xplits is part of the splitstree package. Splitstree is used for analysing and visualising evolutionary data.

xsplits provides a menu driven graphical user interface for splitstree on unix and linux platforms.
See also the splits program, which is a command line program from the splitstree package.

References:
Huson, D.H. SplitsTree: analyzing and visualizing evolutionary data. Bioinformatics. 1998;14(1):68-73. [Entrez]