Corsican Populations Research Articles

Homozygous deletion of HFE is the common cause of hemochromatosis in Sardinia

We recently characterized an Alu-mediated recombination causing the loss of the complete HFE gene sequence. Here, we describe the case of a novel homozygous patient. We further show that HFE deletion results from a founder effect and that it represents the common cause of hemochromatosis in Sardinia. We recently reported the case of a 47-year old woman with a moderate iron overload due to an Alu-mediated recombination causing the loss of the complete HFE gene sequence.1 The same chromosomal alteration was identified by Pelucchi and co-workers in another woman. Despite a younger age at diagnosis (29 years), their patient showed a more impressive iron overload.2 A third case, a man, came to our attention. At the age of 44 he showed a transferrin saturation level of 80% and a serum ferritin level of 2080 μg/L. He was not genotyped for the p.C282Y and p.H63D variations because of an inability to amplify the HFE exons 2 and 4. We confirmed absence of the HFE gene in this patient but we were also interested in its origins. Indeed, the patient and both previously reported women were of Sardinian descent. The Sardinian population is genetically differentiated from the other Caucasian populations.3 It represents a genetic isolate where the p.C282Y mutation is considered as rare or even absent.4 This led us to assume that the HFE deleted allele was present at the population level and, related to a founder effect, was the common cause of hemochromatosis in this Mediterranean island. To characterize the contribution of the HFE deletion in the Sardinian population, we first established the frequency of this mutation in a sample set of 198 controls who originated from different districts of the island (90% of them were from South Sardinia, while the others originated from central and Northern parts of the island). Genotype analysis was performed using a rearrangement specific PCR, as previously described.1 The HFE deletion was detected at the heterozygous state in 4 subjects, giving a carrier frequency of 2.02% and an estimated homozygous frequency of 0.01% (one person in 10,000). We also looked for the p.C282Y mutation. It was identified at the heterozygous state in one of 193 subjects (0.52%). We next proceeded to analyze polymorphic microsatellite repeat markers flanking HFE. Based on results from the consanguineous family reported in our initial study,1 we selected a set of informative markers and defined a first chromosomal region of 12.049 megabases (Mb). This chromosomal region encompassed two HLA-class I loci which were added to the haplotypes analysis. Final results are summarized in Table 1 and Figure 1. A conserved haplotype of 3.150 Mb was deduced from the consideration of alleles shared by the 2 homozygous cases identified by us (P1, P2), and the 4 mutation carriers (MC 1–4). However, a recombination event could account for differences in HLA-A, HLA-B and D6S273 alleles of one of the study subjects (MC 3 in Table 1). This allowed us to consider a common haplotype of 7,359 Mb. Figure 1. Physical map of the chromosome 6 region flanking HFE. Distance between the D6S1621 and D6S2414 marker is indicated in grey; the arrow marks a possible ancestral haplotype. Distance between the D6S1621 and D6S1022 markers is indicated in black; the arrow ... Table 1. Allelic distribution of markers surrounding HFE. *The parentheses mark differences between the 6 individuals; these differences are probably related to a recombination event on chromosome 6 of the mutation carrier number 3. By their position on the same maritime routes, the histories of the West Mediterranean islands are very similar. Studies based on HLA polymorphisms have confirmed singularity of these populations, and have further revealed a close relationship between the Sardinian and Corsican populations. However, it must be pointed out that the HLA-A*2-B*58 haplotype is frequent in Sardinia (4.9%) and almost absent in the other West Mediterranean islands (Corsica and Balearic Islands). In fact, this haplotype could be of African origin.5 If so, comparing frequency of the HFE deleted allele (2%) to that of the HLA-A*2-B*58 haplotype (4.9%), one may assume that deletion of the HFE gene arose in the Sardinian population after contacts with African populations. But an African ancestry for the HFE deletion cannot be completely excluded. To conclude, we show that HFE deletion results from a founder effect rather than that of a mutational hotspot. We also demonstrate that, with an estimated homozygous frequency of one person in 10,000, HFE deletion is the common cause of hemochromatosis in Sardinia.

Local Individual Preferences for Nest Materials in a Passerine Bird

BackgroundVariation in the behavioural repertoire of animals is acquired by learning in a range of animal species. In nest-building birds, the assemblage of nest materials in an appropriate structure is often typical of a bird genus or species. Yet plasticity in the selection of nest materials may be beneficial because the nature and abundance of nest materials vary across habitats. Such plasticity can be learned, either individually or socially. In Corsican populations of blue tits Cyanistes caeruleus, females regularly add in their nests fragments of several species of aromatic plants during the whole breeding period. The selected plants represent a small fraction of the species present in the environment and have positive effects on nestlings.Methodology/Principal FindingsWe investigated spatiotemporal variations of this behaviour to test whether the aromatic plant species composition in nests depends on 1) plant availability in territories, 2) female experience or 3) female identity. Our results indicate that territory plays a very marginal role in the aromatic plant species composition of nests. Female experience is not related to a change in nest plant composition. Actually, this composition clearly depends on female identity, i.e. results from individual preferences which, furthermore, are repeatable both within and across years. A puzzling fact is the strong difference in plant species composition of nests across distinct study plots.Conclusions/SignificanceThis study demonstrates that plant species composition of nests results from individual preferences that are homogeneous within study plots. We propose several hypotheses to interpret this pattern of spatial variation before discussing them in the light of preliminary results. As a conclusion, we cannot exclude the possibility of social transmission of individual preferences for aromatic plants. This is an exciting perspective for further work in birds, where nest construction behaviour has classically been considered as a stereotypic behaviour.

Taxonomy, skull diversity and evolution in a species complex of Myotis (Chiroptera: Vespertilionidae): a geometric morphometric appraisal

Phylogenetic relationships between taxa are not necessarily reflected by morphological data due to widespread homoplasy and convergence. However, combining morphological and molecular data provides insights into the evolution of biological forms and into the potential factors involved. Here we focus on a complex of three taxa of bats with unclear taxonomic affinities: Myotis myotis, Myotis blythii and Myotis punicus. Traditional morphometric methods failed to separate them, whereas recent molecular-based studies suggested that they constitute separate biological species. In the present study, landmark-based geometric morphometrics methods have been used to analyse the skull variability of 218 specimens belonging to this species complex. Patterns of size and shape delimitate three morphological groups that are congruent with the proposed taxonomic assignments, and therefore support species rank for all three major groups. These morphometrics results, however, suggest that M. myotis and M. punicus share shape characteristics in the rostrum and in the posterior part of the skull that differ from M. blythii. Because previous molecular phylogenetic analyses suggested that M. myotis and M. blythii are sister species, we interpret the similitude in skull morphology between M. myotis and M. punicus as a convergence probably related to their similar feeding habits. Within the taxon M. punicus, the skull of Corsican and Sardinian populations significantly differs from that of Maghrebian ones, suggesting the existence of further cryptic taxonomic diversity.

Extirpation and reintroduction of the Corsican red deer Cervus elaphus corsicanus in Corsica

AbstractThe Endangered Corsican red deer Cervus elaphus corsicanus was extirpated from Corsica in the early 1970s, at which time the Sardinian population fell to <250 individuals. The Sardinian authorities agreed to protect this subspecies and to secure its reintroduction in Corsica, a natural choice, considering ethological and historical descriptions. Since the beginning of 1985, when the first deer destined for captive breeding and eventual reintroduction arrived in Corsica, the population increased from 13 Sardinian founders to 106 captive animals under constant monitoring in three enclosures (Quenza, Casabianda and Ania di Fium'Orbu). The sites of Quenza, Chisà and Santo Pietro di Venaco were selected by the Regional Nature Park of Corsica for the reintroduction into the wild that began in 1998. Currently the size of the whole Corsican population is c. 250 individuals. These deer are still closely monitored and studied, both in enclosures and in the wild, to secure the long-term conservation of this subspecies. The Corsican and Sardinian populations together now total slightly >1,000, and the subspecies could therefore be downgraded to Near Threatened on the IUCN Red List.

Mediterranean populations of the lesser white‐toothed shrew (Crocidura suaveolens group): an unexpected puzzle of Pleistocene survivors and prehistoric introductions

An earlier study revealed the strong phylogeographical structure of the lesser white-toothed shrew (Crocidura suaveolens group) within the northern Palaearctic. Here, we aim to reconstruct the colonization history of Mediterranean islands and to clarify the biogeography and phylogeographical relationships of the poorly documented Middle East region with the northern Palaearctic. We performed analyses on 998-bp-long haplotypes of the mitochondrial cytochrome b gene of 143 samples collected around the Mediterranean basin, including islands and the Middle East. The analyses suggest that the Cypriot shrew belongs to the rare group of relict insular Pleistocene mammal taxa that have survived to the present day. In contrast, the Cretan, Corsican and Menorcan populations were independently introduced from the Middle East during the Holocene. The phylogeographical structure of this temperate Palaearctic species within the Middle East appears to be complex and rich in diversity, probably reflecting fragmentation of the area by numerous mountain chains. Four deeply divergent clades of the C. suaveolens group occur in the area, meaning that a hypothetical contact zone remains to be located in central western Iran.

Geographical differentiation, acoustic adaptation and species boundaries in mainland citril finches and insular Corsican finches, superspecies Carduelis [citrinella

AbstractAim In birds, differentiation of acoustic characters is an important mechanism of reproductive isolation that may lead to an ethological–acoustic barrier, resulting in the formation of new species. We examined acoustic variation in mainland citril and insular Corsican finch populations, with the aim of assessing the degree of acoustic differentiation between both members of the superspecies Carduelis [citrinella] and documenting possible variation between local subpopulations that are geographically isolated.Location We chose study sites throughout the geographical ranges of citril and Corsican finches. For the citril finch, we obtained samples from the Black Forest (Germany), the Cevennes (France) and the Pyrenees (Spain); for the Corsican finch, we obtained samples from the islands Capraia and Sardinia (Italy) and Corsica (France).Methods We analysed frequent contact calls and elements of the perch song. Vocalization patterns of the study populations were compared by means of discriminant and hierarchical cluster analyses.Results There were significant differences in vocalization characteristics of perch songs and contact calls, which permitted unambiguous discrimination of citril and Corsican finch populations. However, we also detected significant differences in contact calls between mainland citril finch subpopulations. There was a pattern of clinal variation in vocalization: short, steeply modulated signals in the northern part of the geographical range (Black Forest) and long, shallowly modulated signals in the southern part (Pyrenees).Main conclusions Acoustically, mainland citril and insular Corsican finches separate well in their contact calls and perch songs. However, variation in the two vocalization patterns between subpopulations of mainland citril finches indicates that acoustic characteristics can evolve very quickly, not only on islands but also on the mainland. Local habitat differences may play a crucial role in the rapid evolution of these signals under full or partial isolation of small subpopulations. To judge the importance of signal variation as a pre‐mating isolating barrier, future studies will have to determine whether members of the distinct subpopulations are able to match their signals to each other if they re‐meet, and whether intraspecific species recognition is still possible.

Simultaneous pituitary–gonadal recrudescence in two Corsican populations of male blue tits with asynchronous breeding dates

Animal populations living in geographically variable environments respond to different selection pressures. The adaptive character of the responses to environmental information determines the degree of synchrony of the breeding period with local optimal conditions. An example is provided by two populations of Mediterranean blue tits ( Parus caeruleus) in Corsica, breeding in different habitats, with a 1-month difference in the onset of egg laying. This difference in the onset of lay is supposed to be adaptive because, although chicks from both populations are raised mostly on caterpillars, the timing of the appearance of caterpillars is earlier for populations of tits associated with deciduous oak trees than those associated with evergreen oak trees. Here, we show that, despite the difference in the timing of egg laying, males from these two populations start seasonal hypothalamo–hypophysial–testicular development at approximately the same time, in late winter. Specifically, the vernal recrudescence of brain GnRH-I perikarya and fibers, testes volume and song activity began around the same dates and proceeded at the same pace in late winter in both populations. Plasma testosterone and LH levels displayed seasonal variations that were shifted by less than 2 weeks compared to the 1-month difference in egg laying periods. We hypothesize that the strong selection pressures on these two populations to adapt the timing of their breeding seasons to their local environment may have acted mostly on the female egg laying dates, and not so much on the initiation and rate of seasonal recrudescence of the hypothalamo–hypophysial–testicular activity in males.

Genetic variation of the weasel ( Mustela nivalis) in Corsica based on mitochondrial control region sequences

The weasel (Mustela nivalis, Linnaeus, 1766) is widespread throughout the entire western Palaearctic region, with the exception of several Atlantic islands (Ireland, Iceland and Canary islands). This species is one of the most common Mustelidae inhabiting islands of the Palaearctic region (Masseti 1995). According to De Marinis and Masseti (2003) M. nivalis inhabits all Mediterranean islands larger than 240 km. As often reported for small mammals (Blondel 1995) and specially for rodents (Alder and Levins 1994; Michaux et al. 2002), insular and mainland populations often differ by morphological differences. Insular populations of M. nivalis present several morphological differences, such as larger body size and darker coat colouration, differences that have led to the description of potentially one subspecies per island (Beaucournu and Grulich 1968; De Marinis 1996). In Corsica, an important morphological and morphometrical differentiation from the south of France has been observed by Beaucournu and Grulich (1968) and Salotti (1992). However, no data are available concerning genetic variation between Corsican and European mainland populations. The aim of this study is therefore to compare weasel populations between Corsica and the

Endocrine correlates of the breeding asynchrony between two corsican populations of blue tits ( Parus caeruleus)

Analyses of the development of the reproductive system in seasonally breeding birds in the framework of long-term ecological studies are rare. Here, we present the first results of such a study in two Corsican populations of a European passerine bird, the blue tit ( Parus caeruleus). The two study populations occupy different oak habitats and are separated by only 25 km. Despite their close proximity, they show a one-month difference in onset of egg laying, even after controlling for altitude. This micro-geographic difference in breeding date appears adaptive because both study populations raise chicks when food is most plentiful. In our study, males reached their maximum song activity during the egg-laying stage while maximal testosterone levels and testes sizes were reached 2–3 weeks before egg laying. The rate of development of the reproductive system in males was much faster in the earlier population, in spite of a similar onset of gonad development and song activity for the two study populations. No change in the volume of the song-control nuclei (HVC and RA) could be detected during the study period. Development of brain nuclei was completed 2–3 months before the beginning of intense sexual activity.

Environmental gradients and population divergence contribute to variation in cuticular wax composition in Juniperus communis

The alkane fraction of cuticular lipids was analyzed in populations of Juniperus communis var. saxitilis and var. montana from the Pyrenees, the Alps, Corsica and California. The New World and Old World populations showed highly divergent alkane chain length distributions that were not correlated with climatic variables, suggesting a strong phylogeographic pattern to this holarctic species. Within Europe, the Corsican populations formed a distinct clade, but there was no consistent separation of populations from the Alps and from the Pyrenees. An elevational transect within the Pyrenees revealed a complex pattern for weighted mean alkane chain length ( N) which was greatest at both low and at high elevations. Dispersion about this mean ( d) showed a linear increase with elevation. A matrix of distances based on alkane composition for the Pyrenees populations was correlated with a distance matrix of temperature and an aridity index. Greater weighted mean alkane chain length at low and at high elevations was possibly a result of adaptation to minimize cuticular permeability due to high summer temperatures at low elevation and freezing causing physiological drought at high elevations. It seems probable that environment interactions determining selection forces, together with direct environmental effects may lead to the complex patterns of N and d observed over this elevational transect.

Mitochondrial DNA phylogeography and population history of Meladema diving beetles on the Atlantic Islands and in the Mediterranean basin (Coleoptera, Dytiscidae).

The phylogeny and population history of Meladema diving beetles (Coleoptera, Dytiscidae) were examined using mitochondrial DNA sequence from 16S ribosomal RNA and cytochrome oxidase I genes in 51 individuals from 22 populations of the three extant species (M. imbricata endemic to the western Canary Islands, M. lanio endemic to Madeira and M. coriacea widespread in the Western Mediterranean and on the western Canaries), using a combination of phylogenetic and nested clade analyses. Four main lineages are observed within Meladema, representing the three recognized species plus Corsican populations of M. coriacea. Phylogenetic analyses demonstrate the sister relationship of the two Atlantic Island taxa, and suggest the possible paraphyly of M. coriacea. A molecular clock approach reveals that speciation within the genus occurred in the Early Pleistocene, indicating that the Atlantic Island endemics are not Tertiary relict taxa as had been proposed previously. Our results point to past population bottlenecks in all four lineages, with recent (Late-Middle Pleistocene) range expansion in non-Corsican M. coriacea and M. imbricata. Within the Canary Islands, M. imbricata seems to have independently colonized La Gomera and La Palma from Tenerife (although a colonization of La Palma from La Gomera cannot be discarded), and M. coriacea has independently colonized Tenerife and Gran Canaria from separate mainland lineages. In the Mediterranean basin this species apparently colonized Corsica on a single occasion, relatively early in its evolutionary history (Early Pleistocene), and has colonized Mallorca recently on multiple occasions. On the only island where M. coriacea and M. imbricata are broadly sympatric (Tenerife), we report evidence of bidirectional hybridization between the two species.

Chloroplast DNA variation of white oaks in Italy

Polymorphism in non-coding regions of the chloroplast genome was studied in four white oak species (Q. robur L., Q. petraea (Matt.) Liebl., Q. pubescens Willd. s.l., and Q. frainetto Ten.) in Italy (mainland and associated islands, including Corsica). A total of 924 trees (194 populations) was analysed. This data set also includes results previously obtained on 20 Italian and Corsican populations [Genetics 146 (1997) 1475]. Most of the sampled individuals were classified as Q. pubescens (73.5%). Thirty-four populations out of 194 (17.5%) were polymorphic. The level of population sub-division was very high, as expressed by the value of the coefficient GST=0.870 (hS=0.100, hT=0.776). The highest value of total genetic diversity was calculated in Sardinia and in central Italy; the lowest in southern Italy. The highest values of differentiation among populations occurred in Sardinia (GST=1), and in Corsica (0.927). We found evidence that the Italian oak populations of today mainly originated from Sicilian and Balkan refugia. Their origin and migration routes are more easily seen by considering data separately for the four sampling regions: the north, the centre, the south, and the three main islands. The C (=blue) lineage was common in the southern part of Italy. This may be a trace of a migration from the Balkans via the Adriatic bridge during quaternary cold periods. The northern part of the country had a set of haplotypes similar to the other Alpine regions. Most Sicilian populations are fixed for one of the two haplotypes that probably originated in the island: one spread over the whole Italian peninsula, whereas the other one did not reach the Alps. Results showed that the Appennines may have played a role in the distribution of the haplotypes western and eastern of the mountains chain.

Genetic diversity within and among Pinus pinaster populations: comparison between AFLP and microsatellite markers.

Twenty-three populations of Pinus pinaster (13 Aquitaine populations and 10 Corsican populations) were analysed at three microsatellite loci and 122 AFLP loci. The aims of the study were: (i) to compare levels of within-population and among-population diversity assessed with both kinds of markers; (ii) to compare Aquitaine and Corsican provenances of P. pinaster; and (iii) to know if both markers gave the same information for conservation purposes. Classical population genetics statistics were estimated and the ranking of populations obtained using different markers and/or parameters were compared by computing Spearman's rank correlations. Even though microsatellites showed a higher within-population diversity, they showed the same level of differentiation as AFLP markers. Moreover, both markers also showed a higher genetic diversity in the Aquitaine provenance and a higher differentiation among Corsican populations. AFLPs and microsatellites gave different population diversity rankings. Consequently, the results do not support the potential population identification within each provenance for conservation purposes.

Biochemical biogeography and evolutionary relationships among the six known populations of Stenasellus racovitzai (Crustacea, Isopoda) from Tuscany, Corsica and Sardinia

Allozymic variation at 15 enzymatic loci was studied in six populations of the stygobiont isopod Stenasellus racovitzai. This species belongs to the exclusively stygobiont family Stenasellidae, characterised by morphological, ecological and biogeographical features indicating an extremely ancient separation from a presumed surface ancestor. Here we present allozymic data for six populations of S. racovitzai: two from Tuscany, two from Corsica and two from Sardinia. Levels of genetic divergence indicate differentiation at the species level for four distinct groups of S. racovitzai (one from Tuscany, one from Corsica and two from Sardinia) despite their basic morphological uniformity. In addition, genetic data for the two Corsican populations support the hypothesis of a differential spatial distribution of young offspring and adults. Phylogenetic relationships indicate a more ancient separation of the two Sardinian species, while the Corsican and Tuscan species seem to be more recent and related to each other. Relationships among the populations agree quite well with the palaeogeographical events that affected the sampling area and strongly support the hypothesis that the present distribution resulted from vicariance rather than dispersal.

Geographical patterns of isozyme variation in Mediterranean populations of perennial ryegrass

Twenty-four natural populations of perennial ryegrass, sampled from the Mediterranean area (Italy, Corsica, Sardinia, South of France), have been studied for allelic variation at 13 enzyme loci. The total genetic diversity results mainly from the within-population component whereas a part of the between-population component can be explained by the geographical origins of the populations. Relationships between accessions have been studied using cluster and multivariate analyses such as principal component and discriminant analyses. Finally, the frequency and distribution of the most discriminating allele have been represented on geographic maps. The results indicate that Corsican populations are similar to Italian accessions whereas both French and Sardinian populations differ from all the others. The origins and relationships between each geographical group of accessions are discussed and, taking historical factors into account, we can suggest that Corsican populations have been introduced from Italy to the eastern side of the island.

Breeding Ecology of the Blue Tit Parus caeruleus in Eastern Spain: A Comparison with Other Localities with Special Reference to Corsica

Aspects of the breeding ecology of the Blue Tit Parus caeruleus were studied in intermediate stages of succession in a holm oak forest at Monte Poblet (eastern Spain) from 1985 to 1991. In different years the density in two plots without nestboxes varied between 1.0 and 6.5 pairs per 10 ha. Nestbox introduction seems to have increased the density of breeding pairs. The mean laying date was earlier (6 vs. 13 May) in low altitude (500-750 m a.s.l.) plots than in a high altitude (900-1000 m a.s.l.) plot, but clutch size (6.9 vs. 6.5 eggs) was not significantly different (mean 6.6 eggs). No differences in mean laying dates were found between years. Significant differences in clutch size were found only between two years at the high altitude site. There was a slight, non-significant, seasonal decline in clutch size. No second clutches were laid. These results are discussed in the context of other Mediterranean studies with special focus on the differences and similarities between Corsican and mainland populations. It is shown that most of the characteristics of the Corsican population (i.e. density, habitat use, laying date, clutch size, number of broods per year) are shared by some populations on the mainland. On the other hand, some breeding traits of Blue Tit populations in southern France are closer to those of Central and North European populations than to the Iberian ones.

Bird Species Impoverishment, Niche Expansion, and Density Inflation in Mediterranean Island Habitats

The causes and consequences of three classical features of insular faunas, namely species depauperization, increased population density, and increased niche breadth, were investigated by comparing bird communities in relation to habitat characteristics along ecological successions in southern France and the island of Corsica. Each succession comprised six habitats, which were selected on the basis of vegetation structure. There were nearly as many bird species in Corsica as on the mainland in the entire successional sequence, but fewer species in the late successional forested stages and more species in shrubby stages on the island, because of the shift of many typically forest—dwelling species into matorrals (evergreen Mediterranean shrub communities). Species utilized more habitats and subdivided them less in Corsica than on the mainland. The Corsican forest bird community was composed of a few small—sized resident species with very high populations. Thus insular faunas are very different in early and late stages of succession. These results differ in several respects from those of many earlier mainland—island comparisons, and emphasize the need for comparing a series of habitats between the island and the mainland, rather than a single habitat, as has generally been the case. These differences in species allocation to habitats between the island and the mainland are better explained by two non—mutually exclusive hypotheses than by a release in interspecific competition. The first is the so—called "habitat appropriateness" hypothesis, which predicts that the more closely a habitat resembles that which is optimal for a species on the mainland, the more species will compensate for the population densities of absent competitors. This is the case for the bird communities of the Corsican forests, which exhibit the main features of an insular syndrome, i.e., species impoverishment, high population densities, and intraspecific spillover. It is suggested that given an equitable climate and a stable level of resources, survival on the island is higher than on the mainland, dispersal is restricted, and populations expand into shrubby habitats as a result of spillover from optimal habitats. This explanation is further supported by the second hypothesis, named the "defense hypothesis" (Stamps and Buechner 1985), which stipulates that a stable allocation of resources all the year around in the benign insular environment results in a decrease in the vigor of territorial defense, a decrease in territory size, and an increase in territory overlap, which in turn allows for more individuals to coexist in the same amount of space. Long—term comparative studies on the population biology of tits of the genus Parus have shown that, compared to their mainland counterparts, Corsican populations of tits exhibit social structures supporting this hypothesis. Finally, a clear distinction between communities of early and late stages of succession is discussed in the light of history and speciation patterns in the Mediterranean area. The historical approach helps to explain the convergence of bird community composition on the mainland and the island at late successional stages.

Survie en milieu insulaire : quelle stratégie? Le cas des mésanges en Corse

The breeding biology and demography of Blue tit (Parus caeruleus) and Coal tit (Parus ater) populations of southern France and Corsica were compared from 1976 to 1980. The following differences between the mainland and the island populations were found : 1. — The onset of the breeding season is delayed in Corsica, egg-laying beginning three to four weeks later than on the mainland. 2. — The clutch-size is smaller on the island, the clutch averaging three more eggs on the mainland. 3. — The mortality of the nestlings is also much higher in Corsica than in southern France, due to heavy parasitism by Trypocalliphora sp. and food shortage which cause heavy mortality. 4. — However, the survival rate of adult tits is higher in Corsica than on the mainland. 5. — Contrary to what is the rule in southern France, Corsican tits do not apparently breed at the time of maximum food abundance. The demographic strategies of the Corsican populations of Blue and Coal tits are apparently K-selected.