Morphogeographic variation in the Medicago monantha complex

Morphogeographic variation in the Asian annual Medicago monantha has required clarification. The present numerical taxonomic study in relation to geographical distribution revealed an east–west gradient of the principal correlated characters. Although previous taxonomists had not perceived this gradient as such, in fact it is reflected in traditional taxonomic treatments, i.e., the four commonly recognized subspecies (which are often considered separate species) replace each other in an east–west direction in stepwise overlapping fashion with respect to morphology and geography. The most evident difference observed was with respect to the areas delimited on the surface of the fruit by the intersecting veins; the fruit areoles are more elongated in the western phase than in the east. Given the absence of evident discontinuity or even relative discontinuity in M. monantha, formal delimitation of the traditionally recognized infraspecific taxa seems unjustified. Key words: Medicago monantha, Trigonella, cline, taxonomy, classification, systematics.