Response to Selection for a High or a Low Sex Ratio in Wolbachia-infected Lines of Trichogramma cordubensis Subjected to High Temperature

Trichogramma cordubensis is an egg parasitoid completely infected by endosymbiotic bacteria belonging to the Wolbachia genus and inducing the thelytokous mode of reproduction. Previous results showed that the thelytoky persistence at high temperature is genetically variable. Experimental selection was performed to confirm these results and to determine the possibilities of adaptation to the environment assuming cyclic bisexual reproduction. No selection was efficient and the genetic variability of the sex ratio at high temperature is probably lower than previously assumed. This reduces the adaptive possibilities in the studied Trichogramma species.Установлено, что Trichogramma cordubensis - яйцевой паразит, характеризующийся наличием эндосимбионтных бактерий Wolbachia и телитокическим способом размножения. Отмечено, что устойчивость к высокой температуре у телитокических видов генетически варьирует. Проведена экспериментальная селекция линий с высоким и низким половым индексом для определения возможных адаптаций к условиям окружающей среды, вызывающим двуполый способ размножения. Установлено, что селекция выбранных линий была не эффективной. Генетически обусловленная изменчивость полового индекса при высокой температуре оказалась ниже, чем предполагалось. Отмечено, что это уменьшает адаптивные возможности T. cordubensis

Preliminary inventory of Hymenopteran egg parasitoids from Morocco

Le but de ce travail était de dresser la liste des parasitoïdes oophages du Maroc. Ceux-ci appartiennent à 18 espèces incluses dans quatre familles de Chalcidoidea et à 27 espèces, dont six espèces de Telenomus non décrites, incluses dans deux familles de Proctotrupoidea. Cette liste est accompagnée d’informations (qui sont nouvelles ou issues des travaux de divers auteurs) portant sur la morphologie, quelquefois sur des enzymes étudiées par électrophorèse, sur la distribution et sur la biologie de ces espèces, dont 9 sont nouvelles pour le Maroc. La plupart des espèces vivent aussi en Eurasie ou en Europe (74%) ou dans une zone géographique encore plus large (10%). Toutefois, 13% des espèces semblent endémiques au Maroc. Parmi les espèces non endémiques seules 3% vivent en Afrique. L’inventaire des parasitoïdes oophages marocains est encore très incomplet: il nécessite donc d’autres récoltes qui pourront révéler de nouveaux moyens de lutte biologique

Comparison of Wolbachia Bacterial Density in Females of Four Thelythokous Strains of Trichogramma cordubensis and T. evanescens (Hymenoptera, Trichogrammatidae)

The endosymbionts of the genus Wolbachia infect numerous arthropods and nematods, and often cause different effects on the reproduction of these hosts. The endosymbiotic bacteria Wolbachia induces the thelytokous mode of reproduction in the egg parasitoids of the genus Trichogramma. The Dot-blot technique was performed to compare the symbiont Wolbachia density using the wsp gene of Wolbachia and the 18S gene of Trichogramma. It was established that Wolbachia density is not different in two host species, Trichogramma cordubensis Vargas et Cabello and T. evanescens Haliday.Эндосимбиотические бактерии рода Wolbachia заражают различных артропод и нематод, оказывая различный эффект на их репродуктивные особенности. Бактерии рода Wolbachia вызывают телитокию у яйцеедов рода Trichogramma. Использована техника Dot-blot для сравнения плотности симбионта Wolbachia, с помощью выделения гена wsp у симбионта Wolbachia и гена 18S у Trichogramma. Экспериментально установлено, что плотность Wolbachia у двух видов, Trichogramma cordubensis Vargas et Cabello и T. evanescens Haliday, одинаковая

Heritable symbionts in a world of varying temperature

Heritable microbes represent an important component of the biology, ecology and evolution of many plants, animals and fungi, acting as both parasites and partners. In this review, we examine how heritable symbiont–host interactions may alter host thermal tolerance, and how the dynamics of these interactions may more generally be altered by thermal environment. Obligate symbionts, those required by their host, are considered to represent a thermally sensitive weak point for their host, associated with accumulation of deleterious mutations. As such, these symbionts may represent an important determinant of host thermal envelope and spatial distribution. We then examine the varied relationship between thermal environment and the frequency of facultative symbionts that provide ecologically contingent benefits or act as parasites. We note that some facultative symbionts directly alter host thermotolerance. We outline how thermal environment will alter the benefits/costs of infection more widely, and additionally modulate vertical transmission efficiency. Multiple patterns are observed, with symbionts being cold sensitive in some species and heat sensitive in others, with varying and non-coincident thresholds at which phenotype and transmission are ablated. Nevertheless, it is clear that studies aiming to predict ecological and evolutionary dynamics of symbiont–host interactions need to examine the interaction across a range of thermal environments. Finally, we discuss the importance of thermal sensitivity in predicting the success/failure of symbionts to spread into novel species following natural/engineered introduction

Sélection de deux caractères chez une espèce de Trichogrammes, efficacité parasitaire des souches obtenues (Hym Trichogrammatidae)

Deux caractères ont été séparément ou simultanément sélectionnés chez T brassicae Bezdenko, la fécondité et la «capacité de recherche de l'hôte». Le 1er a connu une amélioration allant jusqu'à 71 % contrairement au 2e. Cet échec peut s'expliquer par une surestimation de l'héritabilité ou par un manque de standardisation de la mesure du caractère. L'augmentation de la fécondité des souches n'a pas eu d'influence nette sur l'efficacité parasitaire appréciée dans des serres. Nous discutons les avantages et inconvénients de diverses stratégies envisageables pour la lutte biologique : maintien, comme actuellement, de la plus grande variabilité génétique possible; sélection de certains caractères au laboratoire; sélection de l'efficacité parasitaire dans des conditions naturelles ou semi-naturelles.Selection of two characteristics in a Trichogramma species: parasitic efficacy of the obtained strains (Hym: Trichogrammatidae). Two characteristics, fecundity and "host-finding capacity", were selected in T brassicae Bezdenko over 5 generations. Three experiments were carried out. The first experiment concerned only fecundity, selected according to 2 methods (mass selection and "by strain" selection) with a pressure of 50%. It allowed fecundity to be improved by up to 52 or 71%. The second experiment concerned only the "host-finding capacity", selected under the same conditions. It did not allow improvement of character. This failure can be explained by an overestimation of the heritability or by a lack of standardization of the measurements. The third experiment concerned the 2 characteristics, separately or simultaneously (by means of an index) selected according to the "by strains" method with a pressure of 66%. The characters were not improved and this failure can be explained by a loss of fecundity variability during the rearing period between the 1st and 3rd experiment. The parasitic efficacy of the strains both selected or not was tested in greenhouses planted with corn where corn borers were released. It was concluded that the increase in fecundity had no clear influence on the biological control. The advantages and disadvantages of different biological control strategies have been discussed: maintaining, as is the current practice, the greatest possible genetic variability; selection of some characteristics in the laboratory; selection of the parasitic efficacy under natural or semi-natural conditions. Methodologies have been suggested and compared