Pathway analysis of Ceratitis capitata (Diptera: Tephritidae) using mitochondrial DNA.

The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method described in a previous publication to document worldwide population structure of Mediterranean fruit flies and analyze probable sources of fly introductions is re-evaluated. Analysis of representatives of the RFLP-based markers using the ND5-tRNA-ND4 mitochondrial locus through DNA sequencing shows that the original markers produced haplotypes that are homoplasic and exclude valuable information. DNA sequences also identified errors in data generated with the protocol because of failure of the XbaI enzyme to efficiently cut PCR product. In all, the PCR-RFLP method is able to document haplotypes present in medfly populations outside of Sub-Saharan Africa and is a cost-effective approach to pathway analysis. New primer pairs for analysis of this locus are reported that reduce the number of PCR steps required to analyze the RFLP marker and the time of each PCR run. For comparison of the PCR-RFLP method, the utility of a DNA sequence-based approach to Mediterranean fruit fly pathway analysis is reported using the ND5-ND4 locus and the proposed "barcode region" of the COI gene. Both gene sequences are more informative than the PCR-RFLP method and document high genetic variation within Sub-Saharan Africa. Application of these methods as tools and their interpretation is discussed.