Trophic and Competitive Interactions among Egg Parasitoids of Stink Bugs

The intra- and inter-trophic interactions in ecosystems can be disrupted by invasive species, with lasting effects on population dynamics of native organisms. An invasive species may be attractive as a prey or host to native species, but if unsuitable for consumption or for development of the natural enemy’s progeny, it constitutes an ‘evolutionary trap’. A possibility of such a trap for native egg parasitoids (Hymenoptera: Scelionidae) exists with the introduction of the exotic brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae). The objective of this thesis is to enhance the understanding of Pentatomidae-Scelionidae host-parasitoid interactions from a behavioural ecology perspective, focusing on factors influencing successful host use by egg parasitoids associated with stink bugs. Behavioural, molecular, and imaging methodologies were employed to elucidate trophic and competitive interactions of native egg parasitoids with invasive host, H. halys, and with an interspecific competitor, the exotic Trissolcus japonicus (Hymenoptera: Scelionidae) egg parasitoid. First, sentinel egg masses were exposed under natural conditions, followed by parasitism quantification, using both traditional (parasitoid emergence) and molecular analysis. Second, the outcomes of competitive interactions between exotic and native egg parasitoids using H. halys as host were characterized and the possibility of their coexistence assessed. Third, an L9 orthogonal array (OA) design was used to rank the influence of host egg mass parameters on parasitoid behaviour and development. Finally, the temporal pattern of parasitoid development in H. halys was examined using a DNA-based approach (PCR) and visualized by X-ray micro-computed tomography (micro-CT). The key finding of this thesis is that the lack of success in H. halys eggs is linked to native parasitoids’ inability to develop in this host (not the rejection of the host). This failure occurs early in the parasitoid development, confirming the evolutionary trap potential of H. halys. The maladaptive decision to oviposit in an unsuitable host is caused by the mismatch between cues females use for host recognition and acceptance, and the expected normal development of the progeny. For some native parasitoids, the impact of the evolutionary trap can be reduced via facultative hyperparasitism of exotic parasitoids; for others, the co-existence is possible due to counterbalance competition

Reproductive behaviour of Western bean cutworm, Striacosta ablicosta (Lepidoptera: Noctuidae), females under different abiotic and biotic conditions

The Western bean cutworm (WBC) recently expanded its range eastward from the western United States into the Great Lakes region. Little is known about the reproductive biology of this potential pest, therefore I studied the calling behaviour (the emission of the sex pheromone by females) under different biotic (age, mating status) and abiotic (temperature, relative humidity) conditions. Sexual maturation, which occurred several days after emergence, indicating that WBC is a migratory species, was not directly affected by temperature but rather by the difference between day and night temperatures. Calling behaviour was influenced by female age, but not the abiotic factors tested. Titers of the sex pheromone did not change with female age suggesting older females that call for longer, may be more attractive than younger conspecifics. Females resumed calling within 48h of mating, and did so earlier than virgin ones, which may explain the high incidence of polyandry in WBC

Does the Response of Insect Herbivores to Cadmium Depend on Their Feeding Strategy?

Phytoremediation has been proposed for the elimination of toxic metals in soil, yet little attention has been given to the performance of insects that feed on contaminant-tolerant plants. We tested the performance of two herbivores with different feeding behaviors, the cabbage looper, Trichoplusia ni, and the green peach aphid, Myzus persicae, reared on cadmium-tolerant Brassica juncea plants that contained different concentrations of cadmium. We also tested the performance of the aphid parasitoid Aphidius colemani developing in aphids reared on plants with different levels of cadmium. The hypothesis tested was that the chewing insect would be more negatively affected than the sucking insect, because of the localization of cadmium within the host plant, and that the aphid parasitoid would not be affected. We also compared the performance of T. ni on artificial diet with different levels of cadmium. Neither the phloem-feeding aphid nor its parasitoid was affected by cadmium in the host plant. The effects of cadmium on the foliage-feeding cabbage looper varied, with negative effects on development observed in experiments with artificial diet but not in those using natural host plants. These data, together with information available in the literature, support the idea that the effects of toxic metals present in a host plant may be influenced by a herbivore’s feeding strategy. However, a wide range of chewing and sucking species needs to be tested to confirm this hypothesis

Familial hypercholesterolaemia in children and adolescents from 48 countries: a cross-sectional study

Background: Approximately 450 000 children are born with familial hypercholesterolaemia worldwide every year, yet only 2·1% of adults with familial hypercholesterolaemia were diagnosed before age 18 years via current diagnostic approaches, which are derived from observations in adults. We aimed to characterise children and adolescents with heterozygous familial hypercholesterolaemia (HeFH) and understand current approaches to the identification and management of familial hypercholesterolaemia to inform future public health strategies. Methods: For this cross-sectional study, we assessed children and adolescents younger than 18 years with a clinical or genetic diagnosis of HeFH at the time of entry into the Familial Hypercholesterolaemia Studies Collaboration (FHSC) registry between Oct 1, 2015, and Jan 31, 2021. Data in the registry were collected from 55 regional or national registries in 48 countries. Diagnoses relying on self-reported history of familial hypercholesterolaemia and suspected secondary hypercholesterolaemia were excluded from the registry; people with untreated LDL cholesterol (LDL-C) of at least 13·0 mmol/L were excluded from this study. Data were assessed overall and by WHO region, World Bank country income status, age, diagnostic criteria, and index-case status. The main outcome of this study was to assess current identification and management of children and adolescents with familial hypercholesterolaemia. Findings: Of 63 093 individuals in the FHSC registry, 11 848 (18·8%) were children or adolescents younger than 18 years with HeFH and were included in this study; 5756 (50·2%) of 11 476 included individuals were female and 5720 (49·8%) were male. Sex data were missing for 372 (3·1%) of 11 848 individuals. Median age at registry entry was 9·6 years (IQR 5·8-13·2). 10 099 (89·9%) of 11 235 included individuals had a final genetically confirmed diagnosis of familial hypercholesterolaemia and 1136 (10·1%) had a clinical diagnosis. Genetically confirmed diagnosis data or clinical diagnosis data were missing for 613 (5·2%) of 11 848 individuals. Genetic diagnosis was more common in children and adolescents from high-income countries (9427 [92·4%] of 10 202) than in children and adolescents from non-high-income countries (199 [48·0%] of 415). 3414 (31·6%) of 10 804 children or adolescents were index cases. Familial-hypercholesterolaemia-related physical signs, cardiovascular risk factors, and cardiovascular disease were uncommon, but were more common in non-high-income countries. 7557 (72·4%) of 10 428 included children or adolescents were not taking lipid-lowering medication (LLM) and had a median LDL-C of 5·00 mmol/L (IQR 4·05-6·08). Compared with genetic diagnosis, the use of unadapted clinical criteria intended for use in adults and reliant on more extreme phenotypes could result in 50-75% of children and adolescents with familial hypercholesterolaemia not being identified. Interpretation: Clinical characteristics observed in adults with familial hypercholesterolaemia are uncommon in children and adolescents with familial hypercholesterolaemia, hence detection in this age group relies on measurement of LDL-C and genetic confirmation. Where genetic testing is unavailable, increased availability and use of LDL-C measurements in the first few years of life could help reduce the current gap between prevalence and detection, enabling increased use of combination LLM to reach recommended LDL-C targets early in life

An exotic parasitoid provides an invasional lifeline for native parasitoids

Abstract The introduction of an exotic species may alter food webs within the ecosystem and significantly affect the biodiversity of indigenous species at different trophic levels. It has been postulated that recent introduction of the brown marmorated stinkbug (Halyomorpha halys (Stål)) represents an evolutionary trap for native parasitoids, as they accept H. halys egg masses as a host but produce no viable progeny. Interspecific interactions between European egg parasitoid, Trissolcus cultratus (Mayr), and an Asian parasitoid, Trissolcus japonicus (Ashmead), were assessed by providing egg masses to T. cultratus at various time intervals following the initial parasitization by T. japonicus. The suitability of the host for the parasitoid development was re‐assessed by providing T. cultratus with fresh and frozen egg masses of various ages. The likelihood of T. cultratus being able to attack previously parasitized egg masses was determined by assessing the duration of egg mass guarding behavior by T. japonicus following parasitization. The results of experiments examining the interspecific interactions between a native European egg parasitoid, T. cultratus, and an Asian parasitoid, T. japonicus (a candidate for the biological control of H. halys), showed that the native species can act as facultative hyperparasitoid of the exotic one. Although this is only possible during certain stages of T. japonicus development, the presence of the introduced parasitoid may reduce the impact of the evolutionary trap for indigenous parasitoid species. There is a possibility that the occurrence of facultative hyperparasitism between scelionid parasitoids associated with stinkbugs is common. This resulting intraguild predation could promote conservation and stabilization of natural communities by impacting the diversity and population dynamics of native stinkbugs and their parasitoids (e.g., by allowing native parasitoids to avoid wasting reproductive effort on unsuitable hosts), or reduce success of biological control programs (e.g., by reducing the population size of the exotic parasitoids)