One of the reasons that dog-strangling vine is so successful is that it thrives in both sun and shade. The conditions here are very dark but the plant has spread rapidly. However, in deep shade, it doesn't appear to flower as prolifically, and therefore doesn't seed as much either. It has been said that seeds produced in these conditions are not as viable as those in sunny sites, but I'm not sure how reliable this information is.

For a brief intro to this invasive plant, and more photos, please see: http://www.pbase.com/fwg/dsv_at_fwg