<p>Род <em>Merodon Meigen</em> (Diptera: Syrphidae) се одликује великм бројем врста које имају&nbsp; функцију у опрашивању&nbsp; биљака. У оквиру овог рода својом разноврсношћу издваја се <em>Merodon aureus</em>&nbsp; група&nbsp; врста коју поред фенотипски различитих одликује и присуство већег броја криптичних&nbsp; врста. Због морфолошке сличности криптичне врсте представљају изазов за таксономе, те су молекуларне методе од посебног значаја. У том светлу примарни циљ овог истраживања је био утврђивање молекуларног диверзитета групе и могућности његове примене у таксономији. Истраживање је било засновано на анализи варијабилности секвенци&nbsp; COI&nbsp; и&nbsp; 28S&nbsp; рРНК гена за 718 јединки 41 описане или новоткривене врсте сирфида. Додатно, тестирана је примењивост мултилокусних&nbsp; ISSR маркера у раздвајању врста&nbsp; <em>M.&nbsp; luteomaculatus</em>&nbsp; комплекса. Узорци су тестирани и на присуство<em> Wolbachia</em> с обзиром да она може утицати на еволуцију митохондријалних гена. Добијени резултати су указали на високу варијабилност секвенци&nbsp; COI&nbsp; гена&nbsp; који се показао корисним у&nbsp; утврђивању граница&nbsp; криптичних&nbsp; врста у анализираним комплексима. Секвенце 28Ѕ рРНК гена у већини случајева нису биле од већег значаја за раздвајање врста, али би могле имати потенцијал у&nbsp; раздвајању комплекса&nbsp; или подгрупа&nbsp; врста као допуна анализи&nbsp; секвенци&nbsp; COI&nbsp; гена. Додатно,&nbsp; ISSR&nbsp; маркери су показали потенцијал за примену у молекуларној таксономији. Све анализиране врсте изузев <em>М. balkanicus</em> су биле заражене&nbsp; <em>Wolbachia,</em> али није утврђена јасна веза између варијабилности&nbsp; секвенци&nbsp; митохондријалног&nbsp; COI гена и инфекционог статуса врста. Утврђен образац генетичке варијабилности је вероватно&nbsp; обликован драстичним климатским променама&nbsp; током Плеистоцена и фрагментацијом хабитата. Да би се донели крајњи закључци о таксономском статусу предложених врста потребно је добијене резултате интегрисати са подацима других релевантних&nbsp; научних дисциплина.</p> / <p>Rod <em>Merodon Meigen</em> (Diptera: Syrphidae) se odlikuje velikm brojem vrsta koje imaju&nbsp; funkciju u oprašivanju&nbsp; biljaka. U okviru ovog roda svojom raznovrsnošću izdvaja se <em>Merodon aureus</em>&nbsp; grupa&nbsp; vrsta koju pored fenotipski različitih odlikuje i prisustvo većeg broja kriptičnih&nbsp; vrsta. Zbog morfološke sličnosti kriptične vrste predstavljaju izazov za taksonome, te su molekularne metode od posebnog značaja. U tom svetlu primarni cilj ovog istraživanja je bio utvrđivanje molekularnog diverziteta grupe i mogućnosti njegove primene u taksonomiji. Istraživanje je bilo zasnovano na analizi varijabilnosti sekvenci&nbsp; COI&nbsp; i&nbsp; 28S&nbsp; rRNK gena za 718 jedinki 41 opisane ili novotkrivene vrste sirfida. Dodatno, testirana je primenjivost multilokusnih&nbsp; ISSR markera u razdvajanju vrsta&nbsp; <em>M.&nbsp; luteomaculatus</em>&nbsp; kompleksa. Uzorci su testirani i na prisustvo<em> Wolbachia</em> s obzirom da ona može uticati na evoluciju mitohondrijalnih gena. Dobijeni rezultati su ukazali na visoku varijabilnost sekvenci&nbsp; COI&nbsp; gena&nbsp; koji se pokazao korisnim u&nbsp; utvrđivanju granica&nbsp; kriptičnih&nbsp; vrsta u analiziranim kompleksima. Sekvence 28Ѕ rRNK gena u većini slučajeva nisu bile od većeg značaja za razdvajanje vrsta, ali bi mogle imati potencijal u&nbsp; razdvajanju kompleksa&nbsp; ili podgrupa&nbsp; vrsta kao dopuna analizi&nbsp; sekvenci&nbsp; COI&nbsp; gena. Dodatno,&nbsp; ISSR&nbsp; markeri su pokazali potencijal za primenu u molekularnoj taksonomiji. Sve analizirane vrste izuzev <em>M. balkanicus</em> su bile zaražene&nbsp; <em>Wolbachia,</em> ali nije utvrđena jasna veza između varijabilnosti&nbsp; sekvenci&nbsp; mitohondrijalnog&nbsp; COI gena i infekcionog statusa vrsta. Utvrđen obrazac genetičke varijabilnosti je verovatno&nbsp; oblikovan drastičnim klimatskim promenama&nbsp; tokom Pleistocena i fragmentacijom habitata. Da bi se doneli krajnji zaključci o taksonomskom statusu predloženih vrsta potrebno je dobijene rezultate integrisati sa podacima drugih relevantnih&nbsp; naučnih disciplina.</p> / <p>Genus<em>&nbsp; Merodon&nbsp; Meigen&nbsp;</em> (Diptera: Syrphidae)&nbsp; is characterized by a large number of species which have a function in plants pollination. Within this genus, <em>Merodon </em>aureus species group is distinguished by its diversity and it is characterized not only by phenotypically divergent species but also with a large number of cryptic species. Because of the high morphological similarity, cryptic species are a challenge for taxonomist, thus molecular methods are of special importance. The primary goal of this research was to determine the molecular diversity of the group and the possibility of its application in taxonomy. The study was based on the sequences variability analysis of COI and 28S rRNA genes for 718 individuals belonging to 41 described or newly discovered hoverfly species. Additionally, the applicability in species delimitation of multilocus marker ISSR was tested on&nbsp; <em>M. luteomaculatus</em>&nbsp; species complex. Specimens have also been tested for<em> Wolbachia</em> since&nbsp; it may affect the evolution of mitochondrial genes. The obtained results indicated a high variability of the COI gene&nbsp; sequences that proved useful for determining the&nbsp; cryptic&nbsp; species boundaries in the analyzed complexes. Sequences of the 28S rRNA gene in&nbsp;&nbsp; most cases were not of much significance for the species delimitation, but they could have the potential to separate species complexes&nbsp; оr subgroups&nbsp; as a complement to the analysis of the COI gene&nbsp; sequences. Additionally, the ISSR markers showed potential for application in molecular taxonomy. All analyzed species&nbsp; except&nbsp; <em>M. balkanicus</em>&nbsp; were infected with&nbsp; <em>Wolbachia</em>, but no clear&nbsp; relation&nbsp; was established between the sequence variability of the mitochondrial COI gene and&nbsp; the infectious status of species. The established pattern of genetic variability is probably shaped&nbsp; by drastic climatic changes during Pleistocene and habitats fragmentation. In order to&nbsp; achieve&nbsp; the final conclusions on the taxonomic status of the proposed species, it is necessary to integrate the obtained results with the data of other&nbsp; relevant scientific disciplines.</p>

No description available.

In this thesis, experiments were conducted in the laboratory and the field to determine whether the provision of floral resources to hoverflies could enhance the biological control of aphids. The overall aim was to clarify hoverfly behaviour and ecology in an agroecosystem in order to understand the potential of these insects for biocontrol under a conservation biological control (CBC) regime. A preliminary experiment in New Zealand compared the effect of different coloured water-traps on catches of the hoverflies Melanostoma fasciatum (Macquart) and Melangyna novaezelandiae (Macquart). Significantly more individuals were caught in completely yellow traps than in traps with green outer walls and yellow inner walls or in completely green traps. This suggested that if a measure of hoverfly numbers relating to a particular distance along a transect is required, consideration should be given to the ability of hoverflies to detect yellow traps from a distance. The use of traps that are green outside would more accurately reflect the local abundance of hoverflies, as the insect would be likely to see the yellow stimulus only when above or close to the trap. Also, the addition of rose water significantly increased the number of M. fasciatum caught. From a suite of flowering plants chosen for their ability in other studies to increase hoverfly visit frequencies, laboratory experiments were conducted in France to determine the plant’s effectiveness at enhancing Episyrphus balteatus (De Geer) ‘fitness’, and to evaluate whether adult feeding on flowers was related to performance. Phacelia (Phacelia tanacetifolia Bentham cv. Balo), followed by buckwheat (Fagopyrum esculentum Moench cv. Katowase) and coriander (Coriandrum sativum L.) gave the optimal reproductive potential of female E. balteatus. There was no correlation between pollen and nectar consumption, and there was no discernible positive correlation between the quantity of pollen ingested and the resulting female performance. Phacelia and buckwheat were then studied as resource subsidies in the field in New Zealand. The effect of incorporating phacelia or buckwheat in the margins of 5 m x 5 m broccoli plots was tested for hoverfly activity and floral ‘preferences’. Hoverflies which had fed on phacelia and buckwheat pollen were found up to 17.5 m from the floral strips and females of M. fasciatum and M. novaezelandiae consumed more phacelia pollen than that of buckwheat in the field. These results support the choice of phacelia as an ideal floral resource subsidy in crops for enhanced biological control by these New Zealand species. The need for studying hoverfly movement in a large-scale field experiment was apparent from the field studies, so the next experiment was carried out in a field 450 × 270 m and flies were marked via their ingestion of the pollen of phacelia. The focus was on the proportion of flies having consumed the pollen. Although large quantities of pollen were found in some hoverfly guts, most did not contain phacelia pollen and very few were captured at 50 m from phacelia, compared with numbers at the border of the floral strip. A possible explanation was that hoverflies feed on a large variety of pollen species, reducing the relative attraction of phacelia flowers. Another possibility was that hoverflies dispersed from the phacelia away from the crop. Also, pollen digestion rates are likely to be a factor. Finally, a series of experiments was conducted in the field and laboratory to study hoverfly efficacy through oviposition and larval behaviour. In field experiments, female M. fasciatum and M. novaezelandiae laid more eggs where buckwheat patches were larger; however higher oviposition rates did not lead to improved aphid population suppression. In greenhouse experiments, larvae of E. balteatus could initiate a decline in aphid numbers at the predator: prey ratio 1: 8.3, however this control did not persist. Experiments in the laboratory showed that hoverfly larvae became more active and left the system while aphid numbers declined or numbers of larvae increased. This behaviour was caused by two factors: hunger and avoidance of conspecific larvae. Further experiments showed that the avoidance of conspecifics was caused by mutual interference rather than cannibalism. The results of this work highlight the importance of hoverfly dispersal ability. Given the observations of foraging behaviour of females and mutual interference observed between larvae, and the lack of success in CBC by hoverflies in experiments at the crop scale, it is essential to assess the impact of insect predators and parasitoids at a landscape scale.

"Summary: The larvae of predatory hoverfly Episyrphus balteatus DeGeer (Diptera: Syrphidae), have limited dispersal ability to forage. The selection of the oviposition site by gravid females is crucial for the survival larvae. Therefore hoverfly females should optimise their foraging behaviour by choosing suitable oviposition sites. The aim of this PhD thesis was to understand how hoverfly females assess aphid patch quality during their egg-laying behaviour. The impact of several factors on the oviposition response of E. balteatus females including host plant, aphid species, aphid colony size, semiochemicals emitted from aphids or their association with host plants, presence of intra- or interspecific competitors and females age, was clearly demonstrated during this research. In the first part, we have shown that E. balteatus females select their oviposition site according to aphid-host plant and aphid species, which is also shown to be related to offspring performance (fitness). Aphid species Myzus persicae (Sulzer) infested-Solanum tuberosum L. was the most preferred aphid-plant combination as an oviposition site by syrphid females. The E. balteatus survival was enhanced in this system and females laid numerous eggs when larvae were reared with M. persicae as prey, especially when the host plant was potato. Broad bean plants Vicia faba infested with Megoura viciae (Buckton) or Acyrthosiphon pisum (Harris) were equally attractive for E. balteatus females. Aphis fabae (Scopoli) was the least preferred aphid. Higher hoverfly fitness was also observed when larvae were reared on M. viciae or A. pisum compared to those reared on A. fabae. Moreover, it was also demonstrated that foraging hoverfly females is guided by different infochemical cues emitted by aphid host plant, such as (E)-β-farnesene, enabling them to locate aphid infested plant and to select an adequate oviposition site. In the second part, the leaf disc system was found to be a practical and efficient method to assess the hoverfly reproductive behaviour under different laboratory conditions. Results also showed that there was a significant quadratic relationship between the released (E)-β-farnesene amounts and aphid colony size, which means that this molecule play important role in oviposition decision made by hoverfly females in response to aphid colony size. In the third part, we have highlighted that the E. balteatus females avoid aphid colonies in which conspecific larvae or their tracks were already present. Similar response was also shown by females to the presence of Harmonia axyridis (Pallas) larval tracks. This oviposition deterring stimulus was also shown to be mediated by odourant cues emitted from larval tracks extracts. It was also demonstrated that the foraging behaviour of hoverfly females was modified by the presence of parasitoids Aphidius ervi (Haliday) in aphid colonies. Females did not exhibit any preference for plants infested with unparasitised or parasitised aphids for 7 days, but they are reluctant to lay eggs in response to the presence of mummies or their exuvia on broad bean plants. Oviposition preference of predatory hoverfly females according to the developmental state of the parasitoid larvae in aphid prey was also found to be related with larval performance. Finally, the age of hoverfly females was found to be an important factor affecting their reproduction ability, suggesting that younger E. balteatus females (2 to 5 weeks old) could be have potential to play a role in biological control of aphids because of their higher reproductive efficiency. All experiments were performed in a laboratory environment and most results obtained are discussed in relation to the context of biological control efforts/Résumé : Les larves du syrphe aphidiphage Episyrphus balteatus (Diptère, Syrphidae) ont une capacité de déplacement limitée. Le choix du site doviposition des femelles est donc crucial pour la survie larvaire. Pour cela, les femelles de ce diptère devraient optimiser leurs choix de sites doviposition pour maximiser les chances de survie de leurs progénitures. Le but de cette thèse de doctorat était de comprendre comment les femelles dE. balteatus évaluent la qualité de patches de pucerons au cours de leur comportement de ponte. La réponse de ponte des femelles dE. balteatus observées à travers plusieurs facteurs a été réalisée, parmi lesquels: la plante hôte, lespèce de pucerons, la taille de la colonie de pucerons, les substances sémiochimiques émises par les pucerons et leurs associations avec leurs plantes hôtes, la présence de compétiteurs intra- ou interspécifiques et l'âge de la femelle. Dans la première partie de ce travail, les résultats obtenus ont permis de mettre en évidence que les femelles dE. balteatus sélectionnent le site de ponte en fonction de la plante hôte et lespèce de puceron, et ce comportement a été aussi montré comme étant lié avec la performance du prédateur (fitness). La combinaison puceron/plante M. persicae/Solanum tuberosum a été la plus préférée par les femelles dE. balteatus, et le fitness de ce prédateur était plus élevé en particulier lorsque les larves sont nourries avec M. persicae élevées sur une plante de pomme de terre. De même, les femelles dE. balteatus ont montré une même préférence pour les deux combinaisons M. viciae/V. faba et A. pisum /V. faba, et un fitness supérieur du prédateur adulte a été aussi observé lorsque les larves sont nourries avec les deux espèces de pucerons. De plus, nous avons aussi montré que les femelles dE. balteatus en recherche de site de ponte sont guidées par des substances volatiles, en particulier le E-(β)-farnésène, émises par les pucerons infestant leur plante hôte. Dans la deuxième partie, le système feuille-disque est démontré comme étant une méthode pratique et efficace pour évaluer le comportement de ponte dE. balteatus au laboratoire sous différentes conditions. Les résultats ont aussi démontré quil y a une relation quadratique entre lémission du E-(β)-farnésène et la taille de colonie de pucerons, ce qui permet de seffectuer que cette molécule a un rôle important dans le comportement de ponte des femelles dE. balteatus en réponse à la taille de la colonie de pucerons. Les résultats obtenus dans la troisième partie, nous ont permis de montrer que les femelles dE. balteatus réduisent leurs pontes dans une colonie de pucerons contenant préalablement des larves de leur propre espèce ou leurs traces. Une réponse similaire a été aussi montrée en présence des substrats préalablement visitées par les larves de coccinelle Harmonia axyridis. Ainsi, la réduction de la ponte des femelles dE. balteatus est provoquée par des substances volatiles émises par les substrats des larves de syrphe. Nous avons aussi démontré que la présence du parasitoïde Aphidius ervi dans une colonie de pucerons a un effet significatif sur le comportement de ponte des femelles dE. balteatus. Les femelles dE. balteatus ne distinguent pas les plants infestées par les pucerons parasités ou non parasités, cependant les femelles réduisent leur pontes en réponse à la présence des pucerons momifiés ou des exuvies de momies. De plus, un fitness supérieur du prédateur a été aussi observé lorsque les larves sont nourries avec lespèce de pucerons A. pisum parasités ou non parasités. Enfin dans la dernière partie, lâge de la femelle dE. balteatus influence significativement leur reproduction, ce qui permet de proposer que les jeunes femelles (2 à 5 semaines) peuvent être plus efficaces dans la lutte biologique contre les pucerons car elles ont une grande efficacité de reproduction. Toutes les expériences ont été effectuées au laboratoire et la plupart des résultats obtenus sont discutés en relation avec le contexte de la lutte biologique".