Of Weeds and Ants

While tending to my gardens I've noticed that in the areas where weeds are the most prevalent, there is always a thriving colony of ants.

I'm wondering about that relationship. Specifically which comes first, the ants or the weeds?

I suppose that tunneling ants may loosen the soil and make it easier for weeds to grow. On the other hand, the underside of the sprouts on a healthy stand of crabgrass manages to stay moist even in the hottest conditions. So maybe the ants are drawn to the moisture.

If I knew where the next weeds were going to sprout, I could study the relationship. But since crabgrass seems to change from microscopic fingers to thick jungle growth overnight, I suppose the answer to which comes first will remain as elusive as the chicken and the egg.