Natal dispersal outcomes are an interplay between environmental conditions and individual phenotypes. Peripheral, isolated populations may experience altered environmental conditions and natal dispersal patterns that differ from populations in contiguous landscapes. We document nonphilopatric, sex-biased natal dispersal in an endangered small mammal, the Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis), restricted to a single mountain. Other North American red squirrel populations are shown to have sex-unbiased, philopatric natal dispersal. We ask what environmental and intrinsic factors may be driving this atypical natal dispersal pattern. We test for the influence of proximate factors and ultimate drivers of natal dispersal: habitat fragmentation, local population density, individual behavior traits, inbreeding avoidance, competition for mates, and competition for resources, allowing us to better understand altered natal dispersal patterns at the periphery of a species' range. A juvenile squirrel's body condition and its mother's mass in spring (a reflection of her intrinsic quality and territory quality) contribute to individual behavioral tendencies for movement and exploration. Resources, behavior, and body condition have the strongest influence on natal dispersal distance, but affect males and females differently. Male natal dispersal distance is positively influenced by its mother's spring body mass and individual tendency for movement; female natal dispersal distance is negatively influenced by its mother's spring body mass and positively influenced by individual tendency for movement. An apparent feedback between environmental variables and subsequent juvenile behavioral state contributes to an altered natal dispersal pattern in a peripheral population, highlighting the importance of studying ecological processes at the both range center and periphery of species' distributions.

Animal personality is found in a wide range of taxa, yet our knowledge of what maintains consistent among-individual variation in behaviour is still incomplete. Many personality traits are associated with fitness, leading to the expectation that, under selection, genetic (and among-individual) variation will be eroded over time. Several adaptive models have been developed in order to explain this maintenance of variation. These include state-dependence, state-behaviour feedback loops, life-history and behavioural coadaptation and the Pace of Life syndrome. These models represent good starting points for thinking about what drives and maintains among-individual variation in behaviour, and while empirical support for these models is mixed, one thing they do have in common is the assumption of a significant genetic basis underpinning personality traits. Significant heritability is required for an evolutionary response to selection and for among-individual variation to be adaptive. The univariate estimates of heritability for personality traits that are growing in the literature, while useful, are likely insufficient to predict how personality traits will respond to selection. This thesis uses the Trinidadian guppy, Poecilia reticulata, and other species to explore patterns of among-individual and genetic variation in personality traits, advocating the benefits of using multivariate perspectives throughout. Firstly, the among-individual covariance structure between measures of boldness, growth and metabolic rate are estimated in a test of the Pace of Life syndrome. Secondly, an appraisal of the relative strength of maternal and genetic effects on offspring personality and how it changes over ontogeny. Next, a comprehensive treatment of sexual dimorphism in behaviour and size followed by analysis of genotype-by-sex interactions using both univariate and multivariate methods. Finally, a comparative analysis of personality in 7 species of small fish, identifying the main axis of among-individual variation from a single assay in each and quantifying the phylogenetic signal.

<p>Understanding the diversity of life is one of the main aims of evolutionary biology, and requires knowledge of the occurrence and causes of adaptive genetic differentiation among geographically distinct populations. Environmental stress caused by acidity may cause strong directional selection in natural populations, but is little explored from an evolutionary perspective. In this thesis, a series of laboratory experiments and field data was used to study evolutionary and ecological responses of amphibians to environmental acidity. </p><p>Local adaptation to acid stress was studied in the moor frog (<i>Rana arvalis)</i>.The results show that acid origin populations have higher acid stress tolerance during the embryonic stages than neutral origin populations, and that acid and neutral origin populations have diverged in embryonic and larval life-histories. The mechanisms underlying adaptive differentiation are partially mediated by maternal effects related to extra-embryonic membranes and egg size. Acid origin females invest in larger eggs and have a stronger egg size-fecundity trade-off than females from neutral areas, likely reflecting adaptive differentiation in maternal investment patterns. </p><p>Potential carry-over effects of low pH, and the effects of UV-b/pH interaction were investigated in the common frog (<i>R. temporaria</i>). The results suggest that amphibian larvae are able to compensate for the negative effects of acidity experienced early in life, if conditions later turn beneficial. <i>R. temporaria</i> populations differed in their sensitivity to synergistic effects of low pH/UV-B, indicating variation in population responses to environmental stress.</p><p>In conclusion, these results suggest rapid evolution in response to human induced environmental change, much of which may be mediated via adaptive maternal effects. Acidification may be a powerful selective force shaping life-history evolution.</p>

Understanding the diversity of life is one of the main aims of evolutionary biology, and requires knowledge of the occurrence and causes of adaptive genetic differentiation among geographically distinct populations. Environmental stress caused by acidity may cause strong directional selection in natural populations, but is little explored from an evolutionary perspective. In this thesis, a series of laboratory experiments and field data was used to study evolutionary and ecological responses of amphibians to environmental acidity. Local adaptation to acid stress was studied in the moor frog (Rana arvalis).The results show that acid origin populations have higher acid stress tolerance during the embryonic stages than neutral origin populations, and that acid and neutral origin populations have diverged in embryonic and larval life-histories. The mechanisms underlying adaptive differentiation are partially mediated by maternal effects related to extra-embryonic membranes and egg size. Acid origin females invest in larger eggs and have a stronger egg size-fecundity trade-off than females from neutral areas, likely reflecting adaptive differentiation in maternal investment patterns. Potential carry-over effects of low pH, and the effects of UV-b/pH interaction were investigated in the common frog (R. temporaria). The results suggest that amphibian larvae are able to compensate for the negative effects of acidity experienced early in life, if conditions later turn beneficial. R. temporaria populations differed in their sensitivity to synergistic effects of low pH/UV-B, indicating variation in population responses to environmental stress. In conclusion, these results suggest rapid evolution in response to human induced environmental change, much of which may be mediated via adaptive maternal effects. Acidification may be a powerful selective force shaping life-history evolution.

<p>This dissertation examines the processes that generate phenotypic variation in life cycles in seasonal environments. Collectively, a life cycle describes the stages an organism passes through during a generation. The timing, or phenology, of these transitions is often influenced by both environmental and allelic variation. Using the model organism Arabidopsis thaliana and both empirical and modeling approaches, I examine how correlations between life-cycle transitions, environment-dependent allelic effects, and epistasis generate patterns of life-cycle variation both within and between generations. In my first chapter, I use experiments to determine that many combinations of genetic, environmental, and developmental factors can create similar germination phenotypes, that maternal effects can influence phenotypes more than genetic differences, and that cross-generational effects can reduce variation in germination timing despite variation in flowering and dispersal time. In my second chapter, I use a modeling approach to consider the entire life cycle. I find that environmental variation is a major driver of phenotypic variation, and that considering the known geographic distribution of allelic variation across the range improves the match of model predictions to phenotypes expressed in natural populations. Specifically, variation in dormancy generated in the previous generation is predicted to cause life-cycle differences within a location, and the geographic distribution of allelic variation in dormancy interacts with local climatic environments to canalize an annual life history across the range. Finally, I test if allelic and environmental variation that affects early life stages can influence the environment experienced during reproduction. This environment determines both the time available for reproduction and the environment experienced during senescence. By implementing simple survival rules for flowering plants in the model, I show that time available for a plant to reproduce depends on earlier phenological traits and varies widely from year to year, location to location, and genotype to genotype. If reproductive trade-offs that underlie the evolution of senescence are environmentally sensitive, these results suggest that genetic variation in earlier life-stage transitions might shape senescence rates and whether they are environmentally responsive. In sum, my dissertation demonstrates the importance of pleiotropy, environment-dependent allelic expression, and epistasis in defining life-cycle variation, and proposes a novel way of predicting these relationships and complex life cycles under seasonal conditions.</p> / Dissertation

Few empirical studies examine the influence that the maternal parasite environment can have on offspring fitness (maternal effects) in invertebrates. Several recent studies have found that mothers can adjust offspring phenotype to counter the negative effects of parasite infection. In this thesis I subjected the parental generation of the host species, Tenebrio molitor (Insecta: Coleoptera), to a high parasite, high density, or control treatment. Offspring were subsequently subjected to either the same stress, the alternate stress, or to the control, and fitness-related life history traits were measured in both generations. The results from this thesis do not support the hypothesis that T. molitor mothers influence offspring fitness in a positive way. Instead, maternal effects led to a reduction in offspring fitness under both types of stress. At least under some environmental conditions, females invest in their fitness at the expense of their offspring.

Few empirical studies examine the influence that the maternal parasite environment can have on offspring fitness (maternal effects) in invertebrates. Several recent studies have found that mothers can adjust offspring phenotype to counter the negative effects of parasite infection. In this thesis I subjected the parental generation of the host species, Tenebrio molitor (Insecta: Coleoptera), to a high parasite, high density, or control treatment. Offspring were subsequently subjected to either the same stress, the alternate stress, or to the control, and fitness-related life history traits were measured in both generations. The results from this thesis do not support the hypothesis that T. molitor mothers influence offspring fitness in a positive way. Instead, maternal effects led to a reduction in offspring fitness under both types of stress. At least under some environmental conditions, females invest in their fitness at the expense of their offspring.

Cardiac, metabolic and growth response of early-stage chicken embryos to perturbations in yolk environment was investigated. Also, effects of parental hypoxia exposure on hypoxia resistance, thermal tolerance and body length of zebrafish larvae were investigated. In the first study, thyroxine, triiodothyronine and testosterone produced differential effects on heart rate and development rate of chicken embryos during the first 4 days of development. Triiodothyronine caused a dose-dependent increase in heart rate when applied at 40 or 70 hours of age, while thyroxine caused a dose-dependent increase in heart rate when applied at 40 hours only. Testosterone and propyl-thiouracil (deiodinase antagonist) did not have an effect on heart rate. Development rate was not changed by thyroxine, triiodothyronine, testosterone or propyl-thiouracil, which suggested that heart rate changes did not result from changes in embryo maturity. In the second study, chicken embryos exposed to yolks of different bird species during early-stage embryonic development showed changes in heart rate, mass-specific oxygen consumption and body mass that scaled with the egg mass, incubation period length, and yolk triiodothyronine and testosterone levels of the species from which yolk was derived. In the third study, this phenomenon was investigated between layer and broiler chickens. Heart rate, oxygen consumption and body mass of broiler and layer embryos were significantly changed by a breed-specific change in yolk environment. Yolk triiodothyronine and testosterone concentrations of broiler and layer eggs did not suggest that these hormones were responsible for physiological and morphological changes observed. The final study demonstrated that hypoxia resistance and body lengths, but not thermal tolerance of zebrafish larvae was increased by parental hypoxia exposure.

Maternal factors have the potential to influence the morphometrics of offspring; however, the magnitude and persistence of those influences are not well known. I investigated the extent to which maternal factors influenced offspring phenotype at the individual and population level for captive white-tailed deer (Odocoileus virginianus) originating from three distinct physiographic regions of Mississippi, USA. First, I tested whether male white-tailed deer displayed improvements in weaponry and body size after two generations of being released from nutritional restrictions. I found that improved nutrition positively influenced all morphometrics; however, we observed variation in magnitude of improvement. Antler size was most responsive to improved nutrition while body mass and skeletal structures were less responsive; potentially indicating an adaptive strategy allowing males to increase yearly reproductive success without jeopardizing lifetime reproductive success. Second, we assessed whether maternal characteristics, early life characteristics or a combination of both persistently influenced morphometrics throughout maturity. I found that late birth date positively influenced offspring body mass through three-years of age; indicating that late-born fawns over-compensated for a late start to life. I also identified an indirect silver-spoon effect as early-, heavy-born fawns were heavy juveniles. In turn, heavy juveniles were also heavy adults. Therefore, male white-tailed deer may gain reproductive opportunities by displaying one of two strategies to increase body mass. Lastly, I estimated heritability for six antler characteristics and quantified the influence of maternal factors such as parturition date and litter size on the predictability of antler size. All antler characteristics were highly heritable. Yearling antler size was a moderate predictor of antler size later in life, but accounting for maternal factors greatly improved predictability. The influence of maternal factors decreased with increasing male age suggesting that compensation for the negative influence of maternal factors may occur after an individual’s first year of life. My results suggest that although antler characteristics are highly heritable, the large influence of maternal factors on predictability indicates that use of yearling antler size as selective harvest criteria may not achieve all management goals.

Doctor of Philosophy / Department of Entomology / J.P. Michaud / James R. Nechols / The manner in which organisms allocate reproductive resources for reproduction is a central question with respect to life history theory. The main objectives of this research were to i) examine lifetime patterns of reproductive allocation in the lady beetles Coleomegilla maculata (DeGeer) and Hippodamia convergens (Guérin-Menéville) (Coleoptera: Coccinellidae) while manipulating environmental conditions that affect female body size (i.e., larval food supply), ii) to study the interaction between factors underlying female body size and the resources available during reproduction, and iii) to explore the maternal effects of female size and age on the development and survival of progeny. When different size classes of females were produced and adult females were maintained with unlimited food, there were no differences in egg size across female size in C. maculata, but egg size increased over time in all females. In H. convergens, only larger females increased egg size over time, and they laid larger eggs, on average, than did small females. Maternal body size was positively correlated with the number of eggs laid per day in both species. When three size classes of females were subjected to a fluctuating food supply as adults, female size was again positively correlated with egg and daily fecundity. Whereas both species varied daily fecundity in response to adult food supply, egg size was unaffected and demonstrated a fixed pattern of change with female age and species-specific effects of maternal body size. To observe maternal effects in H. convergens, three female size classes were again produced and progeny were reared from three different periods of each female‟s reproductive life. Offspring from later oviposition days and larger females developed faster and achieved larger adult size than those reared from earlier oviposition days. Egg size showed inconsistent correlations with developmental parameters and adult progeny size, so other, more cryptic, maternal signals were inferred to signal phenotype development in progeny. A fixed program of producing faster-developing offspring that mature to larger sizes late in the oviposition cycle is adaptive for exploiting ephemeral aphid blooms that exhibit predictable dynamics of declining prey abundance and increasing competition. In the case of H. convergens, resource limitation during development constrained not only body size, fecundity and egg size, but also maternal ability to manipulate progeny phenotypes.