The k/x/ubuntu-desktop packages are metapackages /1/.
"These packages do not contain actual software, they simply depend on other packages to be installed. This setup allows entire sets of software to be installed by selecting only the appropriate metapackage."
The Kubuntu desktop /2/ package is depending/recommending /4/ lot of packages. Some of them could be common with other desktops.
How did you install the desktops ?
The Synaptic and the Muon package managers are keeping history logs or parsing the dpkg log.
Checking installed/updated/removed packages from the dpkg log (command line):
Recent status log:
grep "status installed" /var/log/dpkg.log
grep upgrade /var/log/dpkg.log
grep remove /var/log/dpkg.log
A bit older dpkg log:
grep "status installed" /var/log/dpkg.log.1
grep upgrade /var/log/dpkg.log.1
grep remove /var/log/dpkg.log.1
The oldest logs - rotated dpkg logs (packed): dpkg.log.2.gz, dpkg.log.3.gz...
You could look the log files and search what the xubuntu-desktop, kubuntu-desktop, etc did install.
Keeping own logs. There is the logsave command
:~$ man logsave /3/
logsave - save the output of a command in a logfile
logsave [ -asv ] logfile cmd_prog [ ... ]
The logsave program will execute cmd_prog with the specified argument(s),
and save a copy of its output to logfile.
If the containing directory for logfile does not exist, logsave will
accumulate the output in memory until it can be
written out. A copy of the output will also be written to standard output.
logsave testing_kubuntu-desktop.log sudo apt-get install kubuntu-desktop
With the testing_kubuntu-desktop.log it is a bit easier to remove/purge the unwanted packages.
Recommended packages installed by default
In accordance with the Debian Policy Manual (which says "The 'Recommends' field should list packages that would be found together with this one in all but unusual installations"), the package management system now installs packages listed in the Recommends: field of other installed packages as well as Depends: by default. If you want to avoid this for specific packages, use apt-get --no-install-recommends; if you want to make this permanent, set APT::Install-Recommends "false"; in /etc/apt/apt.conf. Be aware that this may result in missing features in some programs.
(This change was made in Ubuntu 8.10.)