Doctor of Philosophy

dissertationDispersal is the main process leading to gene flow in populations. Gene flow influences the spatial distribution of populations, individuals and genes. Natural populations are typically subdivided, or structured, in space and genetic composition in part due to limited dispersal. Understanding how genetic variation is partitioned and the factors that govern this process is a major goal of evolutionary biologists because the degree to which populations are structured affects rates of local adaptation, speciation and extinction. In my dissertation I examine how one life history trait, phoretic dispersal, influences gene flow and genetic differentiation in populations. Here I compare related and sympatric species that are ecologically very similar, but explicitly differ in dispersal behavior. Wing lice (Columbicola columbae) frequently engage in phoresis or "hitchhike" on the pigeon lousefly (Pseudolynchia canariensis), while body lice (Campanulotes compar) do not. In the first part of my dissertation I characterize the genetic makeup of wing and body lice populations on a local scale. I found that in a geographic area where flies occur, wing lice have significantly less population genetic structure than body lice. Next I identified geographic areas where flies are absent from pigeon populations. Finally, I compared patterns of genetic differentiation on a global scale for wing and body lice populations. I found that in areas without flies, wing lice and body lice have similar patterns of genetic differentiation. These findings strongly suggest that ongoing phoretic dispersal erodes population genetic structure and enhances population connectivity for wing lice

Genome-wide association study meta-analysis of suicide death and suicidal behavior

Suicide is a worldwide health crisis. We aimed to identify genetic risk variants associated with suicide death and suicidal behavior. Meta-analysis for suicide death was performed using 3765 cases from Utah and matching 6572 controls of European ancestry. Meta-analysis for suicidal behavior using data across five cohorts (n = 8315 cases and 256,478 psychiatric or populational controls of European ancestry) was also performed. One locus in neuroligin 1 (NLGN1) passing the genome-wide significance threshold for suicide death was identified (top SNP rs73182688, with p = 5.48 x 10(-8) before and p = 4.55 x 10(-8) after mtCOJO analysis conditioning on MDD to remove genetic effects on suicide mediated by MDD). Conditioning on suicidal attempts did not significantly change the association strength (p = 6.02 x 10(-8)), suggesting suicide death specificity. NLGN1 encodes a member of a family of neuronal cell surface proteins. Members of this family act as splice site-specific ligands for beta-neurexins and may be involved in synaptogenesis. The NRXN-NLGN pathway was previously implicated in suicide, autism, and schizophrenia. We additionally identified ROBO2 and ZNF28 associations with suicidal behavior in the meta-analysis across five cohorts in gene-based association analysis using MAGMA. Lastly, we replicated two loci including variants near SOX5 and LOC101928519 associated with suicidal attempts identified in the ISGC and MVP meta-analysis using the independent FinnGen samples. Suicide death and suicidal behavior showed positive genetic correlations with depression, schizophrenia, pain, and suicidal attempt, and negative genetic correlation with educational attainment. These correlations remained significant after conditioning on depression, suggesting pleiotropic effects among these traits. Bidirectional generalized summary-data-based Mendelian randomization analysis suggests that genetic risk for the suicidal attempt and suicide death are both bi-directionally causal for MDD.Peer reviewe

Dissecting the Shared Genetic Architecture of Suicide Attempt, Psychiatric Disorders, and Known Risk Factors

Background Suicide is a leading cause of death worldwide, and nonfatal suicide attempts, which occur far more frequently, are a major source of disability and social and economic burden. Both have substantial genetic etiology, which is partially shared and partially distinct from that of related psychiatric disorders. Methods We conducted a genome-wide association study (GWAS) of 29,782 suicide attempt (SA) cases and 519,961 controls in the International Suicide Genetics Consortium (ISGC). The GWAS of SA was conditioned on psychiatric disorders using GWAS summary statistics via multitrait-based conditional and joint analysis, to remove genetic effects on SA mediated by psychiatric disorders. We investigated the shared and divergent genetic architectures of SA, psychiatric disorders, and other known risk factors. Results Two loci reached genome-wide significance for SA: the major histocompatibility complex and an intergenic locus on chromosome 7, the latter of which remained associated with SA after conditioning on psychiatric disorders and replicated in an independent cohort from the Million Veteran Program. This locus has been implicated in risk-taking behavior, smoking, and insomnia. SA showed strong genetic correlation with psychiatric disorders, particularly major depression, and also with smoking, pain, risk-taking behavior, sleep disturbances, lower educational attainment, reproductive traits, lower socioeconomic status, and poorer general health. After conditioning on psychiatric disorders, the genetic correlations between SA and psychiatric disorders decreased, whereas those with nonpsychiatric traits remained largely unchanged. Conclusions Our results identify a risk locus that contributes more strongly to SA than other phenotypes and suggest a shared underlying biology between SA and known risk factors that is not mediated by psychiatric disorders.publishedVersio

Dissecting the Shared Genetic Architecture of Suicide Attempt, Psychiatric Disorders, and Known Risk Factors

Background Suicide is a leading cause of death worldwide, and nonfatal suicide attempts, which occur far more frequently, are a major source of disability and social and economic burden. Both have substantial genetic etiology, which is partially shared and partially distinct from that of related psychiatric disorders. Methods We conducted a genome-wide association study (GWAS) of 29,782 suicide attempt (SA) cases and 519,961 controls in the International Suicide Genetics Consortium (ISGC). The GWAS of SA was conditioned on psychiatric disorders using GWAS summary statistics via multitrait-based conditional and joint analysis, to remove genetic effects on SA mediated by psychiatric disorders. We investigated the shared and divergent genetic architectures of SA, psychiatric disorders, and other known risk factors. Results Two loci reached genome-wide significance for SA: the major histocompatibility complex and an intergenic locus on chromosome 7, the latter of which remained associated with SA after conditioning on psychiatric disorders and replicated in an independent cohort from the Million Veteran Program. This locus has been implicated in risk-taking behavior, smoking, and insomnia. SA showed strong genetic correlation with psychiatric disorders, particularly major depression, and also with smoking, pain, risk-taking behavior, sleep disturbances, lower educational attainment, reproductive traits, lower socioeconomic status, and poorer general health. After conditioning on psychiatric disorders, the genetic correlations between SA and psychiatric disorders decreased, whereas those with nonpsychiatric traits remained largely unchanged. Conclusions Our results identify a risk locus that contributes more strongly to SA than other phenotypes and suggest a shared underlying biology between SA and known risk factors that is not mediated by psychiatric disorders.Peer reviewe

New Spiroplasma in parasitic Leptus mites and their Agathemera walking stick hosts from Argentina

Here we report the presence of Spiroplasma 16S rRNA in populations of two parasitic Leptus mites (Leptus sayi; Leptus lomani) and their Agathemera walking stick hosts. In walking sticks Spiroplasmas were detected in the gut, as well as muscle-tissues, but not in eggs. Throughout Argentina 15.4% of L. sayi populations and 14.3% of L. lomani populations surveyed screened positive for Spiroplasma. Phylogenetic analyses (ML, BCMC) place all sequences within the Ixodetis group. Most sequences form a well-supported sister subclade to the rest of Ixodetis. We briefly discuss the role of Leptus mites in the natural transmission of Spiroplasma.Fil: DiBlasi, Emily. State University of New York; Estados UnidosFil: Morse, Solon. State University of New York; Estados UnidosFil: Mayberry, Jason R.. State University of New York; Estados UnidosFil: Avila, Luciano Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Morando, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Dittmar, Katharina. State University of New York; Estados Unido

Data corresponding to Table 2a

Data for GLMM summary testing the probability that a given allele is unique to the subpopulation (private allele) compared to all other lice at each collection site respective of species

Sex ratio at emergence.

<p>Block diagram of percent male to female <i>T. frequens</i>, scaled to 100%, for three sampling months. All months show an excess of females (dark grey), and proportions are very similar throughout.</p

Schematic diagram comparing parasite demography on-host (right panel), and off-host (left panel).

<p><b><u>On-host</u></b> a physical ratio of 1∶1 is observed. Red rectangle represents females with developing offspring, which are not available for reproduction. Females within green rectangle are a mixture of returning females, and teneral females (N). The green rectangles (male and female) on-host represent the operational sex ratio (OSR), which is likely male biased. <b><u>Off-host</u></b>, depositing females leave the hosts (1), and arrive at the pupal field (2), where they give birth to their offspring. Some die due to predation (skull), while new females and males emerge leave the field (3) and return to the general host population (4). Mating ensues, and females become unavailable for mating. The ratio of males and females at emergence is skewed towards females.</p