Clarification on grape nomenclature

It appears I was too hasty in this post in identifying the wild grape as summer grape (Vitis aestivalis).  My grape does match the description in this Virginia Tech data sheet.  However, as this website on Northern Virginia ecology points out, "there are several species of Wild Grape in Virginia, most of which are very similar and difficult to tell apart."  The Digital Atlas of Virginia Flora lists five Vitis species as occurring in Fairfax County:  V. aestivalis, V. labrusca, V. riparia, V. rupestris, and V. vulpina.  I have not yet found a key that distinguishes these five species, so I cannot really identify my grape closer than the generic Vitis spp.