Two months ago I posted a link to screenshots of the tech tree soon after 0.40 was released. I realized today that they aren't accurate. The universal translator event unlocks the universal translator tech and a lot techs that depend on it. Also, there are three events that unlock upgrades to the weapons. All of them are missing from the tech trees I posted for 0.40.
I have made new tech tree pictures that show ALL the techs in the tech trees for Alpha 0.50. You can download a zip file containing them here.