Maternal investment in egg production: environmental and population-specific effects on offspring performance in the snapping shrimp Alpheus nuttingi (Schmitt, 1924) (Decapoda, Alpheidae)

Among marine invertebrates, the overall biomass invested in egg production varies widely within populations, which can result from the interaction of endogenous and exogenous factors. Species that have constant reproduction throughout the year can be good models to study the influence of environmental factors on reproductive processes. We conducted a seasonal comparison of egg production in the intertidal snapping shrimp Alpheus nuttingi, which shows a continuous reproductive pattern, to examine the hypothesis that differences in egg production are driven by environmental conditions and population features. This population showed an uncommon strategy, characterized by females that produce eggs of varying sizes within their clutches, with reduced egg volume when the number of eggs is higher (Spring-Summer). In these seasons, higher temperatures and greater food availability may allow the production of more eggs compared to the Autumn-Winter seasons. Compared to other alpheid shrimps, this population produces small eggs, but in larger numbers. Despite the higher fecundity, the reproductive output is relatively low, this production being supported by the large size of females from the southern Atlantic region. Our findings showed that the egg production of A. nuttingi was greatly influenced by environmental factors. Therefore, this shrimp, and probably other decapods that possess continuous reproduction, adopt different reproductive strategies during the year. (C) Koninklijke Brill NV, Leiden, 2010.

Relationship between oviposition preference and offspring performance in Australian Helicoverpa armigera (Hubner) (Lepidoptera : Noctuidae)

We investigated the oviposition preference and larval performance of Helicoverpa armigera under laboratory conditions to determine if the oviposition preference of individual females on maize, cowpea and cotton correlates with offspring performance on the leaves of the same host plants. The host-plant preference hierarchy of females did not correlate with their offspring performance. Female moths chose host plants that contributed less to their offspring fitness. Plant effects accounted for the largest amount of variation in offspring performance, while the effects of female (family) was low. The offspring of most females (80%, n = 10) were broadly similar, but 20% (two out of 10), showed marked difference in their offspring performance across the host-plant species. Similarly, there was no relation between larval feeding preference and performance. However, like most laboratory experiments, our experi-mental design does not allow the evaluation of ecological factors (for example, natural enemies, host abundance, etc.) that can play an important role in larval performance in the field. Overall, the results highlight the importance of carrying out preference performance analysis on the individual or family level, rather than pooling individuals to obtain average population data.

Transgenerational effects of land use on offspring performance and growth in Trifolium repens

entral European grasslands vary widely in productivity and in mowing and grazing regimes. The resulting differences in competition and heterogeneity among grasslands might have direct effects on plants, but might also affect the growth and morphology of their offspring through maternal effects or adaptive evolution. To test for such transgenerational effects, we grew plants of the clonal herb Trifolium repens from seeds collected in 58 grassland sites differing in productivity and mowing and grazing intensities in different treatments: without competition, with homogeneous competition, and with heterogeneous competition. In the competition-free treatment, T. repens from more productive, less frequently mown, and less intensively grazed sites produced more vegetative offspring, but this was not the case in the other treatments. When grown among or in close proximity to competitors, T. repens plants did not show preferential growth towards open spaces (i.e., no horizontal foraging), but did show strong vertical foraging by petiole elongation. In the homogeneous competition treatment, petiole length increased with the productivity of the parental site, but this was not the case in the heterogeneous competition treatment. Moreover, petiole length increased with mowing frequency and grazing intensity of the parental site in all but the homogeneous competition treatment. In summary, although the expression of differences between plants from sites with different productivities and land-use intensities depended on the experimental treatment, our findings imply that there are transgenerational effects of land use on the morphology and performance of T. repens.

Oviposition behavior and performance aspects of Ascia monuste (Godart, 1919) (Lepidoptera, Pieridae) on kale (Brassica oleracea var. acephala)

Host part selection by ovipositing females of Ascia monuste (Godart, 1919) (Lepidoptera, Pieridae) on kale (Brassica oleracea var. acephala) was determined in greenhouse and field. Performance of offspring (larval period, efficiency of food utilization, number of eggs/female and others) was investigated under laboratory conditions. In the field, the number of A. monuste egg clutches on the apical and medium parts of kale leaves was greater than on the basal part. In greenhouse, A. monuste exhibited a strong preference for the apical part of kale leaves for ovipositing. The best results on food utilization indices, pupal mass and female wing size were obtained with the leaf apical part. This part of kale leaves exhibited the highest nitrogen and protein concentration and the smallest water content, when compared to the other leaf parts. However, the apical part of the leaves seems not to provide ovipositing females with enough protection against birds, making them easy preys in the field. We suggest that good relationship between oviposition preference and performance of offspring was hindered by predation in field conditions.

Pattern of attack of a galling insect reveals an unexpected preference-performance linkage on medium-sized resources

Pattern of attack of a galling insect reveals an unexpected preference-performance linkage on medium-sized resources. The Plant Vigor Hypothesis (PVH) predicts oviposition preference and higher offspring performance on longer and fast-growing shoots, and although several studies have tested its predictions, long-term studies concerning the patterns of host selection by galling species are still lacking. The PVH was tested in this study using Bauhinia brevipes (Fabaceae) as the host of a leaf gall midge, Asphondylia microcapillata (Diptera, Cecidomyiidae) during three consecutive years. Shoots were collected from the same 80 plants between 2001 and 2003 and shoot length, number of healthy and galled leaves, gall number, and mortality factors were recorded. Nearly 600 galls were found on the 5,800 shoots collected. Medium-sized shoots supported from 46 to 70% of all galls, with greater gall survival rate in 2002 and 2003. A decrease in parasitism rate coupled with an increase in gall predation lead to a constant similar gall survivorship rate in all years (x = 22.7%). Although gall abundance varied among years (122 in 2001, 114 in 2002 and 359 in 2003) preference for longer shoots was not observed because the percentage of galled shoots and galled leaves were higher on medium shoot length classes in all years. The observed distribution of gall abundance and galled shoots were always greater than the expected distribution on medium shoot length classes. These findings do not support the PVH, and show that A. microcapillata can maximize the female preference and larval performance on medium-sized shoots of B. brevipes.

Genetic and maternal contributions to offspring viability under different environmental conditions in various salmonids

Summary : Due to anthropogenic impacts and natural fluctuations, fish usually have to cope with constantly changing and often hostile environments. Whereas adult fish have various possibilities to counteract unfavourable environmental conditions, embryos have much fewer options. Besides by their developing immune system, they are protected by the egg envelopes and several immune substances provided by their mothers. In addition to this, they may also adjust their hatching timing in reaction to various risks. However, individuals may vary in their defensive potential. This variation may be either based on their genetics and/or on differential maternal investments and may be dependent on the experienced stress. Nevertheless, in fish, the impact of such parental contributions on embryo and/or juvenile viability is still poorly investigated. The main objective of this thesis was to investigate the importance of paternal (i.e. genetic) and maternal (i.e. genetic + egg investment) contributions to offspring viability under different environmental conditions and at different life stages. In order to investigate this, we used gametes of various salmonids for in vitro fertilisation experiments based on full-factorial breeding designs. The individual studies are summarised in the following chapters: In the first chapter, we tested the effectiveness of the embryonic immune system in Lake whitefish (Coregonus palaea). Namely, we investigated paternal and maternal contributions to the embryos' tolerance to different kinds of pathogen exposure. Additionally, we tested whether an early sub-léthal exposure has a positive or a negative effect on an embryo's susceptibility to later pathogen exposures with the same pathogen. We found that pre-challenged embryos were more susceptible to future challenges. Moreover, pathogen susceptibility was dependent on maternal investments and/or the embryos' own genetics, depending on the challenge level. Chapter 2 summarises a similar study with brown trout (Salmo trutta). In addition to the previously described investigations, we analysed if genetic effects on offspring viability are mediated either by parental MHC genotypes or relatedness based on neutral microsatellite markers, and we tested if males signal their genetic quality either by their body size or their melanin-based skin colouration. We found that embryo survival was lower at higher stress levels and dependent on the embryos' genetics. Addirionally, parents with similar and/or, very common MHC genotypes had higher offspring viabilities. Finally, darker males produced more viable offspring. In the first two chapters we investigated the embryos' defensive potential based on their immune system, i.e. their pathogen tolerance. In chapter 3 we investigate whether hatching timing of Lake whitefìsh (C. palaea) is dependent on parental contributions and/or on pathogen pressure, and whether there are parental-environmental interactions. We found that whitefish embryos hatch earlier under increasing pathogen pressure. Moreover, hatching timing was affected by embryo genetics and/or maternally provided resources, but the magnitude of the effect was dependent on the pathogen. pressure. We also found a significant paternal-environmental interaction, indicating that the hatching efficiency of a certain sib group is dependent on the pathogen environment. Chapter 4 describes an analogous study with brown trout (S. trutta), with similar findings. In the former chapters, we only looked at offspring performance during the embryonic period, and only under semi-natural conditions. In chapter 5 we now test the performance and viability of embryonic and juvenile brown trout (S. trutta) under natural conditions. To measure embryo viability, we put them in brood boxes, buried them in the gravel of a natural river, and analysed survival after several months. To investigate juvenile survival and performance, wé reared embryos under different stress levels in the laboratory and subsequently released the resulting hatchlings in to a closed river section. Juvenile size and survival was then determined one year later. Additionally, we investigated if sires differ in their genetic quality, determined by embryo and juvenile survival as well as juvenile size, and if they signal their quality by either body size or melanin-based body darkness. We found hat juvenile size was dependent on genetic effects and on maternal investment, whereas this was neither the case for embryo nor for juvenile survival. Additionally, we found that offspring of darker males grew larger, and larger juveniles had also an increased survival. Finally, we found acarry-over effect of the early non-lethal challenge: exposing embryos to higher stress levels resulted in smaller juveniles. To evaluate the long-term performance of differently treated groups, mark-recapture studies are inevitable. For this purpose, effective mass-marking techniques are essential. In chapter 6 we tested the suitability of the fluorescent pigment spray marking method for the mass marking of European graylings (Thymallus thymallus), with very promising results. Our in vitro fertilisation studies on whitefish may reveal new insights on potential genetic benefits of mate choice, but the mating system of whitefish under natural conditions is still poorly investigated. In order to study this, we installed underwater cameras at the spawning place of a Coregonus suidteri population, recorded the whole mating period and subsequently analysed the recordings. Confirmations of previous findings as well as exciting new observations are listed and discussed in chapter 7. Dus aux impacts anthropogéniques et aux fluctuations naturelles, les poissons doivent faire face à des environnements en perpétuel changement. Ces changements font que les poissons doivent s'adapter à de nouvelles situations, souvent hostiles pour eux. Les adultes ont différentes possibilités d'échapper à un environnement peu favorable, ce n'est par contre pas le cas des embryons. Les embryons sont protégés d'une part par leur système immunitaire en développement, d'autre part, par la coquille de l'eeuf et différentes substances immunitaires fournies par leur mère. De plus, ils sont capables d'influencer leur propre date d'éclosion en réponse à différents facteurs de stress. Malgré tout, les individus varient dans leur capacité à se défendre. Cette variation peut être basé sur des facteurs génétiques et/ou sur des facteurs maternels, et est dépendante du stress subi. Néanmoins, chez les poissons, l'impact de telles contributions parentales sur la survie d'embryons et/ou juvéniles est peu étudié. L'objectif principal de cette thèse a été d'approfondir les connaissances sur l'importance de la contribution paternelle (c.a.d. génétique) et maternelle (c.a.d. génétique + investissement dans l'oeuf) sur la survie des jeunes dans différentes conditions expérimentales et stades de vie. Pour faire ces analyses, nous avons utilisé des gamètes de divers salmonidés issus de croisements 'full-factorial'. Les différentes expériences sont résumées dans les chapitres suivants: Dans le premier chapitre, nous avons testé l'efficacité du système immunitaire des embryons chez les corégones (Coregonus palea). Plus précisément nous avons étudié la contribution paternelle et maternelle à la tolérance des embryons à différents niveaux de stress pathogène. Nous avons aussi testé, si une première exposition non létale à un pathogène avait un effet positif ou négatif sur la susceptibilité d'un embryon a une deuxième exposition au même pathogène. Nous avons trouvé que des embryons qui avaient été exposés une première fois étaient plus sensibles au pathogène par la suite. Mais aussi que la sensibilité au pathogène était dépendante de l'investissement de la mère et/ou des gènes de l'embryon, dépendamment du niveau de stress. Le deuxième chapitre résume une étude similaire avec des truites (Salmo truffa). Nous avons examiné, si la survie des jeunes variait sous différentes intensités de stress, et si la variance observée était due aux gènes des parents. Nous avons aussi analysé si les effets génétiques sur la survie des juvéniles étaient dus au MHC (Major Histocompatibility Complex) ou au degré de parenté des parents. De plus, nous avons analysé si les mâles signalaient leur qualité génétique par la taille du corps ou par leur coloration noire, due à la mélanine. On a trouvé que la survie des embryons était plus basse quand le niveau de stress était plus haut mais que la variation restait dépendante de la génétique des embryons. De plus, les parents avec des MHC similaires et/ou communs avaient des embryons avec une meilleure survie. Par contre, des parents avec un degré de parenté plus haut produisent des embryons avec une survie plus mauvaise. Finalement nous avons montré que les mâles plus foncés ont des embryons qui survivent mieux, mais que la taille des mâles n'a pas d'influence sur la survie de ces mêmes embryons. Dans les deux premiers chapitres, nous avons étudié le potentiel de défense des embryons basé sur leur système immunitaire, c.a.d. leur tolérance aux pathogènes. Dans le troisième chapitre, nous nous intéressons à la date d'éclosion des corégones (C. palea), pour voir si elle est influencée par les parents ou par la pression des pathogènes, et si il y a une interaction entre ces deux facteurs. Nous avons trouvé que les jeunes naissent plus rapidement lorsque la pression en pathogènes augmente. La date d'éclosion est influencée par la génétique des embryons et/ou l'investissement des parents, mais c'est la magnitude des effets qui est dépendante de la pression du pathogène. Nous avons aussi trouvé une interaction entre l'effet paternel et l'environnement, ce qui indique que la rapidité d'éclosion de certains croisements est dépendante des pathogènes dans l'environnement. Le chapitre 4 décrit une étude analogue avec de truites (S. truffa), avec des résultats sitzimilaires. Dans les précédents chapitres nous nous sommes uniquement concentrés sur les performances des jeunes durant leur stade embryonnaire, et seulement dans des conditions semi naturelles. Dans le chapitre 5 nous testons la performance et la viabilité des embryons et de juvéniles de truites (S. truffa) dans des conditions naturelles. Nous avons trouvé que la taille des juvéniles était dépendante d'effets génétiques et de l'investissement maternel, mais ceci n'était ni les cas pour les survie des embryons et des juvéniles. De plus, nous avons trouvé que les jeunes des mâles plus foncés devenaient plus grands et que les grands ont un meilleur taux de survie. Finalement nous avons trouvé un 'carry-over effect' d'une première exposition non létale à un pathogène: exposer des embryons à des plus hauts niveaux de stress donnait des juvéniles plus petits. Pour évaluer la performance à long terme de groupes traités dé manières différentes, une méthode de marquage-recapture est inévitable. Pour cette raison, des techniques de marquage en masse sont nécessaires. Dans le chapitre 6, nous avons testé l'efficacité de la technique `fluorescent pigment spray marking' pour le marquage en masse de l'Ombre commun (Thymallus thymallus), avec des résultats très prometteurs. Les études de fertilisations in vitro avec les corégones nous donnent une idée du potentiel bénéfice génétique que représente la sélection d'un bon partenaire, même si le système d'accouplement des corégones en milieu naturel reste peu connu. Pour combler cette lacune, nous avons installé des caméras sous-marines autour de la frayère d'une population de corégones (C. suidteri), nous avons enregistré toute la période de reproduction et nous avons analysé les données par la suite. Ainsi, nous avons été capables de confirmer bien des résultats trouvés précédemment, mais aussi de faire de nouvelles observations. Ces résultats sont reportés dans le septième chapitre, où elles sont comparées avec des observations antérieures.

Effects of parental larval diet on egg size and offspring traits in Drosophila.

If a mother's nutritional status predicts the nutritional environment of the offspring, it would be adaptive for mothers experiencing nutritional stress to prime their offspring for a better tolerance to poor nutrition. We report that in Drosophila melanogaster, parents raised on poor larval food laid 3-6% heavier eggs than parents raised on standard food, despite being 30 per cent smaller. Their offspring developed 14 h (4%) faster on the poor food than offspring of well-fed parents. However, they were slightly smaller as adults. Thus, the effects of parental diet on offspring performance under malnutrition apparently involve both adaptive plasticity and maladaptive effects of parental stress.

Organic and conventional fertilizer effects on a tritrophic interaction: parasitism, performance and preference of Cotesia vestalis

Interest in sustainable farming methods that rely on alternatives to conventional synthetic fertilizers and pesticides is increasing. Sustainable farming methods often utilize natural populations of predatory and parasitic species to control populations of herbivores, which may be potential pest species. We investigated the effects of several types of fertilizer, including those typical of sustainable and conventional farming systems, on the interaction between a herbivore and parasitoid. The effects of fertilizer type on percentage parasitism, parasitoid performance, parasitoid attack behaviour and responses to plant volatiles were examined using a model Brassica system, consisting of Brassica oleracea var capitata, Plutella xylostella (Lepidoptera) larvae and Cotesia vestalis (parasitoid). Percentage parasitism was greatest for P. xylostella larvae feeding on plants that had received either a synthetic ammonium nitrate fertilizer or were unfertilized, in comparison to those receiving a composite fertilizer containing hoof and horn. Parasitism was intermediate on plants fertilized with an organically produced animal manure. Male parasitoid tibia length showed the same pattern as percentage parasitism, an indication that offspring performance was maximized on the treatments preferred by female parasitoids for oviposition. Percentage parasitism and parasitoid size were not correlated with foliar nitrogen concentration. The parasitoids did not discriminate between hosts feeding on plants in the four fertilizer treatments in parasitoid behaviour assays, but showed a preference for unfertilized plants in olfactometer experiments. The percentage parasitism and tibia length results provide support for the preference–performance hypothesis

Environment-dependent microevolution in a Mediterranean pine (Pinus pinaster Aiton).

BACKGROUND: A central question for understanding the evolutionary responses of plant species to rapidly changing environments is the assessment of their potential for short-term (in one or a few generations) genetic change. In our study, we consider the case of Pinus pinaster Aiton (maritime pine), a widespread Mediterranean tree, and (i) test, under different experimental conditions (growth chamber and semi-natural), whether higher recruitment in the wild from the most successful mothers is due to better performance of their offspring; and (ii) evaluate genetic change in quantitative traits across generations at two different life stages (mature trees and seedlings) that are known to be under strong selection pressure in forest trees. RESULTS: Genetic control was high for most traits (h2 = 0.137-0.876) under the milder conditions of the growth chamber, but only for ontogenetic change (0.276), total height (0.415) and survival (0.719) under the more stressful semi-natural conditions. Significant phenotypic selection gradients were found in mature trees for traits related to seed quality (germination rate and number of empty seeds). Moreover, female relative reproductive success was significantly correlated with offspring performance for specific leaf area (SLA) in the growth chamber experiment, and stem mass fraction (SMF) in the experiment under semi-natural conditions, two adaptive traits related to abiotic stress-response in pines. Selection gradients based on genetic covariance of seedling traits and responses to selection at this stage involved traits related to biomass allocation (SMF) and growth (as decomposed by a Gompertz model) or delayed ontogenetic change, depending also on the testing environment. CONCLUSIONS: Despite the evidence of microevolutionary change in adaptive traits in maritime pine, directional or disruptive changes are difficult to predict due to variable selection at different life stages and environments. At mature-tree stages, higher female effective reproductive success can be explained by differences in their production of offspring (due to seed quality) and, to a lesser extent, by seemingly better adapted seedlings. Selection gradients and responses to selection for seedlings also differed across experimental conditions. The distinct processes involved at the two life stages (mature trees or seedlings) together with environment-specific responses advice caution when predicting likely evolutionary responses to environmental change in Mediterranean forest trees.

Intra- and intersexual selection and their potential consequences on fitness-relevant traits in several fish species

Résumé : Les mécanismes de sélection sexuelle, en particulier la compétition entre mâles (sélection inter-sexuelle) et le choix des femelles (sélection intra-sexuelle), peuvent fortement influencer le succès reproducteur d'un individu, c'est-à-dire son nombre de descendants. On observe ainsi que les mâles dominants et les mâles élaborant des caractères sexuels secondaires marqués ont un succès reproducteur élevé. Toutefois, le succès reproducteur ne suffit pas pour garantir une contribution génétique élevée, parce que la fitness dépend également de la performance des descendants (c'est-à-dire de leur survie et de leur propre succès reproducteur). Si cette performance dépend en partie des gènes paternels, les males ont un avantage certain à signaler leur qualité aux femelles afin d'atteindre des taux de reproduction élevé. Ce mécanisme de signalisation est connu sous le nom de 'good genes hypothesis', toutefois très peu d'études ont clairement démontré le lien entre la qualité génétique des individus et la signalisation. De plus, la performance des descendants peut aussi dépendre des effets génétiques de compatibilité entre mâles et femelles ('compatible genes'). C'est-à-dire que certains allèles paternels n'apporteraient un avantage aux descendants qu'en combinaison avec certains allèles maternels. Nous avons déterminé, durant la période de reproduction, le statut de dominance des mâles pour deux espèces de poissons d'eau douce : la truite (Salmo trotta) et le vairon (Phoxinus phoxinus), puis nous avons évalué la relation entre le succès reproducteur et le statut de dominance et/ou la quantité de signalisation des caractères sexuels secondaires. Nous avons également fécondés artificiellement des oeufs de truites et de corégones (Coregonus palaea), en croisant chaque mâle avec chaque femelle (full-factorial breeding design). Ce type de design autorise la quantification précise des effets génétiques et permet de séparer les effets de 'good genes' et de 'compatible genes'. Cela a été fait sous différentes intensités de stress bactérien, ainsi que dans des conditions naturelles, et nous avons pu ainsi tester si certains indicateurs de qualité génétique des mâles ('good genes') étaient liés a) à la dominance et/ou b) à l'expression des caractères sexuels secondaires des mâles comme l'intensité mélanique ou la taille des tubercules sexuels. En outre, nous cherchons à savoir si la survie des descendants est liée à certaines combinaison des gènes du complexe d'histocompatibilité majeur (MHC) et/ou à la parenté génétique des parents, les deux traits étant soupçonnés d'avoir des influences génétique de compatibilité (`compatible genes') à la performance des descendants. Nous avons constaté que la dominance des mâles est directement liée à la taille et au poids des mâles (truites, vairons), mais également aux caractères sexuels secondaires (tubercules). De plus, les mâles vairons dominant ont eu un succès de fécondation plus élevés que les mâles subordonnés. Nous montrons que les truites et corégones mâles diffèrent dans leur qualité génétique, qui a été mesurée avéc la survie embryonnaire, le temps avant l'éclosion et enfin la croissance juvénile. Contrairement aux prédictions, la dominance (ou les traits indicatifs de dominance) n'était liée à la qualité génétique, dans aucun des traitements, et ne fonctionne donc pas comme indicateur de qualité. Par contre, la qualité génétique était liée aux caractères sexuels secondaires, particulièrement par la teinte mélanique chez les truites. Les embryons de truites issus de pères sombres survivaient mieux que ceux issus de pères clairs dans des environnements difficiles, de plus leur croissance était plus élevée lors de leur première année dans des conditions naturelles. La taille des juvéniles lors de leur première année est un trait important lié au succès dans la compétition pour des ressources telles qu'abri ou nourriture. De plus, les femelles truites peuvent augmenter la survie de leurs descendants en choisissant des mâles selon leur type de MHC ou selon leur degré de parenté. En outre, chez les corégones, la morphologie des tubercules sexuels ne semble pas signaler la qualité génétique. Nous avons également remarqué que l'exposition à des pathogènes non-létaux pouvait influencer la performance des alevins à court et long terme, probablement en affaiblissant leur système immunitaire. Cette thèse montre que les mâles diffèrent dans leur qualité génétique et que différents mécanismes de sélection inter- ou intra-sexuelle (par exemple la préférence pour des mâles sombres, pour des génotypes MHC ou pour des couples avec degré de parenté basse) pouvait avoir un effet positif sur la qualité des descendants, bien que cet effet génétique pouvait changer au cours du temps et entre différents environnements. Contrairement à nos attentes, le résultat de la compétition intra-sexuelle (la hiérarchie de dominance entre mâles) n'était pas lié à la qualité génétique individuelle ('good genes'). Dans ce sens, ce travail permet également de contribuer à l'explication du fait que la sélection sexuelle, de par sa forte sélection directionnelle, ne conduit pas à la diminution de la variance génétique, mais plutôt à la maintenance du polymorphisme génétique. Summary : Sexual selection mechanisms, especially male-male competition (inteasexual selection) and female mate choice (inteasexual selection), can strongly influence individual mating success, often resulting in dominant males and males with elaborate secondary sexual characters having higher fertilisation success. However, siring a high number of offspring alone does not guarantee high individual fitness, as fitness does also strongly depend on offspring performance (i.e. survival, fecundity). If this superiority in offspring performance depends on paternally inherited genes, the fathers are expected to signal this potential indirect benefit to females in order to attain high mating rates. This mechanism is also known as the 'good genes' hypothesis of sexual selection but until now most studies failed to conclusively show the relation of an individual genetic quality and its potential signalling traits. Further, offspring performance could also depend on compatible gene effects. These are alleles that increase offspring performance only in combination with other specific alleles. We first determined male dominance status from intrasexual competition during mating season for brown trout (Salmo trutta) and European minnows (Phoxinus phoxinus). For minnows we additionally checked if dominance and/or secondary sexual traits were linked to fertilisation success. Further, we artificially fertilised brown trout and alpine whitefish (Coregonus palaea) eggs, following full factorial breeding designs, enabling to properly measure `good gene' and `compatible gene' effects on offspring performance. This was done under different intensities of natural stressors, as well as under natural conditions. This procedure allowed us to test if the obtained male genetic quality measures (good genes effects) were indicated by a) dominance or lay traits linked to dominance and/or by b) secondary sexual characteristics such as melanin-based male skin darkness or breeding tubercles. Further, we investigated if offspring survival was linked to the MHC (major histocompatibility complex) gene combinations and/or to the parental genetic relatedness, as both traits were shown to have 'compatible gene' effects that may influence offspring performance. We found that male dominance in intrasexual competition was positively linked to body size, body weight (brown trout, minnows) but also to elaborate secondary sexual characteristics (breeding tubercles in minnows). Further, dominant minnow males did have an increased fertilisation success compared to subordinate ones. We show that brown trout and whitefish males do usually differ in their genetic quality, which was measured as embryo survival, hatching timing and finally as juvenile growth. Contrary to prediction male dominance or dominance indicating traits do not function as a quality signal as they were not linked to genetic quality. This result was constant when measuring genetic quality under different levels of natural stressors and under natural conditions (brown trout). On the other hand genetic quality seemed to be indicated by secondary sexual characteristics, specifically by melanin-based skin darkness in brown trout as brown trout embryos sired by darker fathers had increased survival rates when raised under harsh conditions and. they grew larger as juveniles after one year of growth in a natural stream, which is an important trait influencing success of juveniles in competition for hidings, food and other resources. Furthermore, brown trout females may increase the survival of their embryos when choosing males according to their MHC genotypes or to the general genetic relatedness between themselves and their potential mates. In whitefish on the other hand breeding tubercle morphology did not seem to signal genetic quality. Eventually, we saw that anon-lethal exposure to pathogens might influence short term and long term offspring performance probably by weakening an exposed individual's immune system. This thesis shows that males usually differ in their genetic quality and that different inter- or intrasexual selection mechanisms (e.g. mate selection favouring dark males, preference for MHC genotype combinations or for unrelated mates) may have strong positive effects on genetically dependent offspring performance but that such genetìc effects can change over time and environments. In contrast to our a priori expectations, the outcome of intrasexual selection, namely male dominance hierarchies, with dominant males often having high fertilisation success, was not linked to individual genetic quality (`good genes'). In this sense the present thesis may also be a helpful contribution to understand why sexual selection does not lead to rapid loss of genetic variation by strong directional selection but could even lead to the maintenance of genetic variation in natural populations.

Testing the effects of genetic crossing distance on embryo survival within a metapopulation of brown trout (Salmo trutta)

Predicting progeny performance from parental genetic divergence can potentially enhance the efficiency of supportive breeding programmes and facilitate risk assessment. Yet, experimental testing of the effects of breeding distance on offspring performance remains rare, especially in wild populations of vertebrates. Recent studies have demonstrated that embryos of salmonid fish are sensitive indicators of additive genetic variance for viability traits. We therefore used gametes of wild brown trout (Salmo trutta) from five genetically distinct populations of a river catchment in Switzerland, and used a full factorial design to produce over 2,000 embryos in 100 different crosses with varying genetic distances (FST range 0.005-0.035). Customized egg capsules allowed recording the survival of individual embryos until hatching under natural field conditions. Our breeding design enabled us to evaluate the role of the environment, of genetic and nongenetic parental contributions, and of interactions between these factors, on embryo viability. We found that embryo survival was strongly affected by maternal environmental (i.e. non-genetic) effects and by the microenvironment, i.e. by the location within the gravel. However, embryo survival was not predicted by population divergence, parental allelic dissimilarity, or heterozygosity, neither in the field nor under laboratory conditions. Our findings suggest that the genetic effects of inter-population hybridization within a genetically differentiated meta-population can be minor in comparison to environmental effects.

(Table 2) Concentrations of persistant organic pollutants in the yolk of glaucous gull eggs, Bjørnøya, Svalbard archipelago

It is largely unknown if and how persistent organic pollutants (POPs) affect the transfer of maternal hormones to eggs. This occurs despite an increasing number of studies relating environmental conditions experienced by female birds at the time of egg formation to maternal hormonal effects. Here we report the concentrations of maternal testosterone, 17beta-estradiol and major classes of POPs (organochlorines, brominated flame retardants and metabolically-derived products) in the yolk of unincubated, third-laid eggs of the glaucous gull (Larus hyperboreus), a top-predator in the Arctic marine environment. Controlled for seasonal and local variation, positive correlations were found between the concentrations of certain POPs and testosterone. Contaminant-related changes in the relative concentrations of testosterone and 17beta-estradiol were also observed. In addition, yolk steroid concentrations were associated with contaminant profiles describing the proportions of different POPs present in the yolk. Eggs from nests in which two sibling eggs hatched or failed to hatch differed in POP profiles and in the relative concentrations of testosterone and 17beta-estradiol. Although the results of this correlative study need to be interpreted with caution, they suggest that contaminant-related changes in yolk steroids may occur, possibly affecting offspring performance over and above toxic effects brought about by POPs in eggs.

Intra-specific variation for host plant use in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae): Implications for management

The polyphagous moth Helicoverpa armigera (Hubner) is one of the world's most important agricultural pests. A number of existing approaches and future designs for management of H. armigera rely on the assumption that moths do not exhibit either genetically and/or non-genetically based variation for host plant utilization. We review recent empirical evidence demonstrating that both these forms of variation influence host plant use in this moth. The significance of this variation in H. armigera in relation to current and future pest management strategies is examined. We provide recommendations on future research needs and directions for sustainable management of H. armigera, under a framework that includes consideration of intra.-specific variation for host use relevant in this and other similar pest species. (C) 2004 Elsevier Ltd. All rights reserved.

Different dietary fibres included in the gestation and lactation diet shape sow's microbiota, modify colostrum and milk composition and affect piglet growth and health

This thesis reports three experimental studies that may contribute to understand how the sources or types of dietary fibres (DFs) included in sow diet with similar level of total DFs influence the composition of colostrum and milk and their related effects on offspring performance and gut microbiota. The first study showed that decreasing the level of hemicelluloses (HCs) in sow’s lactation diet increased the proportion of butyrate and the concentration of volatile fatty acids (VFAs), copper and threonine in milk. Simultaneously, the post-weaning growth of low birthweight piglets was improved, and the diarrhoea occurrence was reduced during the second week post-weaning. The second study showed that the level of HCs in the diet of lactating sows affected their faecal microbiota, modified the VFA profile in sow’s faeces during lactation and barely impacted the faecal microbiota of slow and fast growing piglets. The third study showed that replacing a source soluble DFs by one of insoluble DFs in sow’s diet during late gestation and lactation reduced farrowing duration, increased total VFAs and lactoferrin concentrations in colostrum, improved growth performance from birth to 1 day of lactation, during the post-weaning period and throughout the study, and reduced diarrhoea occurrence during the first week post-weaning. Finally, a fourth study proposed a workflow to analyse low biomass samples from the umbilical cord blood aiming at investigating the existence of a pre-birth microbiota with no substantial findings to confirm this hypothesis. Overall, the results of these studies confirmed that, besides the level of DFs, the sources, and the types of DFs included in the sow's diet shape the sow's microbiota, influence the composition of colostrum and milk, and improve offspring performance, but with limited impacts on the microbiota of piglets.

Offspring size affects the post-metamorphic performance of a colonial marine invertebrate

The positive relationship between offspring size and offspring fitness is a fundamental assumption of life-history theory, but it has received relatively little attention in the marine environment. This is surprising given that substantial intraspecific variation in offspring size is common in marine organisms and there are clear links between larval experience and adult performance. The metamorphosis of most marine invertebrates does not represent a newbeginning, and larval experiences can have effects that carry over to juvenile survival and growth. We show that larval size can have equally important carryover effects in a colonial marine invertebrate. In the bryozoan Bugula neritina, the size of the non-feeding larvae has a prolonged effect on colony performance after metamorphosis. Colonies that came from larger larvae survived better, grew faster, and reproduced sooner or produced more embryos than colonies that came from smaller larvae. These effects crossed generations, with colonies from larger larvae themselves producing larger larvae. These effects were found in two populations (in Australia and in the United States) in contrasting habitats.