Abstracts

Diversity of the Vegetation

According to our investigations 29 species of Euphorbia L. sect. Esula Dumort. from three subsections and seven series are distributed in Northern Asia. Formation of this section has been directly connected with this region where it consists of species from different natural groups, including endemic taxa. Both ecological and geographical evidences support this conclusion. If differentiation of the Northern-Asian species in sect. Holophyllum and sect. Helioscopia was more actively in mountains of Southern Siberia and Central Asia, speciation in section Esula took place mainly on plains, in the steppe, forest-steppe zones of Western and Eastern Siberia. Ecological and geographical data, phylogenetic scheme of relationships in North-Asian spurges do it necessary to change the position of some critical taxa in the system of genus and to describe more natural series of species having different origin.

In a phylogenetic aspect, mesomorphic Manchurian species E. sieboldiana Morr. et Decne. and E. savaryi Kiss. from subsect. Sieboldianae Prokh. are more primitive. They have general similarity to sect. Tulocarpa and differ by large ray-leaves and two-horned glands. Xeromorphic Central-Asian E. potaninii Prokh. from monotypical subsect. Potaniniae Baikov is also quite separate: its capsule are similar to more primitive species from sect. Holophyllum Prokh. (E. rapulum Kar. et Kir., E. blepharophylla Ledeb.). Other 26 species of the section have position in subsect. Esulae Boiss.

The most primitive species is broad-leaves mesomorphic Altai and East-Kazakhstan species E. latifolia Ledeb. which closely connected with E. borodinii Sambuk from Eastern Europe. Both species habitat on the shingle river banks. They relate with series Esulae Prokh., but take separate position.

Xero-mesomorphic European E. lucida Waldst. et Kit., Manchurian E. mandshurica Maxim., E. dahurica Peschkova present broad-leaf thermophylic group genetically connected with East-Asian spurges.

According to D. Geltman (2000), species having think stems, terminal umbel with 3–5 rays, no-yellow raylet leaves in flowering, must be separated from series Esulae and Virgatae Prokh. into new series Leptocaula Geltm. Probably, this group is not natural, but these steppe species present more recent speciation in xerophytic line of development in subsection Esulae. Thus, E. microcapra Prokh., E. kirimzjulica Stepanov, E. karoi Freyn s. str. are moved in new series.

The researches were supported by Russian Foundation for Basic Research (99-07-90222, 01–04–49528, 01–04–48988,), Presidium of Siberian Branch of Russian Academy of Sciences (Integrative grant N66, grant for the Junior scientists 2000-2001).

Note. Abstracts are published in author's edition

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