Allozyme variation in relation to morphology and taxonomy in Medicago sect, Spirocarpos subsect. Intertextae (Fabaceae)

Medicago intertexta and M. ciliaris have been controversially recognized as separate species. The only reliable diagnostic character, gland-tipped tri chomes on the fruits in M. ciliaris, is controlled by presence of a single dominant allele, and such one-character taxonomies are debatable. Contribut ing to the difficulty, M. muricoleptis and M. granadensis, the other two sp ecies of Medicago section Spirocarpos subsection Intertextae, are sometimes confusingly similar to M. intertexta or to each other. Allozyme difference s provided 95% verification of the suitability of the gland-tipped trichome character for separating M. intertexta and M. ciliaris, thus corroborating their recognition as separate taxa. Several measures of allozyme variation indicated that M. intertexta is more polymorphic than its sister species. Heterozygosity was also highest in M. intertexta, suggestive of a higher ou tcrossing rate, which is also consistent with larger floral size. Heterozyg osity of M, intertexta was concentrated in Sicily and nearby countries. Tax onomic difficulties in identifying Sicilian M. intertexta are well known, a nd may be the result of interspecific hybridization and introgression. Medi cago muricoleptis differed from the above two species in the frequency of s everal alleles, while M. granadensis possessed numerous unique alleles cons istent with its complete absence of genetic exchange with the other three s ubstantially interfertile species.