The “Crab_rRNA.meg” file, which is used in this tutorial, can be found in the MEGA/Examples folder (The default location for Windows users is C:\Users\UserName\Documents\MEGA7\Examples\. The default location for Mac users is $HOME/MEGA/Examples, where $HOME is the user’s home directory).
Defining and Editing Groups of Taxa
In MEGA, you can partition data into distinct groups and then evaluate distances within groups, distances between groups, and the net distance between groups.
Example 8.1:
From the main MEGA window, activate the data present in the "Crab_rRNA.meg" file. If necessary, refer to Example 1.2 in the “MEGA Basics” tutorial.
From the main MEGA window launch bar, select Data | Select Taxa and Groups. Notice the left pane called Taxa/Groups and the right pane labeled Ungrouped Taxa.
Press the New Group button found below the Taxa/Groups pane to add a new group to the data. Name this new group “Pagurus” and press Enter.
While holding the Ctrl button on the keyboard, click on all of the items in the Ungrouped Taxa pane that begin with Pagurus. This will highlight them. When they are all highlighted, press the left-facing arrow button found on the vertical toolbar between the two panels (make sure the Pagurus group on the left side is also highlighted otherwise the arrow will not appear).
Select the All group in the Taxa/Groups panel and press the + (add) button found on the vertical toolbar between the two window panes to add a second group. Name this group "Non-Pagurus".
Add the remaining unassigned taxa to this group by using the left arrow and press the Close button at the bottom of the window to exit this view.
Note: Now that groups have been defined, the Compute Within Group Mean, Compute Between Group Means, and Compute Net Between Group Means menu commands from the Distance option on the launch bar may be used to analyze the data.
Close all of the open windows.