<div> <div> <div> <p>Parental care has evolved promote fitness gains. Burying beetles engage in extensive pre- hatching and post-hatching parental care providing several avenues to transmit bacteria to their offspring. One aspect of pre-hatching parental care consists of preserving a small vertebrate carcass via oral and anal secretions, allowing the carcass to be used as a reproductive resource. Post-hatching parental care consists in large part of parental regurgitations of the preserved carcass. We sought to determine if pre-hatching parental care resulted in bacterial transmission from adults to carcasses via anal secretions. We then sought to determine if lab-rearing conditions affected the digestive tract bacterial communities of F1 and F2 generation adults. We finally sought to determine if carcasses and post-hatching parental care in the form of parental regurgitations resulted into bacterial transmission to larvae. Using High-Throughput Illumina MiSeq, we were able to characterize bacterial communities of adult and larval digestive tracts, anal secretions, and unprepared and prepared carcasses. Our results show that bacterial communities of adults are dissimilar from anal secretions and prepared carcasses. We then show that lab-rearing conditions do not significantly alter digestive tract bacterial communities of F1 and F2 generation adults relative to wild caught adults. We proceed to show that larvae receiving parental regurgitations have digestive tract bacterial communities similar to their parents whereas larvae that do not receive parental regurgitations have dissimilar digestive tract bacterial communities from their parents. We further show that bacterial communities of prepared carcasses are dissimilar from all larvae. Our evidence suggests that anal secretions to preserve carcasses for the reproductive bout and have no influence on bacterial transmission to neither carcasses nor larvae. Our evidence also suggests that parental regurgitations influence bacterial transmission to offspring. </p> </div> </div> </div>

There are three social dimensions within a family: parent-parent interactions, parent-offspring interactions, and offspring-offspring interactions. All of these interactions are subject to evolutionary conflict, which occurs whenever interacting individuals have divergent evolutionary interests. Family interactions and family conflict are often influenced by phenotypic and genotypic traits of the parents and the offspring. An important phenotypic trait is body size, which can affect fecundity, mating success, and fighting ability. An important genotypic trait is inbreeding status (i.e., whether an individual is outbred or inbred), which can influence its overall quality or condition. In this thesis, I investigate the independent and interactive effects of inbreeding and parental body size on family interactions in the burying beetle Nicrophorus vespilloides. I first show that the body size of the two parents influences the resolution of sexual conflict over the amount of parental care (Chapter 2) and over the consumption of a shared resource (Chapter 3). Here, the shared resource refers to the carcass from which both the parents and the offspring feed over the course of the breeding attempt. I then show that females that won or lost a fighting contest provide more care to their offspring compared to beetles with no fighting experience (Chapter 4). This indicates that female burying beetles make parental investment decisions based on their experience with a contest (which is independent of body size) rather than the outcome of that contest (which is dependent on body size):. In the second half of my thesis, I examine whether family interactions also influence and are influenced by inbreeding depression (Chapters 5–8). I find that a female's mating preference for an outbred versus an inbred male is conditional on her own inbreeding status: inbred females preferentially mate with outbred males, whereas outbred females are equally likely to mate with an outbred or an inbred male (Chapter 5). Even though sibling competition does not appear to have an effect on the offspring's inbreeding depression (Chapter 6), the presence of the mother during larval development can reduce the severity of inbreeding depression (Chapter 7), and this effect depends on the mother's body size (Chapter 8). In Chapter 9, I discuss the broader implications of these findings for evolutionary biology, ecology, and conservation biology.

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.

Parental care in animals can be costly and is shared between both parents in many bird species. Not surprisingly, most studies of how parental care is shared between the sexes are in sexually dimorphic species, and much less in known about sexually monomorphic species where sex cannot be determined in the field. This has prevented a full understanding of parental care behaviors – which are intrinsically linked to fitness – in species such as the Red-headed Woodpecker (Melanerpes erythrocephalus) that is experiencing population declines throughout much of its range. In this study we assessed whether Redheaded Woodpecker brooding time, nestling provisioning rates, and nest cleaning rates vary as a function of parent sex, habitat type (savanna and closed canopy forest), brood size, nestling age, temperature and/or date. We recorded and analyzed 128 hours of high-quality video from 21 broods at Fort A.P. Hill, Virginia where this species is relatively abundant. We captured and color-banded Red-headed Woodpeckers, taking breast feather samples for genetic sexing, and determined brood size and chick age of nests using an extendable pole camera. Using generalized linear mixed models, we found the best predictor of nestling provisioning was an interaction between chick age and date; older chicks were fed more frequently in early summer (before 7 July) compared to late summer. The seasonal reduction in provisioning could be related to a reduction in resource availability, but whether or not provisioning in later nests affects nestling survival warrants further study. We found chick age and parent sex to be the best predictors in brooding models, with females brooding more when chicks are less than 10 days old and males being the only parent to enter the cavity after 10 days. Additionally, males almost exclusively remove fecal sacs from nests, highlighting an observational method to determine sex of breeding adults in the field. Such division of reproductive roles is similar to what is known for dimorphic woodpecker species and likely indicates energetic constraints due to the need for high parental investment from both sexes. Parental care is inextricably linked with habitat quality and home range size. Parents will travel to obtain the resources necessary to provision their young, and larger home ranges during the demanding nestling provisioning stage may indicate increased effort resulting from fewer available resources near the nest. We estimated home range sizes of 25 breeding adult Red-headed Woodpeckers using PinPoint GPS tags and 95% kernel density estimates (KDEs) with plug-in smoothing factors. We modeled the effects of habitat, sex, nest stage, date, and distance to nearest neighbor on home range estimates. Red-headed Woodpecker males have larger home ranges than females, and late summer home ranges are smaller than those measured before 7 July. More study is needed to determine if sex or date is a stronger factor on home range, given our naive sampling which resulted in more females sampled in late summer and observations that did not continue to the end of the breeding season (late August). Since we found date to be an influential factor to both provisioning rate and home range size, it is possible that seasonal resource changes are an important, unstudied factor related to nationwide declines of this species.

This thesis focuses on the classic problem of investment per offspring. It is an attempt to (i) reconcile theoretical research with empirical methods that can be used to test theory, (ii) test a fundamental prediction that arises from classic theory, and (iii) test one of the more recent theoretical developments. We use Atlantic salmon (Salmo salar) as a model organism. Drawing from the classic Smith–Fretwell model, we provide defensible definitions of offspring fitness that can be used in empirical studies, and we show using simulation that the Weibull-1 statistical model provides the best estimates of optimal investment patterns. Next, we apply these methods to mark-recapture data collected for juvenile Atlantic salmon. This experiment supports the prediction that parental reproductive success is maximized by increasing investment per offspring when environmental conditions become unfavourable. Having verified this prediction, we test a general extension of classic theory which broadly suggests that large-bodied females decrease the quality of the offspring environment, such that larger females in a population ought to invest relatively heavily in investment per offspring. This might occur, for example, when larger females have a greater fecundity and if optimal investment per offspring increases with sibling competition among non-dispersive offspring. The results of this experiment generally do not support the idea that large females decrease the quality of the offspring environment in Atlantic salmon. Finally, we also provide evidence against a verbal hypothesis that attempts to explain inter-population variation in egg size of salmonids as an adaptation to population-specific spawning substrates. We conclude that the classic model of egg-size optimization can be a useful tool for understanding patterns of reproductive allocation in nature, but that investment per offspring is an extremely complex trait that cannot be fully understood by invoking a simple optimality model. Variation in investment per offspring, especially that which occurs within populations, is most parsimoniously attributed to the physiological factors (e.g., variation in testosterone levels), morphological constraints (e.g., the size of the pelvic aperture) and genetic factors (e.g., genetic correlations arising from pleiotropic genes) that affect this phenotype and that constrain adaptive evolution of this trait.

In this thesis, I investigated the role of parental care in evolution. Parents provide the environment in which offspring develop and therefore have a large influence on their offspring's phenotypes, and so are in prime position to influence evolutionary processes. I used an experimental approach, and focused on the burying beetle, Nicrophorus vespilloides. The burying beetle is a perfect system for this question: they exhibit elaborate biparental care which is correlated with rapid speciation in the Nicrophorus genus. I started with a thorough exploration of burying beetle ecology and how the guild structure and interspecific competition in local populations can shape phenotypic evolution of my focal species, N. vespilloides. Interspecific competition shapes how the carrion niche is partitioned, which feeds back onto the evolution of body size within Nicrophorus reducing competition. The evolution of parental care in this genus likely facilitated its adaptive radiation, as parental care is linked with body size, both within and across species. But to what extent does the ecology shape the production and maintenance of phenotypic and genetic variation? I then use a quantitative genetic approach to show that body size and development time of N. vespilloides shows no additive genetic variation. Evolution of these fitness related traits can only occur through maternal effects or sibling effects. I tested this prediction by mimicking the radiation of the burying beetles by imposing my own selection on body size when parents could care for their offspring and when they could not. The presence of post-hatching parental care dramatically changed how populations responded to selection, through a combination of cooperation between parents and offspring, and cooperation between offspring. As well as shaping the evolutionary potential of populations, an experimental change in parental care can induce new selective forces, favouring adaptive novelties for the new social environment. Larvae evolving without parental care evolved disproportionately larger mandibles when small to better adapt them to a life without care. Much is known about the evolution of parental care across the animal kingdom, but what happens next: are the burying beetles a "one-off"? I compiled data across the arthropods comparing clades that exhibit post-hatching parental care with their sister clades and show that clades with care are more species rich. While the mechanism may not be the same as with Nicrophorus, I discussed other potential mechanisms that may be at play in the role of parents in evolution.

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In teleost fish, the main glucocorticoid stress hormone, cortisol, is released via the hypothalamic-pituitary-interrenal (HPI) axis. This thesis examined the premise that social status, maternal experience, and reproductive status affect HPI axis function in fish. Social stress in juvenile rainbow trout (Oncorhynchus mykiss) chronically elevates circulating cortisol levels. In this thesis, social subordinance as well as exogenous cortisol treatment resulted in decreased plasma adrenocorticotropic hormone (ACTH) levels, consistent with a negative feedback role of cortisol in modulating HPI axis activity. At the target tissue level, liver glucocorticoid receptor 2 (GR2) mRNA and total GR protein levels were lower in subordinate fish. Although subordinate fish exhibited elevated resting cortisol levels, cortisol and glucose responses to an acute stressor were attenuated. Using an in vitro head kidney preparation, this attenuated cortisol response was attributed to lower ACTH-stimulated production of cortisol. By contrast, dominant status regulated genes associated with cortisol biosynthesis. The consequences of maternal social status on offspring HPI axis function were investigated in zebrafish (Danio rerio). At 48 hours post-fertilization (hpf), when de novo cortisol synthesis becomes possible, larvae of dominant females exhibited lower baseline cortisol levels accompanied by lower mRNA levels of corticotropin-releasing factor and cytochrome P450 side chain cleavage enzyme. Offspring of subordinate females exhibited attenuated stress-induced levels of cortisol at 144 hpf, perhaps as an adaptive response to maternal stress experience. Finally, modulation of HPI axis function was explored as a mechanism underlying attenuation of the stress response during early paternal care in smallmouth bass (Micropterus dolomieu). In response to a stressor, males guarding free-swimming fry but not eggs elevated plasma ACTH and cortisol as well as mRNA levels of key HPI axis genes. These results point to a hypoactive HPI axis in males during early parental care as a mechanism for resistance to stress in these fish. Collectively, the results of this thesis emphasize the adaptive plasticity of the HPI axis. Activity of the HPI axis in teleost fish can be modulated by the individual’s experience (e.g., social status) or circumstances (e.g., parental care), as well as by maternal stress.

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.

Feather ornaments and its role as a signals in sexual selection has been broadly studied topic in avian biology. However, vast majority of studies focus especially on role of male ornamentation and female preferences in sexual selection. Despite this fact, recent work shows, that similar palette of adaptive functions can be found for female feather ornaments, and male preferences for them, respectively. This study focuses on possible importance of female melanin-based ornaments and other individual on breeding performance in the Northern Lapwing (Vanellus vanellus), common polygynous wader breeding in agricultural landscape. No significant predictor of female investment to egg size was found. Long winged females with bigger proportion of secondaries changed during prenuptial moulting and bigger extent of melanin ornaments tended, surprisingly, to later timing of breeding. Contrary to this trend, extent of female ornamentation seems to be sexually selected trait by males. Analysis of male incubation behavior shows, that males incubate more in nests of more ornamented females, as well as in nests in later incubation stage. These findings seems to be in a good agreement with "Differential allocation hypothesis". On the other site, no effect of clutch egg sizes and timing of breeding was found....