Timing of seed dispersal in Daucus carota L. (Apiaceae)

This study describes the temporal pattern of seed dispersal in Daucus carota and examines the fate of seeds dispersed at different dates in SE Michigan. Plants varied greatly in both time of onset and rate of dispersal. Onset was directly related to flowering time, a phenotypically plastic character, and tended to occur earlier in newly established populations. Dispersal rate was similar for different-aged populations and for plants flowering at different times. The latter indicates that later-flowering plants dispersed a greater proportion of seeds in winter. Seed germination in outdoor plots declined when dispersal was delayed experimentally. Winter dispersal distances over snow surpassed autumn dispersal distances. However, only in some years did conditions (high winds and snow cover) required for longer distance dispersal occur while many seeds were still viable. Survival and reproduction of autumn-versus spring-germinating offspring varied greatly among years in experimental and natural populations. The fate of seeds dispersed at different times is unpredictable, which may explain the extended dispersal pattern observed in D. carota. Individual variation in dispersal rate is associated with environmental uncertainty in 1) timing of conditions suitable for dispersal over snow and 2) relative success of autumn- versus spring-germinating offspring. Early onset of dispersal, more common in the youngest populations, improves chances for local population expansion; late onset of dispersal found in older populations improves chances for new site colonization

The genetics of thermal plasticity in Plantago lanceolata

Phenotypic plasticity, an individual’s phenotypic response to environmental change, is a fundamental characteristic of all life on earth that plays a central role in adaptation, phenotypic differentiation, and speciation. Temperature-sensitive phenotypic plasticity, i.e. thermal plasticity, often increases with latitude, suggesting an increasingly adaptive role of thermal plasticity in predominantly cool, thermally variable environments. While the hypothesis is reasonable, it has not been thoroughly tested. Demonstrating local adaptation of thermal plasticity requires showing that: 1) thermal plasticity increases fitness in high latitude environments, 2) clinal variation arises from natural selection, and not by chance alone, 3) differences in thermal plasticity persist in the presence of gene flow, 4) thermal plasticity has a genetic basis and varies genetically along a latitudinal gradient, 5) thermal plasticity is heritable, and 6) thermal plasticity is a derived phylogenetic character. Today, little is known about the genetic properties of thermal plasticity. I took advantage of natural geographic variation in a widespread perennial herb, Plantago lanceolata to improve our understanding of adaptation along latitudinal clines by examining the genetic features of thermal plasticity. With genetic data I address the questions: 1) Is clinal variation in thermal plasticity best explained by natural selection driven by environmental differences among populations, neutral genetic evolution, or both? 2) What is the genetic architecture of thermal plasticity and single-environment trait variation, and how are they related? 3) Do genetic properties of thermal plasticity mirror phenotypic patterns along a latitudinal gradient? Among 14 European populations of Plantago lanceolata I estimated differentiation in temperature-sensitive floral reflectance plasticity (QST/PST), neutral genetic differentiation (FST & Jost’s D) of AFLP markers, and between-population differences in aspects of the reproductive environment. I used phenotypic QST (PST) vs. FST comparisons to investigate the evolutionary forces responsible for geographic patterns of thermal plasticity, and to determine if differences brought about by neutral evolutionary forces are sufficient to explain these patterns. My data supported the hypothesis that natural selection, driven by environmental properties of the reproductive season, particularly the duration and proportion of time at cool temperatures, has contributed to geographic patterns of thermal plasticity. As between-population differences in these environmental variables increased, differences in thermal plasticity increased more quickly than did neutral genetic differences. To determine the genetic architecture of thermal plasticity I produced an F2 mapping family from parents derived from distant northern and southern European populations that exhibited high (northern parents) and low (southern parents) thermal plasticities of floral reflectance. I then grew parents and offspring in two environments (cool and warm) mimicking what plants would encounter in nature. I attained genetic markers via genotype-by-sequencing (ddRADseq), produced a recombination map and performed QTL mapping of thermal plasticity and single-environment trait values for six traits: floral reflectance, flowering time, rosette diameter, leaf length, leaf fresh mass, and leaf area. My data provides critical genetic support for the hypothesis temperature-sensitive floral reflectance plasticity in P. lanceolata is adaptive in high latitude environments where growing seasons are cool and short. My data confirms thermal plasticity in P. lanceolata has a genetic basis as I found one single QTL underlying the thermal plasticities of three traits, floral reflectance, flowering time and leaf length. Floral reflectance plasticity and flowering time plasticity QTLs colocalized with, and shared phenotypic effects with corresponding single environment QTLs. The leaf length plasticity QTL did not colocalize with any single-environment QTLs, and was influenced by cytoplasm. I did not find evidence plasticity QTLs of different traits were pleiotropic. Additionally, genotypic differences at plasticity QTLs paralleled patterns of plasticity along latitudinal clines. At plasticity QTLs northern genotypes (Danish and Swedish) increased the magnitude of thermal plasticity, while southern genotypes (French and Italian) decreased plasticity

RELATIONSHIPS BETWEEN EDUCATION, PERSONALITY, CHANGE IN PERSONALITY TRAITS, AND THE USE OF MENTAL HEALTH SERVICES AMONG MIDDLE-AGED WOMEN OVER A 10-YEAR TIME SPAN

The purpose of this study was to examine the relationship between various levels of education, personality traits (neuroticism, extraversion, conscientiousness, agreeableness, and openness to experience), personality trait changes over time, and use of mental health services among middle-aged women. The subjects were 1110 women from 40 to 60 years of age responding to the 2005 National Survey of Midlife Development in the United States (MIDUS). The study used logistic regression first to investigate the predictive value of varying levels of education and personality traits on use of services during the past 12 months. A second logistic regression was used to investigate personality trait changes (between 1995 and 2005) on use of services during the past 12 months. Change scores were calculated using the reliable change index (RCI). In the first logistic regression, neuroticism (OR = 1.82, p <.001) and openness to experience (OR = 1.51, p < .05) were associated with significantly increased likelihood of mental health service utilization among middle-aged women. Conscientiousness (OR= 0.65, p < .05), in contrast, was associated with decreased likelihood of use of mental health services. Education and use of mental health services were not significant in the logistic regression. The second regression using the RCI scores was not significant, most likely due to the lack of reliable change for any of the personality traits. The significant association between neuroticism and conscientiousness and the use of mental health services among middle-aged women replicated findings from the 1995 MIDUS survey. However, this is the first study to find significance with openness to experience and use of mental health services among middle-aged women. Implications and future research are discussed