| Malaria kills one to three million people each year, and 90% of the mortality occurs in Sub-Saharan Africa, where mosquitoes of the Anopheles gambiae species complex are the principle vectors. Control of the vector requires an understanding of the species histories and the genetic structure of the mosquito population. This work was undertaken to clarify the phylogenetic relationships amongst the members of the An. gambiae complex using markers on the Y chromosome.;In the process of screening for Y chromosome markers, a family of LTR-retrotransposons was identified, named mtanga. Mtanga-Y elements represent the first Y-linked sequences, and the first members of the Ty1-copia superfamily of retrotransposons, described from this mosquito. Absent from the Y chromosome in other members of the complex, similar but often defective mtanga elements are present elsewhere in these genomes, as well as in An. gambiae. These data are consistent with a relatively recent invasion of the An. gambiae Y chromosome by an intact element.;The ultimate aim of this dissertation was to resolve the controversy regarding the phylogeny of the An. gambiae species complex. The potential for gene flow between species due to the presence of fertile hybrid females has complicated the interpretation of previous phylogenetic studies. It was expected that the Y chromosome was recombinationally isolated, and therefore could not introgress between species. However, sequence similarity with other chromosomes and the lack of monophyly of Y sequences indicated that portions of the Y chromosome may be subject to genetic exchange. Sequences from one marker, 4dF, indicated that its location on the Y chromosome was recombinationally isolated, as the related X chromosome sequences were monophyletic. The phylogeny predicted using 4dF supported the An. gambiae-An. merus sister relationship. These results further suggested that An. arabiensis is the most distant relative of An. gambiae . Therefore, any perceived relationship between An. arabiensis and An. gambiae was likely the result of introgression between these species. Thus, we must recognize that interspecific gene flow may play a significant role in nature, and is important in any vector control program we might utilize. |
