Distance matrices as well as sequence data may come from species, populations, or individuals. These evolutionary entities are designated as OTUs (Operational Taxonomic Units) or taxa. Each taxon must have an identification tag, i.e., a taxon Iabel. In the input files prepared for use in MEGA, these labels should be written according to the following conventions:
‘#’ Sign
Every Iabel must be written on a new line, and a '#' sign must precede the label. There are no restrictions on the length of the Iabels in the data file, but MEGA will truncate all labels longer than 40 characters. These labels are not required to be unique, although identical labels may result in ambiguities and should be avoided.
Characters to use in labels
Taxa labels must start with alphanumeric characters (0-9, a-z, and A-Z) or a special character: dash (-), plus (+) or period (.). After the first character, taxa labels may contain the following additional special characters: underscore (_), asterisk (*), colon (:), round open and close brackets ( ), vertical line (|), back slash (\), and forward slash (/).
For multiple word labels, an underscore can be used to represent a blank space. All underscores are converted into blank spaces, and subsequent displays of the labels show this change. For example, E._coli becomes E. coli.