You're right, it was Topica - here's the list info page:
but trying to subscribe to via that page just leads to error messages. I was able to subscribe via email but it doesn't look like the list is active...yours was one of the last posts to the group back in September.
If you log into Topica you'll be able to see all of the lists that you are subscribed to and/or own. Just click on "My Topica" then "My Lists".
I don't know much about the owner of the list - the only interaction I've had with him was an email back in 2003 about some of our milkweed information that was plagiarized and posted on his commercial site. He thanked me for bringing it to his attention and said he would look into it but the text remains and I haven't pressed the issue. But I digress
We'd be happy to host something here - it's just a matter of getting the word out to those that would be interested in participating in the discussions.