DNA

International audienceThe island of Madagascar is a key hot spot for the genus Euphorbia, with at least 170 native species, almost all endemic. Threatened by habitat loss and illegal collection of wild plants, nearly all Malagasy Euphorbia are listed in CITES Appendices I and II. The absence of a reliable taxonomic revision makes it particularly difficult to identify these plants, even when fertile, and thereby compromises the application of CITES regulations. DNA barcoding, which can facilitate species-level identification irrespective of developmental stage and the presence of flowers or fruits, may be a promising tool for monitoring and controlling trade involving threatened species. In this study, we test the potential value of barcoding on 41 Euphorbia species representative of the genus in Madagascar, using the two widely adopted core barcode markers (matK and rbcL), along with two additional DNA regions, nuclear internal transcribed spacer (ITS) and the chloroplastic intergenic spacer psbA-trnH. For each marker and for selected marker combinations, inter-and intraspecific distance estimates and species discrimination rates are calculated. Results using just the 'official' barcoding markers yield overlapping inter-and intraspecific ranges and species discrimination rates below 60%. When ITS is used, whether alone or in combination with the core markers, species discrimination increases to nearly 100%, whereas the addition of psbA-trnH produces less satisfactory results. This study, the first ever to test barcoding on the large, commercially important genus Euphorbia shows that this method could be developed into a powerful identification tool and thereby contribute to more effective application of CITES regulations

Straightening out the screw-pines : a first step in understanding phylogenetic relationships within Pandanaceae

The Paleotropical monocot family Pandanaceae includes ca. 700 species assigned to four genera: Pandanus (ca. 500 spp.), Freycinetia (ca. 200 spp.), Martellidendron (6 spp.) and Sararanga (2 spp.). The most speciose genus, Pandanus, was classically subdivided into eight subgenera. Previous cladistic analyses revealed that several key morphological characters might have evolved independently several times, thus highlighting the need for a robust molecular phylogenetic framework to elucidate phylogenetic relationships and infrafamilial and in frageneric classification within this group. In this study, three plastid DNA regions (matK, trnQ-rps16, trnL-trnF) and 200 individuals (representing 134 species and 609 newly produced sequences) spanning the taxonomic and biogeographic diversity of the family are analyzed to test the monophyly at the familial and generic levels, and to infer phylogenetic relationships within the family. Particular emphasis is devoted to Pandanus with the aim of recognizing key morphological characters that reflect the evolutionary history of the genus. Phylogenetic inferences support the monophyly of Pandanaceae and establish Sararanga as sister to the rest of the family, with Freycinetia as sister to the Pandanus-Martellidendron pair. Although relationships are not well-resolved within the latter clade, three supported lineages are retrieved: (1) the Acrostigma clade comprising taxa of P. subg. Acrostigma, (2) the Martellidendron clade including taxa assigned to the genus Martellidendron and (3) the core Pandanus clade including taxa of all other subgenera of Pandanus. Morphological and biogeographic evidence supporting clade definitions are discussed in detail. This study provides the first phylogenetic backbone for Pandanaceae, which is sufficiently robust to serve as a springboard for future research into the evolutionary history of this neglected family

On islands, evolutionary but not functional originality is rare [PREPRINT].

Functionally and evolutionary original species are those whose traits or evolutionary history are shared by few others in a given set. These original species promote ecosystem multifunctionality, the ability to cope with an uncertain future, future benefits to society and therefore have a high conservation value. A potential signal of their extinction risks is their rarity (stating for geographic range-restriction in this study). On islands, life in isolation conducted to the rise of a multitude of original forms and functions as well as to high rates of endemism. Not only patterns and processes of insular originality are unexplained but the relationship between originality and rarity is still unknown. The aim of this study is to assess how original insular species are, to explore whether original species are rare or not and to investigate the factors that may explain the rarity of original species. We first compared the functional and evolutionary originality of monocotyledon species and whether continental or insular species were more original. We found that species restricted to islands were more original than continental species and, although functionally and evolutionary original species were dissimilar, many occurred on similar territories so that regional conservation strategies may allow to conserve these distinct forms. Yet, evolutionary original species were significantly more range-restricted than those which were distinct in their traits. Reflecting their rarity, evolutionary original species had low dispersal abilities and were found on islands where settlement may have been facilitated. On the opposite, functionally original species could reach a wider set of islands by being transported on long-distances. While some mechanisms may both explain rarity and originality such as extinctions, others may be specific to each of these biodiversity facets, in particular diversification, niche shift and expansion, and dispersal power. Implications for conservation are huge: original species are range-restricted and mostly found in the most threatened systems of the world, i.e. islands, endangering the reservoir of features against an uncertain future

Phylogeny, evolutionary trends and classification of the Spathelia–Ptaeroxylon clade: morphological and molecular insights

International audienceBACKGROUND AND AIMS: The Spathelia-Ptaeroxylon clade is a group of morphologically diverse plants that have been classified together as a result of molecular phylogenetic studies. The clade is currently included in Rutaceae and recognized at a subfamilial level (Spathelioideae) despite the fact that most of its genera have traditionally been associated with other families and that there are no obvious morphological synapomorphies for the clade. The aim of the present study is to construct phylogenetic trees for the Spathelia-Ptaeroxylon clade and to investigate anatomical characters in order to decide whether it should be kept in Rutaceae or recognized at the familial level. Anatomical characters were plotted on a cladogram to help explain character evolution within the group. Moreover, phylogenetic relationships and generic limits within the clade are also addressed. METHODS: A species-level phylogenetic analysis of the Spathelia-Ptaeroxylon clade based on five plastid DNA regions (rbcL, atpB, trnL-trnF, rps16 and psbA-trnH) was conducted using Bayesian, maximum parsimony and maximum likelihood methods. Leaf and seed anatomical characters of all genera were (re)investigated by light and scanning electron microscopy. KEY RESULTS: With the exception of Spathelia, all genera of the Spathelila-Ptaeroxylon clade are monophyletic. The typical leaf and seed anatomical characters of Rutaceae were found. Further, the presence of oil cells in the leaves provides a possible synapomorphy for the clade. CONCLUSIONS: The Spathelia-Ptaeroxylon clade is well placed in Rutaceae and it is reasonable to unite the genera into one subfamily (Spathelioideae). We propose a new tribal classification of Spathelioideae. A narrow circumscription of Spathelia is established to make the genus monophyletic, and Sohnreyia is resurrected to accommodate the South American species of Spathelia. The most recent common ancestor of Spathelioideae probably had leaves with secretory cavities and oil cells, haplostemonous flowers with appendaged staminal filaments, and a tracheidal tegmen

The ancestral flower of angiosperms and its early diversification.

Recent advances in molecular phylogenetics and a series of important palaeobotanical discoveries have revolutionized our understanding of angiosperm diversification. Yet, the origin and early evolution of their most characteristic feature, the flower, remains poorly understood. In particular, the structure of the ancestral flower of all living angiosperms is still uncertain. Here we report model-based reconstructions for ancestral flowers at the deepest nodes in the phylogeny of angiosperms, using the largest data set of floral traits ever assembled. We reconstruct the ancestral angiosperm flower as bisexual and radially symmetric, with more than two whorls of three separate perianth organs each (undifferentiated tepals), more than two whorls of three separate stamens each, and more than five spirally arranged separate carpels. Although uncertainty remains for some of the characters, our reconstruction allows us to propose a new plausible scenario for the early diversification of flowers, leading to new testable hypotheses for future research on angiosperms

World Flora Online: Placing taxonomists at the heart of a definitive and comprehensive global resource on the world's plants

It is time to synthesize the knowledge that has been generated through more than 260 years of botanical exploration, taxonomic and, more recently, phylogenetic research throughout the world. The adoption of an updated Global Strategy for Plant Conservation (GSPC) in 2011 provided the essential impetus for the development of the World Flora Online (WFO) project. The project represents an international, coordinated effort by the botanical community to achieve GSPC Target 1, an electronic Flora of all plants. It will be a first-ever unique and authoritative global source of information on the world's plant diversity, compiled, curated, moderated and updated by an expert and specialist-based community (Taxonomic Expert Networks - TENs - covering a taxonomic group such as family or order) and actively managed by those who have compiled and contributed the data it includes. Full credit and acknowledgement will be given to the original sources, allowing users to refer back to the primary data. A strength of the project is that it is led and endorsed by a global consortium of more than 40 leading botanical institutions worldwide. A first milestone for producing the World Flora Online is to be accomplished by the end of 2020, but the WFO Consortium is committed to continuing the WFO programme beyond 2020 when it will develop its full impact as the authoritative source of information on the world's plant biodiversity