This ability does t really give a clear guideline to how it's used.
Can you use any trait to combine even Prerequisite traits (without having the Prerequisite.
Or can you attach a t2 trait effectively makeing it a teir 1 trait
Or is it just attaching another trait to this maybe ingnoreing the starting trait limit of one knowledge trait.
In your case, when building your Insekt race you decide you want to take Brood Care, which gives you Adaptive Knowledge 1. You then decide, for your Adaptive Knowledge combo Trait, to take the Harvesters Trait. This is neat because you get the Spores of the Gods stuff for basically just the point cost. But what you're really interested in is that now you can take The Collective Mind from the 2nd Tier of Harvester Traits, because you used Adaptive Knowledge to pick up your required 1st Tier Trait to unlock it.
All in all, you've spent 9 points to do this.
[Environmental Adaptation: Eusocial] Brood Care 2pts: Adaptive Knowledge 1
-Adaptive Knowledge: Harvester 2pts: Spores of the Gods, Harvester, Species Trait Only, Exclusive
[Infestations, Domination, and Knowledge]The Collective 5pts: The Collective Mind 1
As I understand it, Adaptive Knowledge allows you to take X number of additional Traits from the [Infestations, Domination, and Knowledge] lists, combining them with the Brood Care/Advanced Brood Care Trait. 'Insekt Knowledge' in this case is shorthand for an otherwise unwieldy name.
This effectively allows you to take 2/3 Traits for the opportunity cost of one, useful for grabbing 2nd Tier abilities early on, or grabbing the whole Tier quickly. You need to pay the full cost for all of these Traits, however, which can add up quickly.
Of note is that the first Adaptive Knowledge Trait available is itself only 2pts. Taking it can allow you access to 2nd Tier Eusocial and Knowledge Traits for very low cost, counting as only one of your 0-6 starting Traits, and without itself being your one Knowledge selection.