Premise of research. Riparian plants are highly dependent on water sources; consequently, general climatic conditions are less important to these taxa relative to woodland and shrubland species. This ...leads to interesting research questions regarding riparian plant taxa. Research on phylogeography of Mediterranean riparian tree and shrub species is scarce. In this article, we investigated the plastidial genetic diversity in Celtis australis L. (hackberry) and Nerium oleander L. (oleander) throughout the Mediterranean Basin. Both species are distributed in gullies, rivers, and stream banks under warm temperate climates.
Methodology. Eighteen cpSSR loci and three noncoding cpDNA regions (rps16, rpl32-trnL, and trnQ-5′-rps16) were examined to assess the levels and geographic distribution of sequence variation in 41 hackberry and 56 oleander populations. The rpl32-trnL intergenic region was used for molecular dating analysis.
Pivotal results. The respective 2762- and 3134-bp noncoding cpDNA regions sequenced in C. australis and N. oleander, as well as the 22 cpSSR analyzed fragments, exhibited the absence of variability in natural populations throughout the Mediterranean Basin. In N. oleander, two regions (rps16, rpl32-trnL) exhibited variability in three positions, and four cpSSR microsatellite motifs were polymorphic. The polymorphisms were geographically structured, and three haplotypes were characterized, two from Saharan populations and one from Mediterranean populations. Phylogeny and molecular dating analyses resulted in a tree with high consistency values of posteriori probability (PP = 1) and bootstrap support (98%) from the ingroup (N. oleander). The relaxed molecular clock model applied to the calibration of the tree estimates that the diversification of these haplotypes occurred in a range of 7.2–1.2 Ma.
Conclusions. The absence of plastid variability in both hackberry and oleander is explained by a low mutation rate and/or recent recolonization of the Mediterranean Basin. Low temperatures during the Last Glacial Maximum produced freezing water along riparian corridors, with the consequent drastic contraction or even disappearance of both species in the Mediterranean Basin.
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Riella (Riellaceae) is a genus of rare, ephemeral, aquatic liverworts that includes some taxa specialized in growing submerged in brackish, seasonal water ponds and lagoons. One of these species, ...Riella helicophylla is the type of the genus. Apart from being of conservation concern, it has been used as a model organism for cytological and physiological processes. The species was described from Algeria in the mid‐nineteenth century and was not found elsewhere for almost a century, when it was discovered in central Spain. Nonetheless, those new populations were considered morphologically different and served to describe a new variety (var. macrocarpa), and a form (f. latealata) of the latter. The number of population records increased considerably in the following decades, especially in the late twentieth century; at the same time, it was discovered in several countries throughout the Mediterranean basin. Those reports, however, did not account for its infraspecific distinction. As part of a broader study of the genus, in this work, we have revisited the taxonomy of R. helicophylla based on an integrative approach considering morphological and molecular DNA sequence data. Our broadly sampled study revealed that R. helicophylla includes two morphotypes corresponding with the previously recognized varieties of this species. These varieties differ consistently in a number of morphological gametophytic and spore traits. Riella helicophylla was resolved as paraphyletic in phylogenies based on nuclear and plastid DNA sequences. The accessions clustered in two monophyletic clades in concert with morphology, supporting their recognition at the species level. Accordingly, a new combination is proposed, R. macrocarpa, which includes the neglected R. helicophylla var. macrocarpa and R. helicophylla var. macrocarpa f. latealata. Lectotypes are designated for the two latter taxa and for R. helicophylla. The two species are fully described and illustrated, and an updated identification key of the Mediterranean species is included. Updated information on the conservation status of both species is provided.
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Riella Mont. is unusual among bryophyte genera because its species have an ephemeral habit and grow submerged in fresh or brackish waters. Most species show fragmented distribution areas and have few ...known populations and are thus of conservation concern. The flagship Mediterranean species R. helicophylla (Bory & Mont.) Mont. has recently been taxonomically reassessed, and most populations have been placed in a new species, R. macrocarpa (P.Allorge) Puche, Segarra-Moragues, Sabovlj., M.Infante & Heras. Here we describe the development of nuclear microsatellite markers for R. macrocarpa with the aim of characterising the population genetic dynamics of this species of conservation concern, and we report their potential use in other species of the genus.
Nuclear microsatellite markers were isolated from 454 genomic libraries and amplification parameters optimised for the set of loci finally selected.
Nine microsatellite loci were characterised and amplified a total of 53 alleles in a sample of 120 individuals from four populations, having a mean of 5.89 alleles per locus. Unbiased genetic diversity for the polymorphic loci within populations ranged from 0.067 to 0.791. Cross-species transferability assayed in six other species of Riella covering reproductive and taxonomic diversity in the genus showed transferability success rates ranging from 77.8% to 100%, with 33.3% to 57.1% of the successfully transferred loci being polymorphic within species. These markers will be useful for studying population genetic diversity and structure and will contribute towards better conservation management of populations of R. macrocarpa and other species of Riella.
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Species of Riella subgenus Trabutiella are characterized by their winged involucres. Although several species are included in this subgenus, to date only one, R. affinis, is monoicous. During the ...course of a worldwide revision of Riella including samples throughout the distribution area of R. affinis, populations with exceptionally different spore characters were discovered after examination of herbarium and fresh specimens and laboratory cultures. Morphological traits studied included spore characters measured by light and SEM microscopy. All samples had a high gametophytic similarity. Nonetheless, samples from Californian populations differed from the remaining ones of R. affinis in female involucre morphology, and more conspicuously in spore morphology and ornamentation. Statistical analyses of spore morphological traits confirmed the significant differences between the two species. Therefore, a new monoicous species of Riella subgen. Trabutiella is described as R. heliospora. This species can be distinguished from R. affinis by the female involucres with broader wings, the spores showing a triradiate mark on the proximal face, the presence of a conspicuous reticulum of basal membranes on the distal and proximal faces, longer and less dense spines on the distal face, and a conspicuous wing-like marginal webbing at the equatorial plane.
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Riella (Riellaceae, Sphaerocarpales) is a genus of aquatic liverworts with a disjunct worldwide distribution in areas of seasonal Mediterranean-type climates. Its centre of diversity is located in ...the Mediterranean basin, where about half the species number of the genus is concentrated. In the course of a worldwide revision of the genus Riella, plants from a monoicous species with wingless, not papillose and smooth involucres were found in two distant Iberian localities. These plants showed a geminate dorsal wing, unlike the single wing occurring in the remaining species of the genus. This character unambiguously assigns these populations to R. bialata, a species known to date from a single collection in its Algerian type locality. Riella bialata is thus reported as new to Europe. Fresh materials enabled detailed morphological analyses, and the Iberian materials are extensively described and illustrated herein.
The rare aquatic liverwort
(Bory et Mont.) Mont., inhabitant of temporary shallow ponds around the Mediterranean basin, is considered threatened throughout its distribution range. In addition, little ...is known of its biology and ecology or of its role in such an important ecosystem where environmental conditions vary yearly in unpredictable ways. In these variable habitats, due to the seasonal fluctuation of water levels, there is no guarantee of yearly spore input into the spore bank. Spore germination rate and the effects of different culture media in an axenic culture establishment, as well as propagation procedures of
were tested. New insights into the ecology and biology of
are given. Spore dormancy is documented, and the protocols for the in vitro culture establishment, propagation and acclimatization of this liverwort are developed. Dry storage at 20 ± 2 °C for about three months broke the dormancy of spores, which subsequently germinated in a high percentage (over 90%). A two phase (solid and liquid) culture media system was developed for the purpose of achieving fully developed gametophytes. The liquid phase contained electrolytes simulating brackish water.
Riella (Riellaceae, Sphaerocarpales) is a genus of aquatic liverworts with disjunct range in areas of Mediterranean-type climates. Riella has been traditionally subdivided into two subgenera, ...subgenus Riella, whose plants show smooth or papillose female involucres and Trabutiella, whose plants show winged female involucres. To date only three species of Riella are known in France, all belonging to subgenus Riella. During the course of a study of the plant diversity of temporary brackish ponds in the Camargue area (Southern France), soil sediments were collected from 10 localities and cultivated in the laboratory. From cultures of five of these localities emerged dioicous plants of Riella showing winged female involucres that unambiguously assigned them to subgenus Trabutiella. The study of those specimens with Light and Scanning Electron Microscopy allowed us to identify them as R. cossoniana var. cossoniana. Fresh materials allowed for detailed morphological analyses on these new French materials which were fully described and illustrated. These findings represent the first report of a species belonging to subgenus Trabutiella from France and the second European country where R. cossoniana is reported. Four nearby populations occur within the perimeter of the Tour du Valat Regional Natural Reserve, and another in the industrial polygon of the Grand Port Maritime de Marseille.
Tortella bambergeri (Schimp.) Broth. is reported for the first time from northern and central-eastern Spain in the Iberian Peninsula. Diagnostic characters and differentiation from other closely ...related Iberian Tortella taxa are discussed. Furthermore, a map of the currently known distribution of T. bambergeri in Spain, illustrations of the species and an updated key to Iberian Tortella are provided.
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