Abstract
The genusViscum is very suitable for study of structural rearrangements in chromosomes, having very large chromosomes, low basic number and very little polyploidy. An extensive survey of the dioecious speciesV. album (n=10) in Japan has revealed the widespread occurrence of several different chromosomal translocation complexes. Male plants are always heterozygous for large sex-associated translocation complexes, having 6II ⊙8 (six bivalents and a ring-of-eight) or 5II ⊙10 or rarely 4II ⊙12 at meiosis. Female plants are homozygous for these complexes, usually having 10II. There is also a floating ⊙4 which occurs in both male and female plants. Female plants may be heterozygous for another ⊙4 or ⊙6, which do not occur in male plants. Models are presented to account for the relationship between all of the translocations involved.
The high levels of translocation heterozygosity are probably important in maintaining heterozygosity in the species for large complexes of adaptive genes. However the sex-associated permanent translocation heterozygosity may have originally been established as a mechanism to stabilize dioecy based on non-allelic unlinked genes for maleness and femaleness.
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References
Audus, L.J. 1972. Plant Growth Substances. Leonard Hill London.
Baker, H.G. 1967. Support for Baker’s Law-as a rule. Evolution21: 853–856.
Barlow, B.A. andD. Wiens. 1975. Permanent translocation heterozygosity inViscum hildebrandtii Engl. andV. engleri Tiegh. (Viscaceae). Chromosoma53: 265–272.
—. 1976. Translocation heterozygosity and sex ratio inViscum fischeri. Heredity37: 27–40.
——,C. Weins, W.H. Busby andC. Brighton. 1978. Permanent translocation heterozygosity inViscum album andV. cruciatum: sex, association balanced lethals, sex ratios. Heredity40: 33–38.
Bawa, K.S. andP.A. Opler. 1975. Dioecism in tropical forest trees. Evolution29: 167–179.
Bloom, W.L. 1977. Translocation heterozygosity, genetic heterozygosity, and inbreeding inClarkia speciosa. Evolution31: 256–264.
Charlesworth, B. andD. Charlesworth. 1978. A model for the evolution of dioecy and gynodioecy. Amer. Nat.112: 975–997.
Clealand, R.E. 1972.Oenothera: Cytogenetics and Evolution, Academic Press, London.
Coutinho, L. De A. 1957. Observacoes cariologicas enViscum cruciatum ieber. Alguns aspectos da estrutura to centromereo. Genet. Iber.9: 117–127.
Danser, B. 1941. The British-Indian species ofViscum revised and compared with those of South-Eastern Asia, Malaysia, and Australia. Blumea4: 261–319.
James, S.H. 1970. Complex hybridity inIsotoma petraea. Heredity25: 53–77.
Mechelke, F. 1976. Sex-correlated complex heterozygosity inViscum album L. Naturwiss.8: 390.
Ono, T. 1937. On sex chromosomes in wild hops. Bot. Mag. Tokyo51: 110–115.
Ross, M.D. andB.S. Weir. 1976. Maintenance of males and females in hermaphrodite populations and the evolution of dioecy. Evolution30: 425–441.
Smith, B.W. 1972. Evolution of sex determining mechanisms inRumex. Chromosomes Today2: 172–182.
White, M.J.D. 1973. Animal Cytology and Evolution. Cambr. Univ. Press, Cambridge.
Wiens, D. 1975. Chromosome numbers in African and Madagascan Loranthaceae and Viscaceae. Bot. J. Linn. Soc.71: 295–310.
— andB.A. Barlow. 1971. The cytogeography and relationships of the viscaceous and eremolepidaceous mistletoes. Taxon20: 313–332.
— 1973. Unusual translocation heterozygosity in an East African mistletoe (Viscum fischeri). Nature New Biol.243 93–94.
— 1975. Permanent translocation heterozygosity and sex determination in East African mistletoes. Science187: 1208–1209.
— 1979. Translocation heterozygosity and the origin of dioecy inViscum. Heredity42: 201–222.
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Barlow, B.A. Viscum album in Japan: Chromosomal translocations, maintenance of heterozygosity and the evolution of dioecy. Bot Mag Tokyo 94, 21–34 (1981). https://doi.org/10.1007/BF02490200
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DOI: https://doi.org/10.1007/BF02490200