Corsican Populations Research Articles

New Chloroplast Microsatellites in Helichrysum italicum (Roth) G. Don: Their Characterization and Application for the Evaluation of Genetic Resources

Helichrysum italicum (Roth) G. Don is a Mediterranean medicinal plant with great potential in the cosmetics, culinary and pharmaceutical fields due to its unique bioactive compounds. Its recent introduction into agroecosystems has enhanced the exploitation of genetic diversity in natural populations, although limited molecular markers have made this challenging. In the present study, primers were designed for all 43 SSRs (72.1% mononucleotide, 21% dinucleotide and 6.9% trinucleotide repeats) identified in the chloroplast genome. Populations from Cape Kamenjak (Croatia) and Corsica (France) were analyzed with ten carefully selected cpSSR markers. From the initial set of 16 cpSSRs amplified in all samples, 6 cpSSR markers were removed due to low-length polymorphisms, size homoplasy and nucleotide polymorphisms that could not be detected with allele length. Of the 38 haplotypes detected, 32 were unique to their geographic origin. The highest number of private haplotypes was observed in the Cape Kamenjak population (seven out of nine detected). Based on clustering analyses, the Kamenjak population was the most similar to the Capo Pertusato (south Corsica) population, although only one sub-haplotype was shared. Other Corsican populations were more similar to each other. A cross-species transferability test with Helichrysum litoreum Guss. and Helichrysum arenarium (L.) Moench was successfully conducted and private alleles were identified.

New evidence for population-specific responses to drought events from tree ring chronologies of Pinus nigra ssp. laricio across the entire distribution range

• Growth-climate relationships were analysed in black pine (ssp. laricio ). • Drought effects on stem radial growth were studied in representative populations. • Positive impacts of precipitation in spring/summer, but negative in winter, were found. • Corsican populations were more sensitive to drought than populations in southern Italy. • Older trees were more resistant to drought events than younger trees. The increased frequency and severity of drought events due to climate warming is negatively affecting tree radial growth, particularly in drought-prone regions, such as, e.g., the Mediterranean. In this climate change hotspot, populations of the same tree species may show different growth responses to climate, due to the great variety of microclimates and environments that characterise this biogeographic region. In this study, we analysed growth-climate relationships and growth responses to drought events (i.e., resistance, recovery, and resilience) in 13 forest stands of black pine ( Pinus nigra Arnold), encompassing the whole and peculiar distribution range of the ssp. laricio (Calabria, Sicily, Sardinia, and Corsica). Analysis focussed on the 1981–2010 period, which is commonly covered at all sites. Stem radial growth of trees increased under a positive spring/summer water balance. However, abundant winter precipitation had a negative impact on stem radial growth. Populations in Corsica were more sensitive to drought, showing lower resistance and resilience than those in Sicily and Sardinia. Older trees were more resistant to drought events than younger trees. Our results highlight that population-specific responses to drought events are mainly explained by tree age and local environment, suggesting geographically related patterns in tree growth and forest productivity correspond to different populations. Intraspecific variability in sensitivity to drought events should be included in species distribution models to predict the range of forest productivity responses to climate change.

Contribution of a DNA barcode to an assessment of the specificity of ant taxa (Hymenoptera: Formicidae) on Corsica

We used the COI marker, the most popular DNA barcode for the animal kingdom, to assess the taxonomic status of Corsican populations of eight groups of species of ants that occur both on Corsica and the European mainland. (i) In two groups, we detected no genetic differentiation between Corsica and the continent. Absence of differentiation across varieties of Aphaenogaster spinosa within Corsica confirm current synonymies. (ii) In four groups, we detected strong genetic differentiation between Corsica and the continent, confirming recent taxonomic studies based on morphology for three of these groups. For the fourth group, we propose that the status of Corsican populations be raised from sub-species to species: Temnothorax cordieri stat. rev. (iii) In one group, the genetic differentiation and morphological differences do not support splitting and as a consequence we propose to accept the previous synonymy Temnothorax tuberum = Temnothorax melanocephalus. (iv) In Myrmica scabrinodis and Myrmica spinosior, COI sequence information is largely inconsistent with morphology and geography, not only on Corsica but also on the mainland, and should not be used to support taxonomic decisions. Although the use of COI has drawbacks, it is globally consistent with morphology and can be used to complement morphological ant taxonomy. We provide an updated checklist of ants of Corsica.

Dugesia hepta and Dugesia benazzii (Platyhelminthes: Tricladida): two sympatric species with occasional sex?

Dugesia hepta Pala, Casu & Vacca, 1981 and Dugesia benazzii Lepori, 1951 are two freshwater planarian species from the islands of Corsica and Sardinia. Dugesia hepta is endemic of Sardinia and distributed in four northern hydrographic basins where it co-occurs with D. benazzii, which has a wider Tyrrhenian distribution. Although these species have been broadly studied—especially D. benazzii—as regards to their variety of reproductive patterns as well as for their karyological diversity, little is known about them from a molecular phylogenetic perspective. For the first time, we present a molecular phylogenetic tree of the two species and their populations based on two molecular markers—one mitochondrial, Cox1, and one nuclear, Dunuc12. Our results not only confirm that both species are molecularly distinct but also show that D. benazzii’s Corsican and Sardinian populations could belong to separate species. Furthermore, we present the first demonstration of a natural hybridization between different species in the genus Dugesia on the basis of molecular data.

Brown trout (Salmo trutta L.) high genetic diversity around the Tyrrhenian Sea as revealed by nuclear and mitochondrial markers

The brown trout (Salmo trutta L.) is widely distributed all around Europe but its natural diversity is threatened by massive stocking with Atlantic domestic strains. Describing the remaining natural genetic diversity and the proportion of domestic hatchery strains in rivers is a prerequisite for smart conservation. The high genetic diversity of brown trout populations around the Tyrrhenian Sea is well known. Use of twelve microsatellites has allowed description of the natural genetic structure of populations and detection of the consequences of stocking. Mitochondrial DNA control region sequences and the LDH-C1* gene enabled placement of each population into one of the six mitochondrial and two allozymic known evolutionary lineages. The Corsican populations showed low intra-population genetic diversity but an exceptionally high level of inter-population differentiation. More southern Tyrrhenian regions exhibited opposite pattern of diversity, partly due to the Atlantic domestic introgression. Globally, the natural structure outlines two north–south clines: high inter-population differentiation and predominance of the Adriatic lineage in the north, but lower inter-population differentiation and the presence of the natural Atlantic lineage in the south. In addition, the Tyrrhenian region is the contact zone between the widespread Adriatic lineage and a local natural Atlantic lineage probably coming from North Africa through the Strait of Gibraltar.

Prehistoric migrations through the Mediterranean basin shaped Corsican Y-chromosome diversity.

The rarity of human remains makes it difficult to apprehend the first settlements in Corsica. It is admitted that initial colonization could have occurred during the Mesolithic period when glaciations would have shortened the open water travel distance from the continent. Mesolithic sites in Corsica show relatively short and irregular occupation, and suggest discontinuous settling of very mobile groups probably traveling by boat. Previous genetic studies on Corsican populations showed internal differentiation and a relatively poor genetic relationship with continental populations, despite intense historical contacts, however local Mesolithic-based genetic inheritance has never been properly estimated. The aim of this study was to explore the Corsican genetic profile of Y-chromosomes in order to trace the genetic signatures back to the first migrations to Corsica. This study included 321 samples from men throughout Corsica; samples from Provence and Tuscany were added to the cohort. All samples were typed for 92 Y-SNPs, and Y-STRs were also analyzed. Results revealed highly differentiated haplogroup patterns among Corsican populations. Haplogroup G had the highest frequency in Corsica, mostly displaying a unique Y-STR profile. When compared with Provence and Tuscany, Corsican populations displayed limited genetic proximity. Corsican populations present a remarkable Y-chromosome genetic mixture. Although the Corsican Y-chromosome profile shows similarities with both Provence and to a lesser extent Tuscany, it mainly displays its own specificity. This study confirms the high level of genetic diversity in Corsican populations and backs genetic contributions from prehistoric migrations associated with the Mesolithic, Neolithic and Metal Age eras, rather than from historical movements to Corsica, respectively attested by frequencies and TMRCA of haplogroups G2a-L91 and G2a-P15, J2a-M241 and J2-DYS445 = 6, R1b-U152 and R1b-U106. These results suggest that marine routes to reach the Corsican coast in many different points may have led to such a genetic heterogeneity.

Evolutionary history of Podarcis tiliguerta on Corsica and Sardinia

BackgroundPodarcis tiliguerta is a wall lizard endemic to the Mediterranean islands of Corsica and Sardinia. Previous findings of high mtDNA and morphological diversity have led to the suggestion that it may represent a species complex. Here, we analysed mitochondrial and nuclear markers (mtDNA, 3110 bp; 6 nDNA loci, 3961 bp) in P. tiliguerta sampled from thirty-two localities across Corsica and Sardinia.ResultsWe find much greater intraspecific genetic divergence than between sister species of other Mediterranean island Podarcis, i.e., between P. lilfordi and P. pityusensis. We detected three mtDNA clusters in Corsica (North, South-East and South-West) and either two or three in Sardinia (North vs. South) depending on the clustering method. Only one or two nDNA groups were identified within each main island (again, depending on the method). A Bayesian time-calibrated multispecies coalescent tree was obtained from mtDNA and provided statistical support for a Miocene origin of the species (13.87 Ma, 95% HPD: 18.30–10.77 Ma). The posterior mean divergence time for the Corsican and Sardinian lineages was 12.75 Ma ago (95% HPD: 16.94–9.04 Ma).ConclusionThe results support the evolutionary distinctiveness of Corsican and Sardinian populations and also indicate a lack of post-divergence migration despite periods of contact being possible. Further to this, species delimitation analyses of Corsican and Sardinian lineages provided statistical support for their recognition as distinct (sister) taxa. Our results provide new insights into the biogeography of the Mediterranean biodiversity hotspot, and contribute important findings relevant to the systematics and evolution of this speciose lizard genus.

Geographic variation in coal tit song across continents and reduced species recognition between Central European and Mediterranean populations

Intraspecific variation of passerine song may influence mate choice and consequently provides a potential mechanism for premating reproductive isolation in birds. Notable geographic variation of songs is particularly common in widespread bird species, such as the coal tit Periparus ater (Aves, Passeriformes, Paridae) having a large trans-Palearctic distribution range including allopatric populations. In this study, measurement and analysis of 16 song parameters from different Western Palearctic populations showed a relatively uniform song in all continental European and the island populations of Corsica and Sardinia. Song variation among and within these populations seems so variable that there is a broad geographical overlap of acoustic parameters between populations. However, songs from northwest African and Cypriot populations had lowest minimum frequencies and were thus significantly different from continental European, Corsican and Sardinian populations. To test for intraspecific species recognition and potential acoustic isolation of different Palearctic populations, we carried out field playback experiments on Central European coal tit males with songs from populations of the Eurasian (Germany, Latvia, Russian Far East, Japan) and the Mediterranean region (northwest Africa, Cyprus, Corsica, Sardinia). Eurasian song types elicited similar strong territorial reactions in Central European coal tits as local control songs. In contrast, none of the Mediterranean songs evoked any notable reaction. Thus, there is geographic variation in coal tit song across continents that coincides with reduced species recognition between Central European and Mediterranean populations.

The fate of Cystoseira crinita, a forest-forming Fucale (Phaeophyceae, Stramenopiles), in France (North Western Mediterranean Sea)

In the Mediterranean Sea, Fucales, and in particular the species of the genus Cystoseira C. Agardh, are habitat-forming species dominating several benthic assemblages from the littoral fringe down to 70–80 m depth in the clearest waters. They generate high primary production involved in the maintenance of diversified trophic levels, they provide shelter, food, habitat and nursery areas to many species, and they are long-lived species that constitute a good model for studying human impact on species diversity. Cystoseira crinita Duby is a Mediterranean endemic cespitose species, living in shallow waters (0–5 m depth), in places with little wave action and high solar irradiance. To reconstruct the long-term patterns of change in its distribution along the French Mediterranean coast (French Catalonia, Languedoc, Provence, French Riviera and Corsica), all the historical data (published articles, unpublished reports and herbarium vouchers) collected since the 18th century were searched and analysed. To assess the current status of the species, several field surveys were conducted between 2010 and 2016 by snorkelling and SCUBA diving. Cystoseira crinita is currently extinct in French Catalonia, near-extinct in Languedoc and western Provence, and functionally extinct on the French Riviera coast, while the eastern Provence and Corsican populations have remained stable. The main probable causes of decline are habitat destruction and overgrazing by herbivores.

Spatio-temporal genetic variation of the biting midge vector species Culicoides imicola (Ceratopogonidae) Kieffer in France.

BackgroundIntroduction of vector species into new areas represents a main driver for the emergence and worldwide spread of vector-borne diseases. This poses a substantial threat to livestock economies and public health. Culicoides imicola Kieffer, a major vector species of economically important animal viruses, is described with an apparent range expansion in Europe where it has been recorded in south-eastern continental France, its known northern distribution edge. This questioned on further C. imicola population extension and establishment into new territories. Studying the spatio-temporal genetic variation of expanding populations can provide valuable information for the design of reliable models of future spread.MethodsEntomological surveys and population genetic approaches were used to assess the spatio-temporal population dynamics of C. imicola in France. Entomological surveys (2–3 consecutive years) were used to evaluate population abundances and local spread in continental France (28 sites in the Var department) and in Corsica (4 sites). We also genotyped at nine microsatellite loci insects from 3 locations in the Var department over 3 years (2008, 2010 and 2012) and from 6 locations in Corsica over 4 years (2002, 2008, 2010 and 2012).ResultsEntomological surveys confirmed the establishment of C. imicola populations in Var department, but indicated low abundances and no apparent expansion there within the studied period. Higher population abundances were recorded in Corsica. Our genetic data suggested the absence of spatio-temporal genetic changes within each region but a significant increase of the genetic differentiation between Corsican and Var populations through time. The lack of intra-region population structure may result from strong gene flow among populations. We discussed the observed temporal variation between Corsica and Var as being the result of genetic drift following introduction, and/or the genetic characteristics of populations at their range edge.ConclusionsOur results suggest that local range expansion of C. imicola in continental France may be slowed by the low population abundances and unsuitable climatic and environmental conditions.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1426-4) contains supplementary material, which is available to authorized users.

The genetic diversity of Sardinian myrtle (Myrtus communis L.) populations

Background: The myrtle ( Myrtus communis ) is a common shrub widespread in the Mediterranean Basin. Its fruit and leaves exhibit antioxidant, antibacterial and antifungal properties, and are used for their content of essential oils and for their medicinal properties, but most commonly as an ingredient in locally made liquor. The uncontrolled exploitation of natural stands has reduced both the species' geographical coverage and the size of individual populations. The selection of genotypes for controlled cultivation requires a characterization of the genetic diversity present both within and between populations. Results: Genotypic variation was evaluated using ISSR profiling and genetic diversity characterized using standard population genetics approaches. Two major clusters were identified: one capturing all the candidate cultivars selected from various Sardinian localities, and the other wild individuals collected from Asinara, Corsica and Surigheddu. A moderate level of gene flow between the Sardinian and Corsican populations was identified. Discriminant analysis of principal components revealed a level of separation among the wild populations, confirming the population structure identified by the clustering methods. Conclusions: The wild accessions were well differentiated from the candidate cultivars. The level of genetic variability was high. The genetic data were compatible with the notion that myrtle has a mixed pollination system, including both out-pollination by insects and self-pollination. The candidate cultivars are suggested to represent an appropriate basis for directed breeding.

Patterns of Genetic and Reproductive Traits Differentiation in Mainland vs. Corsican Populations of Bumblebees

Populations on islands often exhibit lower levels of genetic variation and ecomorphological divergence compared to their mainland relatives. While phenotypic differentiation in characters, such as size or shape among insular organisms, has been well studied, insular differentiation in quantitative reproductive traits involved in chemical communication has received very little attention to date. Here, we investigated the impact of insularity on two syntopic bumblebee species pairs: one including species that are phylogenetically related (Bombus terrestris and B. lucorum), and the other including species that interact ecologically (B. terrestris and its specific nest inquiline B. vestalis). For each bumblebee species, we characterized the patterns of variation and differentiation of insular (Corsican) vs. mainland (European) populations (i) with four genes (nuclear and mitochondrial, 3781 bp) and (ii) in the chemical composition of male marking secretions (MMS), a key trait for mate attraction in bumblebees, by gas chromatography-mass spectrometry (GC-MS). Our results provide evidence for genetic differentiation in Corsican bumblebees and show that, contrary to theoretical expectations, island populations of bumblebees exhibit levels of genetic variation similar to the mainland populations. Likewise, our comparative chemical analyses of MMS indicate that Corsican populations of bumblebees are significantly differentiated from the mainland yet they hold comparative levels of within-population MMS variability compared to the mainland. Therefore, insularity has led Corsican populations to diverge both genetically and chemically from their mainland relatives, presumably through genetic drift, but without a decrease of genetic diversity in island populations. We hypothesize that MMS divergence in Corsican bumblebees was driven by a persistent lack of gene flow with mainland populations and reinforced by the preference of Corsican females for sympatric (Corsican) MMS. The impoverished Corsican bumblebee fauna has not led to relaxation of stabilizing selection on MMS but to consistent differentiation chemical reproductive traits on the island.

Identification of Sardinian Species ofAstragalusSectionMelanocercis(Fabaceae) by Seed Image Analysis

Using a computer-aided imaging system, the seed morphometric and colorimetric features of Astragalus terraccianoi, A. tegulensis and A. thermensis — all belonging to Astragalus sect. Melanocercis — were measured and analysed. The results confirmed differences between A. terraccianoi and A. tegulensis, as well as the validity of A. tegulensis. Differences between the Corsican and Sardinian populations of A. terraccianoi were also found.

Genetic diversity and structure of a Mediterranean endemic plant in Corsica (Mercurialis corsica, Euphorbiaceae)

AbstractThe island of Corsica is a Mediterranean hotspot of plant biodiversity characterized by a high rate of plant endemism, but also by a lack of studies combining genetic diversity and conservation. In Corsica, the dioecious and Corso‐Sardinian endemic Mercurialis corsica Cosson (Euphorbiaceae) occurs across a wide ecological gradient, but the number of populations have decreased considerably over the last century. The main aim of this study was to examine the patterns of genetic diversity occurring in the Corsican populations of M. corsica, depending on their location and demographic structure. The rDNA sequences did not show the existence of any polymorphism, whereas the cpDNA sequences revealed the divergence of the western Corsican populations. By contrast, when the AFLP markers were examined, although significant levels of differentiation were detected between populations, no distinct geographical patterns were observed except for the pronounced isolation of the Cap Corse genotypes. No significant correlations were found to exist between population size and the genetic diversity indexes used. The results of this study suggest that M. corsica has undergone a complex gene flow history involving past population admixtures, followed by fragmentation processes resulting in population differentiation but no geographical patterns of isolation. These results support the existence of three evolutive conservation units which have to be monitored in priority to determine whether the current pattern of demographic structure is still declining or has stabilized.

Preliminary survey on genetic variation within the Pygmy Algyroides, Algyroides fitzingeri, across Corsica and Sardinia

AbstractAlgyroides fitzingeri is a Corso-Sardinian endemic lizard belonging to a relictual genus within the Lacertini radiation. In recent phylogeographic studies of Corso-Sardinian endemic lizards incongruent patterns are emerging. We investigated the mitochondrial genetic variation of A. fitzingeri across Corsica and Sardinia to obtain a preliminary portrait of its phylogeographic history. This species showed some polymorphism, but with low genetic differentiation between populations, that probably originated during the Pleistocene. Corsican populations are closely related to those from North Sardinia and are likely to have originated from them, given the higher diversity and deeper phylogeographic structure observed in Sardinia than in Corsica. While the phylogeographic structure of A. fitzingeri in Corsica is surprisingly shallow when compared with other co-distributed lizards, in Sardinia a common pattern apparently emerges. Further research is needed to confirm the hypotheses here presented and to provide a conclusive assessment of the phylogeography of this species.

Genetic isolation of insular populations of the Maghrebian bat, Myotis punicus, in the Mediterranean Basin

AbstractAim We investigate the population genetic structure of the Maghrebian bat, Myotis punicus, between the mainland and islands to assess the island colonization pattern and current gene flow between nearby islands and within the mainland.Location North Africa and the Mediterranean islands of Corsica and Sardinia.Methods We sequenced part of the control region (HVII) of 79 bats across 11 colonies. The phylogeographical pattern was assessed by analysing molecular diversity indices, examining differentiation among populations and estimating divergence time. In addition, we genotyped 182 bats across 10 colonies at seven microsatellite loci. We used analysis of molecular variance and a Bayesian approach to infer nuclear population structure. Finally, we estimated sex‐specific dispersal between Corsica and Sardinia.Results Mitochondrial analyses indicated that colonies between Corsica, Sardinia and North Africa are highly differentiated. Within islands there was no difference between colonies, while at the continental level Moroccan and Tunisian populations were highly differentiated. Analyses with seven microsatellite loci showed a similar pattern. The sole difference was the lack of nuclear differentiation between populations in North Africa, suggesting a male‐biased dispersal over the continental area. The divergence time of Sardinian and Corsican populations was estimated to date back to the early and mid‐Pleistocene.Main conclusions Island colonization by the Maghrebian bats seems to have occurred in a stepping‐stone manner and certainly pre‐dated human colonization. Currently, open water seems to prevent exchange of bats between the two islands, despite their ability to fly and the narrowness of the strait of Bonifacio. Corsican and Sardinian populations are thus currently isolated from any continental gene pool and must therefore be considered as different evolutionarily significant units (ESU).

Genetic consequences of intensive management in game birds

Introduction of wildlife for game restocking is one major pathway of genetic homogenization. The red-legged partridge ( Alectoris rufa, Phasianidae), a small game bird native to south-western Europe, is in high demand by hunters and natural populations are constantly supplemented by commercial stocks of captive-bred individuals. Also, in recent years human-mediated hybridization with congeneric chukar partridges ( Alectoris chukar: Greece, Cyprus, from Middle East to East Asia) has been frequently documented in the wild and in captivity. This study attempts to evaluate the genetic consequences of intensive captive breeding and restocking in the A. rufa species. We investigated A. rufa genetic diversity by making comparisons in both a spatial (across the entire species’ range) and a temporal framework. We accomplished this latter by comparing modern vs. ancient partridges resident in museums and collected 1856–1934, well before supplemental stocking became common. Using mtDNA we found significant changes in the haplotype profile of modern vs. ancient A. rufa, and widespread introgression with chukar genes across the entire species range only in modern representatives, with the relevant exception of Corsican populations. However, Random Amplified Polymorphic DNA (RAPD), as opposed to microsatellite DNA markers, showed also modern Corsican populations to harbour many A. rufa × A. chukar hybrids. We conclude that captive breeding programs should make strict use of time-saving and comparatively low cost DNA barcodes to minimize genetic pollution, such as those provided by diagnostic RAPD markers. We also recommend that the active ban on import of exotics and/or hybrids be extended to non-local populations. Altogether this would represent a substantial step forward to preserve A. rufa as well as other game species subjected to similar intensive management.

Mitochondrial phylogeography of the Bedriaga’s rock lizard, Archaeolacerta bedriagae (Reptilia: Lacertidae) endemic to Corsica and Sardinia

Archaeolacerta bedriagae is a rock-dwelling lizard endemic to the Corso-Sardinian insular system. We investigated the phylogeography of the species by using the mitochondrial ND4 and flanking tRNAs genes from 94 specimens belonging to 19 populations. Phylogenetic, Barrier, and SAMOVA analyses revealed a highly structured pattern characterized by two levels of discontinuities in the geographical distribution of mtDNA diversity: (i) a deep phylogeographic break in Northern Corsica between Lineage A, restricted to northernmost Corsica, and Lineage B widespread all over the remaining range of the species, and (ii) some minor phylogeographic discontinuities within lineage B, which is sub-structured into six closely related haplotype clades with remarkable concordance with geography. The first evolutionary event concerning the split between the two main lineages from an ancestral population occurred in the Upper Pliocene (5.87–3.68 mya), while the divergence within lineage B would have started from the Upper Pleistocene (2.5–1.6 mya), between Corsican and Sardinian populations. Somewhat later (1.7–1.1 mya), the Sardinian ancestral population underwent fragmentation into population groups inhabiting North, Central, and South Sardinia. As inferred from previous allozyme surveys, the divergence among population groups would be driven by allopatric fragmentation, while the discrepancy concerning the major partition into two lineages inferred from mtDNA but not apparent in analysis of allozymes needs further investigation.

Phylogeography of the weasel (Mustela nivalis) in the western-Palaearctic region: combined effects of glacial events and human movements

The Iberian, Italian or Balkan peninsulas have been considered as refugia for numerous mammalian species in response to Quaternary climatic fluctuations in Europe. In addition to this 'southerly refugial model', northern refugia have also been described notably for generalist and cold-tolerant species. Here, we investigated the phylogeographic pattern of the weasel (Mustela nivalis) to assess the impact of Quaternary glaciations on the genetic structure, number and location of refugia as well as to determine the impact of human movements on the colonization of Mediterranean islands. We sequenced 1690 bp from the mitochondrial control region and cytochrome b for 88 weasels distributed throughout the western-Palaearctic region, including five Mediterranean islands. Phylogenetic analyses of combined genes produced a clear phylogeographic pattern with two main lineages. The first lineage included all of the western-continental samples (from Spain to Finland) and shows low levels of genetic structure. Demographic analysis highlighted several characteristics of an expanding group, dated approximately at 116 kiloyears (kyr; Riss glaciation). The genetic pattern suggested a northeastern-European origin from which colonization of southwestern Europe took place. The second lineage was divided into five subgroups and indicated a common origin of insular and Moroccan samples from eastern Europe. Eastern-continental weasels did not exhibit signs of sudden expansion, suggesting stable population size during the last ice ages. The time of expansion of Sicilian and Corsican populations was dated around 10 kyr ago, which supports the hypothesis of an early human intervention in the colonization of Mediterranean islands.

The east-west-north colonization history of the Mediterranean and Europe by the coastal plant Carex extensa (Cyperaceae)

Coastal plants are ideal models for studying the colonization routes of species because of the simple linear distributions of these species. Carex extensa occurs mainly in salt marshes along the Mediterranean and European coasts. Variation in cpDNA sequences, amplified fragment length polymorphisms (AFLPs) and simple sequence repeats (SSRs) of 24 populations were analysed to reconstruct its colonization history. Phylogenetic relationships indicate that C. extensa together with the South American Carex vixdentata and the southern African Carex ecklonii form a monophyletic group of halophilic species. Analyses of divergence times suggest that early lineage diversification may have occurred between the late Miocene and the late Pliocene (Messinian crisis). Phylogenetic and network analyses of cpDNA variation revealed the monophyly of the species and an ancestral haplotype contained in populations of the eastern Mediterranean. The AFLP and SSR analyses support a pattern of variation compatible with these two lineages. These analyses also show higher levels of genetic diversity and differentiation in the eastern population group, which underwent an east-to-west Mediterranean colonization. Quaternary climatic oscillations appear to have been responsible for the split between these two lineages. Secondary contacts may have taken place in areas near the Ligurian Sea in agreement with the gene flow detected in Corsican populations. The AFLP and SSR data accord with the 'tabula rasa' hypothesis in which a recent and rapid colonization of northern Europe took place from the western Mediterranean after the Last Glacial Maximum. The unbalanced west-east vs. west-north colonization may be as a result of 'high density blocking' effect.