Perrine Gauthier

Genetic variation and gene flow in Alpine diploid and tetraploid populations of Lotus (L. alpinus (D.C.) Schleicher/L. corniculatus L.). I. Insights from morphological and allozyme markers

The altitudinal distribution, morphology, phenology and allozyme polymorphism at 12 loci were studied in diploid and tetraploid populations of Lotus growing at over 1800 m in the French Alps to clarify relationships between these cytotypes. In general, diploids occurred at higher elevation than tetraploids, although some sites at intermediate elevation contained both cytotypes, diploids predominating in the upper part and tetraploids in the lower part of the contact area. Evidence for an autopolyploid origin of the tetraploids was provided by tetrasomic inheritance at two enzyme loci, although no tetravalents were observed at meiosis. Diploid and tetraploid plants shared morphological traits distinct from those of other Lotus species and showed differences in size, which may be attributable to chromosome doubling. The diploid cytotype, L. alpinus, may thus be the ancestor of the Alpine tetraploids. Both cytotypes showed nearly identical suites of alleles at all loci and very similar genetic parameters, except for heterozygosity, which was higher in the tetraploid plants. However, the occurrence of few alleles specific to each ploidy level indicated limited gene flow between cytotypes, probably as a result of spatial segregation and variation in flowering time. Of the individuals in a tetraploid population, 25% showed morphological traits similar to those observed in L. corniculatus, suggesting genetic introgression between the two tetraploid species.

ONGOING ADAPTATION TO MEDITERRANEAN CLIMATE EXTREMES IN A CHEMICALLY POLYMORPHIC PLANT

Although extreme climatic events may have profound effects on ecological systems, there is a marked lack of information on adaptation to such events. In this study, we employed reciprocal transplantation on both a geographic scale (experimental sites 200 km apart in different parts of the range of the study species) and a local landscape scale (reciprocal populations separated by 2-8 km) to study the performance of different chemical forms of Thymus vulgaris which naturally occur in different climatic environments. Survival and growth were analyzed in relation to long-term and contemporary climate data in natural populations and our experimental sites. The reciprocal transplants involved a period of six years for clones transplanted in experimental field sites on a geographic scale and three years for seedlings transplanted among natural populations at the local landscape level. Cloned transplants on a geographic scale produced evidence for local adaptation to either summer drought, primarily following the extreme summer drought of 2003, or severe early-winter freezing. Chemotypes that show high survival after intense summer drought showed poor survival after intense early- winter freezing and vice versa, results which directly accord with climate data for their original sites. On the local landscape scale, we found further evidence for local adaptation to summer drought but not to winter freezing (probably due to the absence of extreme freezing during the three years of this study). Future modifications to the occurrence and frequency of extreme climate events may have a profound influence on the spatial distribution of thyme chemotypes.

Chloroplast-DNA variation in the genus Lotus (Fabaceae) and further evidence regarding the maternal parentage of Lotus corniculatus L.

Abstract To resolve the maternal parentage of the tetraploid Lotus corniculatus, restriction-site variation of chloroplast DNA (cpDNA) was studied in several accessions of that species, in the four putative parental diploid species, L. tenuis, L. alpinus, L. japonicus and L. uliginosus, and in four phylogenetically more distant diploid species, L. hispidus, L. edulis, L. ornithopodoides and Tetragonolobus maritimus var. siliquosus. Evidence of cpDNA maternal inheritance was obtained by using reciprocal controlled crosses between plants of L. corniculatus and natural tetraploid individuals of L. alpinus showing very distinct restriction patterns. Interspecific cpDNA variation in the eight Lotus species and T. siliquosus was analysed by comparing cpDNA fragment patterns produced by five restriction endonucleases and totalling 304 distinct fragments. Genetic differentiation in cpDNA was very high between the L. corniculatus group and L. hispidus on the one hand, and the three other species on the other hand. Sixteen restriction-site mutations and eight length polymorphisms were identified among the five species of the L. corniculatus group and L. hispidus, Lotus uliginosus, L. alpinus and L. japonicus showed at least six DNA changes with regard to the molecule of L. corniculatus. Accordingly, these species should be excluded as maternal progenitors of L. corniculatus. Conversely, the cpDNA of L. tenuis differed from that of L. corniculatus by only two small-length mutations. As also suggested previously from an analysis of several nuclear markers, the results reported here show decisively that L. tenuis may be considered as the most probable maternal ancestor of L. corniculatus.

Variable Phytotoxic Effects of Thymus vulgaris (Lamiaceae) Terpenes on Associated Species

Thymus vulgaris has a chemical polymorphism in which individual plants have an essential oil dominated by either nonphenolic (geraniol, -terpineol, cis-sabinene hydrate, linalool, or 1,8-cineole) or phenolic (carvacrol and thymol) monoterpenes. Using the geraniol, cis-sabinene hydrate, and the two phenolic chemotypes, we tested three hypotheses: (1) chemotypes vary in their influences on germination and growth of associated plant species, (2) associated species respond differentially to individual chemotypes, and (3) soils under thyme canopies will influence associated species differently than do sterile soils. The study was done in Montpellier, France, in settings mimicking natural conditions. In one experiment, survival of both monocots and dicots from the seed bank was lower in soils collected from under thyme plants of the phenolic chemotypes. In a second experiment, we sowed seeds of Daucus carota, Nigella damascena, and Bromus madritensis into soil collected from under thyme plants and covered with canopies of fresh thyme of each chemotype or into control soils. The species showed differential responses in germination and/or growth to the four chemotypes. In a third experiment, germination and growth of D. carota, N. damascena, Bromus erectus, and Picris hieracoides on sterile soil covered with fresh thyme foliage and controls showed differential responses to the four chemotypes; however, these responses were less marked than those on soils collected under thyme plants. These results—coupled with previous demonstrations of chemotype-influenced differential herbivory and parasitism—illustrate the complex influences of genetic variability on multispecies interactions and the individuality of species responses to toxic chemicals.

Genetic variation and gene flow in Alpine diploid and tetraploid populations of Lotus (L. alpinus (D.C.) Schleicher/L. corniculatus L.). II. Insights from RFLP of chloroplast DNA

RFLP of chloroplast DNA was studied in two diploid (2x) and five tetraploid (4x) populations of Lotus alpinus (D.C.) Schleicher in the French Alps. This was compared with four non-Alpine populations and two cultivars of Lotus corniculatus L. (4x) introduced to the Alpine valleys. Based on the 13 site and 11 length mutations detected, seven distinct haplotypes could be identified, which clustered in two groups, corresponding to the two Lotus species. With only one exception, the diploid and the tetraploid L. alpinus plants had the same haplotype. This is to be expected, because morphological variation and tetrasomic inheritance suggest that the tetraploids were derived from the diploids by autopolyploidy. In L. corniculatus, two very similar haplotypes were found in the natural very distant populations. In contrast, the chloroplast DNA (cpDNA) haplotypes of the two cultivars differed considerably from each other and were more related to those observed in L. alpinus, suggesting that these cultivars may be derived maternally from L. alpinus individuals. In one tetraploid L. alpinus population, a single cpDNA haplotype was identified. As this haplotype was related to those observed in the L. corniculatus group, local genetic introgression may have occurred between 4x L. alpinus plants and cultivated L. corniculatus.

Genetic introgression between tetraploidDactylis glomerata subspp.reichenbachii andglomerata in the French Alps. Insight from morphological and allozyme variation

The morphology, phenology and allozyme polymorphism in seven tetraploidDactylis glomerata populations growing in the French Alps were studied. Based on habitat and morphological characteristics, two of the populations could be classified asD. glomerata subsp.reichenbachii, which is known to comprise diploid and tetraploid plants growing exclusively on dolomite, on south-facing meadows. This subspecies has been previously recorded in the Italian and Swiss Alps but not in the French Alps. The remaining five populations were morphologically intermediate but more similar to the cosmopolitanD. glomerata subsp.glomerata. On the basis of allozyme variation, all populations were more related to subsp.reichenbachii than to the cosmopolitan subsp.glomerata, suggesting that gene flow has occurred between the two tetraploid subspecies. The possibility that selection has acted differently on morphological and allozyme characters is discussed.

Range-Wide Variation in the Ecological Niche and Floral Polymorphism of the Western Mediterranean Geophyte Narcissus dubius Gouan

Premise of research. Comparative studies of variation in the ecology and genetics of natural plant populations located at the limits and in the center of a species range provide fundamental insights into the historical formation of species distribution patterns. Methodology. In this study, we quantify variation in the ecological niche and the expression of a floral polymorphism across the range of the Mediterranean geophyte Narcissus dubius Gouan. An exhaustive data set of known locations was compiled to distinguish groups of geographically central and peripheral populations in both Spain and France. These occur across a double climatic gradient. First, there is a gradient from a hot and dry Mediterranean climatic regime in eastern Spain to a milder Mediterranean climatic regime in southern France (lower maximum temperature and shorter summer drought). Second, there is a shift to a more continental climate in peripheral populations in inland Spain. We also modeled the current climatic niche and produced historical projections of potential glacial refugia for this species. Pivotal results. Peripheral populations showed consistent patterns of ecological niche differences with a less rupicolous ecology, more bare soil, and a higher cover of annual species. The ecological niche was more variable among peripheral populations than among central populations. Peripheral populations showed a repeated pattern of loss of stigma-height polymorphism and floral traits indicative of a reproductive strategy based on within-morph mating (probably selfing to assure seed set). Climate models indicate that contemporary peripheral populations (particularly in Spain) occur in areas that were least likely to have served as glacial refugia. Conclusions. Historical isolation and recolonization may have shaped contemporary patterns of ecological niche and reproductive trait variation among central and peripheral populations.

Ecological niche differentiation in peripheral populations: a comparative analysis of eleven Mediterranean plant species

The ‘central-peripheral’ hypothesis has provided a baseline for many studies of population dynamics and genetic variability at species distribution limits. Although peripheral populations are often assumed to occur in ecologically marginal conditions, little is known about whether they effectively occur in a distinct ecological niche. A cross-taxa analysis of 11 Mediterranean vascular plants were studied. We quantified variation in the ecological niche between populations at the northern range limits of species in Mediterranean France and those in the central part of the distribution in continental Spain or Italy in 2013–2014. We analyzed both the macroecological niche where populations occur in terms of broad habitat and altitudinal range and the micro-ecological niche where individual plants grow in terms of soil and structural biotic and abiotic characteristics. Most species occur in a single broad habitat type common to central and peripheral populations and have a narrower altitudinal range in the latter. In contrast, for the micro-ecological niche we detected marked variation in several niche parameters among central and peripheral populations. Although many differences are species-specific some are common to several species. We found a trend towards narrower microniche breadth in peripheral populations. Our results illustrate the importance of studying the precise ecological characteristics where plants grow and the pertinence of a multi-species approach to correctly assess niche variation. The ecological originality of peripheral populations underlines their evolutionary potential and conservation significance.

Mixed camera viewpoints improve learning medical hand procedure from video in nurse training

Abstract Recent research has shown that camera viewpoints can influence how hand procedures are learnt from videos. However, studies have generally investigated videos showing only single viewpoints, for example, face-to-face or over-the-shoulder. Single views may not be appropriate for learning complex medical procedures involving spatial viewpoint changes. The goal of the present study was to investigate the effect of mixed camera viewpoints on learning a complex medical hand procedure from a video. Using a pretest-posttest paradigm, 43 students at a French nursing school had to learn a complex hand procedure from a video showing an expert nurse teacher inserting an indwelling catheter in a closed system using a simulation mannequin. Three video conditions were compared, delivering the same information in the same amount of time, from different viewpoints: (i) face-to-face only (FtF), (ii) over-the-shoulder only (OtS), and (iii) alternating face-to-face and over-the-shoulder views for each step of the procedure (MixW). The students were randomly assigned (N = 10–11) to one of four groups: the three experimental viewing conditions (FtF, OtS, MixW) and a control condition without video. Pre- and post-tests consisted of performing the hand procedure in a fully equipped full-scale simulation room. Results showed that learners in the mixed viewpoint (MixW) group performed better than the other groups (FtF, OtS, and control condition). Learners in the FtF and OtS groups outperformed those in the control group.