Systematics, biogeography, and character evolution of the legume tribe Fabeae with special focus on the middle-Atlantic island lineages

BACKGROUND

Tribe Fabeae comprises about 380 legume species, including some of the most ancient and important crops like lentil, pea, and broad bean. Breeding efforts in legume crops rely on a detailed knowledge of closest wild relatives and geographic origin. Relationships within the tribe, however, are incompletely known and previous molecular results conflicted with the traditional morphology-based classification. Here we analyse the systematics, biogeography, and character evolution in the tribe based on plastid and nuclear DNA sequences.

RESULTS

Phylogenetic analyses including c. 70% of the species in the tribe show that the genera Vicia and Lathyrus in their current circumscription are not monophyletic: Pisum and Vavilovia are nested in Lathyrus, the genus Lens is nested in Vicia. A small, well-supported clade including Vicia hirsuta, V. sylvatica, and some Mediterranean endemics, is the sister group to all remaining species in the tribe. Fabeae originated in the East Mediterranean region in the Miocene (23-16 million years ago (Ma)) and spread at least 39 times into Eurasia, seven times to the Americas, twice to tropical Africa and four times to Macaronesia. Broad bean (V. faba) and its sister V. paucijuga originated in Asia and might be sister to V. oroboides. Lentil (Lens culinaris ssp. culinaris) is of Mediterranean origin and together with eight very close relatives forms a clade that is nested in the core Vicia, where it evolved c. 14 Ma. The Pisum clade is nested in Lathyrus in a grade with the Mediterranean L. gloeosperma, L. neurolobus, and L. nissolia. The extinct Azorean endemic V. dennesiana belongs in section Cracca and is nested among Mediterranean species. According to our ancestral character state reconstruction results, ancestors of Fabeae had a basic chromosome number of 2n=14, an annual life form, and evenly hairy, dorsiventrally compressed styles.

CONCLUSIONS

Fabeae evolved in the Eastern Mediterranean in the middle Miocene and spread from there across Eurasia, into Tropical Africa, and at least seven times to the Americas. The middle-Atlantic islands were colonized four times but apparently did not serve as stepping-stones for Atlantic crossings. Long-distance dispersal events are relatively common in Fabeae (seven per ten million years). Current generic and infrageneric circumscriptions in Fabeae do not reflect monophyletic groups and should be revised. Suggestions for generic level delimitation are offered.

Cytological and molecular characterization of Vicia barbazitae Ten. & Guss

Vicia barbazitae, a taxon belonging to section Vicia of subgenus Vicia, was recovered and analysed by cytological, karyological and molecular methods with the aim of both proposing a general characterisation of this species and studying the relationships among the species of section Vicia . Phylogenetic relationships among the species of the section Vicia and those of the sections Microcarinae, Wiggersia and Atossa were also analysed. Automated karyotype analysis has been determined after Feulgen's reaction; chromosome banding was performed by sequence-specific fluorochrome staining. Fluorescent chromosome banding showed CMA(+)/DAPI(-) NOR-associated heterochromatin in the satellite pair. Karyomorphological parameters, based on symmetry indices, the dendrogram of linkage distance constructed on 37 chromosome parameters, as well as the molecular data based on internal transcribed spacer sequences provided information about phylogenetic position of this species inside the section Vicia and among the species belonging to the sections Microcarinae, Wiggersia, Atossa and Vicia. From our karyological and molecular results, it emerges that V. barbazitae can be considered a natural member of section Vicia.

[Effects of UV-B radiation on the growth and reproduction of Vicia angustifolia]

A simulation experiment with supplementation and exclusion of solar ultraviolet-B (UV-B) radiation was conducted to study the effects of enhanced and near ambient UV-B radiation on the growth and reproduction of alpine annual pasture Vicia angustifolia on Qinghai-Tibet Plateau. Enhanced UV-B decreased the plant height and biomass, biomass allocation to fruit, flower number, and 100-seed mass significantly, delayed flowering stage, increased the concentration degree of flowering and success rate of reproduction, but had little effect on seed yield. Near ambient UV-B radiation made the plant height increased after an initial decrease, decreased biomass allocation to fruit and 100-seed mass, but little affected flowering duration, flower number, and seed yield. Both enhanced and near ambient UV-B radiation could inhibit the growth and production of V. angustifolia, and the effect of enhanced UV-B radiation was even larger.

Cytology of Vicia species. X. Karyotype evolution and phylogenetic implication in Vicia species of the sections Atossa, Microcarinae, Wiggersia and Vicia

Automated karyotype analyses and sequence of rDNA spacers have been analysed for the species belonging to sections Atossa, Microcarinae, Wiggersia and Vicia. Karyomorphological parameters, based on Rec, Syi and TF% indices, have been determined and evidenced that, in term of symmetry, the karyotype of Vicia lathyroides was the most asymmetric one. A multivariate analysis using 34 karyological parameters, in addition to the symmetry indices, has been carried out and the corresponding dendrogram of linkage distances showed six different groups. Molecular investigations on the inclusive group in study by employing ITS DNA sequences indicated a different pattern of relationships. The cladistic analysis combining the molecular data set with karyological parameters evidenced that the species of sections Vicia and Atossa join closely to each other in a paraphyletic group, which includes the monophyletic section Wiggersia. Therefore, our karyological and molecular data provide information about the phylogenetic position of the analysed species inside the subgenus Vicia and are discussed in relation to previous results obtained by morphology, isozymes and ribosomal genes analyses.

Cytological and molecular characterization of Vicia esdraelonensis Warb. & Eig: a rare taxon

Vicia esdraelonensis, a rare taxon belonging to section Hypechusa of subgenus Vicia, was recovered and analyzed by cytological, karyological, and molecular methods, with the aim of both characterizing this species and furthering our knowledge of the phylogeny of subgenus Vicia. Automated karyotype analysis, nuclear DNA content, and chromatin organization were determined by the Feulgen reaction, as well as chromosome banding after double staining with 4',6-diamidino-2-phenylindole (DAPI) and chromomycin A3. The chromosome number and the nuclear DNA content were in agreement with the values of the species of section Hypechusa. The GC- and AT-rich preferential sites were determined by chromomycin A3 and DAPI staining. Karyomorphological parameters indicated that V. esdraelonensis is in an intermediate position in the spatial representation of the species of section Hypechusa on the basis of symmetry indices, as well as in the dendrogram of linkage distance constructed on 37 chromosome parameters. Molecular data based on internal transcribed spacer sequences show that V. esdraelonensis can doubtlessly be included in section Hypechusa and document its closeness to V. noeana. A cladistic analysis combining the molecular data set with karyological characters is also reported. Karyological, cytological, and molecular data allow characterization of the V. esdraelonensis genome and provide information about the phylogenetic position of this species within the Hyrcanicae series of section Hypechusa.

Phylogenetic significance of stylar features in genus Vicia (Leguminosae): an analysis with molecular phylogeny

Tribe Fabeae consists of five genera, Lathyrus (160 spp.), Lens (4-6 spp.), Pisum (2-3 spp.), Vavilovia (monotypic), and Vicia (160 spp.), and shows a diversity in stylar features. At least six different stylar types are known in the tribe. In order to reclassify the tribe at the rank of genus, we tried to discover apomorphies in stylar features using a molecular phylogenetic study. We surveyed internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA of representative species, selected from each group having different types of styles in the tribe. We paid particular attention in sampling to members of Vicia section Vicilla, as stylar features are heterogeneous within this section. Consequently, our sample set included 15 species of section Vicilla, 23 species of other Fabeae, and two species of Trifolieae, which were used as a sister group of Fabeae. Based on our analysis, we found that a laterally compressed style and an abaxially tufted hairy style would be advanced against a dorsiventrally compressed style and an evenly hairy style, respectively, in genus Vicia. The species group, which shares the latter apomorphy, is composed of 56 species and was dispersed into 11 sections of two subgenera in the recent system of genus Vicia. We consider future revision of Fabeae should treat this species group as a single higher taxon.

Nuclear DNA contents, rDNAs, and karyotype evolution in subgenus Vicia: III. The heterogeneous section Hypechusa

Nuclear DNA contents, automated karyotype analyses, and sequences of internal transcribed spacers from ribosomal genes have been determined in the species belonging to section Hypechusa of the subgenus Vicia. Karyomorphological results and phylogenetic data generated from the comparison of rDNA (genes coding for rRNA) sequences showed that sect. Hypechusa is not monophyletic; however, some monophyletic units are apparent (one including Vicia galeata, V. hyrcanica, V. noeana, and V. tigridis, another including V. assyriaca, V. hybrida, V. melanops, V. mollis, and V. sericocarpa), which partly correspond to morphology-based infrasectional groups. The relationships among these species and the species in sections Faba, Narbonensis, Bithynicae, and Peregrinae have been also investigated.

Phylogenetic analyses within three sections of the genus Vicia

The averaged genomic similarities based on multilocus randomly amplified polymorphic DNA (RAPD) were calculated for eight species representing three sections of the genus Vicia: faba, bithynica and narbonensis. The frequency of appearance of the sequences corresponding to 25 decamers selected at random from genomes of different Fabace species was checked, and a high correlation with the frequency observed for Vicia allowed us to assume their similar weight in typing Vicia species. The RAPD-based similarity coefficients compared with those related to whole genome hybridization with barley rDNA and those based on restriction fragment length polymorphism (RFLP) revealed similar interspecies relationships. The averaged RAPD-based similarity coefficient (Pearson's) was 0.68 for all the species, and was sectionspecific: 0.43 (bithynica), 0.50 (faba) and 0.73 (narbonensis). The averaged similarity coefficient for V. serratifolia (0.63) placed it apart from the rest (0.75) of its section. The results correspond to the interspecies relationships built upon non-genetic data. The averaged similarity coefficient for particular RAPD was related to the presence and type of tandemly repeated motif in a primer: 0.7-0.8 for heterodimers (GC, AG, CA, GT, CT), 0.5-0.6 for homodimers (CC, GG) and 0.6 for no repeat, indicating the sensitivity of diversity range to the type of target sequences.

Nuclear DNA contents, rDNAs, and karyotype evolution in Vicia subgenus Vicia: II. Section Peregrinae

Nuclear DNA contents, automated karyotype analyses, and sequences of rDNA spacers have been determined for the species of Vicia belonging to sect. Peregrinae, as well as for V. mollis. The phylogenetic data generated from the comparison of rDNA sequences and karyomorphological results would both indicate that Vicia mollis is a sister group to sect. Peregrinae. The relationships among the species belonging to the Peregrinae section and species enclosed in sections Faba, Narbonensis, and Bithynicae have been also investigated: a clade including V. mollis and sect. Peregrinae is a sister group to a clade including V. bithynica and sect. Narbonensis. With our choice of outgroup, Vicia faba (including subsp. paucijuga) is external to the above mentioned inclusive group.

Isozyme variation and phylogenetic relationships in Vicia subgenus Cracca (Fabaceae)

BACKGROUND AND AIMS

The phylogenetic relationships among 27 vetch species belonging to the subgenus Cracca of the genus Vicia were studied in comparison with three species of Lathyrus section Lathyrus on the basis of isozyme variation.

METHODS

Isozymes encoded by 15 putative loci of ten enzymes were resolved by polyacrylamide gel electrophoresis and isozyme variation was analysed by using parsimony and neighbour-joining methods.

KEY RESULTS

The analyses revealed 63 parsimony-informative and 36 species-specific orthozymes. Of the latter, 23 are monomophic and are suitable for identification of V. benghalensis, V. palaestina, V. dumetorum, V. pisiformis, V. sylvatica, V. onobrychioides, V. cappadocica, V. cretica, V. articulata, V. tetrasperma, V. ervilia, V. hirsuta and V. loiseleurii. Polymorphism with heterozygous and homozygous isozyme genotypes was found for V. cracca, V. tenuifolia, V. ochroleuca, V. villosa, V. sylvatica, V. cassubica, V. sparsiflora, V. megalotropis, V. altissima, V. onobrychioides, V. cassia, V. cretica and L. heterophyllus, reflecting outcrossing in these species. By contrast, V. benghalensis, V. palaestina, V. disperma, V. dumetorum, V. pisiformis, V. orobus, V. pauciflora, V. tetrasperma and V. loiseleurii had only homozygous isozyme genotypes at polymorphic loci. Isozyme-based phylogenetic trees are presented.

CONCLUSIONS

Sections Cracca, Ervum, Pedunculatae and Lenticula of traditional taxonomy are monophyletic groups, whereas sections Oroboideae (= Vicilla) and Panduratae appear polyphyletic and section Cassubicae is split into two species-couples linked at a low level of support. Treatment of ervoid species in a separate subgenus Ervum is not supported because of its polyphyly.

Specific differentiation in Vicia genus by means of capillary electrophoresis

Capillary electrophoresis has been applied to the discrimination of 13 Vicia species, belonging to four sections of Vicia genus. The studied species necessitate of plant growing tests or DNA molecular markers to be distinguished being their seeds morphologically very similar. Alcoholic/saline extracts from dry cotyledons were separated in uncoated fused-silica capillary with iminodiacetic acid isolectric buffer containing hydroxypropylmethylcellulose and acetonitrile. The low intra-specific variation observed for 11 species, suggests that this approach is suitable to carry out species discrimination. Species-specific peaks were identified for V. articulata, V. atropurpurea, V. bithynica, V. benghalensis, V. disperma, V. ervilia, V. monantha, V. sativa and V. villosa. Conversely, V. lutea, V. melanops and V. peregrina, showing very similar electrophoregrams, require other methodological approaches to be discriminated. The discussed CE method appears to have a potential to be regarded as an alternative tool to identify some Vicia species being far less expensive and time consuming than plant growing tests and DNA molecular markers.