Here’s one interspecies reference you might be interested in that’s also ready at hand for me: Crossing the bitterness out of cucurbita pepo egg gourds - #11 by markwkidd
I was working on the squash related parts of Wikipedia a few months back. Let me try to remember other references that might be useful. I looked at quite a few and they’re getting a bit blurry in retrospect 
when I know there is someone else interested it can help perk up my memory though!