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The previous genetic characterization of the honeybee population of Mauritius Island (Indian Ocean) revealed an ongoing process of hybridization between the first established African subspecies Apis mellifera unicolor and recently imported European subspecies (A. m. ligustica, A. m. carnica and A. m. mellifera). This context offers the rare opportunity to explore the influence of hybridization between African and European honeybees on phenotypic traits out of the case largely studied of the Africanized honeybee (hybrid between A. m. scutellata from South Africa and European subspecies). We thus conducted geometric morphometric analyses on forewings of 283 workers genetically characterized at 14 microsatellite loci to evaluate (1) if the morphological variability coincides well with the neutral genetic variability, (2) if hybrids exhibited rather parental, intermediate or transgressive traits, and (3) to test if fluctuating asymmetry (FA) of size and shape, as a measure of developmental stability, was elevated in hybrids (due to genetic stress) and/or European bees (due to unsuitable environment) compared to African bees. A strong concordance was found between morphological variability and neutral genetic variability, especially for wing shape, based on partial least-square analyses (PLS). However, on average, the morphology of hybrids was more similar to the African bees, potentially reflecting the dynamics and direction of introgression. Significant FA for wing size as well as wing shape was detected, suggesting the overall presence of stress during the development of the studied individuals. In contrast, the asymmetry levels do not differ according to the ancestry (African, European or hybrid) of the individuals. Therefore, if ongoing hybridization contributed to increasing the genetic and phenotypic diversity of the populations and influences its adaptive potential, developmental stressors could not be identified and their evolutionary consequences remain uncertain.

Insular environments are among the most vulnerable ecosystems in the world, partly due to their small size and isolation. In La Reunion, an island in the southwest Indian Ocean, three whitefly species of the Bemisia tabaci (Gennadius) complex of cryptic species coexist: the indigenous species IO, and two exotic invasive species MEAM1 and Med, introduced in the late 1990s and in the early 2010s, respectively. B. tabaci is a major pest distributed worldwide, and a vector of plant viruses, responsible of serious damages on crops. The generalization of the use of pesticides has led to the emergence and rapid evolution of resistance in whitefly populations. In other countries, MEAM1 and Med have already demonstrated high resistance levels to all of the important classes of pesticides. Our objectives were to understand indigenous versus invasive whitefly species distribution in La Reunion, according to the different ecosystems; and how it could be linked to selection pressure of pesticide treatments. To assess species distribution, whiteflies were sampled at 59 collection sites, located all over the island in agroecosystems and natural areas. Molecular (kdr mutation, conferring Pyrethroid resistance) and laboratory bioassays (on three main classes of pesticides: Neonicotinoids, Pyridine azomethine derivatives and Pyrethroids) approaches were conducted on part of the sampled populations to assess pesticide resistance. The indigenous species IO was mainly sampled in natural areas and was found to be sensitive to the three classes of pesticides tested; in addition, no kdr mutation conferring Pyrethroid resistance was detected. The two exotic invasive species MEAM1 and Med were dominant in agrosystems. Most of the MEAM1 populations were found to be resistant to the three classes of pesticides tested, and kdr mutation was detected in both invasive species. Our results are in line with resistance cases reported worldwide in the literature, and suggest that whitefly species distribution in La Reunion could be driven by selection pressure of pesticide treatments.

After 2007, upsurges of whiteflies on cassava plants and high incidences of cassava diseases were observed in Central African Republic. This recent upsurge in the abundance of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) was directly linked to serious damage to cassava crops resulting from spread of whitefly-borne cassava mosaic geminiviruses (CMGs). There is currently very little information describing whitefly populations on cassava and associated crops in Central African Republic. The current study aimed to address this gap, and to determine whether the increasing damage associated with B. tabaci whiteflies was the consequence of a new invasion, or an upsurge of a local population. The molecular genetic identification and phylogenetic relationships of 898 B. tabaci adult individuals collected from representative locations (54) throughout CAR were determined based on their mitochondrial cytochrome oxidase I sequences (mtCOI). Field and ecological data were also collected from each site, including whitefly abundance, CMD incidence, host plants colonized by B. tabaci and agro-ecological zone. Phylogenetic analysis of the whitefly mtCOI sequences indicated that SSA1 (-SG1, -SG2), SSA3, MED, MEAM1 and Indian Ocean (IO) putative species occur in CAR. One specific haplotype of SSA1-SG1 (SSA1-SG1-P18F5) predominated on most cassava plants and at the majority of sites. This haplotype was identical to the SSA1-SG1 Mukono8-4 (KM377961) haplotype that was recorded from Uganda but that also occurs widely in CMD pandemic-affected areas of East Africa. These results suggest that the SSA1-SG1-P18F5 haplotype occurring in CAR represents a recent invasive population, and that it is the likely cause of the increased spread and severity of CMD in CAR. Furthermore, the high mtDNA sequence diversity observed for SSA1 and its broad presence on all sites and host plants sampled suggest that this genetic group was the dominant resident species even before the arrival of this new invasive haplotype.

Dacus ciliatus, the Ethiopian fruit fly, is a major oligophagous pest of cucurbit crops, that is abundant throughout and originates from the African continent. It has extended its range to the Indian Ocean islands becoming an invasive pest of major concern. Although the economic importance of this species is well documented, its large-scale pattern of genetic structuring is poorly known. Hence, the current quarantine methods and management plans still rely on general assumptions concerning its intraspecific variation. The aim of this work was to characterize the large-scale population structure of Dacus ciliatus, and its diversity within Africa (including Indian Ocean Islands) and Israel. Individuals of D. ciliatus were collected from 12 countries (n=1153) distributed in West Africa (Benin, Senegal, Mali, Burkina Faso), East and Southern Africa (Tanzania, South Africa, Mozambique), the Indian Ocean islands (Grande Comore, Mayotte, Mauritius and Réunion) and Israel. They were genotyped at 12 microsatellite loci specifically developed for this species. Genetic diversity was recorded such as genetic discontinuities among geographical regions and levels of population structuring through Bayesian clustering procedures. The optimal genetic structure found with Bayesian clustering procedures separated the whole dataset into three genetic clusters. The first cluster comprised all the mainland African populations, the second one the Mayotte populations and the last genetic cluster comprised the recently invaded Mascarene Islands (Réunion and Mauritius). Grande Comore Island had a mixed pattern between African origin and Mayotte genetic cluster. These results are further discussed regarding the ecological and geographical patterns and genetic differentiation of a population after an invasion in insular environments. (Texte intégral)

Background. Tephritid fruit flies cause severe damage to fruit and vegetable crops in Reunion Island. Instead of the curative approach to reduce existing populations, the first step proposed for their management is sanitation. This method is based on an original technique firstly developed by USDA in Hawaii utilizing a tent-like structure called an "augmentorium" which aims to sequester adult flies emerging from infested fruit while allowing the parasitoids to escape, via a net placed at the top of the structure. This study focused on the performance and the efficiency of the augmentorium prototype recently tested in Reunion Island and particularly (i) the number of adult flies that can potentially be sequestered in an augmentorium in the field; (ii) the efficiency of the net mesh for fly sequestration and parasitoid escape; (iii) the feasibility of producing compost with infested fruit collected in the field. Method. The potential number of flies that could be sequestered was estimated by measuring in the lab the emergence of several species of flies from infested fruit collected in the field from 2005 to 2009 in different sites of the island. Emergence of adult flies was measured for six species of flies: (i) Bactrocera cucurbitae, Dacus ciliatus and D. demmerezi attacking three species of Cucurbits (pumpkin: Cucurbita maxima; cucumber: Cucumis sativus and courgette: Cucurbita pepo); (ii) Bactrocera zonata, Ceratitis rosa and C. capitata attacking one species of fruit (mango: Mangifera indica). The sequestration of three of these fly species (B. cucurbitae, B. zonata and C. capitata) and the escape of two of their parasitoids (Psyttalia fletcheri and Fopius arisanus) were assessed in the Cirad laboratory in Saint-Pierre in 2008. Preliminary tests on the feasibility of producing compost were then conducted in Saint-Pierre in 2009, mixing courgette and other components. Results. Collections of infested fruits showed the following means of emerged adults per kg of fruit: 76 for mango (B. zonata, C. rosa, C. capitata); 217 for cucumber, 340 for pumpkin and 594 for courgette (B. cucurbitae, D. ciliatus, D. demmerezi). The efficiency of the mesh chosen for the prototype of augmentorium (hole area 1.96 mm²) proved to be perfectly effective in the lab with 100% of sequestration of adult flies. In the same way, 100% of the parasitoids were able to escape from the mesh if they choose to do so. In addition, we showed that a ratio of 50:30:20 of courgette, sugar cane stem and chicken litter respectively was well adapted to produce compost. Conclusion. These results confirm the relevance and the efficiency of the augmentorium in an agroecological crop protection. As a sanitation technique against fruit flies, the augmentorium sequesters on average several hundreds of adult flies per kg of infested fruit. As a biological control method, it may contribute to increase parasitoid populations which are often low because of the previous and significant pesticide pressure. The augmentorium can also be considered as a useful tool to produce compost in the context of sustainable agriculture. The technique of sanitation using the augmentorium is now well accepted by farmers in pilot areas in Reunion Island. (Texte intégral)

The study of tri-trophic interactions is a vast field of basic ecological studies which are also of paramount importance for the development of environment-friendly methods of pest management. Within the Diptera, the Tephritidae family represents an interesting model for such studies because of the variable host-specificity of species in this group, and the important role that some natural enemies may play in the regulation of their populations. Furthermore, the great economic importance of many species in this family offers a large array of applications to research results. La Réunion, a French island situated in the south-west of the Indian Ocean, is a favourable area for studying such interactions, because of the number of tephritid species present in the island, and the great variability of its climatic conditions. On fruit crops, a complex of three polyphagous species of tephritids cause considerable damage: the Mediterranean fruit fly, Ceratitis capitata, the Natal fruit fly, Ceratitis rosa, and the Peach fruit fly, Bactrocera zonata. In addition, another complex of Dacini is harmful to cucurbit crops: the Melon fly, Bactrocera cucurbitae, the Ethiopian cucurbit fly, Dacus ciliatus, and the Indian Ocean cucurbit fly, Dacus demmerezi. Conversely, on Solanaceous crops such as tomato, the Tomato fruit fly Neoceratitis cyanescens, is the only species of economic importance. Over the last twenty years, many field studies allowed us to specify the host-range and relative importance of the different species on cultivated crops. Of particular interest are some host preferences observed in the field in some otherwise very polyphagous species, such as C. capitata. Detailed studies (lab, wind tunnel and field cages) were also devoted to the host location behaviour of stenophagous species, taking as a model the tomato fruit fly, N. cyanescens. Other behavioural studies also highlighted the preferences of the different species for particular host-plants during foraging or egg-laying behaviour. More recently, studies were focused on the quality of various host or non-host fruits for the pre-imaginal development of the different species, and its influence on their fitness. Though some indigenous parasitoids of the Mediterranean fruit fly have been recorded in the island, most of the natural regulation by parasitoids is due to exotic species imported through classical biological control programmes. This is particularly the case with two species imported from Hawaii, in collaboration with USDA Hawaii and the University of Hawaii: Psyttalia fletcheri, a larvo-pupal parasitoid of the Melon fly, and, more recently, Fopius arisanus, an egg-pupal parasitoid of some Bactrocera spp. Following the acclimatization of these two species, field studies allowed us to evaluate their host range, favourite habitats, and impact on host species populations. In addition, laboratory, field-cage and wind tunnel studies improved our knowledge of the stimuli involved in host habitat and host selection behaviours. Results of these studies are summarized and discussed in relation to the current state of knowledge of insect-plant and host-parasitoid interactions in tephritids, and to their possible applications in pest management. (Texte intégral)

La mouche de la pêche Bactrocera zonata, connue sur l'Île de la Réunion depuis 1991, s'y comporte en ravageur depuis 2000 notamment sur manguier, goyavier, goyavier de Chine et badamier(1). Que sait-on de cette mouche ? Comment cohabite-t-elle avec les autres mouches téphritides présentes avant elle sur l'île? Ou verra que la compétition entre espèces, mais aussi le besoin de chaleur et l'indifférence à l'humidité, expliquent sa distribution à la Réunion. Celle-ci connue, comment peut-on maîtriser B. zonata ? Une part de la réponse réside probablement dans la lutte biologique par acclimatation d'auxiliaire: un travail avec le parasitoïde Fopius arisanus est en cours. Il y a aussi la lutte intégrée en vergers, déjà menée contre les autres espèces mais à adapter en présence de B. zonata.

Le goyavier-fraise, très répandu sur l'île de la Réunion, est une plante hôte majeure de différentes espèces de mouches des fruits. Les relations entre la dynamique de population des mouches des fruits, la phénologie de la plante hôte et les dégâts sur fruits ont été étudiés. L'évolution saisonnière de l'abondance des mouches des fruits a été étudiée de 1992 à 1994 par piégeage sexuel dans trois zones naturellement envahies par P. cattleianum situées à 100 m, 480 m et 720 m d'altitude sur la côte humide de l'île. Les dégâts sur fruits ont été suivis durant les récoltes. La principale espèce de mouche des fruits capturée sur l'ensemble des sites a été la mouche du Natal, Ceratitis rosa Karsch. La mouche méditerranéenne des fruits, C. capitata (Wiedemann), et la mouche des fruits des Mascareignes, C. catoirii (Guérin-Mèneville), ont été occasionnellement capturées à 100 m et à 480 m d'altitude. Le goyavier-fraise s'avère être une plante hôte pour ces trois espèces du niveau de la mer jusqu'à 500 m d'altitude, avec une nette dominance de C. rosa. Au-delà de 500 m, seule cette espèce a été rencontrée dans les fruits piqués. Les populations de C. rosa ont été faibles durant toute l'année et ont augmenté au moment de la récolte du goyavier-fraise. L'abondance de C. rosa a varié significativement entre les sites, mais sans relation claire avec l'altitude. Ces résultats apportent des informations nouvelles sur la dynamique des populations de la mouche du Natal en relation avec l'une de ses principales plantes hôtes. Ils sont utiles pour définir des programmes de traitements phytosanitaires contre les mouches des fruits dans les vergers commerciaux de goyaviers-fraises.

Les mouches des fruits sont responsables des dégâts majeurs sur les cultures fruitières et maraîchères à la Réunion, à Maurice, aux Seychelles et dans d'autres pays de l'Océan indien. Devant l'ampleur des ravages, des programmes nationaux de lutte ont été engagés sur l'acclimatation des parasitoïdes et le lâcher des mâles stériles. Mais l'arrêt des opérations entraîne une recrudescence des mouches. A la Réunion, une stratégie de lutte est développée par le CIRAD-FLHOR sur le principal ravageur (Ceratitis rosa) : piégeage sexuel, inventaire des ravageurs et des parasitoïdes et essais d'insecticides, en coopération avec d'autres centres de recherche locaux et nationaux