In this study, sequence data from the inert nuclear region ITS1‐5.8S rDNA‐ITS2 and the chloroplast region trnL–F, as well as a few morphological characters, are analysed to the relationships among known annual Poa (bluegrasses). It is shown that all taxa from the Poa annua aggregate distinguished by lemma characters and growth form have identical ITS and trnL–trnF sequences, all ITS sequences of this aggregate are the same as thethose of P. supina, and all trnL–trnF sequences are homologous with those of P. infirma. Furthermore, no differences were found between unusual morphotypes of P. supina with short spinules on their panicle branches and typical plants, but Siberian samples were found to have a slightly differentiated trnL–trnF region. These results suggest a hybrid origin of the Asian annual bluegrasses. Their maternal genome is close to that of P. sect. Homalopoa, but their ITS sequences are different. Some ITS sequences from annual Asian bluegrasses are resolved among representatives of P. sect. Stenopoa while for other (morphologically closely similar) species they fall in a clade with representatives of P. sect. Malacanthae. The latter group is distant from P. sect. Ochlopoa and is better treated as a separate section, viz P. sect. Acroleucae. The American annual bluegrasses are heterogeneous and also rather distant from P. sect. Ochlopoa. Poa chapmaniana, a species with cleistogamic flowers, is nested among the basal Subantarctic sections, far away from the taxa with which it has previously been considered related. It is indeed closer to P. sect. Ochlopoa than to other annual American bluegrasses. Thus, the studied annual species in fact belong to four independent evolutionary lines (or six including the separate genus Eremopoa and the Turkish Poa jubata), one of which, Acroleucae, has gone through three reticulation events. As in previous studies, our analysis did not support the generic status of P. sect. Ochlopoa.

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Variability of morphological characters in Pimpinelk tragium VILL. group was investigated using herbarium material natural populations field sampling and cultivated plants. As a result of anatomical and morphological research, and by means of Principal Component Analysis and Canonical Variance Analysis, two polymorphic species were distinguished -P. tragium VILL. with hairs 0.05-0.2 mm long and P. polyclada BOISS. & HELDR. with hairs 0.3-1 mm long. Both polymorphic taxa include forms differing in density of pubescence and leaf dissection. Distribution of pinnatisect and bipinnatisect leaf forms over the range corresponds to the pattern of summer precipitation and duration of the drought period. In P. tragium several ecotypes could be distinguished, differing in leaf shape and structure, life history and development rhythm. However, recognition of infraspecific taxa is inexpedient and can misrepresent the complicated pattern of morphological variability within P. tragium VILL. IntroductionPimpinella tragium VILL. is a widespread complex of species with great morphological variability and confused taxonomy. It is distributed in the Mediterranean from Spain to Lebanon, in North-West Africa, Asia Minor, the Caucasus, the Central Kopet-Dagh and in the South of the East European Plain.Most taxonomists (BOISSIER 1872; HALACSY 190 1 ; WOLFF 1927) considered P. rragium VJLL.Z u s a m m e n f a s s u n g to be a polymorphic species with several varieties, some widespread over the range of P. tragium, and others are restricted in their distribution. Nevertheless some hardly distinguishable races from Russia and neighbouring tenitories have been treated until now as species (SCHISCHKlN 1950a, b; PIMENOV & TIKHO-MIROV 1981, 1995. SCHISCHKIN recognized nine species, differing in leaf blade dissection, umbel ray number, hair density, fruit size and stylodium length, characters used to char-480 Feddes Repert., Berlin 109 (1998) 7-8 acterize varieties of P. trugiurn in Europe. He did not take into account variability of the characters and transitional forms, so the species identification has been a great problem.TUTIN ( 1968a, b), MATTHEWS ( 1972) Minor.Every taxon described in the P. tragiurn group was characterized by several features, each representing only a small part of general range of values observed in this group. The broad morphological variation of some taxa and transitional forms among them has complicated the taxonomy of this polymorphic group, making the taxonomic rank and relations of the intraspecific taxa uncertain.The aims of our research were I ) to estimate morphological variability in the P. trugiurn group, 2 ) to throw light in differentiation trends in P. trugiurn and 3) to make new taxonomic proposals. Material and methodsWe studied about 2000 specimens from 20 herbaria (B, BAK, BM, DNZ, E, ERE, G, GAL, K, KW, LE, M, MHA, MPU, MW, SO, SOM, TBI. W, YALT) and more than 1500 specimens from 23 natural populations from Asia, the Caucasus, the Crimea, Bulgaria and the East European Plain. We determined leaf sh...

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