Taxas de cruzamento em uma população natural de Cryptocarya Moschata Nees (Lauraceae)

Outcrossing rates of a natural population of Cryptocarya moschata Nees (Lauraceae)

ARTIGOS

Taxas de cruzamento em uma população natural de Cryptocarya Moschata Nees (Lauraceae)

Outcrossing rates of a natural population of Cryptocarya moschata Nees (Lauraceae)

Pedro Luís Rodrigues de Moraes^{I, II}; Reinaldo Monteiro^III

^IBolsa CAPES, parte da tese de Doutoramento

^IILaboratório de Melhoramento de Plantas, CENA-USP, Caixa Postal 96, 13400-970, Piracicaba, SP, Brasil; Autor para correspondência: E-mail: [e-mail]

^IIIDepartamento de Botânica, IB, UNESP, Caixa Postal 199, 13506-900, Rio Claro, SP, Brasil

ABSTRACT

The mating system of the canopy Brazilian Atlantic rain forest tree Cryptocarya moschata was studied at Parque Estadual Carlos Botelho, São Miguel Arcanjo, São Paulo, Brazil. Outcrossing rates were determined through electrophoretic allozyme markers from seedlings germinated of seed cohorts collected from 35 trees. An indirect estimate of the outcrossing rate at equilibrium gave a mean of t^{^}_eq = 0.51. Direct single locus and multilocus outcrossing rate estimates were t^{^}_s = 0.725 ± 0.041 and t^{^}_m = 0.884 ± 0.034, respectively, indicating a predominant outcrossing mating system. Individual trees outcrossing rates ranged from 27 to 100 (x¯ = 87.8) percent, from t^{^}_m calculated by holding the population pollen allele frequency constant for each family. From Ritland's "sibling-pair" model (correlated mating model), correlation of selfing (_r^s) and correlation of outcrossing paternity (_r^p) were 35.7% and 99.0%, respectively. These results corroborate the fact that there is variation in selfing rates among different trees, but it may also have indicated that when there is inbreeding, most seeds in the trees are likely to be full-sibs.

Key words - allozymes, Lauraceae, mating system, Neotropics, Cryptocarya, Atlantic rain forest, Brazil

RESUMO

O sistema de cruzamento da espécie arbórea de dossel da Mata Atlântica brasileira, Cryptocarya moschata, foi estudado a partir de material proveniente do Parque Estadual Carlos Botelho, São Miguel Arcanjo, São Paulo, Brasil. As taxas de cruzamento foram determinadas através de marcadores alozímicos obtidos de plântulas germinadas de coortes de sementes coletadas de 35 árvores. O valor médio da taxa de cruzamento de equilíbrio (estimador indireto) foi t^{^}_eq = 0.51. As estimativas das taxas de cruzamento uniloco e multilocos (estimadores diretos) foram t^{^}_s = 0.725± 0,041 e t^{^}_m = 0,884 ± 0,034, respectivamente, indicando um sistema de cruzamento predominantemente alogâmico. As taxas de cruzamento de árvores individuais variaram de 27 a 100 ( x¯ = 87,8) porcento, a partir de t^{^}_m calculado com as freqüências gênicas de pólen mantidas constantes ao nível populacional. A partir do modelo de "par de irmãos" (modelo de cruzamento correlacionado) de Ritland, a correlação entre duas progênies irmãs oriundas de autofecundação (_r^s) e a correlação entre duas progênies irmãs oriundas de paternidade por exocruzamento (_r^p) foram 35,7% e 99,0%, respectivamente. Esses resultados corroboram o fato de haver variação nas taxas de autocruzamento entre as diferentes árvores, podendo também indicar que quando há endogamia, a maior parte das sementes nas árvores são provavelmente irmãs-germanas.

Palavras-chave: alozimas, Lauraceae, sistema de cruzamento, Neotrópico, Cryptocarya, Mata Atlântica, Brasil

Texto completo disponível apenas em PDF.

Full text available only in PDF format.

Agradecimentos

Ao Prof. Paulo Sodero Martins (in memoriam) pelo inestimável apoio; ao Prof. Roland Vencovsky, pelas sugestões oferecidas ao manuscrito; ao Instituto Florestal de São Paulo pela permissão de coleta de material.

Recebido em 12/04/2002

Revisado em 09/07/2002

Publicado em 07/08/2002

• ALFENAS, A.C., PETERS, I., BRUNE, W. & PASSADOR, G.C. 1991. Eletroforese de proteínas e isoenzimas de fungos e essências florestais. Universidade Federal de Viçosa, Viçosa.
• ALLARD, R.W. & WORKMAN, P.L. 1963. Population studies in predominantly self-pollinated species. IV. Seasonal fluctuations in estimated values of genetic parameters in lima bean populations. Evolution 17:470-480.
• BAWA, K.S. 1974. Breeding systems of tree species of a lowland tropical community. Evolution 28:85-92.
• BAWA, K.S. 1976. Breeding of tropical hardwoods: an evaluation of underlying bases, current status and future prospects. In Tropical trees: variation, breeding and conservation (J. Burley & B.T. Styles, eds.). Academic Press, London, p.43-59.
• BAWA, K.S., PERRY, D.R. & BEACH, J.H. 1985. Reproductive biology of tropical lowland rain forest trees. 1. Sexual systems and incompatibility mechanisms. Am. J. Bot. 72:331-345.
• BOSHIER, D.H., CHASE, M.R. & BAWA, K.S. 1995. Population genetics of Cordia alliodora (Boraginaceae), a neotropical tree. 2. Mating system. Am. J. Bot. 82:476-483.
• BROWN, A.H.D. 1989. Genetic characterization of plant mating systems. In Plant population genetics, breeding and germplasm resources (A.H.D. Brown, M.T. Clegg, A.L. Kahler & B.S. Weir, eds.). Sinauer Associates, Sunderland, p.145-162.
• BROWN, A.H.D. & 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., BARRETT, S.C.H. & MORAN, G.F. 1985. Mating system estimation in forest trees: models, methods and meanings. In Population genetics in forestry (H.R. Gregorius, ed.). Springer-Verlag, Berlin, p.32-49.
• BROWN, A.H.D., MATHESON, A.C. & ELDRIDGE, K.G. 1975. Estimation of the mating system of Eucalyptus obliqua L'Herit. by using allozyme polymorphisms. Austr. J. Bot. 23:931-949.
• BULLOCK, S.H. 1985. Breeding systems in the flora of a tropical deciduous forest in Mexico. Biotropica 17:287-301.
• CHELIAK, W.M., STROBECK, K.M.C., YEH, F.C.H. & DANCIK, B.P. 1983. Estimation of mating system parameters in plant populations using EM algorithm. Theor. Appl. Genet. 65:157-161.
• CLEGG, M.T. 1980. Measuring plant mating systems. Bioscience 30:814-818.
• EL-KASSABY, Y.A. & RITLAND, K. 1987. Low levels of pollen contamination in a Douglas-fir seed orchard as detected by allozyme markers. Silvae Genetica 35:224-229.
• FISHER, R.A. 1941. Average excess and average effect of a gene substitution. Ann. Eugen. 11:53-63.
• HALL, P., ORRELL, L.C. & BAWA, K.S. 1994. Genetic diversity and mating system in a tropical tree, Carapa guianensis (Meliaceae). Am. J. Bot. 81:1104-1111.
• HAMRICK, J.L. 1990. Isozymes and the analysis of genetic structure in plant populations. In Isozymes in plant biology (D.E. Soltis & P.S. Soltis, eds.). Chapman & Hall, London, p.87-105.
• HAMRICK, J.L. & GODT, M.J. 1990. Allozyme diversity in plant species. In Population genetics and germplasm resources in crop improvement (A.H.D. Brown, M.T. Clegg, A.L. Kahler & B.S. Weir, eds.). Sinauer, Sunderland, MA, p. 43-63.
• HAMRICK, J.L. & SCHNABEL, A. 1985. Understanding the genetic structure of plant populations: some old problems and a new approach. In Population genetics in forestry (H.R. Gregorius, ed.). Springer-Verlag, Berlin, p.50-70.
• JAIN, S.K. & WORKMAN, P.L. 1967. Generalized F-statistics and the theory of inbreeding and selection. Nature 214:674-678.
• KAGEYAMA, P.Y. 1990. Genetic structure of tropical tree species of Brazil. In Reproductive ecology of tropical forest plants (K.S. Bawa & M. Hadley, eds.). UNESCO / The Parthenon Publishing Group, Paris, p.375-387.
• KEPHART, S.R. 1990. Starch gel electrophoresis of plant isozymes: a comparative analysis of techniques. Am. J. Bot. 77:693-712.
• LOVELESS, M.D. & HAMRICK, J.L. 1984. Ecological determinants of genetic structure in plant populations. Ann. Rev. Ecol. Syst. 15:65-95.
• MORAN, G.F. & BROWN, A.H.D. 1980. Temporal heterogeneity of outcrossing rates in alpine ash (Eucalyptus delegatensis R. T. Bak.). Theor. Appl. Genet. 57:101-105.
• MORAES, P.L.R., MONTEIRO, R. & VENCOVSKY, R. 1999. Conservação genética de populações de Cryptocarya moschata Nees (Lauraceae) na Mata Atlântica do estado de São Paulo. Rev. Bras. Bot. 22:237-248. (http://www.scielo.br/scielo.php?script=sci_abstract&pid=S0100-84041999000500004&lng=en&nrm=iso)
• MORAES, P.L.R., MONTEIRO, R. & VENCOVSKY, R. 2002. Genetic differentiation and diversity of natural populations of Cryptocarya spp. (Lauraceae) from the Brazilian Atlantic rain forest. Lundiana 3(2) (no prelo).
• MURAWSKI, D.A. & BAWA, K.S. 1994. Genetic structure and mating system of Stemonoporus oblongifolius (Dipterocarpaceae) in Sri Lanka. Am. J. Bot. 81:155-160.
• MURAWSKI, D.A. & HAMRICK, J.L. 1991. The effect of the density of flowering individuals on the mating systems of nine tropical tree species. Heredity 67:167-174.
• MURAWSKI, D.A. & HAMRICK, J.L. 1992a. Mating system and phenology of Ceiba pentandra (Bombacaceae) in Central Panama. J. Hered. 83:401-404.
• MURAWSKI, D.A. & HAMRICK, J.L. 1992b. The mating system of Cavanillesia platanifolia under extremes of flowering-tree density: a test of predictions. Biotropica 24:102-104.
• MURAWSKI, D.A., DAYANANDAN, B. & BAWA, K.S. 1994. Outcrossing rates of two endemic Shorea species from Sri Lankan tropical rain forests. Biotropica 26:23-29.
• MURAWSKI, D.A., HAMRICK, J.L., HUBBELL, S.P. & FOSTER, R.B. 1990. Mating systems of two bombacaceous trees of a neotropical moist forest. Oecologia 82:501-506.
• NEI, M. & SYAKUDO, K. 1958. The estimation of outcrossing in natural populations. Japan. J. Genetics 33:46-51.
• O'MALLEY, D.M. & BAWA, K.S. 1987. Mating system of a tropical rain forest tree species. Am. J. Bot. 74:1143-1149.
• O'MALLEY, D.M., BUCKLEY, D.P., PRANCE, G.T. & BAWA, K.S. 1988. Genetics of Brazil nut (Bertholletia excelsa Humb. & Bonpl.: Lecythidaceae). 2. Mating system. Theor. Appl. Genet. 76:929-932.
• PAIVA, J.R., KAGEYAMA, P.Y. & VENCOVSKY, R. 1993. Outcrossing rates and inbreeding coefficients in rubber trees (Hevea brasiliensis (Willd. ex Adr. de Juss.) Müeller Arg.). Rev. Bras. Genética 16:1003-1011.
• PAIVA, J.R., KAGEYAMA, P.Y. & VENCOVSKY, R. 1994. Genetics of rubber tree (Hevea brasiliensis (Willd. ex Adr. de Juss.) Müll. Arg.) 2. Mating system. Silvae Genetica 43:373-376.
• PÉREZ-NASSER, N., EGUIARTE, L.E. & PIÑERO, D. 1993. Mating system and genetic structure of the distylous tropical tree Psychotria faxlucens (Rubiaceae). Am. J. Bot. 80:45-52.
• RITLAND, K. 1984. The effective proportion of self-fertilization with consanguineous matings in inbred populations. Genetics 106:139-152.
• RITLAND, K. 1989. Correlated matings in the partial selfer Mimulus guttatus Evolution 43:848-859.
• RITLAND, K. 1990. A series of FORTRAN computer programs for estimating plant mating systems. J. Hered. 81:235-237.
• RITLAND, K. & EL-KASSABY, Y.A. 1985. The nature of inbreeding in a seed orchard of Douglas fir as shown by an efficient multilocus model. Theor. Appl. Genet. 71:374-384.
• RITLAND, K. & GANDERS, F.R. 1985. Variation in the ma-ting system of Bidens menziesii (Asteraceae) in relation to population substructure. Heredity 55:235-244.
• RITLAND, K. & JAIN, S. 1981. A model for the estimation of outcrossing rate and gene frequencies using n inde-pendent loci. Heredity 47:35-52.
• ROCHA, O.J. & LOBO, J.A. 1998. Genetic diversity and out-crossing rates in the guanacaste tree (Enterolobium cyclocarpum Jacq.) in the dry forests of Costa Rica. In Recent Advances in Biotechnology for Tree Conserva-tion and Management, Proceedings of an IFS Workshop. International Foundation for Science (IFS), Stockholm, p.65-81.
• SHAW, D.V. & ALLARD, R.W. 1981. Estimation of outcross-ing rates in Douglas-fir using isozyme markers. Theor. Appl. Genet. 62:113-120.
• STACY, E.A., HAMRICK, J.L., NASON, J.D., HUBBELL, S.P., FOSTER, R.B. & CONDIT, R. 1996. Pollen dispersal in low-density populations of three neotropical tree spe-cies. Am. Natur. 148:275-298.
• WRIGHT, S. 1921. Systems of mating. Genetics 6:111-178.
• ZAPATA, T.R. & KALIN-ARROYO, M.T. 1978. Plant repro-ductive ecology of a secondary deciduous tropical fo-rest in Venezuela. Biotropica 10:221-230.

Datas de Publicação

• Publicação nesta coleção
  11 Jun 2013
• Data do Fascículo
  2002

Histórico

• Aceito
  07 Ago 2002
• Revisado
  09 Jul 2002
• Recebido
  12 Abr 2002