Evidence of gene flow between sympatric populations of the Middle East-Asia Minor 1 and Mediterranean putative species of [i]Bemisia tabaci[/i]
Résumé
[i]Bemisia tabaci[/i] is a complex of putative species that exhibit a strong geographical pattern. Crossing experiments have revealed various degrees of reproductive isolation between these nascent species, ranging between fertile first-generation hybrids (F1) and no F1 at all. However, the relevance of these results under natural conditions is generally not known. The worldwide invasion of the putative species Middle East-Asia Minor 1 (MEAM1) has caused secondary contacts between allopatric species, which in turn provide an opportunity to detect potential hybrids in nature. A total of 346 female B. tabaci were collected in 2003 and 2005 in the North East of Morocco and assigned to MEAM1 (119), Mediterranean (Med) (225) and a new putative species (2) using mitochondrial cytochrome oxidase (mtCOI) gene sequences. MEAM1 and Med individuals were characterized at seven microsatellite loci. MEAM1 and Med were found to be sympatric in 11 of 12 samples (6 fields/year). As previously reported from Spain, MEAM1 frequency decreased over time. The genetic data are consistent with a recent introduction of MEAM1. A Bayesian clustering analysis (STRUCTURE) distinguished two groups, which were 100% consistent with the mtCOI groups. From several lines of evidence, two individuals were identified as hybrids. Assignment profiles using NEWHYBRIDS and allele composition indicated that they were not F1 hybrids. The results are discussed in relation to the secondary endosymbiont infection status determined on a sample of individuals, and the contrasting outcomes of the reported crossing experiments between MEAM1 and Med.
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