{"id":{"repo_id":"sherbrooke","oai_identifier":"oai:usherbrooke.scholaris.ca:11143/19927"},"canonical_url":"https://search.dev.ndltd.org/etd/sherbrooke/oai:usherbrooke.scholaris.ca:11143/19927","repository":{"repo_id":"sherbrooke","name":"Université de Sherbrooke","base_url":"https://usherbrooke.scholaris.ca/server/oai/request"},"display":{"title":"Reproductive traits, identity and host preferences of two genetic lines of the seedcorn maggot, Delia platura (Diptera : Anthomyiidae)","abstract":"Future climate change scenarios predict an exacerbation of agricultural pest damage worldwide. Growers are stuck between a rock and a hard place namely the increasing capricious demands of consumers and pressure from pesticide companies to use their products. There has been increasing interest in developing safe alternatives to chemical pesticides which rely heavily on accurate pest species identification and a profound knowledge of the biological traits of such targeted species. One such alternative is the sterile insect technique which consists of releasing sterile individuals that mate with the targeted population but produce infertile eggs, effectively decreasing population levels over time. One obvious impediment to such technique is to release individuals that do not have the capacity to mate with the targeted population due to reproductive incompatibilities. Such situation may arise when dealing with misidentified cryptic species. If the released individuals look the same as the targeted population morphologically but are reproductively incompatible due to being unique biological entities, the technique is bound to fail. This technique has been employed with success for the onion maggot, Delia antiqua, and cabbage maggot, Delia radicum (Diptera: Anthomyiidae), in western Montérégie, Québec. There has been rising interest amongst growers to target another Delia species: the seedcorn maggot, Delia platura. However, two genetic lines (the H- and N- lines) have recently been discovered within D. platura. These lines differ in distribution patterns with the only region of overlap being in eastern Canada. Additionally, field data suggest differences in phenological patterns and relative proportions in different crops between the lines in western Montérégie. Using laboratory-reared colonies originating from the Montérégie region, the present project aims at better understanding the biological traits of the two D. platura lines along with evaluating their reproductive compatibility by comparing different reproductive isolation mechanisms. The initial phase of the project (Chapter 2) consisted of contrasting the reproductive traits of the H- and N-lines. As many dipteran species mate in swarms whose dynamics are highly influenced by group sex ratio and density, we evaluated the effect of these two variables on the mating success, pre-oviposition period and fecundity of the two D. platura lines. By experimentally varying a mating group’s sex ratio and density, we observed an increase in female mating probability as the ratio of males to females increased while group density had negligeable effects. N-line females had a higher mating probability than H-line females in all treatments suggesting that H-line females are choosier towards potential mates than N-line females. This high degree of choosiness may thus be a relevant pre-mating isolation mechanism between the lines. The pre-oviposition period decreased as the ratio of males to female increased at low density only for the N-line while the opposite trend was observed at high density for both lines. The results corroborate field observations of D. platura mating in swarms (which are typically male-biased) and suggest difference in the mating system of the two lines. These differences may affect inter-line mating success along with control methods that target mating such as the sterile insect technique. Using a group composition that optimized mating probability for both lines as determined in Chapter 2 (30 males : 2 females), we conducted inter-line crosses in Chapter 3 to evaluate their reproductive compatibility. We uncovered asymmetrical pre-mating isolation between the lines with H-line females rarely mating with N-line males while N-line females readily mated with H-line males. However, the eggs laid in this type of cross hatched at a 25% lower rate than the inter-line crosses suggesting either post-mating pre-zygotic or post-zygotic isolation. The larvae that successfully hatched from this type of cross had a high degree of developmental success according to the proxies evaluated: survival to adult emergence from puparia, larval and pupal developmental time, pupal weight, and adult sex ratio. Thus, we uncovered no evidence of post-zygotic isolation in this type of cross from the larval hatching to adult emergence stages. Our results point to a partial reproductive isolation between the two lines, suggesting that they are in fact two unique biological entities which could in turn influence the development of species-specific control methods for either line. We thus propose the terminology ‘biotype’ to designate the H- and N- lines to emphasize their biological differences within the agronomic and scientific community. As our results suggest that the agronomic community may actually be dealing with two biological entities, in Chapter 4 we aimed to evaluate their respective host associations by quantifying their degree of acceptance and preference when subjected to yellow onion, sweet corn, soy, radish, broccoli and a soil control in no-choice and choice experiments. In a no-choice setting, the N-line had a higher degree of acceptance on sweet corn compared to the control. While the H-line had a higher degree of acceptance on yellow onion after 24 hours, more eggs were generally laid on each of the 5 crops after 48 hours compared to the control. When subjected to a choice between the substrates, the N-line laid more eggs on all crops except yellow onion than on the control whereas the H-line laid more eggs on each of the 5 crops tested. Although females did not distribute their eggs randomly among substrates, neither biotype showed a high degree of preference in the choice experiment. Additionally, the experimental setting of the choice experiment stimulated females of both biotypes to lay more eggs than in the no-choice experiment. Our results suggest differences in ovipositional behavior between the two biotypes, at least under laboratory conditions. This thesis has demonstrated that the H- and N- lines of D. platura are two unique biological entities that should be taken into account when developing control methods. Specifically, efficient use of the sterile insect release technique would consist of targeted releases in areas where swarms of either biotype are formed and releasing individuals that are of the same biotype as the targeted population. Considering that different stimuli appear to affect oviposition in the two biotypes, further investigation on the specific role of these stimuli will help predict the presence of the biotypes in fields and thus allow for more targeted releases. It is of my optimistic opinion that the upcoming years will prove to be highly fruitful in the development of environmentally safe control methods for both biotypes of Delia platura.","abstract_html":"Future climate change scenarios predict an exacerbation of agricultural pest damage worldwide. Growers are stuck between a rock and a hard place namely the increasing capricious demands of consumers and pressure from pesticide companies to use their products. There has been increasing interest in developing safe alternatives to chemical pesticides which rely heavily on accurate pest species identification and a profound knowledge of the biological traits of such targeted species. One such alternative is the sterile insect technique which consists of releasing sterile individuals that mate with the targeted population but produce infertile eggs, effectively decreasing population levels over time. One obvious impediment to such technique is to release individuals that do not have the capacity to mate with the targeted population due to reproductive incompatibilities. Such situation may arise when dealing with misidentified cryptic species. If the released individuals look the same as the targeted population morphologically but are reproductively incompatible due to being unique biological entities, the technique is bound to fail. This technique has been employed with success for the onion maggot, Delia antiqua, and cabbage maggot, Delia radicum (Diptera: Anthomyiidae), in western Montérégie, Québec. There has been rising interest amongst growers to target another Delia species: the seedcorn maggot, Delia platura. However, two genetic lines (the H- and N- lines) have recently been discovered within D. platura. These lines differ in distribution patterns with the only region of overlap being in eastern Canada. Additionally, field data suggest differences in phenological patterns and relative proportions in different crops between the lines in western Montérégie. Using laboratory-reared colonies originating from the Montérégie region, the present project aims at better understanding the biological traits of the two D. platura lines along with evaluating their reproductive compatibility by comparing different reproductive isolation mechanisms. The initial phase of the project (Chapter 2) consisted of contrasting the reproductive traits of the H- and N-lines. As many dipteran species mate in swarms whose dynamics are highly influenced by group sex ratio and density, we evaluated the effect of these two variables on the mating success, pre-oviposition period and fecundity of the two D. platura lines. By experimentally varying a mating group’s sex ratio and density, we observed an increase in female mating probability as the ratio of males to females increased while group density had negligeable effects. N-line females had a higher mating probability than H-line females in all treatments suggesting that H-line females are choosier towards potential mates than N-line females. This high degree of choosiness may thus be a relevant pre-mating isolation mechanism between the lines. The pre-oviposition period decreased as the ratio of males to female increased at low density only for the N-line while the opposite trend was observed at high density for both lines. The results corroborate field observations of D. platura mating in swarms (which are typically male-biased) and suggest difference in the mating system of the two lines. These differences may affect inter-line mating success along with control methods that target mating such as the sterile insect technique. Using a group composition that optimized mating probability for both lines as determined in Chapter 2 (30 males : 2 females), we conducted inter-line crosses in Chapter 3 to evaluate their reproductive compatibility. We uncovered asymmetrical pre-mating isolation between the lines with H-line females rarely mating with N-line males while N-line females readily mated with H-line males. However, the eggs laid in this type of cross hatched at a 25% lower rate than the inter-line crosses suggesting either post-mating pre-zygotic or post-zygotic isolation. The larvae that successfully hatched from this type of cross had a high degree of developmental success according to the proxies evaluated: survival to adult emergence from puparia, larval and pupal developmental time, pupal weight, and adult sex ratio. Thus, we uncovered no evidence of post-zygotic isolation in this type of cross from the larval hatching to adult emergence stages. Our results point to a partial reproductive isolation between the two lines, suggesting that they are in fact two unique biological entities which could in turn influence the development of species-specific control methods for either line. We thus propose the terminology ‘biotype’ to designate the H- and N- lines to emphasize their biological differences within the agronomic and scientific community. As our results suggest that the agronomic community may actually be dealing with two biological entities, in Chapter 4 we aimed to evaluate their respective host associations by quantifying their degree of acceptance and preference when subjected to yellow onion, sweet corn, soy, radish, broccoli and a soil control in no-choice and choice experiments. In a no-choice setting, the N-line had a higher degree of acceptance on sweet corn compared to the control. While the H-line had a higher degree of acceptance on yellow onion after 24 hours, more eggs were generally laid on each of the 5 crops after 48 hours compared to the control. When subjected to a choice between the substrates, the N-line laid more eggs on all crops except yellow onion than on the control whereas the H-line laid more eggs on each of the 5 crops tested. Although females did not distribute their eggs randomly among substrates, neither biotype showed a high degree of preference in the choice experiment. Additionally, the experimental setting of the choice experiment stimulated females of both biotypes to lay more eggs than in the no-choice experiment. Our results suggest differences in ovipositional behavior between the two biotypes, at least under laboratory conditions. This thesis has demonstrated that the H- and N- lines of D. platura are two unique biological entities that should be taken into account when developing control methods. Specifically, efficient use of the sterile insect release technique would consist of targeted releases in areas where swarms of either biotype are formed and releasing individuals that are of the same biotype as the targeted population. Considering that different stimuli appear to affect oviposition in the two biotypes, further investigation on the specific role of these stimuli will help predict the presence of the biotypes in fields and thus allow for more targeted releases. It is of my optimistic opinion that the upcoming years will prove to be highly fruitful in the development of environmentally safe control methods for both biotypes of Delia platura.","abstract_has_math":false,"creators":["Bush-Beaupré, Allen"],"institution":"Université de Sherbrooke","degree_name":"M. Sc.","degree_level":"Maîtrise","degree_discipline":"Biologie","degree_department":null,"school":null,"contributors":[],"advisors":["Savage, Jade","Bélisle, Marc"],"committee_chairs":[],"committee_members":[],"year":2022,"date_issued":"2022","date_published":"2022","updated_at":"2026-07-27T21:07:53Z","subjects":["Agricultural entomology","Species delimitation","Reproductive behavior","Entomologie agricole","Délimitation des espèces","Comportement reproductif"],"languages":["en"],"rights":[],"rights_urls":["http://creativecommons.org/licenses/by-nc-nd/2.5/ca/"],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/11143/19927","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Savage, Jade","Bélisle, Marc"]},{"key":"dc:creator","label":"Author","values":["Bush-Beaupré, Allen"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2022-11-25T21:42:42Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2022-11-25T21:42:42Z"]},{"key":"dc:date.issued","label":"Date","values":["2022"]},{"key":"dc:publisher","label":"Institution","values":["Université de Sherbrooke"]},{"key":"dc:type","label":"Dc Type","values":["Mémoire de maîtrise"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Biologie"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Maîtrise"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M. 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Growers are stuck between a rock and a hard place namely the increasing capricious demands of consumers and pressure from pesticide companies to use their products. There has been increasing interest in developing safe alternatives to chemical pesticides which rely heavily on accurate pest species identification and a profound knowledge of the biological traits of such targeted species. One such alternative is the sterile insect technique which consists of releasing sterile individuals that mate with the targeted population but produce infertile eggs, effectively decreasing population levels over time. One obvious impediment to such technique is to release individuals that do not have the capacity to mate with the targeted population due to reproductive incompatibilities. Such situation may arise when dealing with misidentified cryptic species. If the released individuals look the same as the targeted population morphologically but are reproductively incompatible due to being unique biological entities, the technique is bound to fail. This technique has been employed with success for the onion maggot, Delia antiqua, and cabbage maggot, Delia radicum (Diptera: Anthomyiidae), in western Montérégie, Québec. There has been rising interest amongst growers to target another Delia species: the seedcorn maggot, Delia platura. However, two genetic lines (the H- and N- lines) have recently been discovered within D. platura. These lines differ in distribution patterns with the only region of overlap being in eastern Canada. Additionally, field data suggest differences in phenological patterns and relative proportions in different crops between the lines in western Montérégie. Using laboratory-reared colonies originating from the Montérégie region, the present project aims at better understanding the biological traits of the two D. platura lines along with evaluating their reproductive compatibility by comparing different reproductive isolation mechanisms. The initial phase of the project (Chapter 2) consisted of contrasting the reproductive traits of the H- and N-lines. As many dipteran species mate in swarms whose dynamics are highly influenced by group sex ratio and density, we evaluated the effect of these two variables on the mating success, pre-oviposition period and fecundity of the two D. platura lines. By experimentally varying a mating group’s sex ratio and density, we observed an increase in female mating probability as the ratio of males to females increased while group density had negligeable effects. N-line females had a higher mating probability than H-line females in all treatments suggesting that H-line females are choosier towards potential mates than N-line females. This high degree of choosiness may thus be a relevant pre-mating isolation mechanism between the lines. The pre-oviposition period decreased as the ratio of males to female increased at low density only for the N-line while the opposite trend was observed at high density for both lines. The results corroborate field observations of D. platura mating in swarms (which are typically male-biased) and suggest difference in the mating system of the two lines. These differences may affect inter-line mating success along with control methods that target mating such as the sterile insect technique. Using a group composition that optimized mating probability for both lines as determined in Chapter 2 (30 males : 2 females), we conducted inter-line crosses in Chapter 3 to evaluate their reproductive compatibility. We uncovered asymmetrical pre-mating isolation between the lines with H-line females rarely mating with N-line males while N-line females readily mated with H-line males. However, the eggs laid in this type of cross hatched at a 25% lower rate than the inter-line crosses suggesting either post-mating pre-zygotic or post-zygotic isolation. The larvae that successfully hatched from this type of cross had a high degree of developmental success according to the proxies evaluated: survival to adult emergence from puparia, larval and pupal developmental time, pupal weight, and adult sex ratio. Thus, we uncovered no evidence of post-zygotic isolation in this type of cross from the larval hatching to adult emergence stages. Our results point to a partial reproductive isolation between the two lines, suggesting that they are in fact two unique biological entities which could in turn influence the development of species-specific control methods for either line. We thus propose the terminology ‘biotype’ to designate the H- and N- lines to emphasize their biological differences within the agronomic and scientific community. As our results suggest that the agronomic community may actually be dealing with two biological entities, in Chapter 4 we aimed to evaluate their respective host associations by quantifying their degree of acceptance and preference when subjected to yellow onion, sweet corn, soy, radish, broccoli and a soil control in no-choice and choice experiments. In a no-choice setting, the N-line had a higher degree of acceptance on sweet corn compared to the control. While the H-line had a higher degree of acceptance on yellow onion after 24 hours, more eggs were generally laid on each of the 5 crops after 48 hours compared to the control. When subjected to a choice between the substrates, the N-line laid more eggs on all crops except yellow onion than on the control whereas the H-line laid more eggs on each of the 5 crops tested. Although females did not distribute their eggs randomly among substrates, neither biotype showed a high degree of preference in the choice experiment. Additionally, the experimental setting of the choice experiment stimulated females of both biotypes to lay more eggs than in the no-choice experiment. Our results suggest differences in ovipositional behavior between the two biotypes, at least under laboratory conditions. This thesis has demonstrated that the H- and N- lines of D. platura are two unique biological entities that should be taken into account when developing control methods. Specifically, efficient use of the sterile insect release technique would consist of targeted releases in areas where swarms of either biotype are formed and releasing individuals that are of the same biotype as the targeted population. Considering that different stimuli appear to affect oviposition in the two biotypes, further investigation on the specific role of these stimuli will help predict the presence of the biotypes in fields and thus allow for more targeted releases. It is of my optimistic opinion that the upcoming years will prove to be highly fruitful in the development of environmentally safe control methods for both biotypes of Delia platura.","Les scénarios de changement climatique à venir prévoient une exacerbation des dégâts causés par les ravageurs agricoles dans le monde entier. On s'intéresse de plus en plus au développement d'alternatives sécuritaires aux pesticides chimiques, qui reposent sur une identification précise des espèces nuisibles et une connaissance approfondie des caractéristiques biologiques des espèces ciblées. L'une de ces alternatives est la technique des insectes stériles qui a été utilisée avec succès pour la mouche de l'oignon, Delia antiqua, et la mouche du chou, Delia radicum (Diptera : Anthomyiidae), dans l'ouest de la Montérégie, au Québec. Les producteurs s'intéressent de plus en plus à une autre espèce de Delia : la mouche des semis, Delia platura. Cependant, deux lignées génétiques (les lignées H- et N-) ont récemment été découvertes au sein de D. platura. Ces lignées diffèrent dans leurs patrons de distribution, la seule région de chevauchement étant l'est du Canada. De plus, des données de terrain suggèrent des différences dans les patrons phénologiques et les proportions relatives dans différentes cultures entre les lignées dans l'ouest de la Montérégie. En utilisant des colonies élevées en laboratoire provenant de la région de la Montérégie, le présent projet vise à mieux comprendre les traits biologiques des deux lignées de D. platura et à évaluer leur compatibilité reproductive en comparant différents mécanismes d'isolement reproductif. La phase initiale du projet (chapitre 2) consistait à contraster les traits reproductifs des lignées H et N. Comme de nombreuses espèces de diptères s'accouplent en essaims dont la dynamique est fortement influencée par le sex-ratio et la densité du groupe, nous avons évalué l'effet de ces deux variables sur le succès d’accouplement, la période de pré-oviposition et la fécondité des deux lignées de D. platura. En faisant varier expérimentalement le sex-ratio et la densité d'un groupe d'accouplement, nous avons observé une augmentation de la probabilité d'accouplement des femelles lorsque le ratio mâles/femelles augmente alors que la densité du groupe a des effets négligeables. Les femelles de la lignée N avaient une probabilité d'accouplement plus élevée que les femelles de la lignée H dans tous les traitements, ce qui suggère que les femelles de la lignée H sont plus sélectives envers les mâles potentiels que les femelles de la lignée N. Ce haut degré de sélectivité peut être considéré comme un facteur d’isolement pré-copulatoire potentiel entre les deux lignées. La période de pré-oviposition a diminué avec l'augmentation du ratio mâles/femelles à faible densité uniquement pour la lignée N, alors que la tendance inverse a été observée à forte densité pour les deux lignées. Les résultats suggèrent une différence dans le système d'accouplement des deux lignées. Ces différences peuvent affecter le succès d’accouplement entre les lignées ainsi que les méthodes de contrôle qui ciblent l'accouplement comme la technique d’insectes stériles. En utilisant une composition de groupe qui optimise la probabilité d'accouplement pour les deux lignées comme déterminé dans le chapitre 2 (30 mâles : 2 femelles), nous avons effectué des croisements inter-lignées dans le chapitre 3 pour évaluer leur compatibilité reproductive. Nous avons découvert un isolation pré-copulatoire asymétrique entre les lignées ; les femelles de la lignée H s'accouplant rarement avec les mâles de la lignée N, alors que les femelles de la lignée N s'accouplent couramment avec les mâles de la lignée H. Cependant, les œufs pondus dans ce type de croisement ont éclos à un taux de 25% inférieur à celui des croisements intra-lignées, ce qui suggère un isolement post-copulatoire pré-zygotique ou post-zygotique. Les larves qui ont éclos avec succès à partir de ce type de croisement ont eu un haut degré de succès de développement selon les proxies évalués : survie jusqu'à l'émergence de l'adulte des puparia, temps de développement larvaire et nymphal, poids nymphal, et sex ratio adulte. Ainsi, nous n'avons découvert aucune preuve d'isolement post-zygotique dans ce type de croisement depuis l'éclosion des larves jusqu'à l'émergence des adultes. Nos résultats indiquent un isolement reproductive partiel entre les deux lignées, ce qui suggère qu'il s'agit en fait de deux entités biologiques uniques qui pourraient à leur tour influencer le développement de méthodes de contrôle spécifiques pour l'une ou l'autre lignée. Nous proposons donc la terminologie 'biotype' pour désigner les lignées H et N afin de souligner leurs différences biologiques au sein de la communauté agronomique et scientifique. Comme nos résultats suggèrent que la communauté agronomique pourrait avoir affaire à deux entités biologiques, nous avons cherché, au chapitre 4, à évaluer leurs associations d'hôtes respectives en quantifiant leur degré d'acceptation et de préférence lorsqu'elles sont soumises à l'oignon jaune, au maïs sucré, au soja, au radis, au brocoli et à un sol témoin dans des expériences de choix et de non-choix. Dans un contexte de non-choix, la lignée N avait un degré d'acceptation plus élevé sur le maïs sucré par rapport au témoin. Alors que la lignée H avait un plus haut degré d'acceptation sur l'oignon jaune après 24 heures, plus d'œufs ont été pondus sur chacune des 5 cultures après 48 heures par rapport au témoin. Bien que les femelles n'aient pas distribué leurs œufs au hasard entre les substrats, aucun des deux biotypes n'a montré un haut degré de préférence dans l'expérience de choix. De plus, le cadre expérimental de l'expérience de choix a stimulé les femelles des deux biotypes à pondre plus d'œufs que dans l'expérience de non-choix. Nos résultats suggèrent des différences dans le comportement de ponte entre les deux biotypes, au moins dans des conditions de laboratoire. Ce mémoire a démontré que les lignées H- et N- de D. platura sont deux entités biologiques uniques qui doivent être prises en compte lors du développement de méthodes de contrôle. Plus précisément, une utilisation efficace de la technique de lâcher d'insectes stériles consisterait à effectuer des lâchers ciblés dans les zones où se forment des essaims de l'un ou l'autre biotype et à relâcher des individus qui sont du même biotype que la population ciblée. Étant donné que différents stimuli semblent affecter la ponte des deux biotypes, des recherches plus poussées sur le rôle spécifique de ces stimuli aideront à prédire la présence des biotypes dans les champs et permettront ainsi des lâchers plus ciblés."]},{"key":"dc:title","label":"Title","values":["Reproductive traits, identity and host preferences of two genetic lines of the seedcorn maggot, Delia platura (Diptera : Anthomyiidae)"]}]}],"canonical_facts":{"dc:contributor.advisor":["Savage, Jade","Bélisle, Marc"],"dc:creator":["Bush-Beaupré, Allen"],"dc:date.accessioned":["2022-11-25T21:42:42Z"],"dc:date.available":["2022-11-25T21:42:42Z"],"dc:date.issued":["2022"],"dc:description.abstract":["Future climate change scenarios predict an exacerbation of agricultural pest damage worldwide. Growers are stuck between a rock and a hard place namely the increasing capricious demands of consumers and pressure from pesticide companies to use their products. There has been increasing interest in developing safe alternatives to chemical pesticides which rely heavily on accurate pest species identification and a profound knowledge of the biological traits of such targeted species. One such alternative is the sterile insect technique which consists of releasing sterile individuals that mate with the targeted population but produce infertile eggs, effectively decreasing population levels over time. One obvious impediment to such technique is to release individuals that do not have the capacity to mate with the targeted population due to reproductive incompatibilities. Such situation may arise when dealing with misidentified cryptic species. If the released individuals look the same as the targeted population morphologically but are reproductively incompatible due to being unique biological entities, the technique is bound to fail. This technique has been employed with success for the onion maggot, Delia antiqua, and cabbage maggot, Delia radicum (Diptera: Anthomyiidae), in western Montérégie, Québec. There has been rising interest amongst growers to target another Delia species: the seedcorn maggot, Delia platura. However, two genetic lines (the H- and N- lines) have recently been discovered within D. platura. These lines differ in distribution patterns with the only region of overlap being in eastern Canada. Additionally, field data suggest differences in phenological patterns and relative proportions in different crops between the lines in western Montérégie. Using laboratory-reared colonies originating from the Montérégie region, the present project aims at better understanding the biological traits of the two D. platura lines along with evaluating their reproductive compatibility by comparing different reproductive isolation mechanisms. The initial phase of the project (Chapter 2) consisted of contrasting the reproductive traits of the H- and N-lines. As many dipteran species mate in swarms whose dynamics are highly influenced by group sex ratio and density, we evaluated the effect of these two variables on the mating success, pre-oviposition period and fecundity of the two D. platura lines. By experimentally varying a mating group’s sex ratio and density, we observed an increase in female mating probability as the ratio of males to females increased while group density had negligeable effects. N-line females had a higher mating probability than H-line females in all treatments suggesting that H-line females are choosier towards potential mates than N-line females. This high degree of choosiness may thus be a relevant pre-mating isolation mechanism between the lines. The pre-oviposition period decreased as the ratio of males to female increased at low density only for the N-line while the opposite trend was observed at high density for both lines. The results corroborate field observations of D. platura mating in swarms (which are typically male-biased) and suggest difference in the mating system of the two lines. These differences may affect inter-line mating success along with control methods that target mating such as the sterile insect technique. Using a group composition that optimized mating probability for both lines as determined in Chapter 2 (30 males : 2 females), we conducted inter-line crosses in Chapter 3 to evaluate their reproductive compatibility. We uncovered asymmetrical pre-mating isolation between the lines with H-line females rarely mating with N-line males while N-line females readily mated with H-line males. However, the eggs laid in this type of cross hatched at a 25% lower rate than the inter-line crosses suggesting either post-mating pre-zygotic or post-zygotic isolation. The larvae that successfully hatched from this type of cross had a high degree of developmental success according to the proxies evaluated: survival to adult emergence from puparia, larval and pupal developmental time, pupal weight, and adult sex ratio. Thus, we uncovered no evidence of post-zygotic isolation in this type of cross from the larval hatching to adult emergence stages. Our results point to a partial reproductive isolation between the two lines, suggesting that they are in fact two unique biological entities which could in turn influence the development of species-specific control methods for either line. We thus propose the terminology ‘biotype’ to designate the H- and N- lines to emphasize their biological differences within the agronomic and scientific community. As our results suggest that the agronomic community may actually be dealing with two biological entities, in Chapter 4 we aimed to evaluate their respective host associations by quantifying their degree of acceptance and preference when subjected to yellow onion, sweet corn, soy, radish, broccoli and a soil control in no-choice and choice experiments. In a no-choice setting, the N-line had a higher degree of acceptance on sweet corn compared to the control. While the H-line had a higher degree of acceptance on yellow onion after 24 hours, more eggs were generally laid on each of the 5 crops after 48 hours compared to the control. When subjected to a choice between the substrates, the N-line laid more eggs on all crops except yellow onion than on the control whereas the H-line laid more eggs on each of the 5 crops tested. Although females did not distribute their eggs randomly among substrates, neither biotype showed a high degree of preference in the choice experiment. Additionally, the experimental setting of the choice experiment stimulated females of both biotypes to lay more eggs than in the no-choice experiment. Our results suggest differences in ovipositional behavior between the two biotypes, at least under laboratory conditions. This thesis has demonstrated that the H- and N- lines of D. platura are two unique biological entities that should be taken into account when developing control methods. Specifically, efficient use of the sterile insect release technique would consist of targeted releases in areas where swarms of either biotype are formed and releasing individuals that are of the same biotype as the targeted population. Considering that different stimuli appear to affect oviposition in the two biotypes, further investigation on the specific role of these stimuli will help predict the presence of the biotypes in fields and thus allow for more targeted releases. It is of my optimistic opinion that the upcoming years will prove to be highly fruitful in the development of environmentally safe control methods for both biotypes of Delia platura.","Les scénarios de changement climatique à venir prévoient une exacerbation des dégâts causés par les ravageurs agricoles dans le monde entier. On s'intéresse de plus en plus au développement d'alternatives sécuritaires aux pesticides chimiques, qui reposent sur une identification précise des espèces nuisibles et une connaissance approfondie des caractéristiques biologiques des espèces ciblées. L'une de ces alternatives est la technique des insectes stériles qui a été utilisée avec succès pour la mouche de l'oignon, Delia antiqua, et la mouche du chou, Delia radicum (Diptera : Anthomyiidae), dans l'ouest de la Montérégie, au Québec. Les producteurs s'intéressent de plus en plus à une autre espèce de Delia : la mouche des semis, Delia platura. Cependant, deux lignées génétiques (les lignées H- et N-) ont récemment été découvertes au sein de D. platura. Ces lignées diffèrent dans leurs patrons de distribution, la seule région de chevauchement étant l'est du Canada. De plus, des données de terrain suggèrent des différences dans les patrons phénologiques et les proportions relatives dans différentes cultures entre les lignées dans l'ouest de la Montérégie. En utilisant des colonies élevées en laboratoire provenant de la région de la Montérégie, le présent projet vise à mieux comprendre les traits biologiques des deux lignées de D. platura et à évaluer leur compatibilité reproductive en comparant différents mécanismes d'isolement reproductif. La phase initiale du projet (chapitre 2) consistait à contraster les traits reproductifs des lignées H et N. Comme de nombreuses espèces de diptères s'accouplent en essaims dont la dynamique est fortement influencée par le sex-ratio et la densité du groupe, nous avons évalué l'effet de ces deux variables sur le succès d’accouplement, la période de pré-oviposition et la fécondité des deux lignées de D. platura. En faisant varier expérimentalement le sex-ratio et la densité d'un groupe d'accouplement, nous avons observé une augmentation de la probabilité d'accouplement des femelles lorsque le ratio mâles/femelles augmente alors que la densité du groupe a des effets négligeables. Les femelles de la lignée N avaient une probabilité d'accouplement plus élevée que les femelles de la lignée H dans tous les traitements, ce qui suggère que les femelles de la lignée H sont plus sélectives envers les mâles potentiels que les femelles de la lignée N. Ce haut degré de sélectivité peut être considéré comme un facteur d’isolement pré-copulatoire potentiel entre les deux lignées. La période de pré-oviposition a diminué avec l'augmentation du ratio mâles/femelles à faible densité uniquement pour la lignée N, alors que la tendance inverse a été observée à forte densité pour les deux lignées. Les résultats suggèrent une différence dans le système d'accouplement des deux lignées. Ces différences peuvent affecter le succès d’accouplement entre les lignées ainsi que les méthodes de contrôle qui ciblent l'accouplement comme la technique d’insectes stériles. En utilisant une composition de groupe qui optimise la probabilité d'accouplement pour les deux lignées comme déterminé dans le chapitre 2 (30 mâles : 2 femelles), nous avons effectué des croisements inter-lignées dans le chapitre 3 pour évaluer leur compatibilité reproductive. Nous avons découvert un isolation pré-copulatoire asymétrique entre les lignées ; les femelles de la lignée H s'accouplant rarement avec les mâles de la lignée N, alors que les femelles de la lignée N s'accouplent couramment avec les mâles de la lignée H. Cependant, les œufs pondus dans ce type de croisement ont éclos à un taux de 25% inférieur à celui des croisements intra-lignées, ce qui suggère un isolement post-copulatoire pré-zygotique ou post-zygotique. Les larves qui ont éclos avec succès à partir de ce type de croisement ont eu un haut degré de succès de développement selon les proxies évalués : survie jusqu'à l'émergence de l'adulte des puparia, temps de développement larvaire et nymphal, poids nymphal, et sex ratio adulte. Ainsi, nous n'avons découvert aucune preuve d'isolement post-zygotique dans ce type de croisement depuis l'éclosion des larves jusqu'à l'émergence des adultes. Nos résultats indiquent un isolement reproductive partiel entre les deux lignées, ce qui suggère qu'il s'agit en fait de deux entités biologiques uniques qui pourraient à leur tour influencer le développement de méthodes de contrôle spécifiques pour l'une ou l'autre lignée. Nous proposons donc la terminologie 'biotype' pour désigner les lignées H et N afin de souligner leurs différences biologiques au sein de la communauté agronomique et scientifique. Comme nos résultats suggèrent que la communauté agronomique pourrait avoir affaire à deux entités biologiques, nous avons cherché, au chapitre 4, à évaluer leurs associations d'hôtes respectives en quantifiant leur degré d'acceptation et de préférence lorsqu'elles sont soumises à l'oignon jaune, au maïs sucré, au soja, au radis, au brocoli et à un sol témoin dans des expériences de choix et de non-choix. Dans un contexte de non-choix, la lignée N avait un degré d'acceptation plus élevé sur le maïs sucré par rapport au témoin. Alors que la lignée H avait un plus haut degré d'acceptation sur l'oignon jaune après 24 heures, plus d'œufs ont été pondus sur chacune des 5 cultures après 48 heures par rapport au témoin. Bien que les femelles n'aient pas distribué leurs œufs au hasard entre les substrats, aucun des deux biotypes n'a montré un haut degré de préférence dans l'expérience de choix. De plus, le cadre expérimental de l'expérience de choix a stimulé les femelles des deux biotypes à pondre plus d'œufs que dans l'expérience de non-choix. Nos résultats suggèrent des différences dans le comportement de ponte entre les deux biotypes, au moins dans des conditions de laboratoire. Ce mémoire a démontré que les lignées H- et N- de D. platura sont deux entités biologiques uniques qui doivent être prises en compte lors du développement de méthodes de contrôle. Plus précisément, une utilisation efficace de la technique de lâcher d'insectes stériles consisterait à effectuer des lâchers ciblés dans les zones où se forment des essaims de l'un ou l'autre biotype et à relâcher des individus qui sont du même biotype que la population ciblée. Étant donné que différents stimuli semblent affecter la ponte des deux biotypes, des recherches plus poussées sur le rôle spécifique de ces stimuli aideront à prédire la présence des biotypes dans les champs et permettront ainsi des lâchers plus ciblés."],"dc:identifier.uri":["http://hdl.handle.net/11143/19927"],"dc:language.iso":["en"],"dc:publisher":["Université de Sherbrooke"],"dc:rights.uri":["http://creativecommons.org/licenses/by-nc-nd/2.5/ca/"],"dc:subject":["Agricultural entomology","Species delimitation","Reproductive behavior","Entomologie agricole","Délimitation des espèces","Comportement reproductif"],"dc:title":["Reproductive traits, identity and host preferences of two genetic lines of the seedcorn maggot, Delia platura (Diptera : Anthomyiidae)"],"dc:type":["Mémoire de maîtrise"],"thesis:degree_discipline":["Biologie"],"thesis:degree_level":["Maîtrise"],"thesis:degree_name":["M. Sc."],"thesis:institution_name":["Université de Sherbrooke"]},"updated_at":"2026-07-27T21:07:53Z"}