Doctor of Philosophy / Division of Biology / Theodore Morgan / Temperature is a critical environmental parameter and thermal variation has significant effects on local adaptation and species distributions in nature. This is especially true for organisms that are isothermal with their environment. Variation in temperature imposes stress and directly influences physiology, behavior, and fitness. Thus, to thrive across a range of thermal environments populations must contain sufficient genetic variation, the capacity to respond plastically, or some combination of both genetic and plastic responses. In this work I first quantified patterns of phenotypic and genetic variation in nature and then dissected the genetic basis of variation in thermal traits. In the first aim I used natural populations of Drosophila melanogaster collected from a latitudinal transect in Argentina to investigate variation in heat stress resistance and cold plasticity within and among populations. I found heat stress resistance was highly variable within populations, but was strongly associated with the monthly maximum average temperature of each site. For cold plasticity I was able to demonstrate significant variation in plasticity within and among populations, however the among population variation was best explained by the altitude of each site. I hypothesized that this was caused by a difference in temperature fluctuations at high altitude sites relative to low altitude sites. To evaluate this hypothesis I paired our study with existing laboratory data that demonstrated significant fitness differences between high and low plasticity (and altitude) sites when these populations were reared in variable thermal environments. Thus, cold plasticity is an adaptive response to environmental variation. The final project focused on understanding the genetic basis of thermal variation. I fine-mapped a single co-localized heat and cold tolerance QTL via deficiency and mutant complementation mapping to identify four novel thermal candidate genes. There was no overlap of the deficiencies or genes associated with cold or heat stress resistance. Sequence analysis of each gene identified the polymorphisms that differentiate the lines. To test for independent associations between these polymorphisms and variation in nature the Drosophila Genome Reference Panel was used to confirm associations between allelic variation and cold tolerance in nature.

This study tests the predictions made by several causal theories proposing different etiologies for childhood-onset and adolescent-onset conduct problems. It investigates a variety of causal factors proven to be important for the development of antisocial behaviors, specifically neuropsychological/cognitive deficits, temperamental vulnerabilities, dysfunctional parenting, deviant peers, and rebelliousness. Current theories generally agree that the early onset pathway is distinguished by interactions between a child with a difficult temperament and dysfunctional parent-child interactions. However, theories differ as to whether they emphasize the temperament and neurocognitive deficits of the child, or the parenting behaviors. In the adolescent onset pathway, theories typically focus on the importance of affiliation with deviant peers but differ as to whether this is attributed to a personality characterized by the rejection of traditional values and rebelliousness as leading to this association or failures in parenting practices. Seventy-eight pre-adjudicated adolescent (ranging in age from 11 to 18) boys housed in two short-term detention facilities and one outpatient program for boys at risk for involvement in the juvenile justice system in southeastern Louisiana participated in the current study. The sample was ethnically diverse (56% African-American) and largely came from facilities serving either a large urban or a largely suburban and rural region of the state. The sample was divided into two groups based on the youngest age of a self-reported delinquent act or parent-reported severe conduct problem. The childhoodonset group (n =47) displayed at least one serious antisocial behavior prior to age 12, whereas the adolescent-onset group (n =31) did not. As predicted, the childhood-onset group showed greater levels of dysfunctional parenting and CU traits. Contrary to predictions, however, this group also showed the strongest affiliation with deviant peers. The only variable strongly associated with the adolescent onset group was lower scores on a measure of traditionalism which indicates less endorsement of traditional values and status hierarchies. The implications of these results for understanding different causal trajectories to antisocial behavior and for designing better prevention and treatment programs for antisocial youth are discussed.

Therapeutic alliance is a robust predictor of future therapeutic outcomes. While treatment of normal children and adolescents is often hard, treating antisocial youth is especially difficult because of the social, cognitive, and emotional deficits experienced by these youth. This study investigated whether differing levels of callous-unemotional (CU) traits influenced the formation of therapeutic alliance in a sample of 51 adjudicated youth in juvenile institutions. Also, we tested whether therapeutic alliance influenced success in the institution and whether this association differed based on levels of CU traits. Results revealed that CU traits and selfreported delinquency were both modestly related to institutional infractions. Children low on both dimensions showed the lowest levels of institutional infractions. Additionally, these findings suggest that children high on both CU traits and delinquency reported better therapeutic alliance, but that youth with high CU traits committed more institutional infractions, despite their level of therapeutic alliance.

Adolescents commit nearly one-fifth of the sex crimes each year. Among those offenders exists a group of adolescent sex offenders with callous and unemotional (CU) traits who seem to show a more severe pattern of sexual offending. The current study attempts to test the importance of these traits by comparing adolescent sex offenders high or low on CU traits based on victim and offense characteristics, and offending history. A sample of 150 detained adolescents with a current sexual offense conviction were assessed through self-report, clinical interview, and file review. Results indicated that after controlling for a history of antisocial behaviors, the high CU group was more likely to have a greater number of victims, use more violence with victims, and engage in more offense planning than the low CU group. The high CU group was also more likely to offend against both strangers and family.

The current study was an investigation of the effectiveness of Functional Family Therapy (FFT) for improving the mental health, behavioral, and legal outcomes for justice-involved adolescents. A primary focus of the investigation was on whether Callous-Unemotional (CU) traits moderated the effects of treatment and whether therapists tailored the intervention to youths with these traits. The sample was 134 youths (15.34 years) who had been arrested and referred to a community mental health center for treatment by trained FFT therapists. Results indicated modest improvement over the course of treatment in the youths' emotional and behavioral functioning. CU traits were found to moderate treatment effects, wherein CU traits were associated with greater emotional and behavioral dysfunction prior to treatment, as well as greater improvement after treatment. However, CU traits also predicted greater self-reported, but not official reports, of delinquency at follow-up. Furthermore, results indicated some evidence for diverging treatment processes for youth with and without CU traits. Specifically, differences in response to changes in negative parenting varied between youth high and low on CU traits for some measures of emotional and behavioral functioning. Overall, FFT was found to be a promising treatment approach, but significant limitations in its effectiveness were also documented.

The purpose of this study was to examine the potential moderating effects of CU traits on the relationship between self-reported social intelligence and aggression in a community sample of boys and girls (ages 14-18). Four subtypes of aggression were measured: reactive overt, reactive relational, proactive overt, and proactive relational. Results indicated that there was not a significant association between social intelligence and any of the aggression subtypes. Neither CU traits nor empathy moderated the association between social intelligence and any of the four subtypes of aggression. Supplementary analyses were conducted to investigate whether level and type of aggression was related to levels of social intelligence and CU traits (or an interaction between the two). Results indicated that at high levels of CU traits, youth exhibited significantly higher levels of proactive overt and reactive overt aggression (t(113.06) than at low levels of CU traits.

Callous-unemotional (CU) traits have been shown to designate a particular subgroup of antisocial youth that are particularly violent, recidivistic, and more likely to continue offending in adulthood. Disordered neuroendocrine function may be a mechanism for the development of CU traits. We examined whether altered stress responsivity served as a mechanism linking stress exposure and the expression of CU traits. Participants were 15 incarcerated adolescent girls with CU traits. Measures of CU traits, stress exposure, and salivary cortisol were collected. Results revealed girls with CU traits had higher morning levels of cortisol, an intact cortisol awakening response (CAR), and flatter diurnal rhythms. Results indicated the type of stressor being measured and time since stressor onset are crucial to the interpretation of neuroendocrine function. We also found support for a neurobiological model for the development of CU traits drawing on the Adaptive Calibration Model. Implications of the study and directions for further research are discussed.

The current study aims to examine whether the association between conduct problems and bullying are accounted for by different factors in those with and without callous-unemotional (CU) traits. Participants included 284 students in the 4th through 7th grades. Results indicated that conduct problems and bullying were significantly correlated, and that this association was not moderated by CU traits. Moreover, anger dysregulation, and to some extent, victimization, were more strongly associated with conduct problems in those with lower levels of CU traits. Furthermore, conduct problems were more strongly related to attitudes towards bullying for those lower on CU traits than for those higher on CU traits. Finally, anger dysregulation, victimization, perceived peer support, and attitudes towards bullying did not account for the association between conduct problems and bullying.

Previous research has demonstrated an association between violence exposure and aggression; however, research exploring the association between violence exposure and the forms and functions of aggression is scarce. The aim of this study was to explore the associations between trauma exposure with both reactive and proactive functions of aggression by examining two potential mediators (e.g., psychopathic traits and emotional dysregulation). Participants included 132 male juvenile offenders mandated to treatment in a residential facility (M = 16.78 years old; SD = 1.25). Results indicate emotional dysregulation partially mediated the association between trauma exposure and reactive aggression while controlling for proactive aggression. However, no evidence was found to support the hypothesis that psychopathic traits mediated the association between trauma exposure and proactive aggression. Results suggest trauma exposure is important in the development of reactive aggression. Thus, treatment approaches for aggressive youth should address issues of trauma exposure.

Secular change has been documented in a number of studies focused on cranial and postcranial morphometrics and nonmetric traits. However, to date, few studies have addressed the potential of temporal change occurring in the expression of cranial nonmetric traits utilized in ancestry estimation. This study examines the effect of secular change on the expression of 23 cranial and mandibular nonmetric traits frequently employed in ancestry estimation; with age-at-death, sex, and year-of-birth of each individual documented for data analysis. Data were collected from European American individuals from the Hamann-Todd Skeletal Collection (n=518) and from the William M. Bass Donated Skeletal Collection (n=602). Individuals were divided into birth-year cohorts as follows: Hamann-Todd Skeletal Collection: 1824-1849 (Cohort 1), 1850-1874 (Cohort 2), 1875-1899 (Cohort 3), and 1900-1924 (Cohort 4); William M. Bass Donated Skeletal Collection: 1900-1924 (Cohort 4), 1925-1949 (Cohort 5), and 1950-1987 (Cohort 6). Pearson’s chi-square analyses produced significant p-values (≤ 0.01) in 19 of the 23 traits between the six birth-year cohorts. Factor maps generated through correspondence analyses were used as visual representations of relative trait expression between the cohorts. Ordinal regression analyses assessed the degree of variation between each cohort in relation to Cohort 1 along with the influence of age-at-death and sex on trait expression. Overall, analyses of the data revealed that secular change has occurred in 11 of the 23 traits, including: anterior nasal spine (ANS), malar tubercle (MT), nasal bone contour (NBC), postbregmatic depression (PBD), supranasal suture (SPS), transverse palatine suture (TPS), zygomaticomaxillary suture (ZS), gonial angle flare (GAF), mandibular tori (MDT), and posterior ramus edge inversion (PREI). Change in trait expression occurred in both males and females in seven traits, including: ANS, MT, TPS, ZS, GAF, MDT, and PREI. Significant change in trait expression occurred predominately between Cohorts 3 and 4 (birth years ranging from 1875 to 1924) and Cohorts 4 and 5 (birth years ranging from 1900 to 1949). This study demonstrates that secular change in nonmetric cranial and mandibular traits has occurred over the last two centuries with the greatest change appearing at the turn of the twentieth century.