›› 2009, Vol. 52 ›› Issue (12): 1349-1355.

• RESEARCH PAPERS • Previous Articles     Next Articles

Genetic differentiation among different geographic populations of the cowpea weevil, Callosobruchus maculatus (Coleoptera: Bruchidae)

  

  • Online:2009-12-20 Published:2009-12-20

Abstract: 【Objective】 Through comparing partial sequences of mitochondrial Cytb and COⅠ genes, to analyze the genetic differentiation among the geographic populations of the cowpea weevil,  Callosobruchus maculatus Fabricius,  and to determine the relationships between the genetic structure of populations and biological invasion and provide an understanding of the evolutionary mechanisms underlying the invasion process.【Methods】 The mtDNA-Cytb and COⅠ regions of 4 populations of C. maculatus from Hainan of China,  Cameroom,  Korea and Thailand,  respectively, were sequenced by direct sequencing method. The mtDNA Cytb and COⅠ sequences among populations of C. maculatus were analyzed using MEGA3.1 and the phylogenetic trees of all haplotypes were constructed using C. chinensis as the out-group. 【Results】 As for the 420 bp mtDNA-Cytb gene of 34 individuals,  14 polymorphic sites and 5 haplotypes were found,  while as for the 822 bp mtDNA-Cytb gene of 33 individuals,  28 polymorphic sites and 9 haplotypes were found. Four haplotypes were rare haplotypes,  typically present in only one or two individuals and representative of a specific population, while other haplotypes were shared by all or partial populations. Molecular variance analysis (AMOVA) demonstrated that the genetic variation was not obvious and mainly occurred within geographic populations. The Fst value and the Nm value showed that not only the gene flow occurred among the four populations, but also the genetic differences did. 【Conclusion】 Given the observed distribution pattern of haplotypes,  China was not the origin of C. maculatus,  while Cameroon was likely to be one of the origins of C. maculatus. Gene flow between Haplotype Cameroon and Haplotype Thailand was relatively abundant, and genetic differentiation among Haplotype China and other haplotypes were relatively large.

Key words: Callosobruchus maculatus, mtDNA-Cytb, mtDNA-COⅠ, haplotype, geographic population, genetic differentiation