The Effects of Social Interactions on Learning and Memory in the Honey Bee Apis Mellifera

The honey bee Apis mellifera has been used to study the genetics of learning and memory for several decades. In Chapter 2, a literature review revealed that learning and memory phenotypes are highly heritable. Several quantitative trait loci and specific genes which code for neurotransmitter receptors were identified. Whereas transcriptomic approaches showed that the process of learning and memory involves hundreds of genes. Although understanding the genetic components is crucial, it is also important to understand how environmental factors affect learning and memory. In Chapter 3, I investigate the effect of social interactions on discrimination learning by randomly assigning bees into three different social groups: 1 bee, 8 bees, and 32 bees. Using the proboscis extension conditioned response test, I found that the fewer social interactions a bee experiences, the more responsive she is to sucrose. Bees raised in groups of 32 had the best performance in discrimination learning

Conservation Genomics of the Declining North American Bumblebee Bombus terricola Reveals Inbreeding and Selection on Immune Genes

The yellow-banded bumblebee Bombus terricola was common in North America but has recently declined and is now on the IUCN Red List of threatened species. The causes of B. terricola’s decline are not well understood. Our objectives were to create a partial genome and then use this to estimate population data of conservation interest, and to determine whether genes showing signs of recent selection suggest a specific cause of decline. First, we generated a draft partial genome (contig set) for B. terricola, sequenced using Pacific Biosciences RS II at an average depth of 35×. Second, we sequenced the individual genomes of 22 bumblebee gynes from Ontario and Quebec using Illumina HiSeq 2500, each at an average depth of 20×, which were used to improve the PacBio genome calls and for population genetic analyses. The latter revealed that several samples had long runs of homozygosity, and individuals had high inbreeding coefficient F, consistent with low effective population size. Our data suggest that B. terricola’s effective population size has decreased orders of magnitude from pre-Holocene levels. We carried out tests of selection to identify genes that may have played a role in ameliorating environmental stressors underlying B. terricola’s decline. Several immune-related genes have signatures of recent positive selection, which is consistent with the pathogen-spillover hypothesis for B. terricola’s decline. The new B. terricola contig set can help solve the mystery of bumblebee decline by enabling functional genomics research to directly assess the health of pollinators and identify the stressors causing declines

What's Really Out There? Investigations into the Effects of Pesticides and Pathogens on Bee Health

Bees provide crucial pollination services to both cultivated and wild plants. In recent decades there were large declines in the populations of several native bee species and in the health of managed honey bee colonies. Neonicotinoid pesticides were suspected to negatively impact the health of native and managed bees, although this topic was hotly contested. Unfortunately, we lacked the knowledge regarding the typical duration that bees were exposed to neonicotinoids. Therefore, I first quantified the dose, duration, and types of chemicals honey bee colonies were exposed to near agricultural corn fields (Chapter 2). I found that honey bee colonies were exposed to a cocktail of chemicals, out of which neonicotinoids were the most likely to pose a health risk. I also found that honey bees were exposed to neonicotinoids for up to four months the majority of the honey bees active season. I then performed a controlled experiment, where I exposed honey bee colonies to neonicotinoids in a manner that mimicked the field exposure (Chapter 2 and 3). I found that this field realistic exposure to neonicotinoids reduced worker life span, increased queenlessness, and impacted both social and innate immunity. Then, I studied the genetic underpinnings of neonicotinoid sensitivity in honey bees (Chapter 4). I found that survival after neonicotinoid exposure was heritable and was associated with natural polymorphisms found in two detoxification genes. Although survival after exposure is a convenient trait to study under laboratory conditions, it offers little insight into the plethora of phenotypes sublethal neonicotinoid exposure can affect. Thus, I used transcriptomics to look into the effects of field and field realistic exposures to neonicotinoids on the brain gene expression of forager and nurse honey bees (Chapter 5). I found that neonicotinoids affected the brain states of foragers and nurses in a different manner, possibly reflecting a consequence of developmental alterations. I then applied transcriptomics tools to a declining bumble bee, Bombus terricola (Chapter 6). I discovered that bumble bees near agriculture had signatures of stress due to pesticides and pathogens. Overall, I found that neonicotinoids and agricultural landscapes put undue stress on the health of bees. My research also highlights the importance of conducting season-long studies and quantifying multiple stressors and phenotypes at a time in ecotoxicological research

Molecular population genetics and phenotypic sensitivity to ethanol for a globally diverse sample of the nematode Caenorhabditis briggsae.

International audienceNew genomic resources and genetic tools of the past few years have advanced the nematode genus Caenorhabditis as a model for comparative biology. However, understanding of natural genetic variation at molecular and phenotypic levels remains rudimentary for most species in this genus, and for C. briggsae in particular. Here we characterize phenotypic variation in C. briggsae's sensitivity to the potentially important and variable environmental toxin, ethanol, for globally diverse strains. We also quantify nucleotide variation in a new sample of 32 strains from four continents, including small islands, and for the closest-known relative of this species (C. sp. 9). We demonstrate that C. briggsae exhibits little heritable variation for the effects of ethanol on the norm of reaction for survival and reproduction. Moreover, C. briggsae does not differ significantly from C. elegans in our assays of its response to this substance that both species likely encounter regularly in habitats of rotting fruit and vegetation. However, we uncover drastically more molecular genetic variation than was known previously for this species, despite most strains, including all island strains, conforming to the broad biogeographic patterns described previously. Using patterns of sequence divergence between populations and between species, we estimate that the self-fertilizing mode of reproduction by hermaphrodites in C. briggsae likely evolved sometime between 0.9 and 10 million generations ago. These insights into C. briggsae's natural history and natural genetic variation greatly expand the potential of this organism as an emerging model for studies in molecular and quantitative genetics, the evolution of development, and ecological genetics

Gender Differences in Second-Level Schooling

This thesis is concerned with gender differences in Irish secondlevel schooling. The problems generated by this type of genderdifferentiation are identified in the maintenance of sex-stereotyped career choices, the status associated with each sex in the labour force, the division of labour in the home and the contribution of the sexes to the general construction of knowledge. The extent to which gender differences exist in schools and in school-related activities is established, and it is shown that considerable variation exists between boys’ and girls’ subject choices and career expectations. It is also revealed that boys’ and girls’ extracurricular activities tend to be determined on the basis of their sex. It is subsequently shown that both sexes perceive and reject the school’s attempt to channel them into sex-stereotyped roles; the extent of this rejection is limited to verbal disagreement as the pupils have limited opportunity to express overt resistance. Finally, the findings indicate that the gender differences in the pupils’ behaviour and attitudes can be attributed to the influence of the home and the peer-group. It is discovered that the pupils do not perceive this influence as readily as they perceive gender-differentiation in the school

Oral Toxicity of Clothianadin and Thiamethoxam in the presence of Linuron and Boscalid

The mortality of worker honeybees in cage experiments with different doses of NNIs in the presence of constant levels of either the herbicide linuron or the fungacide boscalid

The antimicrobial activity of a worker’s hemolymph differs across colonies but not across patrilines.

<p>(A) The average antimicrobial activity of a workers’ hemolymph is significantly larger in colony c2 than colony c10. Workers from different patrilines did not significantly differ with respect to their average antimicrobial activity of their hemolymph in (B) colony c10 and (C) colony c2. Error bars indicate standard error of the mean. Sample size of each patriline is indicated on each bar.</p

No Genetic Tradeoffs between Hygienic Behaviour and Individual Innate Immunity in the Honey Bee, <i>Apis mellifera</i>

<div><p>Many animals have individual and social mechanisms for combating pathogens. Animals may exhibit short-term physiological tradeoffs between social and individual immunity because the latter is often energetically costly. Genetic tradeoffs between these two traits can also occur if mutations that enhance social immunity diminish individual immunity, or vice versa. Physiological tradeoffs between individual and social immunity have been previously documented in insects, but there has been no study of genetic tradeoffs involving these traits. There is strong evidence that some genes influence both innate immunity and behaviour in social insects – a prerequisite for genetic tradeoffs. Quantifying genetic tradeoffs is critical for understanding the evolution of immunity in social insects and for devising effective strategies for breeding disease-resistant pollinator populations. We conducted two experiments to test the hypothesis of a genetic tradeoff between social and individual immunity in the honey bee, <i>Apis mellifera</i>. First, we estimated the relative contribution of genetics to individual variation in innate immunity of honey bee workers, as only heritable traits can experience genetic tradeoffs. Second, we examined if worker bees with hygienic sisters have reduced individual innate immune response. We genotyped several hundred workers from two colonies and found that patriline genotype does not significantly influence the antimicrobial activity of a worker’s hemolymph. Further, we did not find a negative correlation between hygienic behaviour and the average antimicrobial activity of a worker’s hemolymph across 30 honey bee colonies. Taken together, our work indicates no genetic tradeoffs between hygienic behaviour and innate immunity in honey bees. Our work suggests that using artificial selection to increase hygienic behaviour of honey bee colonies is not expected to concurrently compromise individual innate immunity of worker bees.</p></div