The Mediterranean region is a center of species and genetic diversity of many plant groups, which served as a source of recolonization of temperate regions of Eurasia in Holocene. We investigate the evolutionary history of species currently classified in Lotus sect. Bonjeanea in the context of the evolution of the genus Lotus as a whole, using phylogenetic, phylogeographic and dating analyses. Of three species of the section, L. rectus and L. hirsutus have wide Mediterranean distribution while L. strictus has a disjunctive range in Bulgaria, Turkey, Armenia, Eastern Kazakhstan, and adjacent parts of Russia and China. We used entire nuclear ribosomal ITS1-5.8S-ITS2 region (nrITS) and a plastid dataset (rps16 and trnL-F) to reconstruct phylogenetic relationships within Lotus with an extended representation of Bonjeanea group. We analyzed the phylogeographic patterns within each species based on the plastid dataset. For divergence time estimation, the nrITS dataset was analyzed. Our results confirmed the non-monophyletic nature of the section Bonjeanea. They indicate that Lotus is likely to have diverged about 15.87 (9.99–19.81) million years ago (Ma), which is much older than an earlier estimate of ca. 5.54 Ma. Estimated divergence ages within L. strictus, L. rectus, and L. hisrutus (6.1, 4.94, and 4.16 Ma, respectively) well predate the onset of the current type of Mediterranean climate. Our data suggest that relatively ancient geological events and/or climatic changes apparently played roles in early diversification of Lotus and its major clades, as well as in formation of phylogeographic patterns, in at least some species.

Lotus dorycnium s.l. is a complex of taxa traditionally regarded as members of Dorycnium. It has a wide Mediterranean range, extending in the north to Central and Eastern Europe, and in the east to the Crimea, the Caucasus, and the Western Caspian region. Molecular phylogenetic data support placement of the L. dorycnium complex in the genus Lotus. The present study investigated the phylogeny, phylogeography and morphological variability of the L. dorycnium complex across its distribution range to reveal the main trends in genetic and morphological differentiation in this group. The results of the morphological analyses demonstrated some degree of differentiation, with L. d. ssp. herbaceus, ssp. gracilis, and ssp. anatolicus more or less well defined, whereas ssp. dorycnium, ssp. germanicus, and ssp. haussknechtii can be hardly distinguished from each other using morphology. Analyses of the L. dorycnium complex based on nrITS revealed a tendency towards a geographic differentiation into Western, Eastern, and Turkish groups. Phylogenetic and phylogeographic analyses of the same set of specimens using concatenated plastid markers trnL-F, rps16, and psbA-trnH demonstrated a low resolution between the L. dorycnium complex and L. hirsutus, as well as among the taxa within the L. dorycnium complex, which can be interpreted as evidence of an incomplete lineage sorting or hybridization. The evolutionary processes responsible for incongruence in phylogenetic signals between plastid and nuclear sequences of the morphologically well-defined species L. dorycnium and L. hirsutus were most likely localized in the Eastern Mediterranean. A possibility of rare gene exchange between the L. dorycnium complex and the group of L. graecus is revealed for the first time.

The tribe Loteae (Papilioniodeae-Leguminosae), according to plastid data, belongs to the Robinioid clade, which also includes the tribes Robinieae and Sesbanieae. The tribe Loteae contains 16 genera and about two hundred seventy-five species, of which the plastid genomes of five species have been studied to date. The main objectives of our study were to obtain new information on the plastid genome structure of the Loteae representatives in order to assess plastid genome variability and reconstruct phylogenetic relationships within the tribe Loteae. We performed sequencing, assembly, structural and phylogenetic analyses of the Loteae plastid genomes. All assembled Loteae plastomes showed a quadripartite structure with an overall length ranging from 150,069 to 152,206 bp and showed relative stability of inverted repeat borders. The Loteae plastomes demonstrated full collinearity; the most variable sites of the studied plastomes were found in petN-trnC and rps16-accD spacers from the LSC region and in the ycf1 gene within the SSC. All inferred relationships attained maximal support with the Hippocrepis lineage separated first, followed by Coronilla and Anthyllis; Lotus is a sister group to the clade Acmispon + Ornithopus. In this study, completely resolved relationships representing a backbone of plastid phylogeny were produced. The obtained results demonstrated that plastid genomes in the tribe Loteae are structurally conservative in contrast to the closely related tribes Robinieae and Sesbanieae.

С применением бинокулярного микроскопа и СЭМ изучены морфология и ультраструктура семян видов Lotus из секций Dorycnium (L. dorycnium и L. graecus), Bonjeanea (L. rectus, L. hirsutus и L. strictus) и Lotus (L. corniculatus). Семена изученных видов имеют консервативную структуру, характерную для большинства Papilionoideae. Размер, форма и окраска семян лишь частично позволяют разделять виды в исследуемой группе. Наиболее морфологически различимы семена видов из секции Bonjeanea, при этом L. rectus имеет самые мелкие, а L. strictus – самые крупные семена. Размеры семян у видов секции Dorycniumперекрываются как между членами секции, так и с семенами L. hirsutus (секция Bonjeanea). Ультраструктура поверхности семян вокруг рубчика очень стабильна среди изученных видов, тогда как на боковой стороне семян она более изменчива. Типы скульптуры поверхности на боковой стороне семян не сильно коррелируют с таксономическим положением вида, а больше соответствуют эколого-географическим условиям. Так, тип ультраскульптуры с малозаметной первичной скульптурой и толстыми вторичными кутикулярными отложениями выявлен у видов, распространение которых связано со Средиземноморьем (например, L. hirsutus, L. dorycnium subsp. gracilis и частично L. rectus), а ямчато-бугорчатая первичная скульптура с тонкими вторичными кутикулярными отложениями характерна для видов, обитающих в более умеренном климате (L. corniculatus, L. strictus, L. graecus). По толщине эндосперма изученные виды можно разделить на две группы. Мы полагаем, что тонкий эндосперм, обнаруженный у L. strictus и L. corniculatus, может быть признаком, связанным с ускорением развития при распространении из Средиземноморья в умеренную климатическую зону.