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Insects exhibit considerable variety in their morphology and can be found in many diverse habitats. Despite these variations, early neurogenesis seems to be conserved in insects. In all species investigated to date it begins with the formation of neural stem cells (neuroblasts), which establish a distinct internal layer and produce a fixed number of neurons and glial cells. The neuronal cells then form a characteristic rope ladder-like axonal scaffold. However, it is evident that the composition or identity of the individual neurons must have changed during insect evolution to allow for variations in neuronal networks. This raises questions regarding which developmental steps have been changed and the manner in which they have been modified. In order to address these questions, early neurogenesis was analysed in the flour beetle Tribolium castaneum and the results were compared to the well-studied fruit fly Drosophila melanogaster. Initially a map of trunk neuroblasts in T. castaneum was established, which revealed a high degree of conservation in the arrangement of individual neuroblasts compared to D. melanogaster. However, a comparison of the expression patterns of genes that confer regional identity to neuroblasts showed considerable variations. Significant differences in the expression patterns of the segment polarity gene wingless and the columnar gene ventral nerve cord defective (vnd) were found. Furthermore, the impact these changes in neuroblast identity have on the composition and identity of their respective progeny was analysed. As a result changes in the number of Even-skipped and Tailup expressing neurons in T. castaneum embryos were found, with three-fold more Tailup expressing neurons compared to D. melanogaster. To further analyse the role of the neuroblast identity gene vnd in the formation of Even-skipped positive neurons, RNAi gene silencing studies were performed, resulting in the loss of neurons and changes in neuronal migration pattern. In summary, the results demonstrate that evolutionary changes in neuronal networks result from changes in neuroblast identity, which in turn have an impact on the composition of neuronal lineages.

Offspring phenotype can be adaptively altered via maternal non-genetic inheritance. Such ‘maternal effects’ enable females to adjust their per offspring investment in response to variation in the offspring environment, and thus maximise their reproductive success. Consequently they play a pivotal role in population dynamics and the response of species to environmental change. Despite this, little is known about how maternal effects mediate reproductive investment in response to multiple or novel environmental changes, such as those driven by anthropogenic activity. I use the 2-spot ladybird intraguild predation system, where resources and predation risk are highly variable, to explore the role of maternal effects in the response of a native species to an invasive predator, as well as answering outstanding questions about how maternal effects function under complex and antagonistic sets of variables. The results indicate that it is unlikely that maternally mediated changes in egg phenotype will improve the survival of 2-spot ladybird offspring in the face of predation from larvae of the invasive harlequin ladybird. They do, however, demonstrate the importance of studying maternal effects in the context of the multiple environmental factors, which more accurately represent the complex environments in which organisms live and evolve, corroborating recent theoretical predictions. Finally I provide evidence of the multifaceted nature of parental effects in aposematic species and reveal the role that they may play in shaping the variation in defence and warning coloration observed in adult populations.

Inbreeding is associated with reduced fitness, a phenomenon known as inbreeding depression. I investigated direct and indirect effects of inbreeding on social traits associated with parental care in the burying beetle, Nicrophorus vespilloides. This species breeds on small vertebrate carcasses and the parents provide care by maintaining the carcass and regurgitating food to begging larvae. I quantified the survival of outbred offspring produced by inbred and outbred parents. I found that inbred offspring had reduced survival compared to outbred offspring, and that outbred offspring produced by inbred parents survived less well. Such intergenerational effects of inbreeding suggests that inbreeding may affect the amount of parental care provided to offspring. I tested this by investigating the amount of care inbred and outbred male and female parents provided to outbred offspring. I found no reductions in the amount of care provided by inbred parents but found that parents provided more care when their partner was inbred. In addition, I investigated effects of inbreeding on parent-offspring communication, when either female parents or their offspring were inbred. I found that whilst inbred offspring begged less, parents provided inbred offspring with more care. The effects of inbreeding had significant consequences affecting biparental negotiation and parent-offspring communication. Next, I tested for the effects of inbreeding on the antimicrobial properties of secretions that both parents apply to the carcass during larval development. I found that the bactericidal activity of inbred male parents was reduced compared to outbred male parents during the dispersal stages and no evidence for the secretions of inbred and outbred female parents differing. Finally, to test whether the strong inbreeding depression found in this species influenced the mating decisions, I presented females with related or unrelated males, and found no evidence that females avoided inbreeding. These results show that to accurately estimate the fitness consequences of inbreeding the social effects on all individuals within a family must be accounted for.

Parent-offspring communication is widely regarded as having evolved to provide the parent with honest information about the hunger state of its offspring, thus enabling it to mediate conflict over resource allocation between parents and offspring. The conflict is caused by the offspring benefitting from receiving more care than the parents are selected to provide due to the costliness of care. I studied the role of parent-offspring communication as a mediator for the conflict in the burying beetle Nicrophorus vespilloides. The burying beetle is an excellent study system for this question, as the larvae, that are raised on carcasses of small vertebrates and cared for by both the male and the female beetle, beg for food from their parents with highly distinguishable begging displays. First, I examined whether offspring adjusted their begging to different classes, or individual adult beetles. I found that while the larvae did not discriminate between male and female beetles, they adjusted their care to cues indicating individual recognition of adults. Second, I tested whether begging was based on offspring size at egg stage, and found no indication that offspring adjusted their begging to improve their innate quality. Third, I examined whether parental response to begging exhibits behavioural plasticity when the internal clock for the timing of reproduction for the parent, and the demand from the larvae do not meet. I found that the parents adjusted their care based on the amount of begging exhibited by the larvae. Fourth, I investigated whether parental adjustment of care based on offspring begging incurs a reproductive cost to them. I found that the females paid a cost in fecundity, but not in the number of dispersing larvae or their own survival. My original contribution to knowledge is therefore to show through these four studies, that offspring begging is adjusted based on parental cues, and can directly affect proximate parental behaviours, and also incurs a reproductive cost to their future reproductive success, thus providing more experimental evidence for the importance of parent-offspring communication, and its implications to the evolution of parental care.

Ladybird beetles produce a range of alkaloid compounds which are found a high concentration in the haemolymph and released in response to perceived threat. These alkaloids are thought to function as agents of chemical defence and a small number have been shown to antagonise the nicotinic acetylcholine receptor. As intraguild predators, the chemical defence may be under selective pressure from other predatory insects, the alkaloids may therefore have evolved to target insects predominantly. To discover if other ladybird alkaloids show activity at nAChRs and investigate mode of action, alkaloids were extracted from 7-spot, 10-spot, 14-spot, cream spot, pine, orange and harlequin ladybird beetles and purified with acid-base separation. These species are each known to produce a different subset of alkaloids. Their action on nicotinic acetylcholine receptors was investigated by constructing concentration-inhibition plots by co-applying alkaloid extracts with acetylcholine to human embryonic muscle-type of TE671 cells and locust neuronal nAChRs. Peak current, net-charge and late (1 s) current were measured with whole-cell patch-clamp at VH = -75 mV. All alkaloid extracts antagonised the ACh responses of both cell types but potency and selectivity varied. The late current was the most strongly affected current parameter and the most potent antagonists of locust 1 s currents were alkaloids produced by 10-spot, 7-spot, pine and harlequin ladybird with IC50s ranging from 0.29–0.76 μg/mL. The 14-spot, cream spot and orange ladybird alkaloids had higher IC50s, ranging from 1.6-4.9 μg/mL. The IC50 values calculated for all species with, the exception of harlequin and orange ladybirds were significantly lower for locust than human nAChRs and these ranged from 1.3–47.8 μg/mL. The alkaloid extract that showed the highest selectivity for locust nAChRs was that of the 7-spot ladybird, with an IC50 value 58.4 fold lower. The alkaloids of the 10-spot, 14-spot, cream spot and pine ladybird also showed significantly higher potency for locust nAChRs over human nAChRs with IC50s 10.3–35 fold lower. Orange and harlequin ladybird alkaloids did not show higher potency for locust nAChRs. Harlequin ladybird alkaloids were highly potent to the nAChRs of both cell types whereas orange ladybird alkaloids showed low activity. The differences in potency correspond with differences in ecology, with the species that showed highest insect potency often found in close association with other predatory ladybird species. Those that showed low insect potency are arboreal specialists that are less likely to encounter insect predators. To investigate mode of action, ACh concentration-response curves in the presence and absence of harlequin ladybird alkaloid extract were constructed using TE671 cells. Increasing ACh concentrations were unable to overcome the inhibition caused by this alkaloid extract, indicating non-competitive action. Fitting the Woodhull equation to IC50 values calculated at holding potentials of 50, -50, -75, -100 and -120 mV revealed that the antagonism caused by this alkaloid extract was voltagedependent (P = 0.012), with late current IC50s of 23.1, 15.5 and 6 μg/mL at holding potentials of +50, -50 and -120 mV respectively. These data indicate that the active alkaloid(s) within this extract bind at an allosteric site and the strong voltagedependence of inhibition suggests mode of action is open-channel block rather than enhancement of desensitisation. The alkaloid harmonine was separated from other components of the alkaloid extract by thin-layer chromatography and the inhibitory activity tested against both human and locust nAChRs at VH = -75 mV. Both fractions were found to be active and displayed similar inhibitory activity towards human nAChRs with IC50s of 1.68 μg/mL for harmonine and 4.77 μg/mL for other alkaloid compounds. Harmonine was found to be significantly more potent towards locust nAChRs with an IC50 of 0.072 μg/mL as opposed to 3.23 μg/mL. This could indicate that harlequin ladybirds produce several alkaloids with different functions; harmonine may act as a chemical defence compound targeted towards insect predators. The alkaloid extract of the 10-spot ladybird was found to show significantly higher potency towards locust nAChRs than human. One of two alkaloids produced by this species is (-)-adaline. Synthetic (-)-adaline displayed identical inhibitory activity towards both cell types as the alkaloid extract of the 10-spot ladybird. Potency was significantly higher towards locust nAChRs than human, with IC50s of 10.26–45.83 μM against human and 0.55–2.97 μM against locust nAChRs. ACh concentration-response curves showed that (-)-adaline acts non-competitively and IC50 values at different holding potentials reveal that it is strongly voltage-dependent (P = 0.003 in human and P = 0.007 in locust nAChRs) and inactive at positive holding potentials. As with the alkaloid extract of the harlequin ladybird, this alkaloid acts as a non-competitive negative allosteric modulator which shows higher potency for locust over human nAChRs and strong voltage-dependence of inhibition, consistent with open-channel block. A structurally diverse range of ladybird alkaloids displayed inhibitory activity towards both human and insect nAChRs. This inhibition was non-competitive and voltage-dependent for both harlequin ladybird alkaloid extract and adaline, indicating that these alkaloids act as negative allosteric modulators, possibly open-channel blockers. The majority of ladybird alkaloid extracts tested were significantly more potent towards insect than human nAChRs. It remains to be seen whether the activity of these compounds is restricted to the nAChRs, or whether they act as non-selective pore blockers. Ladybird alkaloids appear to represent a library of novel nAChR antagonists, some of which could be further investigated as potential insecticide leads.

All animals interact in some way with microbes during their growth and development. These interactions often prove harmful as animals find themselves exposed to pathogens or the harmful by-products of microbial growth. For many animals avoidance of microbes is difficult or impossible, particularly for species that obligately utilise microbe-laden resources during reproduction. Larvae of the carrion beetle Nicrophorus vespilloides are significantly harmed by the bacteria they encounter during their development on decomposing vertebrate carcasses. However, these effects can be partially ameliorated by parental investment into behaviours which reduce the effects of microbial exposure. In this thesis I focus on two aspects of N. vespilloides response to microbial competition. First I investigate the composition and fitness effects of the application of exogenous secretions by parents and larvae to their breeding resource. This behaviour in parents has long been hypothesized to form an important part of the antimicrobial component of parental care, but this has not been rigorously tested. Nor, prior to my work, has any experimental attention been given to the possibility that larvae also contribute to antimicrobial production while on the carcass. Second I investigate the late-life and intergeneration effects of microbial exposure during development on a range of beetle life history traits including larval body size, brood size and immune function and survival in response to bacterial challenge. My results demonstrate the following: i) that larval N. vespilloides suffer significant harm from microbial competition during development that manifests itself in several ways, e.g. reduced body size, increased susceptibility to infection, or reduced ability of mothers to provide post hatch maternal care; ii) that the effects of microbial competition can be mitigated by parental behaviours that reduce the level of microbial contamination on a resource. Specifically, mothers apply antimicrobial secretions containing lysozyme to the carcass which kills bacteria and significantly increases larval survival; iii) that larvae are not totally reliant on their parents for antimicrobial protection because they too can secrete exogenous antimicrobial compounds similar in activity to their parents and which significantly increase larval fitness; iv) the effects of microbial competition can result in transgenerational effects that reduce offspring fitness but which can also provide context-dependent benefits by increasing larval survival when post-hatch parental care is poor and following challenge with pathogenic infection. By developing on and consuming carrion Nicrophorus larvae and other specialist scavengers experience an extreme example of the challenges faced by opportunistic carrion users or animals that for any reason utilise microbially contaminated resources. This makes them ideal model organisms to study adaptations to the presence of complex microbial communities that may contain both pathogens and toxin producers.

In der Broschüre sind 279 wasserbewohnende Käferarten aus 13 Familien dargestellt. Diese sind als ökologische Gruppe zur Charakterisierung von Gewässern, zur Bioindikation und zum Monitoring von FFH-Gebieten geeignet. Für die Verwendung von Wasserkäfern als Indikatoren im Rahmen von Naturschutzprojekten und der Eingriffsplanung sprechen die hohe Artenzahl sowohl in stehenden als auch in fließenden Gewässern und ihr Vorkommen in temporären Kleingewässern sowie in Überflutungsgewässern. Rote Listen werden regelmäßig aktualisiert. Eine Rote Liste der Wasserkäfer Sachsens erschien zuletzt 1996.

Die Käferarten Heldbock und Eremit sind zwei typische Bewohner alter Laub- und Obstbäume. Die reich bebilderte Broschüre gibt Einblick in das interessante Leben dieser beiden auffälligen Käferarten und zeigt auf, mit welchen oft einfachen Maßnahmen Heldbock und Eremit unterstützt werden können. Beide Arten sind in den letzten Jahrzehnten selten geworden und brauchen Schutz. Durch die Erhaltung von Baumveteranen in unserer Kulturlandschaft wird nicht nur die Lebensgrundlage dieser besonderen Käferarten geschützt, sondern Hunderte weiterer Insektenarten behalten dadurch ebenfalls ihren Lebensraum.

Native to Asia, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is an invasive non-native ladybird in Europe and North America, where it was widely introduced as a biological control agent of aphids and coccids. There were three main objectives of this study: firstly, to investigate the spread and distribution of H. axyridis in Europe from the start of the invasion process; secondly, to study its ecology in Great Britain; and thirdly, to examine its effects on native ladybirds in Britain. In Europe, collaborations with a network of scientists allowed the collation of H. axyridis occurrence data from across the continent. In Great Britain, a web-based public survey (www.harlequin-survey.org) was used, leading to the receipt of over 10,000 verified records of H. axyridis between 2004 and 2008. National land cover data enabled the habitats used by H. axyridis to be identified across Great Britain. These datasets were analysed in order to study the spread and ecology of H. axyridis in Europe and Britain. Fieldwork over a three year period (2006 to 2008) was carried out to examine changes in ladybird species assemblages during the invasion phase of H. axyridis in eastern England. Laboratory work was conducted to detect intraguild predation by H. axyridis, through PCR analyses of gut contents of field-collected ladybirds. In Europe, H. axyridis has spread since 2001 at the rate of approximately 200km yr-1. It has become established in at least 23 European countries. The established range extends from Norway in the north to southern France in the south, and from Ukraine in the east to Great Britain in the west. In the first five years of establishment H. axyridis spread north through Britain at the rate of 105km yr-1 and west at the rate of 145km yr-1. Evidence of the production of two generations per year was found, giving H. axyridis an advantage over most native ladybirds in Britain. Although H. axyridis was very common in urban habitats, it increasingly used semi-natural habitats. In addition, whilst the species was most common on deciduous trees, it was increasingly found on herbaceous plants. Aceraceae, Rosaceae and Malvaceae were the dominant plant families used by H. axyridis, especially for breeding. In eastern England H. axyridis increased from 0.1% to 40% of total ladybirds in three years, whilst native aphidophagous ladybirds declined from 84% to 41% of total ladybirds in the same period. Three species in particular experienced declines: Adalia 2-punctata, Coccinella 7-punctata and Propylea 14-punctata. Harmonia axyridis was the most abundant species by the end of the study. Detection of intraguild predation by one coccinellid on another, in the field in Europe, was shown for the first time using PCR techniques: A. 2-punctata DNA was detected in the gut of one of 112 field-collected H. axyridis. Harmonia axyridis has spread very quickly since 2001 and has become one of the most widely distributed coccinellids in Europe. Populations of native aphidophagous ladybirds were negatively affected by the arrival of H. axyridis, partly through intraguild predation.