Reconstructing ancestral autosomal arrangements in the Anopheles gambiae complex

Members of the Anopheles gambiae complex have remarkably distinct ecological adaptations, behaviors, and degrees of vectorial capacity. Inferring phylogenetic relationships in the complex is crucial for identifying the genomic changes associated with the origin and loss of epidemiologically important traits. However, the high level of sequence similarity, genetic introgression, and shared molecular ancestral polymorphisms makes reconstruction of the A. gambiae complex phylogeny difficult. Phylogenetic relationships among the members of species complexes can be inferred from the distribution of fixed chromosomal inversions if outgroup arrangements are known. The aim of this work is to test a possibility of determining ancestral autosomal arrangements in the A. gambiae complex using outgroup chromosomes and a combination of bioinformatic and cytogenetic approaches. The minimum number of inversions between members of the A. gambiae complex and the outgroup species A. funestus and A. stephensi was calculated using the Multiple Genome Rearrangements (MGR) and Sorting Permutation by Reversals and block-INterchanGes (SPRING) programs. The physical mapping of A. merus chromosomes identified molecular coordinates of the proximal 2Ro+ inversion breakpoint in A. gambiae. DNA probes from 2La+ and 2Ro+ inversion breakpoints of the A. gambiae were mapped to the A. stephensi chromosomes. Assuming monophyletic origin of the inversions, this study concludes that physical mapping of ingroup and outgroup species can be used for identifying inversion breakpoints and ancestral autosomal arrangements within species complexes. Molecular characterization of the breakpoints in both ingroup and outgroup species will provide a solid basis for reconstructing the inversion history in the A. gambiae complex.