Analyses of physiological evolutionary response.

Extreme environments and adaptation.- The evolution of plants in metal-contaminated environments.- Responses of aquatic organisms to pollutant stress: Theoretical and practical implications.- Conifers from the cold.- Genetic variation and environmental stress.- Phenotypic plasticity and fluctuating asymmetry as responses to environmental stress in the butterflyBicyclus anynana.- Environmental stress and the expression of genetic variation.- Worldwide latitudinal clines for the alcohol dehydrogenase polymorphism in Drosophila melanogaster: What is the unit of selection?.- Stress and metabolic regulation inDrosophila.- Acclimation and response to thermal stress.- Phenotypic and evolutionary adaptation of a model bacterial system to stressful thermal environments.- Ecological and evolutionary physiology of heat shock proteins and the stress response inDrosophila: Complementary insights from genetic engineering and natural variation.- High-temperature stress and the evolution of thermal resistance inDrosophila.- Stress, selection and extinction.- Genetic and environmental stress, and the persistence of populations.- Adaptation and extinction in changing environments.- Environmental stress and evolution: A theoretical study.- Stress, developmental stability and sexual selection.- Evolution and stress.- Genetic variability and adaptation to stress.- Stress-resistance genotypes, metabolic efficiency and interpreting evolutionary change.- The Plus ca change model: Explaining stasis and evolution in response to abiotic stress over geological timescales.

This paper presents a unified account of the properties of the measures, Malthusian parameter and entropy in predicting evolutionary change in populations of macromolecules, cells and individuals. The Malthusian parameter describes the intrinsic rate of increase of the population. The entropy describes the intrinsic variability in populations: it characterizes the variability in mutation and replication rates in populations of macromolecules; the rate of decay of synchrony in populations of cells; and the degree of iteroparity in populations of individuals. The Malthusian parameter determines ultimate population numbers: under constant environmental conditions, it is the rate of increase when equilibrium conditions are attained. Entropy determines population stability: the gain in the Malthusian parameter due to small fluctuations in the life-cycle variables is determined by entropy. These properties, which are valid for populations of macromolecules, cells and individuals, show that the Malthusian parameter and entropy act as complimentary fitness indices in understanding evolutionary change in populations.

Levels of Selection

Levels of Selection

Study of adaptive evolutionary changes in populations of invasive species can be advanced through the joint application of quantitative and population genetic methods. Using purple loosestrife as a model system, we investigated the relative roles of natural selection, genetic drift and gene flow in the invasive process by contrasting phenotypical and neutral genetic differentiation among native European and invasive North American populations (Q(ST) - F(ST) analysis). Our results indicate that invasive and native populations harbour comparable levels of amplified fragment length polymorphism variation, a pattern consistent with multiple independent introductions from a diverse European gene pool. However, it was observed that the genetic variation reduced during subsequent invasion, perhaps by founder effects and genetic drift. Comparison of genetically based quantitative trait differentiation (Q(ST)) with its expectation under neutrality (F(ST)) revealed no evidence of disruptive selection (Q(ST) > F(ST)) or stabilizing selection (Q(ST) < F(ST)). One exception was found for only one trait (the number of stems) showing significant sign of stabilizing selection across all populations. This suggests that there are difficulties in distinguishing the effects of nonadaptive population processes and natural selection. Multiple introductions of purple loosestrife may have created a genetic mixture from diverse source populations and increased population genetic diversity, but its link to the adaptive differentiation of invasive North American populations needs further research.

Consideration is given to the case of a daughter population of a sexual species that becomes successfully established in an area previously lacking that species, as has occurred recently in the Krakataus. If the new area is isolated geographically and if the number of founder individuals is small, conventional wisdom foresees a reduction of genetic variability within the colony. This might obstruct genetic adjustment to new conditions. Recent studies of the genetics of such bottlenecked populations, however, show that, in some instances, genetic variability for quantitative traits may actually increase rather than decrease after a bottleneck event. Whereas loss of some quasi-neutral biochemical alleles may occur, the quantitative polygenic balances on which adaptation depends can be carried through the bottleneck into the new population. Novel phenotypes may result from natural selection during the generations that immediately follow the bottleneck. Growing shield volcanoes in particular show rapid turnover of their surfaces such that organisms surviving there must continually recolonize or become extinct. Such species, existing as metapopulations, should be prone to bottleneck effects that produce genetic shifts. Examples are given from Drosophila silvestris on the island of Hawaii. The relevance of such genetic shifts to population structure and evolutionary change in populations is discussed, emphasizing the probable role of metapopulation structure.

Natural selection is the established force driving evolutionary change in populations, however the link between selection and the formation of new species is much less concrete. There is a growing body of evidence that differences in ecological conditions within a species range can lead to adaptive changes in both appearance and underlying genetic background that can lead to the formation of discrete and divergent populations. When these differences accumulate to a degree that prevents genetic exchange, these populations may satisfy many of the categories defining distinct species. In the works described in this thesis, I examine the mechanisms of natural selection driving evolutionary divergence between three adjacent populations of Senecio lautus, a native Australian plant. First, I describe the phenotypic differences that have accumulated between the three populations and use empirical experiments to show that these changes are most likely the result of adaptation to divergent ecological conditions. In the second chapter I examine whether this adaptation to local conditions can influence the rate of gene exchange between populations by quantifying a range of potential ecological and genetic mechanisms that may influence the ability of populations to breed with one another. Results from this experiment suggest that intrinsic genetic differences between populations do not affect gene exchange and that the main barrier to gene flow between populations is associated with different patterns of adaptation preventing immigrant plants from establishing. These findings are consistent with the theories of ecological speciation, where speciation occurs primarily as a result of environmental factors, and I specifically test this hypothesis in chapter IV. The prediction of ecologically dependent hybrid fitness is a unique prediction of ecological speciation, and I use field based reciprocal transplant experiments to determine whether this pattern is observed between S. lautus ecotypes. Together, these chapters provide evidence that natural selection based on ecological variation drives phenotypic divergence between populations, is the major factor preventing gene exchange between populations, and leads to patterns of hybrid fitness that are consistent with the theoretical predictions of ecological speciation.

Experimental evolution can be a useful tool for testing the impact of environmental factors on adaptive changes in populations, and this approach is being increasingly used to understand the potential for evolutionary responses in populations under changing climates. However, selective factors will often be more complex in natural populations than in laboratory environments and produce different patterns of adaptive differentiation. Here we test the ability of laboratory experimental evolution under different temperature cycles to reproduce well-known patterns of clinal variation in Drosophila melanogaster. Six fluctuating thermal regimes mimicking the natural temperature conditions along the east coast of Australia were initiated. Contrary to expectations, on the basis of field patterns there was no evidence for adaptation to thermal regimes as reflected by changes in cold and heat resistance after 1-3 years of laboratory natural selection. While laboratory evolution led to changes in starvation resistance, development time, and body size, patterns were not consistent with those seen in natural populations. These findings highlight the complexity of factors affecting trait evolution in natural populations and indicate that caution is required when inferring likely evolutionary responses from the outcome of experimental evolution studies.

Teleological reasoning is viewed as a major hurdle to evolution education, and yet, eliciting, interpreting, and reflecting upon teleological language presents an arguably greater challenge to the evolution educator and researcher. This article argues that making explicit the role of behavior as a causal factor in the evolution of particular traits may prove productive in helping students to link their everyday experience of behavior to evolutionary changes in populations in ways congruent with scientific perspectives. We present a teaching tool, used widely in other parts of science and science education, yet perhaps underutilized in human evolution education—the causal map—as a novel direction for driving conceptual change in the classroom about the role of organism behavior and other factors in evolutionary change. We describe the scientific and conceptual basis for using such causal maps in human evolution education, as well as theoretical considerations for implementing the causal mapping tool in human evolution classrooms. Finally, we offer considerations for future research and educational design.

Since stress can be defined as anything which reduces growth or performance, it follows that, if appropriate genetic variability is present, classical evolutionary changes in populations are to be expected in any situation where a consistent stress is occurring. There is now considerable evidence for such evolution, producing constitutive adaptations in plants in response to stress, which are specific to the stress concerned. Stress may however operate in a temporary or fluctuating manner. In these situations, facultative adaptations, able to be produced within a single genotype through phenotypic plasticity, will be more appropriate. Very different specific phenotypic response systems, both morphological or physiological, can be found in plants in relation to different fluctuating stresses, operating over a wide range of time scales. These response systems are under normal genetic control and appear to be products of normal evolutionary processes. They can however have quite complex features, analogous to the behavioural response systems in animals.

Climate change is one of the greatest challenges that wildlife is facing. Rapid shifts in climatic conditions may accelerate evolutionary changes in populations as a result of strong selective pressure. Most studies focus on the impact of climatic conditions on phenologies and annual cycles, whereas there are fewer reports of empirical support for climate-driven changes in the phenotypic variability of free-living populations. We investigated whether climatic variables explain the prevalence of colour polymorphism in a population of the grass snake (Natrix natrix) with two morphotypes, the melanistic and non-melanistic ones, in the period 1981-2013. We found that the prevalence of the black phenotype was negatively related to spring temperature and winter harshness, expressed as the number of snow days. According to the thermal melanism hypothesis, a high predation rate during warmer springs may override relaxed thermal benefits and vice versa, i.e. black individuals may perform better than typical ones when thermal conditions in spring are unfavourable. In turn, because they are smaller, melanistic individuals may be exposed to a higher risk of winter mortality, particularly during longer winters. We highlight the need for more studies on the effects of climatic conditions on temporal variation in melanism prevalence in other populations and species as well as in various geographic regions.

The spread of Ophiostoma novo-ulmi across Europe, North America and central Asia, resulted in the current, highly destructive Dutch elm disease (DED) pandemic, replacing O. ulmi, responsible for the first DED pandemic in the early 1900s. This process has resulted in a series of remarkable evolutionary and adaptive developments. Studies of O. novo- ulmi populations in the 1980s, especially in Spain and Portugal, showed the following: 1) that O. novo-ulmi initially spread across Europe as a series of genetic clones; 2) that deleterious RNA viruses were transmitted within the O. novo-ulmi clones; 3) that natural hybrids between O. novo-ulmi subspecies americana and subsp. novo-ulmi, emerged widely across Europe; 4) that there has also been a widespread emergence, across Europe, of natural hybrids between O. novo-ulmi subspecies americana and also subsp. novo-ulmi. The factors driving these changes have been examined by molecular analysis. Results show: 1) that the rapid change from clonality to genetic variability involved the acquisition of ‘useful’ mating type, vegetative compatibility type and other genes by O. novo-ulmi from O. ulmi via lateral (or interspecies) gene transfer; whereas ‘unuseful’ O. ulmi genes were discarded; 2) that the RNA viruses occurring in the O. novo-ulmi populations probably originated from O. ulmi; and 3) and that where O. novo-ulmi subsp. americana and subsp. novo-ulmi co-exist, natural hybrids are occurring very freely; in some areas most O. novo-ulmi isolates are already complex subspp. americana x novo-ulmi hybrids. These phenomena features are unique, and have considerable implications for the invasion history, successful spread and future behaviour of O. novo-ulmi.

When prey experience size-based harvesting by predators, they are not only subject to selection due to larger individuals being preferentially harvested but also selection due to reductions in population density. Density-dependent selection represents one of the most basic interactions between ecology and evolution. Yet, the reduction in density associated with exploitation has not been tested as a possible driving force of observed evolutionary changes in populations harvested size-dependently. Using an artificial selection experiment with a mixture of Daphnia clones, we partition the evolutionary effects of size-based harvesting into the effects of removing large individuals and the effects of lowering the population density. We show that both size selection and density-dependent selection are significant drivers of life-history evolution. Importantly, these drivers affected different life-history traits with size-selective harvesting selecting for slower juvenile growth rates and a larger size at maturity, and low-density selecting for reduced reproductive output.

The role of zoonoses in changes of animal populations and communities is considered. The analysis was carried out using examples of population dynamics of small mammals distributed in the Crimean Peninsula, under the influence of the main zoonoses common for this territory, in particular tularaemia, leptospirosis, Marseille fever, viral tick-borne encephalitis, Ixodes tick-borne borreliosis, Crimea-Congo fever, KU fever, HFRS, and many others. Such data were analysed according to databases on the state of small-mammal populations and zoonoses common in these populations, obtained by original studies over the past 40 years. The role of zoonoses as factors of evolutionary changes in populations of small mammals is considered, in particular as a factor of mortality leading to significant reductions in population numbers and fragmentation of species ranges, as well as factors determining co-evolution of pathogens, vectors (arthropods), and small-mammals as hosts. Both groups of factors lead to the formation of population diversity due to changes in character variability and the formation of new characters associated with adaptations to zoonoses.

Inbreeding has the potential to cause evolutionary changes in populations, although these changes are likely to drive populations to extinction through inbreeding depression and reductions in genetic diversity. We investigated the mating system and late-stage inbreeding depression (delta) in 10 populations of Magnolia stellata using nine microsatellite markers and evaluated the effects of population size and the degree of population isolation through inbreeding and inbreeding depression on the persistence of populations. The outcrossing rates were very similar (approximately 0.7) among populations, but the correlations of paternity, fractions of biparental inbreeding and inbreeding coefficients at the seed stage (F(S)) varied among populations, suggesting that the level of outcrossing was similar among populations, while the quality of it was not. A significant negative correlation was detected between F(S) and population size. The average value of delta was 0.709, and the values in six of the 10 populations were significant. The values of delta differed among populations, although clear relationships with population size and the degree of population isolation were not detected. However, in one population, which was very small and located in the edge of the species' range, we obtained a very low value of delta (-0.096), which may be indicative of purging or the fixation of deleterious alleles. Existing M. stellata populations that are small (and thus might be expected to have higher frequencies of inbreeding) and have large values of delta may be in danger of declining, even if the populations are located within the central region of the species' range.