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

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

Resumos

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.

alozimas; Lauraceae; sistema de cruzamento; Neotrópico; Cryptocarya; Mata Atlântica; Brasil


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.

allozymes; Lauraceae; mating system; Neotropics; Cryptocarya; Atlantic rain forest; Brazil


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 MoraesI, II; Reinaldo MonteiroIII

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: plmoraes@cena.usp.br

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

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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

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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
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