Peopling of three Mediterranean islands (Corsica,Sardinia, and Sicily) inferred by Y-chromosome biallelic variability

An informative set of biallelic polymorphisms was used to study the structure of Y-chromosome variability in a sample from the Mediterranean islands of Corsica and Sicily, and compared with data on Sardinia to gain insights into the ethnogenesis of these island populations. The results were interpreted in a broader Mediterranean context by including in the analysis neighboring populations previously studied with the same methodology. All samples studied were enclosed in the comparable spectrum of European Y-chromosome variability. Pronounced differences were observed between the islands as well as in the percentages of haplotypes previously shown to have distinctive patterns of continental phylogeography. Approximately 60% of the Sicilian haplotypes are also prevalent in Southern Italy and Greece. Conversely, the Corsican sample had elevated levels of alternative haplotypes common in Northern Italy. Sardinia showed a haplotype ratio similar to that observed in Corsica, but with a remarkable difference in the presence of a lineage defined by marker M26, which approaches 35% in Sardinia but seems absent in Corsica. Although geographically adjacent, the data suggest different colonization histories and a minimal amount of recent gene flow between them. Our results identify possible ancestral continental sources of the various island populations and underscore the influence of founder effect and genetic drift. The Y-chromosome data are consistent with comparable mtDNA data at the RFLP haplogroup level of resolution, as well as linguistic and historic knowledge.     

Frequency distribution of mitochondrial DNA haplogroups in Corsica and Sardinia

Mitochondrial DNA (mtDNA) polymorphisms were analyzed by polymerase chain reaction amplification and haplogroup-specific restriction screening in populations from Corsica and Sardinia. These included 56 individuals from the area of Corte, central Corsica (France), 51 individuals from Gallura, northern Sardinia (Italy), and 45 individuals from Barbagia, central Sardinia. The screening revealed that about 95% of mtDNAs could be grouped in 8 of the 9 European haplogroups, including H-K, T-V, and X. Our results confirmed that these haplogroups encompass virtually all the mitochondrial lineages present in Europe and can be detected in both northern and southern European populations. We also discovered 2 restriction sites (-73 Alw441 and +75 SphI) that allow the detection of informative nucleotide changes in the second hypervariable segment of the control region, which help to detect the haplogroup identity of mtDNAs without requiring further DNA sequencing. Haplogroup H was the most common mtDNA lineage in this sample, reaching frequencies from about 40% in Corsican and Gallurese populations, to about 65% in the Barbagian population. Haplogroup V, possibly originating in the Iberian peninsula, was found only in the central Sardinian sample. Of the 5 Corsican mtDNAs belonging to the haplogroup T, 4 had a restriction fragment length polymorphism found only in this population. It seems that this mutation originated in Corsica and has had time to spread in the area, since the maternal grandmothers of the subjects came from different villages of the island. The sample from central Sardinia shows a remarkable discontinuity with those from the northern part of the island and from Corsica. Gallura and Corsica seem to have undergone a more recent peopling event, possibly related to the arrival of new mitochondrial variability from continental Italy, while Barbagia has apparently maintained more archaic haplotypes.     

Satyrinae butterflies from Sardinia and Corsica show a kaleidoscopic intraspecific biogeography (Lepidoptera,Nymphlidae)

The Mediterranean islands of Sardinia and Corsica are known for their multitude of endemics. Butterflies in particular have received much attention. However, no comprehensive studies aiming to compare populations of butterflies from Sardinia and Corsica with those from the neighbouring mainland and Sicily have been carried out. In the present study, the eleven Satyrinae species inhabiting Sardinia and Corsica islands were examined and compared with continental and Sicilian populations by means of geometric morphometrics of male genitalia. Relative warp computation, discriminant analyses, hierarchical clustering, and cross‐validation tests were used to identify coherent distributional patterns including both islands and mainland populations. The eleven species showed multifaceted distributional patterns, although three main conclusions can be drawn: (1) populations from North Africa and Spain are generally different from those belonging to the Italian Peninsula; (2) populations from Sardinia and Sicily often resemble the North Africa/Spain ones; Corsica shows transitional populations similar to those from France; and (3) sea barriers represent filters to dispersal, although their efficacy appears to be unrelated to their extension. Indeed, the short sea straits between Sardinia and Corsica and between Sicily and the Italian Peninsula revealed a strong effectiveness with respect to preventing faunal exchanges; populations giving onto sea channels between Corsica and Northern Italy and between Sicily and Tunisia showed a higher similarity. A comparison of island and mainland distributions of the eleven taxa have helped to unravel the complex co‐occurrence of historical factors, refugial dynamics, and recent (post‐glacial) dispersal with respect to shaping the populations of Mediterranean island butterflies. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 195–212.     

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

Aim 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).     

β-Globin gene cluster haplotypes in Yanomama Indians from the Amazon region of Brazil

Summary Six polymorphic restriction enzyme sites in the beta-globin gene cluster were investigated in Yanomama Indians from the Amazon region of Brazil, using the polymerase chain reaction (PCR) technique. Four haplotypes were identified; the haplotype frequency distribution is similar to those reported for Polynesians, Micronesians and most Asian populations.     

Predicting distribution of <Emphasis Type="Italic">Zygaena</Emphasis> moths on West Mediterranean islands. Implications for biogeography and conservation (Lepidoptera Zygaenidae)

In this paper a conservation biogeography approach has been applied to predict distribution and conservation priorities in West Mediterranean Zygaena moths. The presence/absence matrix data for mainland region and for the three largest islands (Sardinia, Corsica and Sicily) has been analyzed. The analyses have been performed on individual species and revealed that species distribution in the Mediterranean mainland can be largely predicted. However, Sardinia and Corsica islands showed highly impoverished faunas while Sicily did not revealed a lower richness than predicted. Logistic regressions at individual species level showed that several taxa, predicted to be present in Sardinia and Corsica are actually absent. For Sicily the opposite trend was obtained and several unpredicted species actually occur on this island. Conversely to butterflies, ecological traits did not differ between predicted and unpredicted Sicilian species, suggesting that ancient and stochastic colonisations are responsible for the occurrence of several species. Due to the very low probabilities that relict populations could re-colonize islands following possible extinctions, they are suggested to deserve particular conservation efforts. In particular, Z. orana from Sardinia, Z. corsica from Corsica and Z. trifolii, Z. purpuralis and Z. carniolica from Sicily showed distinctive biogeographic patterns and/or particular rarity.     

Genetic structure of insular Mediterranean populations of the house mouse

The genetic structure of six western Mediterranean island populations of Mus musculus domesticus were investigated by means of an electrophoretic analysis at 34 loci and compared to that of five neighbouring mainland populations. No reduction in variability (H = 0.09 for both island and mainland samples) was observed in the island populations except for a very small island (6 ha), in which one-third of the variability was lost. Patterns of colonization inferred from a Wagner cluster analysis and the distribution of rare variants suggest that, although these island populations are clearly related to European mainland mice, their genetic structure is the result of multiple founding events from sources dispersed throughout the Mediterranean Basin. Furthermore, the presence of the same rare alleles in Sardinia, Corsica and Piana, suggest that the three islands share a common history of colonization.
Estimates of genetic distance and gene flow indicate that the level of genie differentiation is greater between island and mainland populations that between the latter due to geographic isolation. Multiple founder events and post-colonization evolution are the factors that best explain the observed levels of genie variability and differentiation in these Mediterranean islands.     

Similarities in the surnames of island and continental populations of the north-western Mediterranean area

This paper compares the structures of the surnames of 75 municipal populations living in six north-western Mediterranean regions. Its purpose is to unravel the relations between the local populations in Corsica and Sardinia and the links between these populations and those living in the Italian and French continental territory. On the basis of the matrix of similarity of surnames, some topological representations have been drafted showing the above-mentioned relations between populations under the light of their geographical position, their recent history and studies of genetic analysis. Corsica has an eterogeneous surname structure and evident similarity of the north with Tuscany and some centres of continental France. When only the populations of Sardinia were taken into consideration, it emerged that they differ among each other in relation to their geographical position and their history; when, instead, they were considered in relation to other populations outside the island, it was possible to observe that they form a highly different cluster. This study also identified many differences in the analysed geographical areas of Sardinia. In the minor islands - Elba, Giglio, Capraia - the structure of the surnames has a Tuscan origin as well as some similarity with other geographically distant areas, as in the case of the island of Giglio, if compared with some communities of Liguria.     

Genetic diversity and evolutionary history of the Tyrrhenian treefrog Hyla sarda (Anura: Hylidae): adding pieces to the puzzle of Corsica–Sardinia biota

The Corsica–Sardinia archipelago is a hotspot of Mediterranean biodiversity. Although tempo and mode of arrival of species to this archipelago and phylogenetic relationships with continental species have been investigated in many taxa, very little is known about the current genetic structure and evolutionary history subsequent to arrival. In the present study, we investigated genetic variation within and among populations of the Tyrrhenian treefrog Hyla sarda, a species endemic to the Corsica–Sardinia microplate and the surrounding islands, by means of allozyme electrophoresis. Low genetic divergence (mean D_nei = 0.01) and no appreciable differences in the levels and distribution of genetic variability (H_E: 0.06–0.09) were observed among all but one populations (Elba). Historical demographic and isolation‐by‐distance analyses indicated that this diffused genetic homogeneity could be the result of recent demographic expansion. Along with paleoenvironmental data, such expansion could have occurred during the last glacial phase, when wide and persistent land bridges connected the main islands and a widening of lowland areas occurred. This scenario is unprecedented among Corsica–Sardinia species. Together with the lack of concordance even among the few previously studied species, this suggests either that species had largely independent responses to paleoenvironmental changes, or that most of the history of assembly of the Corsica–Sardinia biota is yet to be written. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 159–167.     

Evidence supporting a single origin of the beta(C)-globin gene in blacks.

In order to characterize the origin(s) of the beta C-globin gene in blacks, 25 chromosomes bearing this gene were characterized at eight polymorphic restriction sites within the beta-globin gene cluster. Twenty-two of the 25 chromosomes were identical at all sites and possessed a haplotype seen only infrequently among beta A-bearing chromosomes in black Americans. Two different haplotypes were observed among the three exceptional chromosomes. These haplotypes were identical to the most common beta C allele in the 3' end of the beta-globin gene cluster, but differed in the 5' region. Partial haplotype analysis on an additional 14 beta C alleles demonstrated complete association with the typical beta C-associated polymorphisms in the 3' region of the cluster. These data can be most easily explained by a single origin of the mutation followed by spread of the mutation to other haplotypes through meiotic recombination 5' to the beta-globin gene.     

Molecular basis of HbE-beta-thalassemia and the origin of HbE in northeast Thailand: identification of one novel mutation using amplified DNA from buffy coat specimens

Amplification of DNA via polymerase chain reaction directly from a small amount of a buffy coat fraction was used to study the molecular basis of HbE-beta-thalassemia in the northeastern Thai population. Eight different mutations including the new one causing a beta o-thalassemia phenotype were detected. This novel mutation is an amber mutation at codon 26, which occurs at the same position as that of HbE; the most common hemoglobin variant in Southeast Asian countries. A pitfall in detection of the HbE mutation by restriction enzyme analysis was pointed out and differential diagnosis of the HbE mutation and the novel one by using allele specific oligonucleotide probes were described. Analysis of polymorphic restriction sites in the beta-globin gene cluster containing the beta E gene revealed two previously undescribed haplotypes in the Southeast Asian populations, which provide evidence for the multiple origins of beta E gene in Southeast Asian populations.     

Beta-globin gene haplotypes in Polynesians are predominantly southern Chinese in type

beta-Globin gene haplotypes obtained in Polynesian Samoans were similar to those described in Southern Chinese. An atypical HindIII restriction fragment length polymorphism detected with pRK29, a 3' beta-globin gene probe, was present at a gene frequency of 7% in Samoans. Haplotype patterns suggest that this polymorphism may have arisen by 1 or 2 mutational events. DNA haplotypes derived from the beta-globin gene cluster confirm nuclear and mitochondrial DNA data that Polynesian precursor populations were East Asian in origin.     

Conservation biogeography of large Mediterranean islands. Butterfly impoverishment, conservation priorities and inferences for an ecologica "island paradigm"

Conservation biogeography is considered the Cinderella of biological conservation. Nevertheless biogeography provides the basis for establishing species distributions over space and time, therefore conservation priorities among areas and individual species. We demonstrate that there is no need to simplify analyses by using subsets of species (rare species, endemics) as surrogates. In doing so, we apply strict biogeographical techniques to determine butterfly impoverishment on three of the west Mediterranean's largest islands (Sardinia, Corsica and Sicily). The analyses performed on species, both collectively and individually, reveal that regional species richness in the Mediterranean zone can be largely predicted by latitude, altitude and latitudinal range (maximum minus minimum latitude), but that Sardinia and Corsica have clearly impoverished faunas. Logistic regression at individual species level demonstrates that several species, predicted to be present in these islands on the basis of their continental distributions, are actually absent. When compared with species that are present in these islands, such missing species are disclosed as having ecological traits which reduce their colonization capability. Probabilities of occurrence are calculated for each species on each island; they reflect the potential for each butterfly species to migrate to and colonise each island, and can be considered as a measure of conservation value. As such, species present on islands but having low immigration probabilities are predicted to represent isolated populations from the mainland that are unlikely to re-colonize the islands in the case of extinction. Island endemic species and races are shown to have lower occurrence probabilities compared to widespread species occurring on islands and illustrate the usefulness of occurrence probabilities for identifying isolated populations in need of conservation attention.     

Genetic differences among mainland and insular forms of the Citril Finch Serinus citrinella

The Citril Finch Serinus citrinella breeds in several mountains of central and southern Europe and on Corsica, Sardinia and Tuscany islands. Several studies have emphasized differences in phenotype and vocalization, and some authors consider mainland and insular forms to be two distinct species. A genetic approach based on the sequences of a mitochondrial DNA fragment was used to estimate genetic distance separating several populations. Individuals from the Alps and the Pyrenees belong to one group and the individuals from Corsica to the second. These results, discussed together with data on ecology, biometrics and vocalization, suggest keeping only one polytypic species which includes two distinct forms.     

Distribution of genetic diversity within and between Western Mediterranean island populations of the black rat Rattus rattus (L. 1758)

Genetic diversity was estimated by allozyme analysis at 26 loci in black rat populations (Rattus rattus) from 15 western Mediterranean islands (Hyéres, Corsica, Sardinia and related islets). Although overall variability levels were low (H = 0.025), the mean heterozygosity values for the islands were similar to those for three reference mainland populations. Within the islands, however, genetic diversity varied in relation to island size and geographic isolation. In particular, most small insular populations were significantly more variable than those on both large and isolated islands. The generic relationships between island populations were established by F_ST analyses indicating possible geographic origins and patterns of colonization. The maintenance of unexpectedly high levels of variability in the small island populations is discussed in relation to changes in the demographic and social structure observed in these populations. These island populations of black rat illustrate how genetic diversity may be efficiently maintained in a series of interconnected spatially fragmented populations.     

Hemoglobin E in Europeans: further evidence for multiple origins of the beta E-globin gene

We have determined haplotypes for the known restriction site polymorphisms in the beta-globin gene cluster in two families of European ancestry containing individuals who are heterozygous for hemoglobin E. In both families, the beta E mutation is associated with a haplotype not previously found among the haplotypes of beta E chromosomes in Southeast Asia. Moreover, in one family, the mutation is present in a beta-gene framework not found in beta E chromosomes of Southeast Asia. These data provide further evidence of multiple independent origins of the beta E mutation in human populations.     

Population structure in Mediterranean islands and risk of genetic invasion in Culexpipiens L. (Diptera: Culicidae)

The mosquito Culex pipiens is subjected to organophosphate treatments in both Corsica and southern Sardinia, but the resistance gene A2-B2, which is currently in a worldwide expansion, has only reached Sardinia. In order to understand this situation, the genetic structure of populations sampled in Sardinia and Corsica was assessed using 15 isozymes. Two loci (HK1 and HK2) were not taken into account because of the possibility of selection. For trie other loci, statistical independence was not rejected for all possible pairs, and no deviation from Hardy-Weinberg expectations was apparent. Low but significant genie differentiation was present between Corsica and Sardinia, as well as between northern and southern Sardinia, despite a large number of effective migrants per generation. These results are discussed in the context of the high probability of extinction/recolonization of breeding sites, the flight migration ability of this mosquito, and the pleiotropic cost of insecticide resistances genes. It is concluded that A2-B2 resistance is unlikely to reach Corsica from southern Sardinia, unless accidental human transportation occurs.     

The role of western Mediterranean islands in the evolutionary diversification of the spotted flycatcher Muscicapa striata,a long‐distance migratory passerine species

We investigated the evolutionary history of the spotted flycatcher Muscicapa striata, a long distance migratory passerine having a widespread range, using mitochondrial markers and nuclear introns. Our mitochondrial results reveal the existence of one insular lineage restricted to the western Mediterranean islands (Balearics, Corsica, Sardinia) and possibly to the Tyrrhenian coast of Italy that diverged from the mainland lineages around 1 Mya. Mitochondrial genetic distance between insular and mainland lineages is around 3.5%. Limited levels of shared nuclear alleles among insular and mainland populations further support the genetic distinctiveness of insular spotted flycatchers with respect to their mainland counterparts. Moreover, lack of mitochondrial haplotypes sharing between Balearic birds (M. s. balearica) and Corso‐Sardinian birds (M. s. tyrrhenica) suggest the absence of recent matrilineal gene flow between these two insular subspecies. Accordingly, we suggest that insular spotted flycatchers could be treated as one polytypic species (Muscicapa tyrrhenica) that differs from M. striata in morphology, migration, mitochondrial and nuclear DNA and comprises two subspecies (the nominate and M. t. balearica) that diverged recently phenotypically and in mitochondrial DNA and but still share the same nuclear alleles. This study provides an interesting case‐study illustrating the crucial role of western Mediterranean islands in the evolution of a passerine showing high dispersal capabilities. Our genetic results highlight the role of glacial refugia of these islands that allowed initial allopatric divergence of insular populations. We hypothesize that differences in migratory and breeding phenology may prevent any current gene flow between insular and mainland populations of the spotted flycatcher that temporarily share the same insular habitats during the spring migration.     

Phylogeny of human beta-globin haplotypes and its implications for recent human evolution

The evolutionary histories and relationships among African, Eurasian, and Pacific Island populations are investigated by using observations on five polymorphic restriction sites in the beta-globin gene cluster. We present new data on 222 chromosomes from a global sample and combine these with previously published observations on 591 chromosomes. It is shown that the data are rich in rare haplotypes and that rare variants are not helpful for standard methods of population structure analysis. Consequently, a new approach is developed. We first consider the phylogeny of beta-globin haplotypes. The roles of mutation, gene conversion, and recombination in the generation of haplotype diversity are specifically focused upon. The relationships among human populations are then inferred from the phylogenetic relationships among the haplotypes, their presence or absence, and frequencies within populations. Questions regarding whether or not a phyletic process can account for relationships among the major geographical populations and whether or not an extant human population exhibits the qualities that would be expected of an ancestral group are addressed. The results of this analysis support an African origin for modern Homo sapiens and a phyletic structuring of the major geographical regions. However, it is shown that divergence times for the various populations cannot be determined from these data.     

Phylogeography and founder effect of the endangered Corsican red deer (<Emphasis Type="Italic">Cervus elaphus corsicanus</Emphasis>)

Red deer (n = 149) from eight geographical locations, including the endangered endemic populations from the Tyrrhenian islands (Sardinia and Corsica), were analysed at eight polymorphic microsatellite loci. Two questions were addressed: (1) Is there a founder effect in the Corsican population, which was reintroduced to the island using Sardinian deer after the species’ extinction on Corsica? (2) What is the origin of the Tyrrhenian or Corsican red deer (Cervus elaphus corsicanus)? Our results showed signs of a founder effect for the red deer on Corsica in that these deer showed differentiation from the Sardinian population as measured by F_ST values, assignment tests (with and without a priori definition of populations) and individual-based dendrograms. Genetic variability, however, did not differ significantly between the two populations. With respect to the phylogeography of C. e. corsicanus we found that both deer from North-Africa and Mesola on the Italian mainland were genetically close to the Corsican red deer, but phylogenetic trees based on genetic distances were only poorly supported statistically. Among all populations studied the Mesola red deer showed the lowest distance values from Corsican red deer and yielded allele frequencies that were more similar to those of C. e. corsicanus than were those of North-African red deer. These results are in line with recent palaeontological and archaeozoological findings which suggest that the Corsican red deer is derived from small Italian red deer introduced from the mainland to Sardinia and Corsica during the Late Neolithic and just before the beginning of Classical Antiquity, respectively. They also suggest a possible recent introduction of Tyrrhenian red deer to North-Africa (rather than the other way around), thus accounting for the close genetic relationship (especially based on mitochondrial DNA) that has repeatedly been found between C. e. corsicanus and C. e. barbarus.