Fuzzy species limits in Mediterranean gorgonians (Cnidaria, Octocorallia): inferences on speciation processes

The study of the interplay between speciation and hybridization is of primary importance in evolutionary biology. Octocorals are ecologically important species whose shallow phylogenetic relationships often remain to be studied. In the Mediterranean Sea, three congeneric octocorals can be observed in sympatry: Eunicella verrucosa, Eunicella cavolini and Eunicella singularis. They display morphological differences and E.singularis hosts photosynthetic Symbiodinium, contrary to the two other species. Two nuclear sequence markers were used to study speciation and gene flow between these species, through network analysis and Approximate Bayesian Computation (ABC). Shared sequences indicated the possibility of hybridization or incomplete lineage sorting. According to ABC, a scenario of gene flow through secondary contact was the best model to explain these results. At the intraspecific level, neither geographical nor ecological isolation corresponded to distinct genetic lineages in E.cavolini. These results are discussed in the light of the potential role of ecology and genetic incompatibilities in the persistence of species limits.French National Research Agency (ANR) program Adacni (ANR) [ANR-12-ADAP-0016]CNRSHubert Curien 'Tassili' program [12MDU853]CCMAR Strategic Plan from Fundacao para a Ciencia e a Tecnologia-FCT [PEst-C/MAR/LA0015/2011,FEDERinfo:eu-repo/semantics/publishedVersio

Evolutive divergence and reproductive isolation of ascidians (genus Ciona), introduced and native to Europe

Du fait de la complexité des processus de spéciation, l'étude des relations évolutives entre espèces nécessite une approche intégrative. Nous avons combiné croisements expérimentaux et études moléculaires (séquençage mitochondrial et RAD-seq) pour étudier les relations évolutives entre espèces indigènes et introduites du genre Ciona, en Europe. Nous avons examiné deux mécanismes post-zygotiques restant à explorer pour expliquer l'absence d'introgression de C. robusta et C. intestinalis dans leur zone de sympatrie en Manche : 1) la contre-sélection des hybrides par l'environnement (température et salinité) et 2) des incompatibilités de type Dobzhansky-Muller (DMIs). L'absence de dépression hybride (étudiée chez 725 hybrides F1) nous a conduit à rejeter le premier mécanisme. Le second a été exploré grâce à l'étude de sept familles double-hybrides ou issues de rétrocroisements, analysées par RAD-seq. Une stérilité sur la fonction mâle des hybrides F1 et d'importantes distorsions de ségrégation sont en faveur de la présence de DMIs. Nous avons étendu notre étude à d'autres espèces du genre Ciona. Les principaux résultats, notamment soutenus par une approche phylogénomique (7 taxons - 89 individus), sont : 1) la remise en cause du statut d'espèce de C. roulei par rapport à C. intestinalis (probablement deux lignées allopatriques), 2) les premières données montrant la forte divergence évolutive de C. edwardsi avec les autres Ciona spp. et 3) la présence de variabilité génétique et/ou d'introgression chez C. intestinalis type C et type D. Ces résultats ouvrent d'intéressantes perspectives de recherches dont des études populationnelles des espèces présentes en Méditerranée.Speciation is a complex process. Evolutionary relationships between close species thus required an integrative approach. We combined experimental crosses and molecular data (mitochondrial and RAD-tag sequencing) to investigate evolutionary relationships between native and non-indigenous species of the genus Ciona nowadays found in Europe. We studied two post-zygotic mechanisms, still to be examined, to explain the lack of introgression between C. robusta and C. intestinalis in their sympatric range –i.e. the English Channel: i) selection against hybrids, by the environment (here temperature and salinity) and ii) Dobzhansky-Muller incompatibilities (DMIs). The absence of outbreeding depression (over 725 F1-hybrids) makes unlikely the first mechanism. The second has been investigated with seven families of F2-hybrids and backcrosses, all studied with RAD-tag sequences. Male sterility on F1-hybrids and many segregation distortions are in favor of presence of DMIs. We then expanded our study to other Ciona species. The main outcomes, supported by a phylogenomic approach (7 taxa - 89 individuals) are: 1) a needed reappraisal of the species status of C. roulei and C. intestinalis, which are most likely two allopatric lineages of a same species (as defined by biological and phylogenetic species concepts), 2) the first data showing that C. edwardsi is strongly evolutionary divergent from the other Ciona species and 3) the presence of unexpected genetic variability and/or introgression in C. intestinalis type C and D. All together these results open new research perspectives, in particular based on population studies of the species nowadays found in the Mediterranean Sea

Coupling molecular data and experimental crosses sheds light about species delineation: a case study with the genus Ciona

Abstract Molecular studies sometimes reveal evolutionary divergence within accepted species. Such findings can initiate taxonomic revision, as exemplified in the formerly recognized species Ciona intestinalis. While an increasing number of studies have examined the ecology, reproductive barriers and genetics of C. intestinalis and C. robusta, there are still much uncertainties regarding other species of this genus. Using experimental crosses and mitochondrial data, we investigated the evolutionary relationships among four native and introduced Ciona spp., found in sympatry in the Mediterranean Sea or English Channel. Outcome of 62 bi-parental reciprocal crosses between C. intestinalis, C. robusta, C. roulei and C. edwardsi showed that C. edwardsi is reproductively isolated from the other taxa, which is in agreement with its distinct location in the phylogenetic tree. Conversely, hybrids are easily obtained in both direction when crossing C. intestinalis and C. roulei, reinforcing the hypothesis of two genetically differentiated lineages but likely being from a same species. Altogether, this study sheds light on the evolutionary relationship in this complex genus. It also calls for further investigation notably based on genome-wide investigation to better describe the evolutionary history within the genus Ciona, a challenging task in a changing world where biological introductions are shuffling species distribution

Nitric oxide (NO) photo-release in a series of ruthenium–nitrosyl complexes: new experimental insights in the search for a comprehensive mechanism

International audienceA series of four ruthenium(ii) complexes built from the [Ru(terpy)(bipy)(NO)](3+) core (terpy is 2,2:6,2-terpyridine and bipy is 2,2-bipyridine) are investigated. They differ by the presence of zero, one, two, or three 4-(4-methoxyphenyl) (MP) electron donor substituents introduced at different positions on the pyridine fragments to increase the intramolecular charge transfer capabilities towards the strongly withdrawing nitrosyl (NO) ligand. The UV-visible spectra reflect the presence and position of the MP substituents on the complexes. In the case of species containing the 4-(MP)-terpy ligand, a low-lying transition is identified as arising from 4-(MP)-terpy to Ru(NO) intramolecular charge transfer, which is further confirmed by TD-DFT analysis. Irradiation performed at = 436 nm on this isolated transition for different complexes leads to quantum yields of NO photo-release equal to 0.002 and 0.011, in a ratio of 6 (instead of 1), which allows concluding non-ambiguously that a single electron transition cannot account for the NO release mechanism

trans-Chloridotetrakis(4-methylpyridine-κN)(nitrosyl-κN)ruthenium(II) bis(hexafluoridophosphate) acetone 0.75-solvate

The title compound, [RuCl(NO)(C6H7N)4](PF6)2·0.75(CH3)2CO, comprises four ligands of 4-picoline in equatorial position around the central atom. Overall, the complex features an octahedral coordination environment around the central RuII atom, with the chlorido ligand trans to the nitrosyl. The bond length of the nitrosyl N=O ligand is 1.140 (5) Å, while the angle Ru—N=O is 179.0 (4)°. The asymmetric unit contains four PF6− counter-anions, two with occupancy of 0.25 and one with occupancy of 0.5. One PF6− anion is disordered over two sets of sites and one other is disordered with an acetone molecule that occupies the same site

Crystal structure of 1,1′-(pyridine-2,6-diyl)bis[ N -(pyridin-2-ylmethyl)methanaminium] dichloride dihydrate

International audienceIn the title compound, C 19 H 23 N 5 2+ ·2Cl − ·2H 2 O, the two pyridine side arms are not coplanar, with the terminal pyridine rings subtending a dihedral angle of 26.45 (6)°. In the crystal, hydrogen bonds, intermolecular C—H...Cl contacts and a weak C—H...O interaction connect the molecule with neighbouring chloride counter-anions and lattice water molecules. The crystal packing also features by π–π interactions with centroid-centroid distances of 3.4864 (12) and 3.5129 (13) Å

Ruthenium nitrosyl complexes with NO release capability: the use of fluorene as an antenna

International audienceA ruthenium nitrosyl complex of formula [Ru$^{II}$(fluorene(C6)CH$_2$O-terpy)(bipy)(NO)]$^{3+}$ (AC) in which fluorene(C6) is the 9,9-dihexylfluorene, terpy the 2,2’;6’,2’’-terpyridine, and bipy the 2,2’-bipyridine is presented with its related [Ru$^{II}$(MeO-terpy)(bipy)(NO)]$^{3+}$ (C) and 9,9-dihexylfluorene 2-hydroxymethylfluorene (A) building blocks. The reference complex C undergoes NO release capabilities under irradiations at λ = 365 nm. The effect of the introduction of the fluorescent A antenna within the resulting AC complex is discussed both experimentally and theoretically. The importance of the encaging parameter defined as Φ$_{AC}$ x I$_{AC}$, in which I$_{AC}$ is the quantity of light absorbed by AC and Φ$_{AC}$ the quantum yield of NO release is evidenced and found concentration dependent. The conditions of optimization of the antenna approach to maximize Φ$_{AC}$ x I$_{AC}$ are discussed. The crystal structure of [Ru$^{II}$(fluorene(C6)CH$_2$O-terpy)(bipy)(NO$_2$)](PF6) last intermediate in the synthesis of AC is also presented

Mechanism and oxidation state involved in the nitric oxide (NO) photorelease in a terpyridine-bipyridine-based ruthenium nitrosyl complex

International audienc