Phylogeny and introgression in African mosquitoes Anopheles gambiae species complex

Thursday 31 October 2019, 1.00PM

Speaker(s): Ziheng Yang, University College London

Knowledge of evolutionary relationships among Anopheles gambiae mosquitoes is important to identifying genomic changes associated with malaria vector capacity and to developing effective malaria control strategies.  Yet  phylogenetic inference in this case is extremely challenging because the species arose through a rapid succession of speciation events and because they undergo extensive cross-species hybridisation.  Despite numerous phylogenetic analyses and the sequencing of whole genomes, the phylogeny in the Anopheles gambiae species complex has not been confidently resolved.  We extract over 80,000 coding and noncoding short segments from the genomes of six members of the species complex and use a Bayesian method under the multispecies coalescent model to infer the species tree, which takes into account genealogical fluctuations across the genome due to the coalescent process and uncertainty in the gene genealogies due to limited information in each segment of the genome.  We have obtained a robust estimate of the species tree from the distal region of the X chromosome: (A. merus, ((A. melas, (A. arabiensis, A. quadriannulatus)), (A. gambiae, A. coluzzii))), with A. merus to be the earliest branching species.  This species tree agrees with the rare events of chromosome inversions and is consistent with known patterns of cross-species introgression.  We use simulation to demonstrate that the species tree inferred in a previous phylogenomic study is an artifact of the sliding-windows approach used, which fails to account for the coalescent process.  Our analysis highlights the importance of accommodating deep coalescence and cross-species introgression in phylogenomic analyses of species that arose through recent radiative speciation events. Thawornwattana Y, Dalquen DA, Yang Z. 2018. Coalescent analysis of phylogenomic data confidently resolves the species relationships in the Anopheles gambiae species complex. Mol Biol Evol 35:2512-2527.

Location: Dianna Bowles Lecture Theatre B/K/018