Abstract
Algebraic models of gynodioecy show that the effects on the equilibrium sex ratio of the relative survival and seed production of the sexes and of inbreeding of male-fertile plants are identical for all genic modes of inheritance, provided that different genotypes among male-fertile plants (or among females) do not differ in average fitness. The effects of three modes of inbreeding on equilibrium sex ratios are examined. If there is competition between self- and cross-fertilization of male-fertile individuals, a stable sexual dimorphism can be maintained by an outbreeding advantage of females if both the proportion of cross-fertilized seeds among those borne on male-fertile individuals,t, and the inbreeding depression (fitness inbred/outbred seeds),i, are less than one half. A lower frequency of females is obtained for the same values oft andi if self-fertilization precedes cross-fertilization. If self-fertilization follows cross-fertilization, gynodioecy cannot be maintained by an outbreeding advantage of females. When the sex phenotypes of gynodioecious populations are determined by cytoplasmic inheritance, females need only a slight advantage over males in survival, ovule production or outbreeding to persist at equilibrium. When determined by nuclear genes, androdioecy can be maintained by greater fecundity or a higher survival rate of males than of female-fertile plants, but not by an outbreeding advantage. Androdioecy cannot be maintained with cytoplasmic inheritance of sex. The models suggest explanations for the more frequent occurrence of gynodioecy than of andrdioecy, the high frequency of gynodioecy in Hawaii and New Zealand, and the origin of gynodioecy from hermaphrodite but not from monoecious ancestors.
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References
Baker, H. G. (1955). Self-compatibility and establishment after “long-distance” dispersal.Evolution 9: 347–349.
Baker, H. G. (1967). Support for Baker's Law—as a Rule.Evolution 21: 853–856.
Burrows, C. J. (1960). Studies in Pimelea. I. The Breeding System.Trans. R. Soc. N.Z. 88: 29–45.
Carlquist, S. (1966). The biota of long-distance dispersal. IV. Genetic systems in the floras of oceanic islands.Evolution 20: 433–455.
Carlquist, S. (1973). Island Biology. Columbia University Press, New York.
Connor, H. E. (1960). Breeding systems in New Zealand grasses. III. Festuceae, Aveneae and Agrostideae.N.Z. Jl agric. Res. 3: 728–733.
Connor, H. E. (1973). Breeding systems in Cortaderia.Evolution 27: 663–678.
Darwin, C. (1877). The different forms of flowers on plants of the same species. Murray, London.
Frankel, O. H. &J. B. Hair, (1937). Studies on the cytology, genetics and taxonomy of New Zealand Hebe and Veronica (Part 1).N.Z. Jl Sci. Technol. 18: 669–687.
Gillett, G. W. (1972). The role of hybridization in the evolution of the Hawaiian flora. In: Taxonomy, phytogeography and evolution, (ed. byD. H. Valentine), pp. 205–209. Academic Press, London.
Gilmartin, A. J. (1968). Baker's law and dioecism in the Hawaiian flora; an apparent contradiction.Pacif. Sci. 22: 285–292.
Godley, E. J. (1966). Breeding systems in New Zealand plants. 4. Self-sterility in Pentachondra pumila.N.Z. Jl Bot. 4: 249–254.
Heine, E. M. (1937). Observations on the pollination of New Zealand flowering plants.Trans. R. Soc. N.Z. 67: 133–148.
Ho, Tai-Ying &M. D. Ross (1973). Maintenance of male sterility in plant populations. II. Heterotic models.Heredity 31: 282–286.
Jain, S. K. (1959). Male sterility in flowering plants.Biblphia genet. 18: 101–166.
Jain, S. K. (1961). On the possible adaptive significance of male sterility in predominantly inbreeding populations.Genetics 46: 1237–1240.
Laser, K. D. &N. R. Lersten (1972). Anatomy and cytology of microsporogenesis in cytoplasmic male sterile angiosperms.Bot. Rev. 38: 425–454.
Lewis, D. (1941). Male sterility in natural populations of hermaphrodite plants.New Phytol. 40: 56–63.
Lloyd, D. G. (1973). Sex ratios in sexually dimorphic Umbelliferae.Heredity 31: 239–249.
Lloyd, D. G. (1974a). Theoretical sex ratios of dioecious and gynodioecious angiosperms.Heredity 32: 11–34.
Lloyd, D. G. (1974b). The genetic contribution of individual males and females in dioecious and gynodioecious angiosperms.Heredity 32: 45–51.
McComb, J. A. (1966). The sex forms of species in the flora of the south west of Western Australia.Aust. J. Bot. 14: 303–316.
Rick, C. M. (1948). Genetics and development of nine male-sterile tomato mutants.Hilgardia 18: 599–633.
Ross, M. D. (1970). Evolution of dioecy from gynodioecy.Evolution 24: 847–828.
Ross, M. D. &R. F. Shaw (1971). Maintenance of male sterility in plant populations.Heredity 26: 1–8.
Thomson, G. (1880). On the fertilization, etc., of New Zealand flowering plants.Trans. N. Z. Inst. 13: 244–291.
Valdeyron, G., B. Dommee &A. Valdeyron, (1973). Gynodioecy; another computer simulation model.Am. Nat. 107: 454–459.
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Lloyd, D.G. The maintenance of gynodioecy and androdioecy in angiosperms. Genetica 45, 325–339 (1975). https://doi.org/10.1007/BF01508307
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DOI: https://doi.org/10.1007/BF01508307