Abstract
Outcrossing rates, seed yields and the incidence of seed abortion were estimated in different-sized populations of a rare clonal mallee, Eucalyptus argutifolia Grayling and Brooker. Multi-locus estimates of the outcrossing rate were high in most populations (tm = 0.79–0.96), and no relationship between population size and the outcrossing rate was evident. In addition, significant amounts of interspecific hybridization were found in some small populations (up to 47 per cent of the seeds assayed). These estimates were much higher than expected, as it was apparent that the potential for geitonogamous pollination far exceeded that of outcrossing. Pollination experiments indicated that E. argutifolia is self-compatible, and therefore the higher than expected outcrossing rates were attributed to inbreeding depression. This view was supported by substantial levels (over 50 per cent) of seed abortion. Selection against homozygotes was also evident during later stages of development, and this resulted in adult populations having genotypic proportions similar to those expected under random mating (complete outcrossing). It was suggested that this selection later in the life cycle offset the purging of early-acting lethal (and semi-lethal) recessives and may explain why even small populations maintain high genetic loads. Similar explanations may be applied to other mass-flowering eucalypts that maintain strong inbreeding depression despite a mixed-mating system.
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Ashton, D H. 1975. Studies of flowering behaviour in Eucalyptus regnans F. Muell. Aust J Bot, 23, 399–411.
Barrett, S C H, and Charlesworth, D. 1991. Effect of a change in the level of inbreeding on the genetic load. Nature, 352, 522–524.
Barrett, S C H, and Kohn, J R. 1991. Genetic and evolutionary consequences of small population size in plants: implications for conservation. In: Falk, D. A. and Holsinger, K. E. (eds) Genetics and Conservation of Rare Plants, pp. 3–30. Oxford University Press, Oxford.
Boland, D J, Brooker, M I H, and Turnball, J W. 1980. Eucalyptus Seed. CSIRO, Canberra.
Brooker, M I H, and Kleinig, D A. 1990. Field Guide to Eucalypts: Volume 2 South-western and Southern Australia, Inkata Press, Melbourne.
Brown, A H D. 1970. The estimation of Wright's fixation index from genotypic frequencies. Genetica, 41, 399–406.
Brown, A H D, and Allard, R W. 1970. Estimation of the mating system in open-pollinated maize populations using isozyme polymorphisms. Genetics, 66, 133–145.
Brown, A H D, and Weir, B S. 1983. Measuring genetic variability in plant populations. In: Tanksley, S. D. and Orton, T. J. (eds) Isozymes in Plant Genetics and Breeding, Part A, pp. 219–239. Elsevier Science Publishers, Amsterdam.
Brown, A H D, Burdon, J J, and Jarosz, A M. 1989. Isozyme analysis of plant mating system. In: Soltis, D. E. and Soltis, P. M. (eds) Isozymes in Plant Biology, pp. 73–86. Dioscorides Press, Portland, OR.
Carr, S G M, and Carr, D J. 1962. Convergence and progression in Eucalyptus and Symphyomyrtus. Nature, 196, 969–972.
Charlesworth, D, and Charlesworth, B. 1987. Inbreeding depression and its evolutionary consequences. Ann Rev Ecol Syst, 18, 237–268.
Constantine, C C, Hobbs, R P, and Lymbery, A J. 1994. FORTRAN programs for analysing population structure from multilocus genotypic data. J Hered, 85, 336–337.
Cunningham, T M. 1957. Seed production and seed fall of Eucalyptus regnans F. Muell. Aust For, 21, 30–39.
Eckert, C G, and Barrett, S C H. 1994. Post-pollination mechanisms and the maintenance of outcrossing in selfcompatible, tristylous, Decodon verticillatus (Lythra-ceae). Heredity, 72, 396–411.
Ellis, M F, and Sedgley, M. 1992. Floral morphology and breeding system of three species of Eucalyptus, Section Bisectaria (Myrtaceae). Aust J Bot, 40, 249–262.
Florence, R G. 1964. A comparative study of flowering and seed production in six blackbutt (Eucalyptus pilularis Sm.) forest stands. Aust For, 28, 23–33.
Fripp, Y J. 1982. Allozyme variation and mating system in two populations of Eucalyptus kitsoniana (Luehm.) Maiden. Aust For Res, 13, 1–10.
Griffin, A R. 1980. Floral phenology of a stand of mountain ash (Eucalyptus regnans F. Muell.) in Gippsland, Victoria. Aust J Bot, 28, 393–404.
Griffin, A R, and Hand, F C. 1979. Post-anthesis development of flowers of Eucalyptus regnans F. Muell. and the timing of artificial pollination. Aust For Res, 9, 9–15.
Griffin, A R, Moran, G F, and Fripp, Y J. 1987. Preferential outcrossing in Eucalyptus regnans F. Muell. Aust J Bot, 35, 465–475.
Griffin, A R, Burgess, I P, and Wolf, L. 1988. Patterns of natural and manipulated hybridisation in the genus Eucalyptus L'Hérit.—a review. Aust J Bot, 36, 41–66.
Handel, S N. 1985. The intrusion of clonal growth patterns on plant breeding systems. Am Nat, 125, 367–384.
Hodgson, L M. 1976. Some aspects of flowering and reproductive behaviour in Eucalyptus grandis (Hill) Maiden at J. D. M. Keet forest research station. 2. The fruit, seed, seedlings, self-fertility, selfing and inbreeding effects. S Afr For J, 98, 32–43.
Husband, B C, and Schemske, D W. 1995. Magnitude and timing of inbreeding depression in a diploid population of Epilobium angustifolium (Onagraceae). Heredity, 75, 206–215.
James, S H, and Kennington, W J. 1993. Selection against homozygotes and resource allocation in the mating system of Eucalyptus camaldulensis Dehnh. Aust J Bot, 41, 381–391.
Jeník, J. 1994. Clonal growth in woody plants: a review. Folia Geo Phyto, 29, 291–306.
Karron, J D, Thumser, N N, Tucker, R, and Hesse-Nauer, A J. 1995. The influence of population density on outcrossing rates in Mimulus ringens. Heredity, 75, 175–180.
Kennington, W J, and James, S H. 1997. Contrasting patterns of clonality in two closely related mallee species from Western Australia, Eucalyptus argutifolia and E. obtusiflora (Myrtaceae).Aust J Bot, in press.
Kenrick, J, and Knox, R B. 1985. Self-incompatibility in the nitrogen fixing tree Acacia retinodes. Theor Appl Genet, 69, 481–488.
Lande, R, and Schemske, D W. 1985. The evolution of self-fertilization and inbreeding depression in plants. I. Genetic models. Evolution, 39, 24–40.
Lande, R, Schemske, D W, and Schultz, S T. 1994. High inbreeding depression, selective interference among loci, and the threshold selfing rate for purging recessive lethal mutations. Evolution, 48, 965–978.
Lindman, H R. 1974. Analysis of Variance in Complex Experimental Designs. W. H. Freeman, New York.
Martin, F W. 1959. Staining and observing pollen tubes in the style by means of fluorescence. Stain Technol, 34, 125–128.
Moran, G F. 1992. Patterns of genetic diversity in Australian tree species. New Forests, 6, 49–66.
Moran, G F, and Bell, J C. 1983. Eucalyptus. In: Tanksley, S. D. and Orton, T. J. (eds) Isozymes in Plant Genetics and Breeding, Part B, pp. 423–441. Elsevier Science Publishers, Amsterdam.
Moran, G F, and Hopper, S D. 1983. Genetic diversity and the insular population structure of the rare granite rock species, Eucalyptus caesia Benth. Aust J Bot, 31, 162–172.
Phillips, M A, and Brown, A H D. 1977. Mating system and hybridity in Eucalyptus pauciflora. Aust J Biol Sci, 30, 337–344.
Potts, B M, Potts, W C, and Cauvin, B. 1987. Inbreeding and interspecific hybridization in Eucalyptus gunnii. Silvae Genet, 36, 194–198.
Pryor, L D. 1951. Controlled pollination of Eucalyptus. Proc Linn Soc, N S W, 76, 135–139.
Pryor, L D, and Johnson, L A S. 1971. A Classification of the Eucalypts. Australian National University Press, Canberra.
Reinartz, J A, and Les, D H. 1994. Bottleneck-induced dissolution of self-incompatibility and breeding system consequences in Aster furcatus (Asteraceae). Am J Bot, 81, 446–455.
Ritland, K. 1990. A series of FORTRAN computer programs for estimating plant mating systems. J Hered, 81, 235–237.
Ritland, K, and Jain, S. 1981. A model for the estimation of outcrossing rate and gene frequencies using n independent loci. Heredity, 47, 35–52.
Sampson, J F, Hopper, S D, and James, S H. 1988. Genetic diversity and the conservation of Eucalyptus crucis Maiden. Aust J Bot, 36, 447–460.
Sampson, J F, Hopper, S D, and James, S H. 1989. The mating system and population genetic structure in a bird-pollinated mallee, Eucalyptus rhodantha. Heredity, 63, 383–393.
Sedgley, M. 1989. Ovule and seed development in Eucalyptus woodwardii Maiden (Symphyomyrtus). Bot Gaz, 150, 271–280.
Sedgley, M, and Smith, R M. 1989. Pistil receptivity and pollen tube growth in relation to the breeding system of Eucalyptus woodwardii (Symphyomyrtus: Myrtaceae). Ann Bot, 64, 21–31.
Sedgley, M, Hand, F C, Smith, R M, and Griffin, A R. 1989. Pollen tube growth and early seed development in Eucalyptus regnans F. Muell. (Myrtaceae) in relation to ovule structure and preferential outcrossing. Aust J Bot, 37, 397–411.
Stace, H M. 1995. Protogyny, self-incompatibility, and pollination in Anthocercis gracilis (Solanaceae). Aust J Bot, 43, 451–459.
Tibbits, W N. 1988. Germination and morphology of progeny from controlled pollinations of Eucalyptus nitens (Deane and Maiden) Maiden. Aust J Bot, 36, 677–691.
Weir, B S. 1990. Genetic Data Analysis. Sinauer Associates, Sunderland, MA.
Wiens, D. 1984. Ovule survivorship, brood size, life history, breeding systems, and reproductive success in plants. Oecologia, 64, 47–53.
Wiens, D, Calvin, C L, Wilson, C A, Davern, C I, Frank, D, and Seavey, S R. 1987. Reproductive success, spontaneous embryo abortion, and genetic load in flowering plants. Oecologia, 71, 501–509.
Zar, J H. 1984. Biostatistical Analysis, 2nd edn. Prentice-Hall, Englewood Cliffs, NJ.
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Kennington, W., James, S. The effect of small population size on the mating system of a rare clonal mallee, Eucalyptus argutifolia (Myrtaceae). Heredity 78, 252–260 (1997). https://doi.org/10.1038/hdy.1997.39
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DOI: https://doi.org/10.1038/hdy.1997.39
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