CVTree provides such an alignment-free and parameterfree phylogenetic tool using composition vectors (CVs) inferred from whole genome data (1) . As a web server, it was first introduced in 2004 (2). The CV method has been effectively apaplied to phylogenetic study of viruses (3, 4) , chloroplasts (5) , prokaryotes (1, 6, 7) and fungi (submitted for publication). So far, the CV method has been cited in more than 70 papers not of our own, including some reviews (8, 9) .