The genus Armeria includes ca. 110 species distributed primarily in the Northern hemisphere with its maximum diversity concentrated in the western Mediterranean. Reticulation has been proposed as a significant cause for such diversity based on various evidence. To test this hypothesis with molecular data, a parsimony analysis of 55 ITS sequences from 34 taxa was carried out. Results yielded 30 most parsimonious trees differing only in terminal and subterminal clades. Topology is otherwise consistent in recognizing 5 major well supported clades. Several facts suggest the interpretation that shared nucleotide positions supporting the major clades are due not to common ancestry but to extensive gene flow: 1) different accessions (13) from the same subspecies (A. villosa subsp. longiaristata) appear in three of the five major clades; 2) each of the five major clades contains accessions of at least one of the six subspecies recognized within A. villosa; 3) four out of the five major clades are geographically restricted to clearly delimited areas within southern Spain so that the composition of those clades is congruent not with the systematic placement of the sample but with its geographical origin. Further, this interpretation is consistent with morphological patterns (viz. sympatric distinct taxa sharing sets of morphological traits) as well as with previous evidence revealing low internal reproductive barriers. Low homoplasy levels (C.I.=0.85 excluding uniformative characters) indicate that the trees fit very accurately the ITS data. On the other hand, high consistency index is quite unexpected given the fact that reticulations may introduce considerable distortion in cladograms. We argue that active concerted evolution, documented using artificial F1 hybrids and backcrosses, coupled with the low internal barriers and with the extensive gene flow scenario can explain the low homoplasy levels.

Key words: Armeria, hybrids, ITS, Plumbaginaceae, reticulate evolution