The distribution of beetles in the Family Silphidae has not been well studied in Virginia.  The primary purpose of this study was to survey silphid beetles in a more systematic manner across different geographic regions of the state, with a special consideration for Nicrophorus species.  The seasonal abundance and diversity of silphid beetles in Montgomery County, Virginia, was also examined.  Baited pitfall traps were used to sample beetle distribution and abundance, and were placed in each of the five geographical regions of Virginia in the summers of 2007 and 2008.  Traps were placed approximately one kilometer apart and were checked daily over a five day period for each of three sampling periods.  A total of 4375 silphid beetles, consisting of 11 species in four genera, were collected in ten counties with beetles in the subfamily Silphinae being predominant.  Within the Nicrophorinae, Nicrophorus tomentosus and N. orbicollis were dominant in 2007; whereas in the summer of 2008, N. tomentosus and N. pustulatus were the most commonly collected.  Contingency analyses indicated that species abundance was associated with sampling period and geographic region.  Nicrophorus americanus was not collected during either summer of surveying and only three N. carolinus were trapped in Suffolk County in the summer of 2008.  For the Montgomery County survey, a total of 3276 beetles were found between the middle of April and the middle of October.  The prevalent species within Nicrophorinae was Nicrophorus tomentosus and within the Silphinae it was Necrophila americana.  Species abundance was associated with sampling period. / Master of Science in Life Sciences

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.

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.

Body size is one of the most commonly studied traits of an organism, which is largely due to its direct correlation with fitness, life history strategy, and physiology of the organism. Patterns of body size distribution are also often studied. The distribution of body size within species is looked at for suggestions of differential mating strategies or niche variation among ontogenetic development. Patterns are also examined among species to determine the effects of competition, environmental factors, and phylogenetic inertia. Finally, the distribution of body size across the geographic range of a species or group of closely related is looked at for indications of the effects of climate and resource availability on body size at different latitudes and altitudes. In this collection of research, I address the evolution and importance of body size in burying beetles (genus Nicrophorus). Body size is important to several aspects of burying beetle natural history, including competitive ability, fitness, parental care, climate tolerance, and locomotor activity. In Chapter 1, I use a large data set of body size measurements for seventy of the seventy-three Nicrophorus species to make inferences about the distribution of body size within the genus, across its geographic range, and the importance of body size in speciation. I found that the range of body sizes is not normally distributed, with an overrepresentation of small-sized species. I also found that expansion of the burying beetle range has been restricted by their inability to tolerate warm, dry climates, and therefore the majority of burying beetle diversity occurs in the temperature mid-latitudes of the northern hemisphere. Body size also seems to be important in speciation, as almost all sister taxa are significantly different in body size. In Chapter 2 I use common garden experiments to assess the importance of body size for males and females in competition, reproductive output, and starvation resistance. Body size is equally important for both sexes in starvation resistance, but it is more important for males in competitions for carcasses and for females in reproductive output. In Chapter 3 I test for fitness consequences of multigenerational effects of body size in offspring. I found that the larger offspring that are produced by larger mothers and on larger carcasses had higher fitness than small offspring. In Chapter 4 I test for the possibility of brood parasitism in two species of burying beetles, N. guttula and N. marginatus, which co-occur over part of their geographic ranges. I found that both species are able to detect and remove parasitic larvae. Finally, in Chapter 5 I compiled parent and offspring body sizes from seven species of burying beetles and use them to compare the heritability of body size among species using comparative techniques and a meta-analysis. I found that body size heritability is different between species, but is low for the genus as a whole. Together, these projects provide valuable information on the evolutionary significance of body size in Nicrophorus, and indicate compelling questions for future research into the evolution of body size in burying beetles.

Nicrophorus americanus is a federally endangered species whose range has decreased dramatically since the 1920s. It is a nocturnal species that is only active from May to September when temperatures reach at least 15.5°C for three nights in a row. It once ranged throughout North America, from Maine and the southern parts of Canada, west to South Dakota and south to Texas. The historic Texas population consists of four Texas specimens from the 1880s residing at the Philadelphia Academy of Science Invertebrate Collection. Since then, there were no confirmed specimens in Texas, until 2003 when a single individual was found in Lamar County, Texas. The population discovered in Lamar County has been on a steady decrease from 2005, 223 individuals captured, until 2008 only 8 individuals captured. Since 2008, no individuals have been captured in Texas, despite intense surveys. It is possible that the Texas population is a sink population with the Oklahoma population to its north, acting as the source. Genetic analysis of the Texas and Oklahoma populations would help to answer this question and analysis of the entire population may answer questions to why the species declined leaving only the peripheral populations. The specific habitat variables that caused the population to re-colonize and go extinct in Texas are unclear, but when determined could play a critical role in managing the population. / text

In this thesis I investigated the genetic basis of several behaviours to answer questions surrounding the evolution and mechanistic basis of behaviour. Firstly, I took a single-gene approach to investigate the influence of fruitless (fru) on the courtship behaviour of Drosophila. fru is an alternatively-spliced transcription factor that is necessary for the production of male sexual behaviours, and has also been implicated in producing species-specific differences in courtship song. I investigated the patterns of selection acting on fru at the sequence level and found that positive selection was restricted to the alternatively spliced exons of fru. From this I hypothesised that the positively selected changes in fru would contribute to species-specific differences in courtship song. To test this I examined how isoform-specific fru loss-of-function mutants influence courtship song, and generated “species-swapped” flies whereby regions of fru that showed evidence for positive selection were transferred from four species of Drosophila, into D. melanogaster. Contrary to prediction, I found flies that lacked isoforms containing positively selected regions did not show any differences in courtship song. Unfortunately “species-swapped” flies were not generated in time to examine phenotypes and neuroanatomy as intended. Next, I examined the genetic basis of cold acclimation in two species of Drosophila using a transcriptomic approach. I found that the genes differentially expressed in response to cold acclimation were largely different in each of the species; however, the biological processes they were involved in were broadly similar. Finally, I investigated the transcriptomic changes associated with parental care in the burying beetle Nicrophorus vespilloides to determine if males and females alter the genes they express when parenting alone versus with a partner. I found that males greatly reduced their transcriptional response when parenting with a partner, suggesting they reduce the care they provide when present with a female.