Latitudinal clines of allelic frequencies  in Mediterranean populations  of Ceratitis capitata (Wiedemann)

Kourti, A.; Hatzopoulos, P.

doi:10.1051/gse:19950301

Cited by 4 publications

(8 citation statements)

References 16 publications

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“…These results, in combination with others reported for this species (Gasperi et al, 1991;Kourti & Hatzopoulos, 1995;Malacrida et al, 1998;Kourti, 2002), suggest that gene flow in combination with selection and drift are probably responsible for the differences in enzyme allele frequencies observed in geographically dispersed populations of this fly. The occurrence of significant gene flow between populations provides interesting additional supporting evidence for their dispersal potential.…”

Section: Discussionsupporting

confidence: 83%

“…Similar results have been reported for natural populations of Drosophila melanogaster Meigen and Drosophila willistoni Sturtevant (Diptera: Drosophilidae) (Johnson & Schaffer, 1973;Voelker et al, 1978;Singh & Rhomberg, 1987;Nevo et al, 1998). In most of the cases studied, there is a correlation between allelic frequencies and environmental variables that clearly favours the selection hypothesis (Schaffer & Johnson, 1974;Kusakabe & Mukai, 1984;Barker et al, 1986;Kourti & Hatzopoulos, 1995;Loxdale & Lushai, 2001). As gene flow and genetic drift are expected to affect all loci similarly, the presence of heterogeneity in the data indicates the operation of natural selection (Slatkin, 1987).…”

Section: Discussionsupporting

confidence: 77%

“…The most remarkable aspect of table 6 is that the patterns of variation between temperate and tropical populations, as revealed at certain loci, are repeated on separate continents. In addition, the set includes loci that have shown clinal patterns in previous studies (Kourti & Hatzopoulos, 1995).…”

Section: Discussionmentioning

confidence: 99%

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Estimates of gene flow from rare alleles in natural populations of medfly Ceratitis capitata (Diptera: Tephritidae)

Kourti

2004

Bull. Entomol. Res.

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Gene flow based on the spatial distribution of rare alleles at 25 gene loci was estimated in 15 populations of Ceratitis capitata (Wiedemann) from different parts of the world. Estimates of Nm, the number of migrants exchanged per generation among populations in different regions of the world, appeared to be quite similar, ranging from 3.36 in tropical Africa to 2.94 in the New World and 2.72 in Mediterranean basin populations. This suggests that gene flow among neighbouring populations of medfly is quite extensive. The genetic differentiation in American, Mediterranean and African populations was related to major climatic differences between North and South. These differences arise mainly from five loci that showed gene frequency patterns suggestive of latitudinal clines in allele frequencies. The clinal variation was such that tropical-subtropical populations were more heterozygous than temperate populations. It was concluded that gene flow, counteracting the forces of natural selection and genetic drift, determines the extent to which geographical populations of C. capitata are differentiated.

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Section: Discussionsupporting

confidence: 83%

Section: Discussionsupporting

confidence: 77%

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Estimates of gene flow from rare alleles in natural populations of medfly Ceratitis capitata (Diptera: Tephritidae)

Kourti

2004

Bull. Entomol. Res.

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“…Our results show that polymorphic loci are homogeneous with respect to all measured parameters of variation heterozygosity, fixation index and latitudinal variation in allele frequencies. Together, these parameters were able to identify a class consisting of ca one third polymorphic loci, or about 20 % of all loci studied, most of which have clinal variation ( Kourti and Hatzopoulos 1995) which is suggestive of balancing selection…”

Section: Discussionmentioning

confidence: 99%

“…This differentiation is partly due to a very high frequency in some populations of an allele that is uncommon in most localities and partly to loci (e.g. Pep 3 ) that show a clinal variation in the ratios of the most abundant alleles ( Kourti and Hatzopoulos 1995). However, it should be stated that other loci showing latitudinal clines have an F ST value (16 to18 %) within the steeper bell‐shaped intermediate distribution (e.g .…”

Section: Discussionmentioning

confidence: 99%

Estimates of heterozygosity and patterns of geographic differentiation in natural populations of the medfly (Ceratitis capitata)

Kourti

2002

Hereditas

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Allozyme variation at 25 gene loci was studied in fifteen populations of Ceratitis capitata (Wiedemann) (medfly) originating from different countries. The study of genetic variation in natural populations of medfly was undertaken to identify different groups of polymorphic loci whose variation patterns might suggest different kinds of selection forces. The findings of this study are as follows: (1) the African populations have mean heterozygosity 17.8 % and the introduced 5.7 %. (2) An average population is polymorphic for 22.3% of the gene loci and an average individual is heterozygous for 8.7 % of its gene loci. (3) The within population heterozygosity (HS) is divided into two groups. The first had an HS varying from 0 to 20 % and the second from 35 to 43 %. This abrupt transition between the two groups provides initial clues about selection on at least some loci. (4) The FST (fixation index) values have a wide range among loci from 40.7 % (Pep3) to 0 (Adh). The differentiation could be partly due to drift and partly by some sort of selection that affects particular genes. (5) Total heterozygosity (HT) could be separated into two groups with a gap between 20 % and 40 %. This distribution can sort out loci under purifying selection (low HT) and balancing selection (high HT). In conclusion, different evolutionary forces could have contributed to genetic changes during colonization by the medfly. In addition to the bottleneck effect, natural selection may have played an important role in the observed differences in the patterns of variation seen for different groups of loci in natural populations of C. capitata.

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Allozyme polymorphism in populations ofCeratitis capitatafrom Algeria, the northwestern Mediterranean coast and Reunion Island

Oukil

Bues

Toubon

et al. 2002

Fruits

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Introduction. In Algeria, the Mediterranean fruit fly Ceratitis capitata Wiedmann constitutes the main obstacle to production and exportation of many fruits. In studies of the genetic structure differences of medfly populations, certain authors, using molecular markers, observed the existence of different patterns among the pest Mediterranean populations. A clear understanding of the source and migration of the Mediterranean fruit fly would be useful for undertaking a successful eradication or control program. For this reason, preliminary work sought to compare the genetic structure of Algerian populations of C. capitata with that of other populations situated either in the western Indian ocean or on the northwestern Mediterranean coast. Materials and methods. The study of enzyme polymorphism allowed the comparison of the genetic structure of four Algerian populations of Ceratitis capitata with one from Reunion Island and five other populations collected from the northwestern Mediterranean coast (France and Spain). Enzyme analyses were performed on ground pest adults electrophoresed on a starch gel. Fifteen loci were analyzed for each population. Results and discussion. In spite of a wide geographic distribution of the analyzed populations (from a latitude of 24°to 44°N), no gradient of allelic frequencies was observed for any of the polymorphic loci. A higher genetic variability was observed in the population of Reunion Island than in the populations of Algeria or the northwestern Mediterranean coast. No genetic differentiation was observed among the populations of southern Algeria (Djanet and Ghardaïa) and northern Algeria (Boufarik and Oran). Algeria / France / Spain / Reunion / Ceratitis capitata / fruit damaging insects / enzyme polymorphism Polymorphisme enzymatique de populations de Ceratitis capitata originaires d'Algérie, du littoral nord-ouest méditerranéen et de l'île de la Réunion. Résumé-Introduction. En Algérie, la mouche méditerranéenne des fruits, Ceratitis capitata, est le principal obstacle à la production et l'exportation de fruits. En étudiant les différences de structures génétiques entre populations de mouches des fruits à partir de marqueurs moléculaires, certains auteurs ont observé l'existence de comportements différents parmi les populations méditerranéennes du ravageur. Une bonne compréhension de l'origine et de la migration de l'insecte serait utile pour entreprendre son éradication ou adopter des mesures de contrôle. Pour cette raison, des travaux préliminaires ont cherché à comparer la structure génétique de populations algériennes de C. capitata avec celle d'autres populations localisées ou dans l'ouest de l'océan Indien, ou sur le littoral nord-ouest de la Méditerranée. Matériel et méthodes. L'étude du polymorphisme enzymatique de C. capitata a permis de comparer la structure génétique de quatre populations d'Algérie avec celle de l'île de la Réunion et cinq autres populations prélevées sur la côte nord-ouest de la Méditerranée (France et Espagne). Des analyses d'enzymes ont été ef...

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Latitudinal clines of allelic frequencies in Mediterranean populations of Ceratitis capitata (Wiedemann)

Cited by 4 publications

References 16 publications

Estimates of gene flow from rare alleles in natural populations of medfly Ceratitis capitata (Diptera: Tephritidae)

Estimates of gene flow from rare alleles in natural populations of medfly Ceratitis capitata (Diptera: Tephritidae)

Estimates of heterozygosity and patterns of geographic differentiation in natural populations of the medfly (Ceratitis capitata)

Allozyme polymorphism in populations ofCeratitis capitatafrom Algeria, the northwestern Mediterranean coast and Reunion Island

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