Lowland temperature preferences - Anyone know of scientific studies?

I had always been told that lowlanders preferred temperatures that were both warm and constant. But, this doesn't quite make sense - even in the jungle, there's some nighttime cooling. In the thickest rainforests it might be tough to notice, but I don't think Nepenthes usually live in the densest inner regions of understory. Recently I read - perhaps on the CP FAQ but I can't remember - that a drop of about 8C is appropriate. I know we all have differing opinions and experiences on the matter, but does anyone have some studies they can refer me to? I'm curious to see some hard data.
Thanks,
~Joe

I can't offer a scientific study, but my lowland neps seem to appreciate a modest drop in temperature at night.

Well...This isn't a scientific study by any means, but I did come across this and would assume the temps given are most likely correct.

http://www.angelfire.com/al/IeDa/sabah.html