Why do responses to Google Groups emails create new conversations?

I use Google Groups and Gmail. Responses to messages sent to Google Groups appear as brand new conversations in Gmail when the group is set up to use a tag in the subject.

For example:

[mailList] conversationTitle
[mailList] re: conversationTitle

get counted as seperate conversations... because the ‘re:’ is after the [mailList] instead of in front of it.

Is there a way to get the responses to be under the original conversation thread?