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We performed a molecular phylogenetic study based on the nuclear ribosomal internal and external transcribed spacer (ITS and ETS). Thirty-one annual Medicago species were included in the study, representing more than half of the genus and 85% of the annuals of the genus. Major incongruences were found between phylogenetic relationships and morphological classification of the genus. Morphological and cytological traits were mapped onto the phylogeny. The most parsimonious reconstruction suggested an ancestral spiny state and a recurrent transition from spiny to spineless state. From the ancestral state of 2n=16, three loss events of chromosomes must have occurred leading to the same specific number of 14 chromosomes whereas species having 30 chromosomes form a monophyletic clade., (Copyright 1998 Academic Press.)

Sequences of the internal transcribed spacers (ITSs) of 18S-26S nuclear ribosomal DNA were used to resolve phylogenetic relationships and chromosomal evolution among 14 species of the genus Hypochaeris (Asteraceae). Parsimony analysis was performed for phylogenetic reconstruction, and sequence divergence between species was estimated. Pairwise sequence divergence within Hypochaeris genus ranged from 0% to 25.68% in ITS1 and from 0% to 17.08% in ITS2. A highly resolved strict-consensus tree was obtained that showed the phylogenetically useful information of ITS sequences within the genus Hypochaeris. Four clades could be well distinguished, one of them formed by the single species H. robertia, which appeared to be the most related to the ancestral species of the genus. The results agree with taxonomic classification based on morphological data, and the tree obtained, when indels are coded as missing data, aggregates the species having the same chromosome number, except in one clade. According to the ITS phylogenetic tree, the chromosomal evolution within the genus Hypochaeris conflicts with the previous hypothesis and suggests that karyotype evolution in Hypochaeris was accompanied with both decreasing and increasing dysploidy, probably with several chromosomal rearrangements, and from an ancestral basic chromosome number of 4 or 5.

The generic boundaries within the sub-family Silenoideae (Caryophyllaceae), and especially within the complex Silene-Lychnis-Melandrium have long been controversial. These 3 genes are now grouped in a single genus: Silene. In order to test the monophyly of this genus and to clarify intra-generic phylogenetic relationships, we compared ITS sequences of 22 species of Euromediterranean Silene chosen throughout the classification, and 4 putative outgroup species. The genus Silene in its current circumscription formed a well-supported monophyletic group. Lychnis and Melandrium species are scattered within the genus Silene. The monotypic genus Cucubalus also fell within the Silene clade.

We have sequenced the chloroplast gene rps4 of 72 species; the sequence of 6 more species was found in the databanks. The 78 species were chosen so as to be representative of two taxonomic levels: the family, with 39 Poaceae, and the class, with 28 additional monocot species. Eleven dicots and other land plants were used as outgroups to the monocots. The 78 sequences were aligned by eye. Phylogenetic reconstruction was performed using the Wagner parsimony method: our first results were in contradiction with classical systematics, due to a local minimum. We then used the results obtained with the new distance method Anataxis to redraw a new tree and carry on further the parsimony calculations starting from this Anataxis tree. Up to 20,000 most parsimonious trees were thus obtained. The robustness of our results was checked by the bootstrap test and decay analyses. The Anataxis and the strict consensus tree fitted the general features of land plant evolution. Some of our results concerning relationships within the monocots corroborated those obtained with the chloroplast gene rbcL. Both genes raise questions concerning the monocot superorders as defined in a previous classification. This study proves the rps4 gene to be a useful phylogenetic tool within the Poaceae family and the Monocotyledonae order.

Phylogenetic relationships based on internal transcribed spacer (ITS) sequences were used to assess evolutionary trends in genome structure within the genusPennisetumon the basis of observed variations in genome size, basic chromosome numbers (x=5, 7, 8 and 9) and ploidy level (from 2x to 8x). The evolutionary reconstruction is congruent with the gene pool classification and in agreement with some morphological grouping. Pearl millet,P. glaucum, together with elephant grass,P. purpureum, form a monophyletic group with a basic chromosome number of x=7 but different chromosome sizes. The ancestral characters of the genus are x=9 small chromosomes, an apomictic mode of reproduction and a perennial life cycle. Species with basic chromosome numbers of x=5, 7 and 8 appear in the most recently divergent clades, indicating that the genome structure inPennisetummight have evolved towards a reduced chromosome number and an increased chromosome size. [ABSTRACT FROM AUTHOR]