The American brine shrimp as an exotic invasive species in the western Mediterranean

The hypersaline environments and salterns present in the western Mediterranean region (including Italy, southern France, the Iberian Peninsula and Morocco) contain autochthonous forms of the brine shrimp Artemia, with parthenogenetic diploid and tetraploid strains coexisting with the bisexual species A. salina. Introduced populations of the American brine shrimp A. franciscana have also been recorded in these Mediterranean environments since the 1980s. Based on brine shrimp cyst samples collected in these countries from 1980 until 2002, we were able to establish the present distribution of autochthonous brine shrimps and of A. franciscana, which is shown to be an expanding invasive species. The results obtained show that A. franciscana is now the dominant Artemia species in Portuguese salterns, along the French Mediterranean coast and in Cadiz bay (Spain). Co-occurrence of autochthonous (parthenogenetic) and American brine shrimp populations was observed in Morocco (Mar Chica) and France (Aigues Mortes), whereas A. franciscana was not found in Italian cyst samples. The results suggest these exotic A. franciscana populations originate as intentional or non-intentional inoculations through aquacultural (hatchery effluents) or pet market activities, and suggest that the native species can be rapidly replaced by the exotic species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Highly repetitive DNA sequence in parthenogeneticArtemia

Summary The study of the structural organization of the eukaryotic genome is one of the most important tools for disclosing the evolutionary relationships between species.Artemia (Crustacea, Phyllopoda) offers a very interesting model for speciation studies. The genus, distributed all over the world, comprises both bisexual sibling species and parthenogenetic populations, exhibiting different chromosome numbers (diploidy, polyploidy, and heteroploidy).Digestion of genomic DNA of the parthenogeneticArtemia sp. from Tsing-Tao (China) with the restriction enzymes Eco RI and Alu I reveals that a highly repetitive sequence of 133 bp is present. The Eco RI fragment has been cloned and characterized by genomic organization. The distribution of the Eco RI family of repeats was also studied in several bisexual and parthenogeneticArtemia populations and compared with an Alu I repetitive fragment previously identified inArtemia franciscana.     

Speciation in the Artemia genus: Mitochondrial DNA analysis of bisexual and parthenogenetic brine shrimps

From the cloned mitochondrial DNAs (mtDNAs) isolated from two bisexual species, one Mediterranean, Artemia salina, and one American, Artemia franciscana, and two parthenogenetic (diploid and tetraploid) strains of Artemia parthenogenetica collected in Spain, physical maps have been constructed and compared. They are extremely different among themselves, much more than the differences between Drosophila melanogaster and D. yakuba and in the same range of different mammalian species such as mouse/rat or man/cow. The nucleotide sequences of two regions of mtDNA encoding parts of the cytochrome c oxidase subunit I (COI) and cytochrome b (Cytb) genes have been determined in the two bisexual species and the two parthenogenetic strains. Comparisons of these sequences have revealed a high degree of divergence at the nucleotide level, averaging more than 15%, in agreement with the differences found in the physical maps. The majority of the nucleotide changes are silent and there is a strong bias toward transitions, with the CT substitutions being highly predominant. The evolutionary distance between the two Artemia parthenogenetica is high and there is no clear relationship with any of the bisexual species, including the one present nowadays in Spain. Using a combination of molecular (mtDNA) and morphological markers it is possible to conclude that all of these Artemia isolates should be actually considered as belonging to different species, even the two Artemia parthenogenetica diploidica and tetraploidica.On sabbatical leave from Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense de Madridearly Italian artemiologists to designate the Medi-Beatriz Batuecas died in an accident during the Christmas holy days of 1988 after she had initiated this workCorrespondence to: R. Garesse     

Potential for parthenogenesis of virgin females in a bisexual population of the geographically parthenogenetic mayfly Ephoron shigae (Insecta: Ephemeroptera,Polymitarcyidae)

The burrowing polymitarcyid mayfly Ephoron shigae is a geographically parthenogenetic species. Interestingly, the distributions of the bisexual and unisexual populations overlap broadly in their respective geographic ranges. In this mayfly, obligatory diploid thelytoky appears within unisexual populations. In the present study, we examined the potential for parthenogenesis or the parthenogenetic ability of females in a bisexual population aiming to understand the emergence of unisexual populations. The results obtained revealed that females in the examined bisexual populations showed a potential for diploid thelytoky as also seen in the unisexual populations, although, in females from bisexual populations, the development success rates of their unfertilized eggs were considerably lower than those of virgin females from unisexual populations. In the three bisexual reproducing species (Ephemera japonica, Ephemera strigata, and Ephemera orientalis) in the closely‐related family Ephemeridae, diploid thelytoky (i.e. tychoparthenogenesis; < 3%) was also observed. However, in this case, the parthenogenetic development success rates of unfertilized eggs were significantly lower than those of virgin females in the bisexual (Hino‐yosui Irrigation Canal) population of E. shigae. Accordingly, we suggest that parthenogenetic ability (i.e. tychoparthenogenesis or facultative parthenogenesis) in bisexual populations of E. shigae may facilitate the evolutionary transition to unisexual populations with fully obligatory parthenogenesis. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 326–334.     

Characterizing bisexual Artemia populations by isoelectric focusing

Isoelectric focusing (IEF) of protein extracts, -Esterase and Phosphoglucose isomerase, from groups of Artemia adults from different bisexual populations were studied. Both gave clear separation between the Old and New World species. The second was more polymorphic, allowing a discrimination among Mediterranean populations.     

Ecological rather than geographical isolation dominates Quaternary formation of Mediterranean Cistus species

The lack of a comparative approach makes it impossible to determine the main factors influencing colonization and evolution in plants. Here we conducted the first comparative study of a characteristic Mediterranean lineage (white‐flowered Cistus) taking advantage of its well‐known phylogenetic relationships. A two‐scale approach was applied to address the hypothesis of higher levels of isolation in mountain than in lowland species. First, a time‐calibrated phylogeny using plastid sequences of Cistaceae suggested that the origin of Cistus species postdated both the refilling of the Mediterranean Sea (5.59–5.33 Ma) and the onset of the Mediterranean climate (3.2 Ma). Two hundred and sixty‐three additional, plastid sequences from 111 populations showed different numbers of haplotypes in C. laurifolius (7), C. monspeliensis (2) and C. salviifolius (7). Although haplotype sharing among disjunct populations was observed in all species, phylogeographic analyses revealed haplotype lineages exclusive to Europe or Africa only in the mountain species (C. laurifolius). Isolation by either geographical distance or sea barriers was not significantly supported for the lowland species (C. monspeliensis; C. ladanifer from a previous study). The same is true for the less habitat‐specific species of the lineage (C. salviifolius). Comparative phylogeography of the Cistus species leads us to interpret a general pattern of active colonization surpassing Mediterranean barriers. In contrast, ecological conditions (precipitation, temperature, soils) appear to have determined the distribution of the Cistus species of Mediterranean mountains. This study further provides molecular evidence for multiple colonization patterns in the course of successful adaptation of Cistus species to Mediterranean habitats.     

Geographic parthenogenesis and the common tea‐tree stick insect of New Zealand

Worldwide, parthenogenetic reproduction has evolved many times in the stick insects (Phasmatidae). Many parthenogenetic stick insects show the distribution pattern known as geographic parthenogenesis, in that they occupy habitats that are at higher altitude or latitude compared with their sexual relatives. Although it is often assumed that, in the short term, parthenogenetic populations will have a reproductive advantage over sexual populations; this is not necessarily the case. We present data on the distribution and evolutionary relationships of sexual and asexual populations of the New Zealand stick insect, Clitarchus hookeri. Males are common in the northern half of the species’ range but rare or absent elsewhere, and we found that most C. hookeri from putative‐parthenogenetic populations share a common ancestor. Female stick insects from bisexual populations of Clitarchus hookeri are capable of parthenogenetic reproduction, but those insects from putative‐parthenogenetic populations produced few offspring via sexual reproduction when males were available. We found similar fertility (hatching success) in mated and virgin females. Mated females produce equal numbers of male and female offspring, with most hatching about 9–16 weeks after laying. In contrast, most eggs from unmated females took longer to hatch (21–23 weeks), and most offspring were female. It appears that all C. hookeri females are capable of parthenogenetic reproduction, and thus could benefit from the numerical advantage this yields. Nevertheless, our phylogeographic evidence shows that the majority of all‐female populations over a wide geographic area originate from a single loss of sexual reproduction.     

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.     

The barriers to oceanic island radiation in bryophytes: insights from the phylogeography of the moss Grimmia montana

Aim In contrast to angiosperms, bryophytes do not appear to have radiated in Macaronesia and the western Mediterranean. We evaluate if: (1) the apparent lack of radiation in bryophytes reflects our failure to recognize cryptic endemic species; (2) bryophytes are characterized by extremely low evolutionary rates; or (3) bryophytes have a high dispersal ability, which prevents genetic isolation. Location Worldwide, with a special emphasis on Macaronesia and the western Mediterranean. Methods Three chloroplast regions were sequenced from samples of the moss Grimmia montana from its entire distribution range. Network analyses, Fst and Nst statistics were used to describe and interpret the phylogeographical signal in the data. Results Despite significant phylogeographical signal in the chloroplast genome, which demonstrates limits to gene flow at the continental scale, repeated sister group relationships observed among accessions from different geographical areas suggest recurrent colonization patterns. These observations are consistent with mounting evidence that intercontinental distributions exhibited by many bryophyte species result from long‐distance dispersal rather than continental drift. Madeiran and western Mediterranean island haplotypes are either shared by, or closely related to, European and North American ones. Fst values between Madeira, western Mediterranean islands, North America and Europe are not significantly different from zero, and suggest that Madeira and the south‐western Mediterranean are subject to strong transatlantic gene flow. By contrast, haplotypes found in the Canary Islands are shared or closely related to those of populations from south‐western Europe or southern Africa. Main conclusions Multiple origins and colonization events are not consistent with the hypothesis of a relictual origin of the Macaronesian moss flora. One possible reason for the failure of taxa that experienced multiple colonization events to radiate is niche pre‐emption. We suggest that strong gene flow, coupled with the occupancy of all suitable niches, either by earlier conspecific colonizers or by other species, could be the mechanism preventing island radiation in G. montana and other cryptogams with high long‐distance dispersal abilities.     

Variations in repetitive DNA and heterochromatin in the genus Artemia

The genus Artemia (Crustacea, Phyllopoda) is widely distributed all over the world as a result partly of natural colonization and partly of spread by birds and man. Artemia offers a very interesting model for speciation studies, since the genus comprises both bisexual sibling species and parthenogenetic populations, exhibiting different chromosome numbers (diploidy, heteroploidy and polyploidy). The finding of the clustered repetitive AluI DNA family in the heterochromatin of A. franciscana can provide a useful tool for investigating the relationship between the members of the genus Artemia at the molecular level. Sixteen strains of Artemia, comprising sibling species and parthenogenetic populations, were analysed for the presence of AluI repetitive DNA by dot-blot hybridization. The observed variation in the content of repetitive DNA together with genetical, biological and geological data, support the hypothesis that Artemia living in the New World are derived from ancestral species that evolved in the Mediterranean area.     

ELECTROPHORETIC ENZYME ANALYSIS OF NORTH AMERICAN AND EASTERN ASIAN POPULATIONS OF AGASTACHE SECT. AGASTACHE (LABIATAE)

Agastache sect. Agastache consists of seven species in North America and one disjunct in eastern Asia. Starch-gel electrophoresis of enzymatic proteins was employed to assess genetic relationships among these species and to estimate the amount of genetic divergence between the North American and Asian populations. Species of the western United States appear to be better adapted for outcrossing than are the others and are much more genetically variable, with higher levels of heterozygosity per individual, more alleles per species, and higher percentages of polymorphic loci per population. Nonmetric multidimensional scaling of Nei's genetic distances among 32 populations partitioned the section into four discrete groups: 1) A. nepetoides (eastern North America), 2) A. scrophulariifolia and A. foeniculum (eastern and central North America), 3) the four species of the western United States (A. urticifolia, A. occidentalis, A. parvifolia and A. cusickii) and 4) A. rugosa (eastern Asia). Asian Agastache, separated from its American congeners for over twelve million years, differed from American populations at two of fifteen loci surveyed. Nei's genetic distances between Asian and North American populations ranged from 0.2877 to 0.6734.     

Molecular diversity of species of the Elymus trachycaulus species complex and their relationships to non-North American taxa

Species of the E. trachycaulus complex species are known for their morphological variability, but little is known about their genetic basis. The delimitation of taxa within the complex has been controversial and difficult. E. trachycaulus is predominantly self-pollinating, and lacks clear morphological boundaries between it and E. alaskanus. Another controversial taxonomic issue of E. trachycaulus is the relationships of this complex species to non-North American E. caninus. The objectives of this study were to examine genetic diversity and the systematic relationships among the species of the E. trachycaulus complex and their relationships with E. caninus, E. alaskanus and E. mutabilis. Random amplified polymorphic DNA method was used to study 35 accessions of E. trachycaulus complex and other Elymus species. Higher genetic variation was detected within species of E. trachycaulus complex. Eurasian accessions are as variable as the North American ones. Both UPGMA and NJ analyses did not show clearly separation among species of the E. trachycaulus complex. No clear association between geographic origin and genetic grouping among these species was found. Eurasian E. trachycaulus probably originated from multiple North American populations.     

Rapid expansion of the distributional range and the population genetic structure of the freshwater amphipod <Emphasis Type="Italic">Crangonyx floridanus</Emphasis> in Japan

The freshwater amphipod Crangonyx floridanus (Amphipoda: Crangonyctidae) is considered to have been recently introduced from North America to Japan, and the recorded sites at which it has been collected now cover nearly all of Japan except for the northern part. In this study, we surveyed further areas outside of its known distribution range, and examined the population genetic structure and the phylogenetic relationships between Japanese and North American populations of this species based on nuclear (18S rRNA) and mitochondrial (COI) DNA sequences. We found that this amphipod has already reached Hokkaido, northernmost Japan, which suggests that it has undergone rapid expansion in a pattern of concentric circles from the central part of Japan. Genetic analysis showed that the Japanese population is genetically homogeneous, in contrast to the genetic diversification of this species seen in North American Crangonyx populations. The process of introducing, establishing, and expanding this amphipod in Japan may be explained as follows. A limited number of individuals from a North American native population were probably inadvertently introduced and established somewhere within the Kanto region. The local population size then increased and its distribution range expanded rapidly across Japan.     

Genetic diversity,sexual condition,and microhabitat preference determine mating patterns in Sphagnum (Sphagnaceae) peat‐mosses

In bryophytes, the possibility of intragametophytic selfing creates complex mating patterns that are not possible in seed plants, although relatively little is known about patterns of inbreeding in natural populations. In the peat‐moss genus Sphagnum, taxa are generally bisexual (gametophytes produce both sperm and egg) or unisexual (gametes produced by separate male and female plants). We sampled populations of 14 species, aiming to assess inbreeding variation and inbreeding depression in sporophytes, and to evaluate correlations between sexual expression, mating systems, and microhabitat preferences. We sampled maternal gametophytes and their attached sporophytes at 12–19 microsatellite loci. Bisexual species exhibited higher levels of inbreeding than unisexual species but did generally engage in some outcrossing. Inbreeding depression did not appear to be common in either unisexual or bisexual species. Genetic diversity was higher in populations of unisexual species compared to populations of bisexual species. We found a significant association between species microhabitat preference and population genetic diversity: species preferring hummocks (high above water table) had populations with lower diversity than species inhabiting hollows (at the water table). We also found a significant interaction between sexual condition, microhabitat preference, and inbreeding coefficients, suggesting a vital role for species ecology in determining mating patterns in Sphagnum populations. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115 , 96–113.     

Cryptic invasion in Southern Europe: The case of <Emphasis Type="Italic">Ferrissia fragilis</Emphasis> (Pulmonata: Ancylidae) Mediterranean populations

Four populations of the North American ancylid gastropod Ferrissia fragilis have been found in Southern Italy, thus expanding the known Eurasian distribution range of this invasive gastropod to the Mediterranean area. Both mitochondrial markers used for the molecular identification of the sampled specimens (16S and COI) showed a modest to absent haplotypic diversity in the studied Ferrissia populations from Europe and Asia, and their perfect identity with some of the haplotypes observed in North American F. fragilis populations. In the light of the scarce molecular diversity observed in the whole Palaearctic area and of the growing evidences for the ongoing spreading of the species in Europe, the occurrence of a single invasion event from North America possibly linked with aquarium plant trade followed by a rapid spreading of the species in Eurasia is suggested. The record of F. fragilis in Southern Italy caused some doubts on the presence of autochthonous Ferrissia populations in Europe and on the actual existence of Ferrissia wautieri. A molecular analysis of Ferrissia specimens from the loci typici of F. wautieri (Northern Italy) and F. clessiniana (Egypt) is definitely opportune.     

Balearic insular isolation and large continental spread framed the phylogeography of the western Mediterranean Cheirolophus intybaceus s.l. (Asteraceae)

Recent Quaternary geological and climate events have shaped the evolutionary histories of plant species in the Mediterranean basin, one of the most important hotspots of biodiversity. Genetic analyses of the western Mediterranean Cheirolophus intybaceus s.l. (Asteraceae) based on AFLP were conducted to establish the relationships between its close species and populations, to reconstruct the phylogeography of the group and to analyse potential unidirectional versus bidirectional dispersals between the Ibero‐Provençal belt and the Balearic Islands. AFLP data revealed two main genetic groups, one constituted by the Balearic populations and Garraf (NE Iberia) and the other formed by the remaining mainland populations that were further sub‐structured into two geographically separated subgroups (SE + E Iberia and NE Iberia + SW France). Genetic diversity and spatial structure analyses suggested a mid‐Pleistocene scenario for the origin of C. intybaceus in southern Iberia, followed by dispersal to the north and a single colonisation event of the Balearic archipelago from the near Dianic NE Iberian area. This hypothesis was supported by paleogeographic data, which showed the existence of terrestrial connections between the continent and the islands during the Middle–Late Pleistocene marine regressions, whereas the more recent single back‐colonisation of the mainland from Mallorca might be explained by several hypotheses, such as long‐distance dispersal mediated by migratory marine birds or sea currents.     

Phenotypic diversification and island evolution of pipistrelle bats (Pipistrellus pipistrellus group) in the Mediterranean region inferred from geometric morphometrics and molecular phylogenetics

Aim The Mediterranean Basin is a centre of radiation for numerous species groups. To increase our understanding of the mechanisms underlying speciation and radiation events in this region, we assessed the phenotypic variability within the Pipistrellus pipistrellus–pygmaeus–hanaki species complex. Although bats form the second largest mammalian order, studies of insular evolution in this group are scarce. We approached this problem from a microevolutionary perspective and tested for the recurrence of the insular syndrome. Location The Mediterranean Basin, with a special focus on isolated populations from Corsica, the Maghreb, Cyprus, Cyrenaica and Crete. Methods Phenotypic variability was assessed by cranial morphometrics using the coordinates of 41 3D landmarks and associated geometric‐morphometric methods. We analysed 125 specimens representing all of the lineages in the species complex. Differences between taxa and between insular and continental populations in cranial size, shape, form and allometries were tested using analyses of variance and visualized using boxplots and canonical variate analysis. Relationships between molecular data from a previous study (cytochrome b sequences) and morphometric data were tested with co‐inertia analyses (RV test) and multivariate regressions. Results The three species were relatively well differentiated in cranial size and shape, and each species showed a significant amount of inter‐population variability. Comparisons of pairs of insular versus continental populations revealed heterogeneities in cranial patterns among island phenotypes, suggesting no recurrent insular syndrome. Molecular and phenotypic traits were correlated, except for molecular and lateral cranium shape. Main conclusions The Pipistrellus pipistrellus – pygmaeus – hanaki species complex exhibits phenotypic variability as a result of the fragmentation of its distribution (especially on islands), its phylogenetic and phylogeographic history and, most probably, other evolutionary factors that were not investigated in this study. We found no recurrent pattern of evolution on islands, indicating that site‐specific factors play a prevailing role on Mediterranean islands. The correlation between molecular and phenotypic data is incomplete, suggesting that factors other than phylogenetic relationships, potentially connected with feeding ecology, have played a role in shaping cranial morphology in this species complex.     

Historical museum collections clarify the evolutionary history of cryptic species radiation in the world's largest amphibians

Inaccurate taxonomic assessment of threatened populations can hinder conservation prioritization and management, with human‐mediated population movements obscuring biogeographic patterns and confounding reconstructions of evolutionary history. Giant salamanders were formerly distributed widely across China, and are interpreted as a single species, Andrias davidianus. Previous phylogenetic studies have identified distinct Chinese giant salamander lineages but were unable to associate these consistently with different landscapes, probably because population structure has been modified by human‐mediated translocations for recent commercial farming. We investigated the evolutionary history and relationships of allopatric Chinese giant salamander populations with Next‐Generation Sequencing methods, using historical museum specimens and late 20th‐century samples, and retrieved partial or near‐complete mitogenomes for 17 individuals. Samples from populations unlikely to have been affected by translocations form three clades from separate regions of China, spatially congruent with isolation by either major river drainages or mountain ranges. Pliocene–Pleistocene divergences for these clades are consistent with topographic modification of southern China associated with uplift of the Qinghai‐Tibet Plateau. General Mixed Yule Coalescent model analysis indicates that these clades represent separate species: Andrias davidianus (Blanchard, 1871) (northern Yangtze/Sichuan), Andrias sligoi (Boulenger, 1924) (Pearl/Nanling), and an undescribed species (Huangshan). Andrias sligoi is possibly the world's largest amphibian. Inclusion of additional reportedly wild samples from areas of known giant salamander exploitation and movement leads to increasing loss of biogeographic signal. Wild Chinese giant salamander populations are now critically depleted or extirpated, and conservation actions should be updated to recognize the existence of multiple species.     

High levels of population subdivision in a morphologically conserved Mediterranean toad (Alytes cisternasii) result from recent,multiple refugia: evidence from mtDNA,microsatellites and nuclear genealogies

Pleistocene glaciations often resulted in differentiation of taxa in southern European peninsulas, producing the high levels of endemism characteristic of these regions (e.g. the Iberian Peninsula). Despite their small ranges, endemic species often exhibit high levels of intraspecific differentiation as a result of a complex evolutionary history dominated by successive cycles of fragmentation, expansion and subsequent admixture of populations. Most evidence so far has come from the study of species with an Atlantic distribution in northwestern Iberia, and taxa restricted to Mediterranean‐type habitats remain poorly studied. The Iberian Midwife toad (Alytes cisternasii) is a morphologically conserved species endemic to southwestern and central Iberia and a typical inhabitant of Mediterranean habitats. Applying highly variable genetic markers from both mitochondrial and nuclear genomes to samples collected across the species’ range, we found evidence of high population subdivision within A. cisternasii. Mitochondrial haplotypes and microsatellites show geographically concordant patterns of genetic diversity, suggesting population fragmentation into several refugia during Pleistocene glaciations followed by subsequent events of geographical and demographic expansions with secondary contact. In addition, the absence of variation at the nuclear β‐fibint7 and Ppp3caint4 gene fragments suggests that populations of A. cisternasii have been recurrently affected by episodes of extinction and recolonization, and that documented patterns of population subdivision are the outcome of recent and multiple refugia. We discuss the evolutionary history of the species with particular interest in the increasing relevance of Mediterranean refugia for the survival of genetically differentiated populations during the Pleistocene glaciations as revealed by studies in co‐distributed taxa.     

Dispersion pattern of the medfly from its geographic centre of origin and genetic relationships of the medfly with two close relatives

We used three different approaches, a phylogenetic analysis, the principal component analysis, and Gabriel Graphs, to study the dispersion of the medfly from its geographic centre of origin. Our analysis was based on 13 enzyme polymorphisms detected electrophoretically in 15 natural populations coming from distinct geographic areas. The results indicate that (i) there is a clear-cut separation of the native African from the introduced populations, (ii) the population from Spain seems to connect the African and the Mediterranean or American populations, and (iii) the Mediterranean populations as well as the American ones comprise two distinct groups of closely related populations.We have also estimated a phylogenetic tree for 3 species of the genus Ceratitis: C. capitata, C. rosa and C. nigra, based on electrophoretic data under the assumption of a molecular clock. The results suggest that C. capitata and C. rosa are more closely related to each other than either is to C. nigra.