvania State University, 328 Mueller Laboratory, University Park, PA 16802
Edited by Daniel L. Hartl, Harvard University, Cambridge, MA, and approved June 13, 2007 (received for review April 16, 2007)
Abstract
Recent studies of developmental biology have shown that the genes controlling phenotypic characters expressed in the early stage of development are highly conserved and that recent evolutionary changes have occurred primarily in the characters expressed in later stages of development. Even the genes controlling the latter characters are generally conserved, but there is a large component of neutral or nearly neutral genetic variation within and between closely related species. Phenotypic evolution occurs primarily by mutation of genes that interact with one another in the developmental process. The enormous amount of phenotypic diversity among different phyla or classes of organisms is a product of accumulation of novel mutations and their conservation that have facilitated adaptation to different environments. Novel mutations may be incorporated into the genome by natural selection (elimination of preexisting genotypes) or by random processes such as genetic and genomic drift. However, once the mutations are incorporated into the genome, they may generate developmental constraints that will affect the future direction of phenotypic evolution. It appears that the driving force of phenotypic evolution is mutation, and natural selection is of secondary importance.
Footnotes
E-mail: nxm2@psu.edu
Author contributions: M.N. wrote the paper.
The author declares no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at
Abbreviations: GRN, gene regulatory network; MC1R, melanocortin-1 receptor; OR, olfactory receptor.
© 2007 by The National Academy of Sciences of the USA
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Masatoshi Nei *
Author Affiliations
Institute of Molecular Evolutionary Genetics and Department of Biology, Pennsylvania State University, 328 Mueller Laboratory, University Park, PA 16802
Edited by Daniel L. Hartl, Harvard University, Cambridge, MA, and approved June 13, 2007 (received for review April 16, 2007)
Abstract
Recent studies of developmental biology have shown that the genes controlling phenotypic characters expressed in the early stage of development are highly conserved and that recent evolutionary changes have occurred primarily in the characters expressed in later stages of development. Even the genes controlling the latter characters are generally conserved, but there is a large component of neutral or nearly neutral genetic variation within and between closely related species. Phenotypic evolution occurs primarily by mutation of genes that interact with one another in the developmental process. The enormous amount of phenotypic diversity among different phyla or classes of organisms is a product of accumulation of novel mutations and their conservation that have facilitated adaptation to different environments. Novel mutations may be incorporated into the genome by natural selection (elimination of preexisting genotypes) or by random processes such as genetic and genomic drift. However, once the mutations are incorporated into the genome, they may generate developmental constraints that will affect the future direction of phenotypic evolution. It appears that the driving force of phenotypic evolution is mutation, and natural selection is of secondary importance.
Footnotes
E-mail: nxm2@psu.edu
The author declares no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at
Abbreviations: GRN, gene regulatory network; MC1R, melanocortin-1 receptor; OR, olfactory receptor.
© 2007 by The National Academy of Sciences of the USA
