A maximum pseudo-likelihood approach for phylogenetic networks

To tackle incongruence, the topological conflict between different gene trees, phylogenomic studies couple concatenation with practices such as rogue taxon removal or the use of slowly evolving genes. Phylogenomic analysis of 1,070 orthologues from 23 yeast genomes identified 1,070 distinct gene trees, which were all incongruent with the phylogeny inferred from concatenation. Incongruence severity increased for shorter internodes located deeper in the phylogeny. Notably, whereas most practices had little or negative impact on the yeast phylogeny, the use of genes or internodes with high average internode support significantly improved the robustness of inference. We obtained similar results in analyses of vertebrate and metazoan phylogenomic data sets. These results question the exclusive reliance on concatenation and associated practices, and argue that selecting genes with strong phylogenetic signals and demonstrating the absence of significant incongruence are essential for accurately reconstructing ancient divergences.

Seq-Gen is a program that will simulate the evolution of nucleotide sequences along a phylogeny, using common models of the substitution process. A range of models of molecular evolution are implemented, including the general reversible model. Nucleotide frequencies and other parameters of the model may be given and site-specific rate heterogeneity can also be incorporated in a number of ways. Any number of trees may be read in and the program will produce any number of data sets for each tree. Thus, large sets of replicate simulations can be easily created. This can be used to test phylogenetic hypotheses using the parametric bootstrap. Seq-Gen can be obtained by WWW from http:/(/)evolve.zoo.ox.ac.uk/Seq-Gen/seq-gen.html++ + or by FTP from ftp:/(/)evolve.zoo.ox.ac.uk/packages/Seq-Gen/. The package includes the source code, manual and example files. An Apple Macintosh version is available from the same sites.

Introgressive hybridization is now recognized as a widespread phenomenon, but its role in evolution remains contested. Here, we use newly available reference genome assemblies to investigate phylogenetic relationships and introgression in a medically important group of Afrotropical mosquito sibling species. We have identified the correct species branching order to resolve a contentious phylogeny and show that lineages leading to the principal vectors of human malaria were among the first to split. Pervasive autosomal introgression between these malaria vectors means that only a small fraction of the genome, mainly on the X chromosome, has not crossed species boundaries. Our results suggest that traits enhancing vectorial capacity may be gained through interspecific gene flow, including between nonsister species.