Genetic structure of Ceratitis capitata populations
Ceratitis capitata (EPPO A2 quarantine pest) is thought to originate from sub-Saharan Africa and has been introduced into several other parts of the world. It was reported from the Mediterranean region in the early 19th century, and was well established in the New World by the early 20th century. In continental USA, and more particularly in California, there is a debate on the following issues: 1) whether fruit fly populations in different years and localities represent independent infestations (single introduction of the pest followed by fluctuation of populations levels between detectable and non-detectable levels and dispersal) or new introduction events; 2) origin of the introduction(s). Studies were carried out on the variation of mtDNA using 3 restriction enzymes of more than 100 populations of C. capitata collected from South and Central America, USA, Mediterranean countries, sub-Saharan Africa and Australia. Results showed that the highest levels of mtDNA diversity are found in samples from the sub-Saharan region (8 different haplotypes), which supports the hypothesis of the origin of C. capitata. Lower levels were found in the Mediterranean region (2 haplotypes). In South and Central American populations, the situation is quite different, as results showed that in most countries populations are based on a single haplotype, which may differ from one country to another. This could reflect multiple introductions into the New World. However, it is felt that further studies are needed, in particular on the situation in USA, using additional molecular markers and behavioural characteristics, in order better to understand patterns of variation among populations of C. capitata.
Sources
Gasparich, G.E.; Silva, J.G.; Han, H.Y.; McPheron, B.A.; Steck, G.J.; Sheppard, W.S. (1999) Population genetic structure of Mediterranean fruit fly (Diptera: Tephritidae) and implications for worldwide colonization patterns.
Annals of the Entomological Society of America, 90(6), 790-797.