Wild populations and selected cultivated accessions of the genus Pisum are evaluated for morphological characters, allozymes, RAPDs, ISSRs and ITS sequences. Tests of skewness and partition homogeneity indicate that each of these individual data sets exhibits strong phylogenetic signal (g1 values ranging from -0.631 to -0.755, P<<0.01), and sufficient congruence (P values ranging from 0.516 to 1.000) to support their combination in a single data set. Even the small number of morphological characters generally organizes the species into traditional taxonomic groupings using both maximum parsimony and bootstrap methods. Individual and combined molecular data sets support several of these same associations. Decay indices and other branch values for the comparatively data-rich ISSR and RAPD trees reveal strong support for three nodes that: 1) separate P. fulvum from the P. humile, P. elatius and P. sativum ingroup; 2) establish the northern humile, elatius and sativum clade; and 3) define sativum as a monophyletic group. The southern humile populations form a clade that is distinct from fulvum and also from elatius, sativum and even northern humile in the combined-data tree; although, the southern humile node is supported only tenuously by the individual molecular trees. The RAPD trees suggest that elatius may be the sister taxon to the cultivated sativum, a relationship that is observed in the combined-data tree. By comparison, the ISSR trees present only modest support for northern humile as the closest relative of the domesticated pea. A small number of polymorphic ITS sites places northern humile further from sativum and emphasizes the close affinity among all the non-fulvum peas. Species fulvum is clearly the most distinct of the pea taxa in every analysis.

Key words: allozymes, ISSRs, ITS, phylogenetics, Pisum, RAPDs