Hostname: page-component-848d4c4894-ndmmz Total loading time: 0 Render date: 2024-05-26T10:12:04.264Z Has data issue: false hasContentIssue false

Genic heterozygosity and rate of speciation

Published online by Cambridge University Press:  08 February 2016

John C. Avise*
Department of Zoology, University of Georgia; Athens, Georgia 30602


The hypothesis is proposed that mean level of heterozygosity is functionally related to rate of speciation in evolutionary phylads. Under this hypothesis, phylads which speciate more rapidly do so because of increased level of within-species genetic variability which is then available to conversion to species differences under appropriate ecological or environmental conditions. An important corollary is that rate of speciation could be limited in phylads with low genetic variability, irrespective of environmental considerations.

This hypothesis has been tested with respect to electrophoretically detectable variation in products of structural genes in two families of North American fishes characterized by grossly different rates of speciation. Totals of 69 species of the highly speciose Cyprinidae, and 19 species of the relatively depauperate Centrarchidae, were assayed for mean level of heterozygosity at 11–24 genetic loci. Since Cyprinidae and Centrarchidae exhibit on the average nearly identical levels of genic variation (Ĥ = 0.052 ± 0.004, and Ĥ = 0.049 ± 0.009, respectively), the hypothesis that level of heterozygosity affects rate of speciation in these fishes is not supported.

Nonetheless, the amount of genic variability in both Cyprinidae and Centrarchidae is large, comparable to mean levels in previously studied vertebrates. The great wealth of genome variability, reflected in the electrophoretic variation present in virtually all outcrossing organisms, apparently can accommodate considerable flexibility in rate and pattern of evolutionary response to the various environmental regimes challenging organisms.

Research Article
Copyright © The Paleontological Society 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


Literature Cited

Allard, R. W. 1975. The mating system and microevolution. Genetics. 79:115126.Google ScholarPubMed
Avise, J. C. 1974. Systematic value of electrophoretic data. Syst. Zool. 23:465481.CrossRefGoogle Scholar
Avise, J. C. and Ayala, F. J. 1976. Genetic differentiation in speciose versus depauperate phylads: evidence from the California minnows. Evolution. 30:4658.CrossRefGoogle ScholarPubMed
Avise, J. C. and Smith, M. H. 1974. Biochemical genetics of sunfish II. Genic similarity between hybridizing species. Am. Nat. 108:458472.CrossRefGoogle Scholar
Avise, J. C. and Smith, M. H. 1977. Gene frequency comparisons between sunfish (family Centrarchidae) populations at various stages of evolutionary divergence. Syst. Zool. In press.CrossRefGoogle Scholar
Ayala, F. J. 1975. Genetic differentiation during the speciation process. Evol. Biol. 8:178.Google Scholar
Ayala, F. J. 1976. Molecular Evolution. 277 pp. Sinauer; Sunderland, Mass.Google Scholar
Ayala, F. J., Hedgecock, D., Zumwalt, G. S., and Valentine, J. W. 1973. Genetic variation in Tridacna maxima, an ecological analog of some unsuccessful evolutionary lineages. Evolution. 27:177191.Google ScholarPubMed
Ayala, F. J., Powell, J. R., Tracey, M. L., Mourão, C. A., and Pérez-Salas, S. 1972. Enzyme variability in the Drosophila willistoni group. IV. Genetic variation in natural populations of Drosophila willistoni. Genetics. 70:113139.CrossRefGoogle ScholarPubMed
Ayala, F. J., Valentine, J. W., Barr, L. G., and Zumwalt, G. S. 1974. Genetic variability in a temperate intertidal phoronid, Phoronopsis veridis. Biochem. Genet. 11:413427.CrossRefGoogle Scholar
Berger, E. 1976. Heterosis and the maintenance of enzyme polymorphism. Am. Nat. 110:823839.CrossRefGoogle Scholar
Branson, B. A. and Moore, G. A. 1962. The lateralis components of the acoustico-lateralis system in the sunfish family Centrarchidae. Copeia. 1962:1108.CrossRefGoogle Scholar
Carson, H. L. 1959. Genetic conditions which promote or retard the formation of species. Cold Spring Harbor Symp. Quant. Biol. 24:87105.CrossRefGoogle ScholarPubMed
Carson, H. L. 1968. The population flush and its genetic consequences. Pp. 123137. In: Lewontin, R. C., ed. Population Biology and Evolution. Syracuse Univ. Press; New York.Google Scholar
Fuerst, P. A., Chakraborty, A., and Nei, M. 1977. Statistical studies on protein polymorphism in natural populations. I. Distribution of single locus heterozygosity. Genetics. 86:455483.CrossRefGoogle ScholarPubMed
Gosline, W. A. 1971. Functional Morphology and Classification of Teleostean Fishes. Univ. Press of Hawaii; Honolulu.CrossRefGoogle Scholar
Gosline, W. A. 1974. Certain lateral-line canals of the head in cyprinid fishes, with particular reference to the derivation of North American forms. Jap. J. Ichthyol. 21:915.Google Scholar
Grant, V. 1963. The Origin of Adaptations. Columbia Univ. Press; New York.Google Scholar
Hubbs, C. 1955. Hybridization between fish species in nature. Syst. Zool. 4:120.CrossRefGoogle Scholar
Hutchinson, G. E. 1959. Homage to Santa Rosalia or why are there so many kinds of animals? Am. Nat. 93:145159.CrossRefGoogle Scholar
Huxley, J. S. 1942. Evolution, the Modern Synthesis. Harper and Brothers; New York.Google Scholar
Kimura, M. and Ohta, T. 1971. Protein polymorphisms as a phase of molecular evolution. Nature. 29:467469.CrossRefGoogle Scholar
Levins, R. 1968. Evolution in Changing Environments. Princeton Monogr. Pop. Biol. 2.CrossRefGoogle Scholar
Lewontin, R. C. 1974. The Genetic Basis of Evolutionary Change. Columbia Univ. Press; New York.Google Scholar
McDonald, J. F. and Ayala, F. J. 1974. Genetic response to environmental heterogeneity. Nature. 250:572574.CrossRefGoogle ScholarPubMed
Mayr, E. 1963. Animal Species and Evolution. Harvard Univ. Press; Cambridge, Mass.CrossRefGoogle Scholar
Miller, R. R. 1959. Origin and affinities of the freshwater fish fauna of western North America. In: Zoogeogr. Hubbs, C. L., ed. Am. Assoc. Adv. Sci. Pub. 51:187222.Google Scholar
Miller, R. R. 1965. Quaternary freshwater fishes of North America. Pp. 569581. In: The Quaternary of the United States. Princeton Univ. Press; Princeton, New Jersey.Google Scholar
Nei, M. 1975. Molecular Population Genetics and Evolution. North-Holland; Amsterdam.Google ScholarPubMed
Nei, M., Maruyama, T., and Chakraborty, R. 1975. The bottleneck effect and genetic variability in populations. Evolution. 29:110.CrossRefGoogle ScholarPubMed
Nei, M. and Roychoudhury, A. K. 1974. Sampling variances of heterozygosity and genetic distance. Genetics. 76:379390.CrossRefGoogle ScholarPubMed
Powell, J. R. 1971. Genetic polymorphisms in varied environments. Science. 174:10351036.CrossRefGoogle ScholarPubMed
Powell, J. R. 1976. Protein variation in natural populations of animals. Evol. Biol. 8:79119.Google Scholar
Rensch, B. 1959. Evolution Above the Species Level. Methuen and Co.; London.CrossRefGoogle Scholar
Roberts, F. L. 1964. A chromosome study of twenty species of Centrarchidae. J. Morph. 115:401418.CrossRefGoogle ScholarPubMed
Romer, A. S. 1966. Vertebrate Paleontology. Univ. Chicago Press; Chicago, Illinois.Google Scholar
Selander, R. K. 1976. Genic variation in natural populations. Pp. 2145. In: Ayala, F. J., ed. Molecular Evolution. Sinauer; Sunderland, Mass.Google Scholar
Selander, R. K. and Kaufman, D. W. 1973. Genic variability and strategies of adaptation in animals. Proc. Nat. Acad. Sci. 70:18751877.CrossRefGoogle ScholarPubMed
Selander, R. K., Smith, M. H., Yang, S. Y., Johnson, W. E., and Gentry, J. B. 1971. Biochemical polymorphism and systematics in the genus Peromyscus. I. Variation in the old-field mouse (Peromyscus polionotus). Studies in Genetics VI, Univ. Texas Publ. 7103:4990.Google Scholar
Selander, R. K., Yang, S. Y., Lewontin, R. C., and Johnson, W. E. 1970. Genetic variation in the horseshoe crab (Limulus polyphemus), a phylogenetic “relic.” Evolution. 24:402414.Google ScholarPubMed
Simpson, G. G. 1944. The Major Features of Evolution. Columbia Univ. Press; New York.Google Scholar
Soulé, M. 1971. The variation problem: the gene flow-variation hypothesis. Taxon. 20:3750.CrossRefGoogle Scholar
Soulé, M. 1976. Allozyme variation: its determinants in space and time. Pp. 6077. In: Ayala, F. J., ed. Molecular Evolution. Sinauer; Sunderland, Mass.Google Scholar
Stebbins, G. L. 1971. Processes of Organic Evolution. Prentice-Hall; Englewood Cliffs, New Jersey.Google Scholar
Valentine, J. W. 1976. Genetic strategies of adaptation. Pp. 7894. In: Ayala, F. J., ed. Molecular Evolution. Sinauer; Sunderland, Mass.Google Scholar
Valentine, J. W. and Ayala, F. J. 1974. Genetic variation in Frieleia halli, a deep-sea brachiopod. Deep-Sea Res. 22:3744.Google Scholar