Principal classifications of Vitis have been made by Planchon and Foex in France and by Munson and Bailey in the United States.
These classifications are characterized by a wide disparity in the number and geographical origin of Vitis forms studied, in the recognition of species validity, and in the interpretation of species relationships.
The development of quantitative methods of measuring similarities between organisms and grouping these organisms into classes on the basis of similarities offers an additional means of reducing subjectivity in assessing affinity among species of Vitis.
Details on the procedures and statisticat techniques for these methods are described by Sokal and Sneath.
The objectives of this study were to quantify the degree of resemblance shown among various Vitis species based on a large number of characters, and to compare the phenetic relationships thus indicated with the classical systematic interpretations.
A Taximetric Study of Interspecific Variation in Vitis
1969, Sonderdruck aus der Zeitschrift ‘Vitis’, vol 8, pages 177 – 187