Origin and dispersal of the cotton boll weevil (Coleoptera: Curculionidae) in South America: a mtDNA phylogeographic study.

CONFALONIERI, VIVIANA ANDREA; SCATAGLINI, MARÍA AMALIA; LANTERI, ANALÍA ALICIA

Foz de Iguazú, Brasil.

Congreso; XXI International Congress of Entomology; 2000

Sociedade Entomológica do Brasil

The boll weevil Anthonomus grandis is the most harmful insect pest of cotton in the Americas. Since its first report damaging that culture, there have been considerable efforts to address the question of its place of origin, original hosts and pathways of dispersal. Most authors proposed that the boll weevil was indigenous to tropical lowlands of Mexico and reached its present distribution by extending its range northward to Southern United States and southward to Central and South America. The hypothesis of north american dispersal is well supported by data on host plants and geographic variation of morphological characters and would have taken place in both, prehistoric and historic times. On the contrary, the history of the boll weevil in South America is poorly known, and its presence would be associated to cotton cultivation. The main goal of the present contribution is to test the hypothesis on the origin of south american populations by means of a phylogeographic analysis using sequences of the mitochondrial gene Cytochrome Oxidase I. We analized populations from Brazil, Argentina, Paraguay, USA and Mexico. The genetic relationships of the 17 haplotypes found were inferred by cladistics analysis. The mexican population and the sample from the National Park Iguazú (Arg.)display the highest number of haplotypes and sequences divergence, typical of original central populations. In the most parsimonius trees obtained there are three main groups of haplotypes: 1) from Mexico; 2) from National Park Iguazú (Arg.) and 3) from USA, Paraguay and Brazil. The latter clade includes one haplotype present in the three samples wich could be considered ancestral of this group. This results support the hypothesis that boll weevis from cotton areas of Brasil and Paraguay were introduced from USA. On the other hand, weevils collected on native plants of National Park Iguazú would correspond to an ancestral population, established prior to cotton cultivation.