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Vaccinium myrtillus L., Vaccinium uliginosum L. and Vaccinium vitis-idaea L. are perennial, cold-adapted clonal shrubs distributed throughout Europe, northern Asia and North America. Due to their usage in food (berries) and pharmaceutical industry (berries and leaves), their natural populations are exposed to anthropogenic and other impacts that affect their genetic make-up. We analyzed 14 fragmentary distributed and small-sized peripheral populations of these species from the Balkans, which represents the southeastern-European marginal area of their wide European distributions, using RAPD molecular markers. The contemporary genetic patterns in all three species within the Balkans were generally similar, and in comparison to previous reports on populations of these species found in northward Europe, where they have a more continuous distribution, the levels of genetic diversity were more or less halved, genetic differentiation was several times higher, gene flow exceptionally low, and the expected prevalence of clonal individuals was lacking. The population dynamics of all three species within the Balkans was complex and distinct, and was characterized by a past admixture of individuals from discrete populations of the same species and interspecific hybridisation not only between V. myrtillus and V. vitis-idaea but also between V. uliginosum and V. vitis-idaea, the latter not being reported to date. Conservation measures suitable for preservation of presumably genetically distinct portions of the Balkans' gene pools of studied species have been suggested, while the utility of interspecific hybrids in breeding programs and/or in food/pharmaceutical industry is yet to be assessed. Ministry of Education, Science and Technological Development of the Republic of Serbia {[}III 43007, OI 173030]

Understanding the factors determining genetic diversity and structure in peripheral populations is a long-standing goal of evolutionary biogeography, yet little empirical information is available for tropical species. In this study, we combine information from nuclear microsatellite markers and niche modelling to analyse the factors structuring genetic variation across the southernmost populations of the tropical oak Quercus segoviensis. First, we tested the hypothesis that genetic variability decreases with population isolation and increases with local habitat suitability and stability since the Last Glacial Maximum (LGM). Second, we employed a recently developed multiple matrix regression with randomisation (MMRR) approach to study the factors associated with genetic divergence among the studied populations and test the relative contribution of environmental and geographic isolation to contemporary patterns of genetic differentiation. We found that genetic diversity was negatively correlated with average genetic differentiation with other populations, indicating that isolation and limited gene flow have contributed to erode genetic variability in some populations. Considering the relatively small size of the study area (, JO and RB were supported by Severo Ochoa, Juan de la Cierva (MICINN) and JAE-Doc (CSIC) post-doctoral fellowships.This work received financial support from grants D/7592/07(AECID) and UNCM08-1E-018 (FEDER).

International audience; We investigated patterns of genetic structure in two sister kelp species to explore how distribution width along the shore, zonation, latitudinal distribution and historical factors contribute to contrasting patterns of genetic diversity. We implemented a hierarchical sampling scheme to compare patterns of genetic diversity and structure in these two kelp species co-distributed along the coasts of Brittany (France) using a total of 12 microsatellites, nine for Laminaria hyperborea and 11 for Laminaria digitata, of which eight amplified in both species. The genetic diversity and connectivity of L. hyperborea populations were greater than those of L. digitata populations in accordance with the larger cross-shore distribution width along the coast and the greater depth occupied by L. hyperborea populations in contrast to L. digitata populations. In addition, marginal populations showed reduced genetic diversity and connectivity, which erased isolation-by-distance patterns in both species. As L. digitata encounters its southern range limit in southern Brittany (SBr) while L. hyperborea extends down to mid-Portugal, it was possible to distinguish the effect of habitat continuity from range edge effects. We found that L. digitata did not harbour high regional diversity at its southern edge, as expected in a typical rear edge, suggesting that refuges from the last glacial maximum for L. digitata were probably not located in SBr, but most likely further north. For both species, the highest levels of genetic diversity were found in the Iroise Sea and Morlaix Bay, the two regions in which they are being currently harvested. Preserving genetic diversity of these two foundation species in these areas should, thus, be a priority for the management of this resource in Brittany.

The North-Atlantic has warmed faster than all other ocean basins and climate change scenarios predict sea surface temperature isotherms to shift up to 600km northwards by the end of the 21st century. The pole-ward shift has already begun for many temperate seaweed species that are important intertidal foundation species. We asked the question: Where will climate change have the greatest impact on three foundational, macroalgal species that occur along North-Atlantic shores: Fucus serratus, Fucus vesiculosus, and Ascophyllum nodosum? To predict distributional changes of these key species under three IPCC (Intergovernmental Panel on Climate Change) climate change scenarios (A2, A1B, and B1) over the coming two centuries, we generated Ecological Niche Models with the program MAXENT. Model predictions suggest that these three species will shift northwards as an assemblage or “unit” and that phytogeographic changes will be most pronounced in the southern Arctic and the southern temperate provinces. Our models predict that Arctic shores in Canada, Greenland, and Spitsbergen will become suitable for all three species by 2100. Shores south of 45° North will become unsuitable for at least two of the three focal species on both the Northwest- and Northeast-Atlantic coasts by 2200. If these foundational species are unable to adapt to the rising temperatures, they will lose their centers of genetic diversity and their loss will trigger an unpredictable shift in the North-Atlantic intertidal ecosystem.

Anthropogenic disturbances are major threats to coastal biodiversity and may exert drastic effects on natural populations occurring at the borders of the geographical distribution of species, which are thus already experiencing sub-optimal environmental conditions. In this paper, we examined the effects of experimental intensities of human trampling on temporal and spa - tial variance of the brown seaweed Ascophyllum nodosum and associated organisms in north Por tugal. This is the southernmost population of A. nodosum in Europe and shows morphological and demographic traits that are different from those of populations from more central locations within its range of distribution. Results indicated that high trampling intensity reduced the small- scale spatial heterogeneity in the abundance of A. nodosum, whose cover was stabilized around relatively low values, and of the associated red algae Polysiphonia lanosa and Rhodothamniella floridula; however, it increased the spatial variance of limpets and green foliose macroalgae of the genus Ulva. Idiosyncratic responses in temporal patterns were also documented, with high tram- pling intensity causing relatively larger fluctuations in the structure of whole A. nodosum associ- ated assemblages and in the abundance of Ulva spp., and smaller fluctuations in the cover of Fucus vesiculosus. The present findings are key to predicting the relatively unstudied responses of coastal populations of A. nodosum to increasing anthropogenic disturbance and have important implications for the management and conservation of the examined population, which represents a relevant component of the biodiversity of European rocky shores.

We addressed the question if local adaptation to a thermal gradient is possible in spite of a high gene flow among closely spaced populations of two species of Drosophila from the island of La Gomera (Canary Islands). Variation in multiple traits related to stress resistance in different life stages was measured in both species in flies collected from five localities at different altitudes and thereby with different climatic conditions. Based on microsatellite loci, the populations were not genetically differentiated. However, 18 of the 24 independent traits measured showed significant differentiation among populations of Drosophila buzzatii, but only nine of 25 for Drosophila simulans. This difference in the number of traits might reflect higher habitat specificity and thus higher potential for local adaptation of D. buzzatii than D. simulans. We found clinal variation, as some traits showed significant linear regressions on altitude, but more on altitude cubed.

The IUCN criteria 2001 are considered one of the best methods to evaluate species extinction risk at the global and regional levels. The aim of this work is to test the applicability of the IUCN criteria to peripheral isolated plant populations (PIPPs). PIPPs have been a topic of scientific debate in Conservation Biology for about 15 years and international conventions such as ESPC address the issue of their conservation. Conservation measures often rely on Red Lists based on IUCN criteria, but there is little evidence supporting their application to PIPPs. In this work, we tested the hypothesis that PIPPs' intrinsic restricted range and rarity lead to the overestimation of their extinction risk. We compared and analyzed four IUCN criteria (A, B, C, D), considering 17 species with PIPPs in different Italian administrative regions. Special attention must be given to the spatial scale at which PIPPs are assessed, the evaluation of the threats affecting the populations, and their decline. PIPPs should not be assessed within political boundaries and we propose a new area designation that better corresponds to the characteristics of PIPPs. Criterion B is strongly biased by restricted range and overestimates the extinction risk of PIPPs, particularly when the population decline is only suspected and not observed. In this case, criterion D more accurately assesses the status of PIPPs. Criterion A is also suitable for assessing PIPPs, because it is not affected by their phytogeographic rarity. The proposed statements could also be valid for the global assessment of narrow endemic species. © Springer Science+Business Media B.V. 2009.

International audience; Background and Aims: Marginal populations of widely distributed species can be of high conservation interest when they hold a significant or unique portion of the genetic diversity of the species. However, such genetic information is frequently lacking. Here the relevance of genetic surveys to develop efficient conservation strategies for such populations is illustrated using cork oak (Quercus suber) from Minorca (Balearic Islands, Spain) as a case study. Cork oak is highly endangered on the island, where no more than 67 individuals live in small, isolated stands in siliceous sites. As a consequence, it was recently granted protected status. Methods: Two Bayesian clustering approaches were used to analyse the genetic structure of the Minorcan population, on the basis of nuclear microsatellite data. The different groups within the island were also compared with additional island and continental populations surrounding Minorca. Key Results: Very high genetic diversity was found, with values comparable with those observed in continental parts of the species' range. Furthermore, the Minorcan oak stands were highly differentiated from one another and were genetically related to different continental populations of France and Spain. Conclusions: The high levels of genetic diversity and inter-stands differentiation make Minorcan cork oak eligible for specific conservation efforts. The relationship of Minorcan stands to different continental populations in France and Spain probably reflects multiple colonization events. However, discrepancy between chloroplast DNA- and nuclear DNA-based groups does not support a simple scenario of recent introduction. Gene exchanges between neighbouring cork oak stands and with holm oak have created specific and exceptional genetic combinations. They also constitute a wide range of potential genetic resources for research on adaptation to new environmental conditions. Conservation guidelines that take into account these findings are provided.

Small plant populations are more prone to extinction due to the loss of genetic variation through random genetic drift, increased selfing, and mating among related individuals. To date, most researchers dealing with genetic erosion in fragmented plant populations have focused on threatened or rare species. We raise the question whether common plant species are as susceptible to habitat fragmentation as rare species. We conducted a formal meta-analysis of habitat fragmentation studies that reported both population size and population genetic diversity. We estimated the overall weighted mean and variance of the correlation coefficients among four different measures of genetic diversity and plant population size. We then tested whether rarity, mating system, and plant longevity are potential moderators of the relationship between population size and genetic diversity. Mean gene diversity, percent polymorphic loci, and allelic richness across studies were positively and highly significantly correlated with population size, whereas no significant relationship was found between population size and the inbreeding coefficient. Genetic diversity of self-compatible species was less affected by decreasing population size than that of obligate outcrossing and self-compatible but mainly outcrossing species. Longevity did not affect the population genetic response to fragmentation. Our most important finding, however, was that common species were as, or more, susceptible to the population genetic consequences of habitat fragmentation than rare species, even when historically or naturally rare species were excluded from the analysis. These results are dramatic in that many more plant species than previously assumed may be vulnerable to genetic erosion and loss of genetic diversity as a result of ongoing fragmentation processes. This implies that many fragmented habitats have become unable to support plant populations that are large enough to maintain a mutation-drift balance and that occupied habitat fragments have become too isolated to allow sufficient gene flow to enable replenishment of lost alleles. ispartof: Conservation Biology vol:21 issue:3 pages:823-831 ispartof: location:United States status: published

Marginal populations are usually located at the edge of the species' range, constituting small isolates that grow in suboptimal environments. In widely distributed conifers, such as pines, marginal populations have often been considered recent or rare colonizing events without ecological relevance. The Canary Island pine provides an excellent case to study the significance of critically endangered marginal populations (from 20 to a few hundred trees) in an endemic conifer that is also extensively used in commercial plantations. Our chloroplast microsatellite (cpSSR) survey showed contrasting values of haplotypic genetic diversity in marginal populations of Canary Island pine, from very low at Garabato (northern La Gomera) and Anaga (Tenerife), located within broad-leaved tree formations, to very high in Gran Canaria marginal populations (Arguineguin and Galdar). Competition with broad-leaved vegetation, after rare long-distance colonization events, might explain present-day low levels of variation in Garabato and Anaga. Gran Canaria and southern La Gomera relict populations, which contain high haplotypic diversity, are probably remnants of larger populations severely reduced by adverse climatic conditions and human activities, the latter starting shortly after the European colonization of the islands in the XV century. Given the extremely low population numbers and a general lack of natural regeneration, the risk of extinction in the near future is high in marginal populations of Canary Island pine. Conservation activities are urgently required and should focus on the highly diverse Gran Canaria and southern La Gomera pine marginal populations. Here, the establishment of in situ genetic reserves (Arguineguin and Imada), and multifunctional ex situ collections (Arguineguin and Galdar), such as seed orchards, is highly recommended. In addition, common garden experiments to test the performance of potentially drought-tolerant genotypes from Arguineguin (southernmost Gran Canaria's relict) and potential risks due to inbreeding and/or outbreeding depression should be established. © 2005 Elsevier Ltd. All rights reserved.

Genetic structure and genetic diversity in fourteen autochthonous populations of Pinus sylvestris L. from the Iberian peninsula and two populations from the Massif Central in France were studied at eleven isoenzymatic polymorphic loci. The studied populations formed two genetically similar but heterogeneous groups. The first group consist of populations localized in North-Eastern Spain with two genetically distinct populations. The second includes populations of the West-Central part of the Iberian peninsula. Populations from the Massif Central in France are diverse from those of Spain, but are similar to the group from North- part of the Iberian peninsula. The existence of significant numbers of private alleles in Spanish populations which were not observed in populations from the Massif Central, suggests that the Scots pine from the Iberian peninsula probably did not take part in the colonization of Europe after the last glaciations and represents original ancient tertiary gene pools.

Eighteen spontaneous populations of cork oak (Quercus suber) from Spain (14), Portugal (1), Morocco (1) and Italy (2), were surveyed at 14 loci from 12 enzyme systems. Percentage of polymorphic loci (64%), mean number of alleles (2.07), and mean expected heterozygosity (0.158) values were within the ranges described for the genus. Populations from the central range of the species and from peripheral areas were evaluated, and differences between these two kinds were assessed. Significant lower diversity (number of alleles and expected heterozygosity) was found for the most isolated and small size populations in contrast to central forests, showing the existence of mechanisms maintaining the levels of diversity even in some isolated stands. Interpopulation diversity (F(st)) is 3.3%, indicating extensive gene flows or recent postglacial expansion. A possible recent bottleneck is detected in two populations by comparing actual with expected heterozygosity from the number of detected alleles.

In Belgium, at the north-western margin of its geographical range, Silene nutans is a rare species, which has evolved a silicicolous (Si) and a calcicolous (Ca) ecotype, with contrasting morphometric traits. Genetic diversity and population genetic structure were examined for seven allozyme loci in 16 Si and 18 Ca populations (a total of 567 individuals). High genetic variation was found at both the ecotypic and population level, and no significant correlation was found between population size and any measure of genetic variation. The maintenance of high levels of genetic diversity in small, marginal populations might be explained by the perennial, long-lived life form and the outcrossing breeding system of the species. Additionally, low F(ST)-values suggested that efficient gene flow was occurring within both ecotypes. Genetic distance measures and cluster analysis using UPGMA on the distance matrix revealed that the populations were differentiated according to their ecotypic property in two distinct gene pools. It is argued that the congruence of allozymic and morphometric differentiation between edaphic races is unusual for an outcrossing species. This finding, together with previous observations of isolating mechanisms between ecotypes, strongly suggests that incipient speciation is occurring within Silene nutans at the margin of its geographical range., SCOPUS: ar.j, info:eu-repo/semantics/published

This study focuses on the spatio-temporal varibility of reproduction in silver fir (Abies alba), in its French rear edge populations in the Mont Ventoux and Lure mountain. Usually, marginal populations contrast from core populations with lower and more variable densities. In our populations of firs, we found that lower densitiy leads to higher selfing rates through a mass-action law at both population and individual levels. As a consequence, germinative abilities were lower for seeds from lower density populations, mainly because of inbreeeding depression. But this was balanced by a higher survival rates at the seedling stage. A more efficient genetic purge could explain this. However, in our populations, a lower density also induced a lower effective seed production, through an increased rate of empty seeds. This can result from pollen limitation. Indeed, genetic analyses revealed a rather high spatial genetic structure of pollen pool, indicating a limited dispersal with a mean dispersal distance between 20 and 50m. This limited dispersal also induced a high interindividual variability of the mating system mainly due to variations of local density and individual pollen production. Finally, we found strong inter-annual variations of the pollen pools : giving an inter-mothers differentiation of 8%, we obtained an inter-annual differenciation of 13% within mothers. The year with the higher pollen productions also presented the lower overall genetic diversity. Thus this study confirms the necessity to consider multiple years in studies on the reproduction of a perennial tree such as fir, either for theoretical concerns of for practical questions focused on the management of genetic diversity, Cette thèse s'intéresse aux variations spatio-temporelles de la reproduction du sapin pectiné (Abies alba), en limite sud de son aire de répartition dans les populations du mont Ventoux et de la montagne de Lure. En général, les populations marginales présentent des densités faibles et variables. Pour nos populations de sapins, nous avons montré que les densités faibles entraînent une augmentation des taux d'autofécondation par loi d'action de masse, à l'échelle de la population mais également individuelle. Les populations moins denses présentent également une réduction du taux de germination par expression de la dépression de consanguinité, mais qui est compensée par une meilleure survie des semis pouvant provenir d'une purge plus efficace du fardeau génétique. Cependant, la diminution de la densité entraîne dans nos populations une baisse de la production efficace de graines par augmentation du taux de graines vides, probablement à cause d'une dispersion du pollen limitée. En effet, nos analyses génétiques conduisent à une distance de dispersion moyenne estimée de 20 à 50m. Cette faible dispersion induit également une forte variabilité individuelle du régime de reproduction liée aux variations locales de densité et de productions individuelles de pollen. Finalement, nous avons trouvé des variations inter-annuelles importantes de la structure génétique spatiale du nuage de pollen avec une différenciation entre arbres-mères de 8% et une différenciation entre années au sein des mères de 13%. Les années avec les plus fortes productions de pollen étaient également celles avec la plus faible diversité génétique globale. Cette étude confirme donc la nécessité de considérer de multiples années quand on s'intéresse à la reproduction d'une espèce pérenne comme le sapin, à la fois pour des études théoriques et pour des questions centrées sur la gestion de la diversité