Tracing Ancient Human Migrations into Sahul Using Hepatitis B Virus Genomes

We announce the release of Reconstruct Ancestral State in Phylogenies (RASP), a user-friendly software package for inferring historical biogeography through reconstructing ancestral geographic distributions on phylogenetic trees. RASP utilizes the widely used Statistical-Dispersal Vicariance Analysis (S-DIVA), the Dispersal-Extinction-Cladogenesis (DEC) model (Lagrange), a Statistical DEC model (S-DEC) and BayArea. It provides a graphical user interface (GUI) to specify a phylogenetic tree or set of trees and geographic distribution constraints, draws pie charts on the nodes of a phylogenetic tree to indicate levels of uncertainty, and generates high-quality exportable graphical results. RASP can run on both Windows and Mac OS X platforms. All documentation and source code for RASP is freely available at http://mnh.scu.edu.cn/soft/blog/RASP.

GenBank® is a comprehensive database that contains publicly available DNA sequences for more than 165 000 named organisms, obtained primarily through submissions from individual laboratories and batch submissions from large-scale sequencing projects. Most submissions are made using the web-based BankIt or standalone Sequin programs and accession numbers are assigned by GenBank staff upon receipt. Daily data exchange with the EMBL Data Library in the UK and the DNA Data Bank of Japan helps to ensure worldwide coverage. GenBank is accessible through NCBI's retrieval system, Entrez, which integrates data from the major DNA and protein sequence databases along with taxonomy, genome, mapping, protein structure and domain information, and the biomedical journal literature via PubMed. BLAST provides sequence similarity searches of GenBank and other sequence databases. Complete bimonthly releases and daily updates of the GenBank database are available by FTP. To access GenBank and its related retrieval and analysis services, go to the NCBI Homepage at http://www.ncbi.nlm.nih.gov.

Statistical tests for detecting mosaic structure or recombination among nucleotide sequences usually rely on identifying a pattern or a signal that would be unlikely to appear under clonal reproduction. Dozens of such tests have been described, but many are hampered by long running times, confounding of selection and recombination, and/or inability to isolate the mosaic-producing event. We introduce a test that is exact, nonparametric, rapidly computable, free of the infinite-sites assumption, able to distinguish between recombination and variation in mutation/fixation rates, and able to identify the breakpoints and sequences involved in the mosaic-producing event. Our test considers three sequences at a time: two parent sequences that may have recombined, with one or two breakpoints, to form the third sequence (the child sequence). Excess similarity of the child sequence to a candidate recombinant of the parents is a sign of recombination; we take the maximum value of this excess similarity as our test statistic Delta(m,n,b). We present a method for rapidly calculating the distribution of Delta(m,n,b) and demonstrate that it has comparable power to and a much improved running time over previous methods, especially in detecting recombination in large data sets.