We investigate the genetic diversity and demographic patterns of the Silene paradoxa group from s... more We investigate the genetic diversity and demographic patterns of the Silene paradoxa group from section Siphonomorpha, which includes the three species S. paradoxa, S. fruticosa and S. aristidis. Eight additional taxa, belonging to the same section, were also included in this study for comparative purposes: S. nutans, S. viridiflora and six species of the italica complex. The nuclear internal transcribed spacer (ITS) and the two chloroplast spacers trnH-psbA and trnS-trnG show that the paradoxa group constitutes a separate genetic lineage within section Siphonomorpha and includes three well-differentiated species, characterized by different levels of genetic diversity and demographic histories. All three species showed specific haplotypes and ITS variants, intraspecific variation and contrasting demographic histories. S. paradoxa probably followed a demographic expansion scenario, whereas S. fruticosa and S. aristidis most likely went through spatial expansions in the past. Chasmophyte species and species from open rocky habitats are found in both the paradoxa group and the italica complex, suggesting that the switch between the chasmophytic and open habitats occurred at least twice in the Siphonomorpha section.
Botanical Journal of the Linnean Society, Mar 1, 2017
The Silene gigantea complex is characterized by a high degree of morphological variability that r... more The Silene gigantea complex is characterized by a high degree of morphological variability that resulted in the description of three subspecies across its distribution range from the Balkan Peninsula to Southwest Asia and Cyprus. In this work, we used nuclear and plastid markers in Bayesian phylogeographic analyses to investigate the taxonomy and the evolutionary history of S. gigantea. The results from plastid DNA partly support the existing taxonomic assessments since S. gigantea subsp. rhodopea is monophyletic, whereas S. gigantea subspp. gigantea and hellenica are clearly polyphyletic. This pattern suggests that a strong morphological convergence is associated with chasmophytic conditions. The results also suggest that the populations from the Epirus region (north-western Greece) did not arise from hybridization as previously claimed, but correspond to a new evolutionary lineage that is consequently described and named S. gigantea subsp. epirota. An identification key to the four subspecies is also given. Our phylogeographic study further highlights a genetic continuity across populations from the central and eastern Greek mainland to Chios and Turkey, all of them sharing the same plastid DNA haplotype and belonging to the same nuclear cluster. In addition, at least two separate colonization events are suggested for Crete. The Bayesian phylogeographic reconstruction clearly points to a post-Messinian diversification across the Aegean area. Considering the low seed dispersal ability of S. gigantea, a continuum of ancestral populations between islands and the mainland is assumed to have occurred during the last glaciations and to have played a key role in colonization processes.
Abstracl. A nove! mcthod using 6-dimcthylaminopurinc (6-0MAP) has rcccntly bccn dcmonstrated to b... more Abstracl. A nove! mcthod using 6-dimcthylaminopurinc (6-0MAP) has rcccntly bccn dcmonstrated to bc a good triploid inductor for bivalvc molluscs. Thc cffccts of 6-0MAP concentration, timing of trcatment aftcr fertilization. and treatment duration on survival and triploid induclion of Crassastrea gigas (Thunberg) embryos wcre examined. A.n influcnce of sperm concentration was also detected and discussed. Survival loO-stage was invcrscly re!ated to 6-0MAP concentration and the percentage of triploids was shown to bc 6-0MAP dose dependenl. Two optimal moments for treatment application were delcrmined. cor rcsponding to extrusions of the firsl and sceond polar bodies. Optimal treatment of 450 pmolll 6-0MAP bcginning 15 min after fertilization over a lOmin period yiclded mcan survival to O-stagc of 64% with a mean of 85% triploid production. As a comparison, a sample trcated with 1 mg/l of cytoehalasin B (CB). 20 min aftcr fertilization over a 15 min pelriod, yieldcd a me an survival to O-stage of only 36% with a mean of 95% triploid production. The advantages of 6-0MAP ovcr CB arc clearly identified: this chemical is noll carcinogcnic, cheapcr than cytochalasin Band much casier to use as it is water soluble.
Molecular Phylogenetics and Evolution, Dec 1, 2010
The history and diversification of the genus Ilex (Aquifoliaceae), based on 108 different species... more The history and diversification of the genus Ilex (Aquifoliaceae), based on 108 different species (116 specimens), are inferred from the analysis of two nuclear (ITS and nepGS) and three plastid (rbcL, trnL-F and atpB-rbcL) sequences. Nuclear and plastid trees are highly incongruent and the nuclear tree is more compatible with current taxonomic classifications than the plastid one. The most recent common ancestor (MRCA) of extant species is dated from the Miocene, although the Ilex stem lineage can be traced back to the late Cretaceous, according to fossil records. This suggests extensive lineage extinctions between the Cretaceous and Miocene and may also explain the difficulties encountered in defining the relationships between Ilex and its closest relatives. The MRCA ancestral area was identified as being in the North Hemisphere (North America and/or East Asia). Several bidirectional North America/East Asia and North America/South America dispersal events are proposed to explain observed geographic and phylogenetic patterns. Hybridization and introgression events between distantly related lineages are also inferred, indicating weak reproductive barriers between species in Ilex.
Genetic variability at five microsatellite loci was analysed in three hatchery-propagated populat... more Genetic variability at five microsatellite loci was analysed in three hatchery-propagated populations of the flat oyster, Ostrea edulis. These populations were part of a selection programme for resistance to the protozoan parasite Bonamia ostreae and were produced by mass spawns, without control of the genealogy. Evidence for population bottlenecks and inbreeding was sought. A reduction in the number of alleles, mainly due to the loss of rare alleles, was observed in all selected populations, relative to the natural population from which they were derived. Heterozygote excesses were observed in two populations, and were attributed to substructuring of the population into a small number of families. Pedigree reconstruction showed that these two populations were produced by at most two spawning events involving a limited number of parents. Most individuals within these populations are half or full-sib, as shown by relatedness coefficients. The occurrence of population bottlenecks was supported by estimates of effective number of breeders derived by three methods : temporal variance in allelic frequencies, heterozygote excess, and a new method based on reduction in the number of alleles. The estimates from the different methods were consistent. The evidence for bottleneck and small effective number of breeders are expected to lead to increasing inbreeding, and have important consequences for the future management of the three O. edulis selected populations.
Tree species belonging to genus Astronium Jacq. (Anacardiaceae R. Br.) can be sometimes difficult... more Tree species belonging to genus Astronium Jacq. (Anacardiaceae R. Br.) can be sometimes difficult to identify on the sole basis of the morphological traits of the leaves. Individuals collected from Paraguay and Argentina were a priori identified in the field as Astronium urundeuva (Allemão) Engl., Astronium balansae Engl. and Astronium fraxinifolium Spreng., although no flowers nor fruits were found at the time of sampling. These were analysed with six microsatellites and two chloroplast markers. Using a bayesian approach on the microsatellite data, each individual was assigned to one of three distinct clusters that subsequently appeared to correspond to the previously described species. Astronium fraxinifolium was identified as the most differentiated species with both microsatellites and chloroplast data, although its leaf morphology is close to the one of Astronium urundeuva. The lower differentiation levels reported among Astronium urundeuva and Astronium balansae, despite their different leaf morphologies, was attributed to a more recent divergence of Résumé CAETANO, S., L. NUSBAUMER & Y. NACIRI (2008). Chloroplaste et marqueurs microsatellites chez Astronium urundeuva (Allemão) Engl. et autres espèces apparentées d'Anacardiaceae: vers une définition du complexe d'espèces? Candollea 63: 115-130. En anglais, résumés anglais et français. Les espèces d'arbres appartenant au genre Astronium Jacq. (Anacardiaceae R. Br.) sont parfois difficiles à identifier sur la seule base des caractères morphologiques des feuilles. Des individus, a priori identifiés lors de la récolte comme étant Astronium urundeuva (Allemão) Engl., Astronium balansae Engl. et Astronium fraxinifolium Spreng., bien que ne présentant ni fleurs ni fruits au moment de l'échantillonnage, ont été collectés au Paraguay et en Argentine. Ils ont été analysés à l'aide de six marqueurs nucléaires microsatellites et de deux intergènes chloroplastiques. Sur la base des résultats obtenus sur les microsatellites, et en utilisant une approche bayésienne qui ne fait aucune utilisation de l'appartenance spécifique supposée, chaque individu a été assigné à l'un des trois groupes désignés par l'analyse. Ces trois groupes se sont avérés être exactement superposables aux trois espèces supposées. Astronium fraxinifolium est l'espèce la plus différenciée des deux autres, à la fois pour les microsatellites et les marqueurs chloroplastiques, bien que la morphologie de ses feuilles soit très
ABSTRACTWith the realization that much of the biological diversity on Earth has been generated by... more ABSTRACTWith the realization that much of the biological diversity on Earth has been generated by discrete evolutionary radiations, there has been a rapid increase in research into the biotic (key innovations) and abiotic (key environments) circumstances in which such radiations took place. Here we focus on the potential importance of population genetic structure and trait genetic architecture in explaining radiations. We propose a verbal model describing the stages of an evolutionary radiation: first invading a suitable adaptive zone and expanding both spatially and ecologically through this zone; secondly, diverging genetically into numerous distinct populations; and, finally, speciating. There are numerous examples of the first stage; the difficulty, however, is explaining how genetic diversification can take place from the establishment of a, presumably, genetically depauperate population in a new adaptive zone. We explore the potential roles of epigenetics and transposable elements (TEs), of neutral process such as genetic drift in combination with trait genetic architecture, of gene flow limitation through isolation by distance (IBD), isolation by ecology and isolation by colonization, the possible role of intra‐specific competition, and that of admixture and hybridization in increasing the genetic diversity of the founding populations. We show that many of the predictions of this model are corroborated. Most radiations occur in complex adaptive zones, which facilitate the establishment of many small populations exposed to genetic drift and divergent selection. We also show that many radiations (especially those resulting from long‐distance dispersal) were established by polyploid lineages, and that many radiating lineages have small genome sizes. However, there are several other predictions which are not (yet) possible to test: that epigenetics has played a role in radiations, that radiations occur more frequently in clades with small gene flow distances, or that the ancestors of radiations had large fundamental niches. At least some of these may be testable in the future as more genome and epigenome data become available. The implication of this model is that many radiations may be hard polytomies because the genetic divergence leading to speciation happens within a very short time, and that the divergence history may be further obscured by hybridization. Furthermore, it suggests that only lineages with the appropriate genetic architecture will be able to radiate, and that such a radiation will happen in a meta‐population environment. Understanding the genetic architecture of a lineage may be an essential part of accounting for why some lineages radiate, and some do not.
We investigated the role of the number of loci coding for a neutral trait on the release of addit... more We investigated the role of the number of loci coding for a neutral trait on the release of additive variance for this trait after population bottlenecks. Different bottleneck sizes and durations were tested for various matrices of genotypic values, with initial conditions covering the allele frequency space. We used three different types of matrices. First, we extended Cheverud and Routman's model by defining matrices of ''pure'' epistasis for three and four independent loci; second, we used genotypic values drawn randomly from uniform, normal, and exponential distributions; and third we used two models of simple metabolic pathways leading to physiological epistasis. For all these matrices of genotypic values except the dominant metabolic pathway, we find that, as the number of loci increases from two to three and four, an increase in the release of additive variance is occurring. The amount of additive variance released for a given set of genotypic values is a function of the inbreeding coefficient, independently of the size and duration of the bottleneck. The level of inbreeding necessary to achieve maximum release in additive variance increases with the number of loci. We find that additive-by-additive epistasis is the type of epistasis most easily converted into additive variance. For a wide range of models, our results show that epistasis, rather than dominance, plays a significant role in the increase of additive variance following bottlenecks.
ABSTRACT Eight polymorphic microsatellites were developed in the perennial herbaceous Aster amell... more ABSTRACT Eight polymorphic microsatellites were developed in the perennial herbaceous Aster amellus L. (Asteraceae) and characterized on three populations from France and Switzerland. The number of alleles ranged between four and 30 depending on the locus, and the mean number of effective alleles was 5.8. The average gene diversity equalled 0.744 (range: 0.419–0.957) and the overall differentiation was found significant (θ = 0.092, P < 0.01). Three loci displayed significant heterozygote deficiencies, which might indicate the presence of null alleles. Amplifications were detected on eight loci in Aster alpinus L.
Primers for four loci that amplify cpDNA regions have been designed for population genetic analys... more Primers for four loci that amplify cpDNA regions have been designed for population genetic analyses in Dicranum scoparium Hedw. and compared with trnL(UAA)5¢exon-trnF. All loci showed intraspecific variation with a number of haplotypes ranging between two and six. trnH-psbA Dic showed an intercontinental disjunction, but no variability within the four Swiss populations surveyed, whereas the three remaining loci displayed intrapopulation variability in at least one population (rps19-rpl2, rpoB, trnT-rps4). These primers were additionally tested on 22 bryophytes and three fern species. The primers amplified mostly in mosses and liverworts, but less well in ferns, pointing to their evolutionary distance from the bryophytes.
Sperm form and size is tremendously variable within and across species. However, a general explan... more Sperm form and size is tremendously variable within and across species. However, a general explanation for this variation is lacking. It has been suggested that sperm size may influence sperm competition, and there is evidence for this in some taxa but not others. In addition to normal fertilizing sperm, a number of molluscs and insects produce nonfertile sperm that are also extremely morphologically variable, and distinct from fertilizing forms. There is evidence that nonfertile sperm play an indirect role in sperm competition by decreasing female remating propensity in Lepidopterans, but in most taxa the function of parasperm is unknown. We investigated the role of nonfertile (oligopyrene) sperm during sperm competition in the fresh water snail Viviparus ater. Previous studies found that the proportion of oligopyrene sperm increased with the risk of sperm competition, and hence it seems likely that these sperm influence fertilization success during competitive matings. In mating experiments in which females were sequentially housed with males, we examined a range of male characteristics which potentially influence fertilization success. We found that the size of oligopyrene sperm was the best predictor of fertilization success, with males having the longer sperm siring the highest proportion of offspring. Furthermore, we found a positive shell size and sperm concentration effect on paternity, and females with multiply sired families produced more offspring than females mating with only one male. This result suggests polyandry is beneficial for female snails.
La discussion generale organisee a la fin de la deuxieme journee a fait ressortir les points suiv... more La discussion generale organisee a la fin de la deuxieme journee a fait ressortir les points suivants: 1- Les participants se sont declares satisfaits de la tenue de la reunion, tant dans son deroulement, que dans les echanges d'informations auxquels elle a donne lieu. La quantite et la qualite des resultats presentes a permis de mettre en evidence la puissance d'analyse que represente le travail en reseau. 2-L'importance de la valorisation des resultats a ete soulignee a plusieurs reprises. La diffusion de l'information devrait se faire dans un premier temps par la voie de rapport internes a la DRV, puis par la voie d'articles publies dans des revues scientifiques. Sur le programme C. gigas triploides , une premiere diffusion des resultats obtenus en Normandie est d'ores et deja envisagee (communication au congres CIEM de Dublin, Octobre 1993). 3-La question de la formalisation du Reseau a ete posee. Les participants ont convenu d'un commun accord de con...
Cette etude a ete menee dans le but de reintroduire, par la selection, la culture du millet setar... more Cette etude a ete menee dans le but de reintroduire, par la selection, la culture du millet setaria italica en alsace. L'objectif principal etait de preciser les bases genetiques de la variation et de creer une variabilite nouvelle. L'etude de 15 lignees d'origines differentes en 2 lieux et 2 densites puis pour 4 dates de semis montre une grande sensibilite du millet au conditions experimentales et souligne l'importance des interactions ge. L'analyse des correlations genetiques met en evidence des liaisons potentiellement valorisables dans le cadre d'un schema de selection multivariable. L'analyse des correlations environnementales permet une approche plus physiologique de l'integration des caracteres. L'etude des generations f2 et f3 d'un demi-diallele 66 sans diagonale souligne, pour tous les caracteres, l'importance de l'epistasie et la reduction des heterosis residuels au niveau f2 et f3. L'heterosis est souvent fonction de la ...
The Ciminalis section of Gentiana comprises seven species, two of them growing on siliceous subst... more The Ciminalis section of Gentiana comprises seven species, two of them growing on siliceous substrates (G. alpina, and G. acaulis), the other ones being calcareous taxa (G. clusii, G. angustifolia, G. ligustica, G. occidentalis and G. dinarica). A total of 515 individuals from 183 populations over the entire Ciminalis distribution range was analysed using four chloroplast loci (trnH-psbA, matK, rpoB and rpoC1) and the nuclear ribosomal marker ITS2. The siliceous species display only two chloroplast haplotypes each and are both characterized by patterns of range expansions all over the Alps. Conversely, the calcareous species are on average more diverse (two to 13 haplotypes per species) with strong patterns of local structuring. We suggest that the occurrence of many calcareous refugia at the periphery of the Alps must have led to local adaptation and morphological diversification, and helped preserving intraspecific diversities during the last glaciations for the associated taxa. ITS2 was more efficient in delineating species boundaries than the chloroplast markers for which several haplotypes are shared among species. This might be either due to chloroplast capture among species and/or to recent divergence. Species adapted to the same substrate are generally only distantly related when they co-occur in the same place. For both types of markers, G. clusii is found genetically distant from all other species.
SummaryRhizobia, soil bacteria of the Rhizobiales, enter the roots of homologous legumes, where t... more SummaryRhizobia, soil bacteria of the Rhizobiales, enter the roots of homologous legumes, where they induce the formation of nitrogen‐fixing nodules. Signals emanating from both symbiotic partners control nodule development. Efficient nodulation requires precise, temporal regulation of symbiotic genes. Roots continuously release flavonoids that interact with transcriptional activators of the LysR family. NodD proteins, which are members of this family, act both as sensors of the environment and modulate the expression of genes preceded by conserved promoter sequences called nod‐boxes. The symbiotic plasmid of the broad host‐range Rhizobium sp. NGR234 caries 19 nod‐boxes (NB1 to NB19), all of which were cloned upstream of a lacZ‐reporter gene. A flavonoid, daidzein was able to induce 18 of the 19 nod‐boxes in a NodD1‐dependent manner. Interestingly, induction of four nod‐boxes (NB6, NB15, NB16 and NB17) is highly dependent on NodD2 and was delayed in comparison with the others. ...
During the course of a revision of the Malagasy species of the family Sapotaceae, two new species... more During the course of a revision of the Malagasy species of the family Sapotaceae, two new species from the dry forest belonging to the highly-diverse endemic genus Capurodendron Aubrév. were discovered. The first one, C. mikearum L. Gaut. & Boluda, earlier hypothesised to be a hybrid, emerged as a valid species without any hybrid signal, based on a combination of genetic and morphological analyses of a species complex from the southwestern region. The second species, C. namorokense L. Gaut. & Boluda, occupies a basal position in the same species clade. It is clearly morphologically distinct and geographically distant, so far only being known from northwestern Madagascar. Both species are described and illustrated by line drawings and field photographs. Preliminary conservation assessments using the IUCN Red List criteria indicate that both species are threatened (EN and CR, respectively). Résumé GAUTIER, L., C. G. BOLUDA, R. RANDRIANAIVO & Y. NACIRI (2022). Deux nouvelles espèces supplémentaires dans le genre endémique malgache hautement diversifié Capurodendron (Sapotaceae). Candollea 77: 119-126. En anglais, résumés anglais et français.
We investigate the genetic diversity and demographic patterns of the Silene paradoxa group from s... more We investigate the genetic diversity and demographic patterns of the Silene paradoxa group from section Siphonomorpha, which includes the three species S. paradoxa, S. fruticosa and S. aristidis. Eight additional taxa, belonging to the same section, were also included in this study for comparative purposes: S. nutans, S. viridiflora and six species of the italica complex. The nuclear internal transcribed spacer (ITS) and the two chloroplast spacers trnH-psbA and trnS-trnG show that the paradoxa group constitutes a separate genetic lineage within section Siphonomorpha and includes three well-differentiated species, characterized by different levels of genetic diversity and demographic histories. All three species showed specific haplotypes and ITS variants, intraspecific variation and contrasting demographic histories. S. paradoxa probably followed a demographic expansion scenario, whereas S. fruticosa and S. aristidis most likely went through spatial expansions in the past. Chasmophyte species and species from open rocky habitats are found in both the paradoxa group and the italica complex, suggesting that the switch between the chasmophytic and open habitats occurred at least twice in the Siphonomorpha section.
Botanical Journal of the Linnean Society, Mar 1, 2017
The Silene gigantea complex is characterized by a high degree of morphological variability that r... more The Silene gigantea complex is characterized by a high degree of morphological variability that resulted in the description of three subspecies across its distribution range from the Balkan Peninsula to Southwest Asia and Cyprus. In this work, we used nuclear and plastid markers in Bayesian phylogeographic analyses to investigate the taxonomy and the evolutionary history of S. gigantea. The results from plastid DNA partly support the existing taxonomic assessments since S. gigantea subsp. rhodopea is monophyletic, whereas S. gigantea subspp. gigantea and hellenica are clearly polyphyletic. This pattern suggests that a strong morphological convergence is associated with chasmophytic conditions. The results also suggest that the populations from the Epirus region (north-western Greece) did not arise from hybridization as previously claimed, but correspond to a new evolutionary lineage that is consequently described and named S. gigantea subsp. epirota. An identification key to the four subspecies is also given. Our phylogeographic study further highlights a genetic continuity across populations from the central and eastern Greek mainland to Chios and Turkey, all of them sharing the same plastid DNA haplotype and belonging to the same nuclear cluster. In addition, at least two separate colonization events are suggested for Crete. The Bayesian phylogeographic reconstruction clearly points to a post-Messinian diversification across the Aegean area. Considering the low seed dispersal ability of S. gigantea, a continuum of ancestral populations between islands and the mainland is assumed to have occurred during the last glaciations and to have played a key role in colonization processes.
Abstracl. A nove! mcthod using 6-dimcthylaminopurinc (6-0MAP) has rcccntly bccn dcmonstrated to b... more Abstracl. A nove! mcthod using 6-dimcthylaminopurinc (6-0MAP) has rcccntly bccn dcmonstrated to bc a good triploid inductor for bivalvc molluscs. Thc cffccts of 6-0MAP concentration, timing of trcatment aftcr fertilization. and treatment duration on survival and triploid induclion of Crassastrea gigas (Thunberg) embryos wcre examined. A.n influcnce of sperm concentration was also detected and discussed. Survival loO-stage was invcrscly re!ated to 6-0MAP concentration and the percentage of triploids was shown to bc 6-0MAP dose dependenl. Two optimal moments for treatment application were delcrmined. cor rcsponding to extrusions of the firsl and sceond polar bodies. Optimal treatment of 450 pmolll 6-0MAP bcginning 15 min after fertilization over a lOmin period yiclded mcan survival to O-stagc of 64% with a mean of 85% triploid production. As a comparison, a sample trcated with 1 mg/l of cytoehalasin B (CB). 20 min aftcr fertilization over a 15 min pelriod, yieldcd a me an survival to O-stage of only 36% with a mean of 95% triploid production. The advantages of 6-0MAP ovcr CB arc clearly identified: this chemical is noll carcinogcnic, cheapcr than cytochalasin Band much casier to use as it is water soluble.
Molecular Phylogenetics and Evolution, Dec 1, 2010
The history and diversification of the genus Ilex (Aquifoliaceae), based on 108 different species... more The history and diversification of the genus Ilex (Aquifoliaceae), based on 108 different species (116 specimens), are inferred from the analysis of two nuclear (ITS and nepGS) and three plastid (rbcL, trnL-F and atpB-rbcL) sequences. Nuclear and plastid trees are highly incongruent and the nuclear tree is more compatible with current taxonomic classifications than the plastid one. The most recent common ancestor (MRCA) of extant species is dated from the Miocene, although the Ilex stem lineage can be traced back to the late Cretaceous, according to fossil records. This suggests extensive lineage extinctions between the Cretaceous and Miocene and may also explain the difficulties encountered in defining the relationships between Ilex and its closest relatives. The MRCA ancestral area was identified as being in the North Hemisphere (North America and/or East Asia). Several bidirectional North America/East Asia and North America/South America dispersal events are proposed to explain observed geographic and phylogenetic patterns. Hybridization and introgression events between distantly related lineages are also inferred, indicating weak reproductive barriers between species in Ilex.
Genetic variability at five microsatellite loci was analysed in three hatchery-propagated populat... more Genetic variability at five microsatellite loci was analysed in three hatchery-propagated populations of the flat oyster, Ostrea edulis. These populations were part of a selection programme for resistance to the protozoan parasite Bonamia ostreae and were produced by mass spawns, without control of the genealogy. Evidence for population bottlenecks and inbreeding was sought. A reduction in the number of alleles, mainly due to the loss of rare alleles, was observed in all selected populations, relative to the natural population from which they were derived. Heterozygote excesses were observed in two populations, and were attributed to substructuring of the population into a small number of families. Pedigree reconstruction showed that these two populations were produced by at most two spawning events involving a limited number of parents. Most individuals within these populations are half or full-sib, as shown by relatedness coefficients. The occurrence of population bottlenecks was supported by estimates of effective number of breeders derived by three methods : temporal variance in allelic frequencies, heterozygote excess, and a new method based on reduction in the number of alleles. The estimates from the different methods were consistent. The evidence for bottleneck and small effective number of breeders are expected to lead to increasing inbreeding, and have important consequences for the future management of the three O. edulis selected populations.
Tree species belonging to genus Astronium Jacq. (Anacardiaceae R. Br.) can be sometimes difficult... more Tree species belonging to genus Astronium Jacq. (Anacardiaceae R. Br.) can be sometimes difficult to identify on the sole basis of the morphological traits of the leaves. Individuals collected from Paraguay and Argentina were a priori identified in the field as Astronium urundeuva (Allemão) Engl., Astronium balansae Engl. and Astronium fraxinifolium Spreng., although no flowers nor fruits were found at the time of sampling. These were analysed with six microsatellites and two chloroplast markers. Using a bayesian approach on the microsatellite data, each individual was assigned to one of three distinct clusters that subsequently appeared to correspond to the previously described species. Astronium fraxinifolium was identified as the most differentiated species with both microsatellites and chloroplast data, although its leaf morphology is close to the one of Astronium urundeuva. The lower differentiation levels reported among Astronium urundeuva and Astronium balansae, despite their different leaf morphologies, was attributed to a more recent divergence of Résumé CAETANO, S., L. NUSBAUMER & Y. NACIRI (2008). Chloroplaste et marqueurs microsatellites chez Astronium urundeuva (Allemão) Engl. et autres espèces apparentées d'Anacardiaceae: vers une définition du complexe d'espèces? Candollea 63: 115-130. En anglais, résumés anglais et français. Les espèces d'arbres appartenant au genre Astronium Jacq. (Anacardiaceae R. Br.) sont parfois difficiles à identifier sur la seule base des caractères morphologiques des feuilles. Des individus, a priori identifiés lors de la récolte comme étant Astronium urundeuva (Allemão) Engl., Astronium balansae Engl. et Astronium fraxinifolium Spreng., bien que ne présentant ni fleurs ni fruits au moment de l'échantillonnage, ont été collectés au Paraguay et en Argentine. Ils ont été analysés à l'aide de six marqueurs nucléaires microsatellites et de deux intergènes chloroplastiques. Sur la base des résultats obtenus sur les microsatellites, et en utilisant une approche bayésienne qui ne fait aucune utilisation de l'appartenance spécifique supposée, chaque individu a été assigné à l'un des trois groupes désignés par l'analyse. Ces trois groupes se sont avérés être exactement superposables aux trois espèces supposées. Astronium fraxinifolium est l'espèce la plus différenciée des deux autres, à la fois pour les microsatellites et les marqueurs chloroplastiques, bien que la morphologie de ses feuilles soit très
ABSTRACTWith the realization that much of the biological diversity on Earth has been generated by... more ABSTRACTWith the realization that much of the biological diversity on Earth has been generated by discrete evolutionary radiations, there has been a rapid increase in research into the biotic (key innovations) and abiotic (key environments) circumstances in which such radiations took place. Here we focus on the potential importance of population genetic structure and trait genetic architecture in explaining radiations. We propose a verbal model describing the stages of an evolutionary radiation: first invading a suitable adaptive zone and expanding both spatially and ecologically through this zone; secondly, diverging genetically into numerous distinct populations; and, finally, speciating. There are numerous examples of the first stage; the difficulty, however, is explaining how genetic diversification can take place from the establishment of a, presumably, genetically depauperate population in a new adaptive zone. We explore the potential roles of epigenetics and transposable elements (TEs), of neutral process such as genetic drift in combination with trait genetic architecture, of gene flow limitation through isolation by distance (IBD), isolation by ecology and isolation by colonization, the possible role of intra‐specific competition, and that of admixture and hybridization in increasing the genetic diversity of the founding populations. We show that many of the predictions of this model are corroborated. Most radiations occur in complex adaptive zones, which facilitate the establishment of many small populations exposed to genetic drift and divergent selection. We also show that many radiations (especially those resulting from long‐distance dispersal) were established by polyploid lineages, and that many radiating lineages have small genome sizes. However, there are several other predictions which are not (yet) possible to test: that epigenetics has played a role in radiations, that radiations occur more frequently in clades with small gene flow distances, or that the ancestors of radiations had large fundamental niches. At least some of these may be testable in the future as more genome and epigenome data become available. The implication of this model is that many radiations may be hard polytomies because the genetic divergence leading to speciation happens within a very short time, and that the divergence history may be further obscured by hybridization. Furthermore, it suggests that only lineages with the appropriate genetic architecture will be able to radiate, and that such a radiation will happen in a meta‐population environment. Understanding the genetic architecture of a lineage may be an essential part of accounting for why some lineages radiate, and some do not.
We investigated the role of the number of loci coding for a neutral trait on the release of addit... more We investigated the role of the number of loci coding for a neutral trait on the release of additive variance for this trait after population bottlenecks. Different bottleneck sizes and durations were tested for various matrices of genotypic values, with initial conditions covering the allele frequency space. We used three different types of matrices. First, we extended Cheverud and Routman's model by defining matrices of ''pure'' epistasis for three and four independent loci; second, we used genotypic values drawn randomly from uniform, normal, and exponential distributions; and third we used two models of simple metabolic pathways leading to physiological epistasis. For all these matrices of genotypic values except the dominant metabolic pathway, we find that, as the number of loci increases from two to three and four, an increase in the release of additive variance is occurring. The amount of additive variance released for a given set of genotypic values is a function of the inbreeding coefficient, independently of the size and duration of the bottleneck. The level of inbreeding necessary to achieve maximum release in additive variance increases with the number of loci. We find that additive-by-additive epistasis is the type of epistasis most easily converted into additive variance. For a wide range of models, our results show that epistasis, rather than dominance, plays a significant role in the increase of additive variance following bottlenecks.
ABSTRACT Eight polymorphic microsatellites were developed in the perennial herbaceous Aster amell... more ABSTRACT Eight polymorphic microsatellites were developed in the perennial herbaceous Aster amellus L. (Asteraceae) and characterized on three populations from France and Switzerland. The number of alleles ranged between four and 30 depending on the locus, and the mean number of effective alleles was 5.8. The average gene diversity equalled 0.744 (range: 0.419–0.957) and the overall differentiation was found significant (θ = 0.092, P < 0.01). Three loci displayed significant heterozygote deficiencies, which might indicate the presence of null alleles. Amplifications were detected on eight loci in Aster alpinus L.
Primers for four loci that amplify cpDNA regions have been designed for population genetic analys... more Primers for four loci that amplify cpDNA regions have been designed for population genetic analyses in Dicranum scoparium Hedw. and compared with trnL(UAA)5¢exon-trnF. All loci showed intraspecific variation with a number of haplotypes ranging between two and six. trnH-psbA Dic showed an intercontinental disjunction, but no variability within the four Swiss populations surveyed, whereas the three remaining loci displayed intrapopulation variability in at least one population (rps19-rpl2, rpoB, trnT-rps4). These primers were additionally tested on 22 bryophytes and three fern species. The primers amplified mostly in mosses and liverworts, but less well in ferns, pointing to their evolutionary distance from the bryophytes.
Sperm form and size is tremendously variable within and across species. However, a general explan... more Sperm form and size is tremendously variable within and across species. However, a general explanation for this variation is lacking. It has been suggested that sperm size may influence sperm competition, and there is evidence for this in some taxa but not others. In addition to normal fertilizing sperm, a number of molluscs and insects produce nonfertile sperm that are also extremely morphologically variable, and distinct from fertilizing forms. There is evidence that nonfertile sperm play an indirect role in sperm competition by decreasing female remating propensity in Lepidopterans, but in most taxa the function of parasperm is unknown. We investigated the role of nonfertile (oligopyrene) sperm during sperm competition in the fresh water snail Viviparus ater. Previous studies found that the proportion of oligopyrene sperm increased with the risk of sperm competition, and hence it seems likely that these sperm influence fertilization success during competitive matings. In mating experiments in which females were sequentially housed with males, we examined a range of male characteristics which potentially influence fertilization success. We found that the size of oligopyrene sperm was the best predictor of fertilization success, with males having the longer sperm siring the highest proportion of offspring. Furthermore, we found a positive shell size and sperm concentration effect on paternity, and females with multiply sired families produced more offspring than females mating with only one male. This result suggests polyandry is beneficial for female snails.
La discussion generale organisee a la fin de la deuxieme journee a fait ressortir les points suiv... more La discussion generale organisee a la fin de la deuxieme journee a fait ressortir les points suivants: 1- Les participants se sont declares satisfaits de la tenue de la reunion, tant dans son deroulement, que dans les echanges d'informations auxquels elle a donne lieu. La quantite et la qualite des resultats presentes a permis de mettre en evidence la puissance d'analyse que represente le travail en reseau. 2-L'importance de la valorisation des resultats a ete soulignee a plusieurs reprises. La diffusion de l'information devrait se faire dans un premier temps par la voie de rapport internes a la DRV, puis par la voie d'articles publies dans des revues scientifiques. Sur le programme C. gigas triploides , une premiere diffusion des resultats obtenus en Normandie est d'ores et deja envisagee (communication au congres CIEM de Dublin, Octobre 1993). 3-La question de la formalisation du Reseau a ete posee. Les participants ont convenu d'un commun accord de con...
Cette etude a ete menee dans le but de reintroduire, par la selection, la culture du millet setar... more Cette etude a ete menee dans le but de reintroduire, par la selection, la culture du millet setaria italica en alsace. L'objectif principal etait de preciser les bases genetiques de la variation et de creer une variabilite nouvelle. L'etude de 15 lignees d'origines differentes en 2 lieux et 2 densites puis pour 4 dates de semis montre une grande sensibilite du millet au conditions experimentales et souligne l'importance des interactions ge. L'analyse des correlations genetiques met en evidence des liaisons potentiellement valorisables dans le cadre d'un schema de selection multivariable. L'analyse des correlations environnementales permet une approche plus physiologique de l'integration des caracteres. L'etude des generations f2 et f3 d'un demi-diallele 66 sans diagonale souligne, pour tous les caracteres, l'importance de l'epistasie et la reduction des heterosis residuels au niveau f2 et f3. L'heterosis est souvent fonction de la ...
The Ciminalis section of Gentiana comprises seven species, two of them growing on siliceous subst... more The Ciminalis section of Gentiana comprises seven species, two of them growing on siliceous substrates (G. alpina, and G. acaulis), the other ones being calcareous taxa (G. clusii, G. angustifolia, G. ligustica, G. occidentalis and G. dinarica). A total of 515 individuals from 183 populations over the entire Ciminalis distribution range was analysed using four chloroplast loci (trnH-psbA, matK, rpoB and rpoC1) and the nuclear ribosomal marker ITS2. The siliceous species display only two chloroplast haplotypes each and are both characterized by patterns of range expansions all over the Alps. Conversely, the calcareous species are on average more diverse (two to 13 haplotypes per species) with strong patterns of local structuring. We suggest that the occurrence of many calcareous refugia at the periphery of the Alps must have led to local adaptation and morphological diversification, and helped preserving intraspecific diversities during the last glaciations for the associated taxa. ITS2 was more efficient in delineating species boundaries than the chloroplast markers for which several haplotypes are shared among species. This might be either due to chloroplast capture among species and/or to recent divergence. Species adapted to the same substrate are generally only distantly related when they co-occur in the same place. For both types of markers, G. clusii is found genetically distant from all other species.
SummaryRhizobia, soil bacteria of the Rhizobiales, enter the roots of homologous legumes, where t... more SummaryRhizobia, soil bacteria of the Rhizobiales, enter the roots of homologous legumes, where they induce the formation of nitrogen‐fixing nodules. Signals emanating from both symbiotic partners control nodule development. Efficient nodulation requires precise, temporal regulation of symbiotic genes. Roots continuously release flavonoids that interact with transcriptional activators of the LysR family. NodD proteins, which are members of this family, act both as sensors of the environment and modulate the expression of genes preceded by conserved promoter sequences called nod‐boxes. The symbiotic plasmid of the broad host‐range Rhizobium sp. NGR234 caries 19 nod‐boxes (NB1 to NB19), all of which were cloned upstream of a lacZ‐reporter gene. A flavonoid, daidzein was able to induce 18 of the 19 nod‐boxes in a NodD1‐dependent manner. Interestingly, induction of four nod‐boxes (NB6, NB15, NB16 and NB17) is highly dependent on NodD2 and was delayed in comparison with the others. ...
During the course of a revision of the Malagasy species of the family Sapotaceae, two new species... more During the course of a revision of the Malagasy species of the family Sapotaceae, two new species from the dry forest belonging to the highly-diverse endemic genus Capurodendron Aubrév. were discovered. The first one, C. mikearum L. Gaut. & Boluda, earlier hypothesised to be a hybrid, emerged as a valid species without any hybrid signal, based on a combination of genetic and morphological analyses of a species complex from the southwestern region. The second species, C. namorokense L. Gaut. & Boluda, occupies a basal position in the same species clade. It is clearly morphologically distinct and geographically distant, so far only being known from northwestern Madagascar. Both species are described and illustrated by line drawings and field photographs. Preliminary conservation assessments using the IUCN Red List criteria indicate that both species are threatened (EN and CR, respectively). Résumé GAUTIER, L., C. G. BOLUDA, R. RANDRIANAIVO & Y. NACIRI (2022). Deux nouvelles espèces supplémentaires dans le genre endémique malgache hautement diversifié Capurodendron (Sapotaceae). Candollea 77: 119-126. En anglais, résumés anglais et français.
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