Der Einfluß „normaler“ Temperaturen auf Lebensprozesse bei wechselwarmen Tieren unter Ausschluß der Wachstums- und Entwicklungsprozesse

This review summarizes especially literature published since 1955. It deals with reactions, regulations and acclimations (adaptations) and does not attempt to exclude overlappings in regard to terminological classifications; acclimatizations (according to the terminology ofProsser 1958) are not discussed and the problem of usefulness of a response (in the sense of a selective advantage) is avoided. In order to characterize the dependence of life processes on experimental temperatures, Q₁₀ orμ-values are used. These values can differ greatly, e. g. in different organ functions, partial functions of an organ, in case of varying functional states of an organ, equal organ functions in different races or species, etc. Parts of r-t curves of biological importance show sometimes especially low temperature coefficients — a fact not always caused by endogenous reaction norms, but sometimes also by regulations or adaptations. R-t curves can also be influenced in different ways by the size of the test animal; this may be demonstrated both in interracial and interspecific comparisons as well as by comparing different states of growth of one and the same species. In cases of capacity adaptation, temperature coefficients may also depend on the adaptation temperature. Seasonal influences on r-t curves are dealt with only briefly; they can be caused by various factors (adaptation temperature, photoperiod, endogenous rhythm, etc.). Experimental results may be complicated by over- and undershoots, particularly if the test temperature is changed rapidly. Over- and undershoots can be immediate reactions (“Einschwingprozesse”); but also longer lasting after-effects may be observed due to stress phenomena releasing counter-reactions of the body, rendering exact experiments more difficult. Damages which require repair may also occur. Stress phenomena can be observed on the basis of enzyme activities or of changes in RNA-content. Some examples are presented concerning regulations via integrative systems, and the possibilities for separating such regulations from reactions and adaptations are discussed. It is necessary to distinguish between genetic and non-genetic adaptations; the latter have been studied much more intensively. Changes in adaptation temperature can cause quantitative changes in important substances (e. g. contents of water and salt, proteins, fats, RNA, DNA) or in r-t curves of which several types can be distinguished; in some cases classifications are very difficult, e. g. in regard to some enzyme activities. The prerequisites concerning exact experimentation in regard to capacity adaptation are described. A non-genetic adaptation may manifest itself at all organismic levels (intact animals, isolated organs, cell metabolism, etc.). General rules for determining the presence of a capacity adaptation are difficult to establish; apparently it is more often to be found in aquatic than in terrestrial animals. Degree and type of adaptation can be different in regard to different functions of one and the same organ, tissues of the same animal, or cell metabolic processes of the same tissue. Furthermore, the metabolic pathway may depend on the adaptation temperature. Though relatively rapid capacity adaptations can be found, acclimations generally compensate for long lasting temperature changes. The mechanism of adaptation often depends on temperature, but may still function at temperatures below zero; it is still insufficiently known; an attempt to analyze the mechanism of adaptation is undertaken using the respiration of the eelAnguilla anguilla as an example. Influences of the central nervous system, body fluids and hormones are discussed.     

DNA methylation as a possible mechanism affecting ability of natural populations to adapt to changing climate

Environmentally induced epigenetic variation has been recently recognized as a possible mechanism allowing plants to rapidly adapt to novel conditions. Despite increasing evidence on the topic, little is known on how epigenetic variation affects responses of natural populations to changing climate. We studied the effects of experimental demethylation (DNA methylation is an important mediator of heritable control of gene expression) on performance of a clonal grass, Festuca rubra, coming from localities with contrasting temperature and moisture regimes. We compared performance of demethylated and control plants from different populations under two contrasting climatic scenarios and explored whether the response to demethylation depended on genetic relatedness of the plants. Demethylation significantly affected plant performance. Its effects interacted with population of origin and partly with conditions of cultivation. The effects of demethylation also varied between distinct genotypes with more closely related genotypes showing more similar response to demethylation. For belowground biomass, demethylated plants showed signs of adaptation to drought that were not apparent in plants that were naturally methylated. The results suggest that DNA methylation may modify the response of this species to moisture. DNA methylation may thus affect the ability of clonal plants to adapt to novel climatic conditions. Whether this variation in DNA methylation may also occur under natural conditions, however, remains to be explored. Despite the significant interactions between population of origin and demethylation, our data do not provide clear evidence that DNA methylation enabled adaptation to different environments. In fact, we obtained stronger evidence of local adaptation in demethylated than in naturally‐methylated plants. As changes in DNA methylation may be quite dynamic, it is thus possible that epigenetic variation can mask plant adaptations to conditions of their origin due to pre‐cultivation of the plants under standardized conditions. This possibility should be considered in future experiments exploring plant adaptations.     

Role of cryptic genes in microbial evolution

Cryptic genes are phenotypically silent DNA sequences, not normally expressed during the life cycle of an individual. They may, however, be activated in a few individuals of a large population by mutation, recombination, insertion elements, or other genetic mechanisms. A consideration of the microbial literature concerning biochemical evolution, physiology, and taxonomy provides the basis for a hypothesis of microbial adaptation and evolution by mutational activation of cryptic genes. Evidence is presented, and a mathematical model is derived, indicating that powerful and biologically important mechanisms exist to prevent the loss of cryptic genes. We propose that cryptic genes persist as a vital element of the genetic repertoire, ready for recall by mutational activation in future generations. Cryptic genes provide a versatile endogenous genetic reservoir that enhances the adaptive potential of a species by a mechanism that is independent of genetic exchange.      

Visceral helminth communities of an insular population of feral swine

Nine species of helminths, all nematodes, were recovered from the viscera of 48 feral swine (Sus scrofa) from Cumberland Island, Georgia. Both the overdispersed frequency distributions and the abundances of the four common species of helminths (Stephanurus dentatus, Metastrongylus apri, M. pudendotectus and Gongylonema pulchrum) did not vary significantly across the main and interactive effects of host sex and/or seasons. Whether or not the present low population densities of feral swine on Cumberland Island has influenced the pattern of fluctuations in abundances of helminth species across seasons as often observed in helminth communities from other hosts was not resolved. The apparent recent decline in prevalences and abundances, and the loss of certain species from the helminth communities of feral swine on the island may be explained partially by the decreasing transmission potentials of direct life cycle species caused by a recent marked reduction of numbers of individuals in the host population. Conversely, the apparent increased prevalence and abundance of three species of helminths (S. dentatus, M. apri and M. pudendotectus) may be related to their common utilization of earthworms as paratenic or intermediate hosts. Gongylonema pulchrum was the only helminth in which abundances seemed to remain unchanged. This was the only species that was not strictly host specific to feral swine. We found no evidence that helminth infections were responsible for morbidity or mortality in this feral swine population.     

Facial symmetry and judgements of apparent health: Support for a “good genes” explanation of the attractiveness–symmetry relationship

The “good genes” explanation of attractiveness posits that mate preferences favour healthy individuals due to direct and indirect benefits associated with the selection of a healthy mate. Consequently, attractiveness judgements are likely to reflect judgements of apparent health. One physical characteristic that may inform health judgements is fluctuating asymmetry as it may act as a visual marker for genetic quality and developmental stability. Consistent with these suggestions, a number of studies have found relationships between facial symmetry and facial attractiveness. In Study 1, the interplay between facial symmetry, attractiveness, and judgements of apparent health was explored within a partial correlation design. Findings suggest that the attractiveness–symmetry relationship is mediated by a link between judgements of apparent health and facial symmetry. In Study 2, an opposite-sex bias in sensitivity to facial symmetry was observed when judging health. Thus, perceptual analysis of symmetry may be an adaptation facilitating discrimination between potential mates on the basis of apparent health. The findings of both studies are consistent with a “good genes” explanation of the attractiveness–symmetry relationship and problematic for the claim that symmetry is attractive as a by-product of the ease with which the visual recognition system processes symmetric stimuli.     

Organisms of deep sea hydrothermal vents as a source for studying adaptation and evolution

It has been postulated that life originated in a similar environment to those of deep sea hydrothermal vents. These environments are located along volcanic ridges and are characterized by extreme conditions such as unique physical properties (temperature, pressure), chemical toxicity, and absence of photosynthesis. However, numerous living organisms have been discovered in these hostile environments, including a variety of microorganisms and many animal species which live in intimate and complex symbioses with sulfo-oxidizing and methanotrophic bacteria. Recent proteomic analyses of the endosymbiont ofRiftia pachyptila and genome sequences of some free living and symbiotic bacteria have provided complementary information about the potential metabolic and genomic capacities of these organisms. The evolution of these adaptive strategies is connected with different mechanisms of genetic adaptation including horizontal gene transfer and . various structural and functional mutations. Therefore, the organisms in this environment are good models for studying the evolution of prokaryotes and eukaryotes as well as different aspects of the biology of adaptation. This review describes some current research concerning metabolic and plausible genetic adaptations of organisms in a deep sea environment, usingRiftia pachyptila as model.     

The importance of phenotypic plasticity and local adaptation in driving intraspecific variability in thermal niches of marine macrophytes

Climate change is driving the redistribution of species at a global scale and documenting and predicting species' responses to warming is a principal focus of contemporary ecology. When interpreting and predicting their responses to warming, species are generally treated as single homogenous physiological units. However, local adaptation and phenotypic plasticity can result in intraspecific differences in thermal niche. Therefore, population loss may also not only occur from trailing edges. In species with low dispersal capacity this will have profound impacts for the species as a whole, as local population loss will not be offset by immigration of warm tolerant individuals. Recent evidence from terrestrial forests has shown that incorporation of intraspecific variation in thermal niche is vital to accurately predicting species responses to warming. However, marine macrophytes (i.e. seagrasses and seaweeds) that form some of the world's most productive and diverse ecosystems have not been examined in the same context. We conducted a literature review to determine how common intraspecific variation in thermal physiology is in marine macrophytes. We find that 90% of studies identified (n = 42) found clear differences in thermal niche between geographically separated populations. Therefore, non‐trailing edge populations may also be vulnerable to future warming trends and given their limited dispersal capacity, such population loss may not be offset by immigration. We also explore how next generation sequencing (NGS) is allowing unprecedented mechanistic insight into plasticity and adaptation. We conclude that in the ‘genomic era’ it may be possible to link understanding of plasticity and adaptation at the genetic level through to changes in populations providing novel insights on the redistribution of populations under future climate change.     

植物生活史繁殖对策与干扰关系的研究

植物生活史繁殖对策研究是涉及植物的适应或进化、生态系统退化与恢复过程、生物多样性保护等多方面理论生态学和应用生态学研究内容的生态学研究领域。按Grime的植物生活史繁殖对策分类、植物营养繁殖与干扰适应、种子形态学与干扰适应、土壤种子库与干扰适应、植物繁殖体传播和萌发与干扰适应论述了当今极受关注的植物生活史繁殖对策与干扰关系,简述了我国干旱区干扰与植物生活史繁殖对策关系研究。     

Stress and adaptation in conservation genetics

Stress, adaptation and evolution are major concerns in conservation biology. Stresses from pollution, climatic changes, disease etc. may affect population persistence. Further, stress typically occurs when species are placed in captivity. Threatened species are usually managed to conserve their ability to adapt to environmental changes, whilst species in captivity undergo adaptations that are deleterious upon reintroduction into the wild. In model studies using Drosophila melanogaster, we have found that; (a) inbreeding and loss of genetic variation reduced resistance to the stress of disease, (b) extinction rates under inbreeding are elevated by stress, (c) adaptive evolutionary potential in an increasingly stressful environment is reduced in small population, (d) rates of inbreeding are elevated under stressful conditions, (e) genetic adaptation to captivity reduces fitness when populations are reintroduced into the 'wild', and (f) the deleterious effects of adaptation on reintroduction success can be reduced by population fragmentation.     

Genetic and epigenetic variations associated with adaptation to heterogeneous habitat conditions in a deciduous shrub

Environmentally induced phenotypic plasticity is thought to play an important role in the adaption of plant populations to heterogeneous habitat conditions, and yet the importance of epigenetic variation as a mechanism of adaptive plasticity in natural plant populations still merits further research. In this study, we investigated populations of Vitex negundo var. heterophylla (Chinese chastetree) from adjacent habitat types at seven sampling sites. Using several functional traits, we detected a significant differentiation between habitat types. With amplified fragment length polymorphisms (AFLP) and methylation‐sensitive AFLP (MSAP), we found relatively high levels of genetic and epigenetic diversity but very low genetic and epigenetic differences between habitats within sites. Bayesian clustering showed a remarkable habitat‐related differentiation and more genetic loci associated with the habitat type than epigenetic, suggesting that the adaptation to the habitat is genetically based. However, we did not find any significant correlation between genetic or epigenetic variation and habitat using simple and partial Mantel tests. Moreover, we found no correlation between genetic and ecologically relevant phenotypic variation and a significant correlation between epigenetic and phenotypic variation. Although we did not find any direct relationship between epigenetic variation and habitat environment, our findings suggest that epigenetic variation may complement genetic variation as a source of functional phenotypic diversity associated with adaptation to the heterogeneous habitat in natural plant populations.     

寄生蠕虫的群体遗传学研究

寄生蠕虫群体遗传学研究常用的遗传标记有等位酶、线粒体DNA、随机扩增多态性DNA或扩增性片段长度多态性和微卫星DNA等。应用这些遗传标记的研究表明,大多数寄生蠕虫群体遗传结构有不同水平的变异,这些变异的产生主要与寄生虫的生活史和群体生态、宿主的地理分布和环境等因素有关,并因此提出了有关遗传变异的一些假说。本文对寄生蠕虫群体遗传学的研究作一综述。 Abstract:Genetic markers including allozyme,mtDNA,RAPD/RFLP and micro DNA have been used in the research of helminth population genetics.Available data on helminth genetic variability have shown that most helminth populations exhibit different levels of genetic variation resulting mainly from the pattern of life cycle,geographical distribution and parasite-host interaction,and several hypotheses have been proposed to explain the genetic variation.     

Landscape structure and genetic architecture jointly impact rates of niche evolution

Evolutionary adaptation is a key driver of species' range dynamics. Understanding the factors that affect rates of adaptation at range margins is thus crucial for interpreting and predicting changes in species' ranges. The spatial structure of environmental conditions is one of the determinants of whether and how quickly adaptations occur. However, while landscape structures at range edges are typically complex, most theoretical work has so far focused on relatively simple environmental geometries. Using an individual‐based allelic model, we explore the effects of different landscape structures on the rate of adaptation to novel environments and investigate how these structures interact with the genetic architecture of the trait governing adaptation and the dispersal capacity of the considered species. Generally, we find that rapid adaptation is favored by a good match between the coarseness of the trait's genetic architecture (many loci of small effects versus few loci of large effects) and the coarseness of the landscape (abruptness of transitions in environmental conditions). For example, in rugged landscapes, adaptation is quicker for genetic architectures with few loci of large effects, while for shallow gradients the opposite is true. Moreover, dispersal capacities affect the rate of adaptation by modulating the ‘apparent coarseness’ of the landscape: a gradient perceived as smooth by species with limited dispersal capacities appears rather steep for highly dispersive ones. We also find that the distribution of evolving phenotypes strongly depends on the interplay of landscape structure and dispersal capacities, ranging from two distinct phenotypes for most rugged landscapes, over the co‐occurrence of an additional third phenotype for highly dispersive species, to the whole range of phenotypes on smooth gradients. By identifying basic factors that drive the fixation probability of newly arising beneficial mutations, we hope to further broaden the understanding of evolutionary adaptation at range margins and, hence, species' range dynamics.     

Tolerance of freezing in caterpillars of the New Zealand Magpie moth (Nyctemera annulata)

In most insects known to tolerate freezing, the adaptation has been completely canalized and permanently incorporated into the genotype, either as a perennial or seasonal phenotypic switch. The exceptions to this (i.e. insects for which the adaptation is, in some manner, incomplete) represent examples of considerable evolutionary interest. To date, the few examples known of incomplete adaptation are readily identified by survival metrics. Caterpillars of the New Zealand Magpie moth (Nyctemera annulata Boisduval) represent a previously undescribed stage in the adaptive continuum of freeze tolerant insects from freeze avoidance to tolerance: a form of freeze tolerance that is intermediate between partial and complete freeze tolerance, the relative ‘incompleteness’ of which, is only apparent using indices of extended fitness (successful metamorphosis). This intermediate form is characterized by: the capacity to mechanistically tolerate equilibrium freezing (>75% survival); a narrow survival envelope below equilibrium freezing temperatures (3–4 °C); and a limited ability to complete metamorphosis after freezing (approximately 27% emergence). The low temperature capabilities of these caterpillars provide support for the hypothesis that the capacity to mechanistically tolerate internal extracellular ice formation by freeze tolerant holometabolous insects is acquired prior to the metabolic adaptations necessary to enable continuation of the life cycle.     

Mitochondrial OXPHOS genes provides insights into genetics basis of hypoxia adaptation in anchialine cave shrimps

Cave shrimps from the genera Typhlatya, Stygiocaris and Typhlopatsa (TST complex) comprises twenty cave-adapted taxa, which mainly occur in the anchialine environment. Anchialine habitats may undergo drastic environmental fluctuations, including spatial and temporal changes in salinity, temperature, and dissolved oxygen content. Previous studies of crustaceans from anchialine caves suggest that they have possessed morphological, behavioral, and physiological adaptations to cope with the extreme conditions, similar to other cave-dwelling crustaceans. However, the genetic basis has not been thoroughly explored in crustaceans from anchialine habitats, which can experience hypoxic regimes. To test whether the TST shrimp-complex hypoxia adaptations matched adaptive evolution of mitochondrial OXPHOS genes. The 13 OXPHOS genes from mitochondrial genomes of 98 shrimps and 1 outgroup were examined. For each of these genes was investigated and compared to orthologous sequences using both gene (i.e. branch-site and Datamonkey) and protein (i.e. TreeSAAP) level approaches. Positive selection was detected in 11 of the 13 candidate genes, and the radical amino acid changes sites scattered throughout the entire TST complex phylogeny. Additionally, a series of parallel/convergent amino acid substitutions were identified in mitochondrial OXPHOS genes of TST complex shrimps, which reflect functional convergence or similar genetic mechanisms of cave adaptation. The extensive occurrence of positive selection is suggestive of their essential role in adaptation to hypoxic anchialine environment, and further implying that TST complex shrimps might have acquired a finely capacity for energy metabolism. These results provided some new insights into the genetic basis of anchialine hypoxia adaptation.     

Special symposium: In vitro plant recalcitrance loss of plant organogenic totipotency in the course of In vitro neoplastic progression

Summary The aptitude for organogenesis from normal hormone-dependent cultures very commonly decreases as the tissues are serially subcultured. The reasons for the loss of regenerative ability may vary under different circumstances: genetic variation in the cell population, epigenetic changes, disappearance of an organogenesis-promoting substance, etc. The same reasons may be evoked for the progressive and eventually irreversible loss of organogenic totipotency in the course of neoplastic progressions from hormone-independent tumors and hyperhydric teratomas to cancers. As in animal cells, plant cells at the end of a neoplastic progression have probably undergone several independent genetic accidents with cumulative effects. They indeed are characterized by atypical biochemical cycles from which they are apparently unable to escape. The metabolic changes are probably not the primary defects that cause cancer, rather they may allow the cells to survive. How these changes, namely an oxidative stress, affect organogenesis is not known. The literature focuses on somatic mutations and epigenetic changes that cause aberrant regulation of cell cycle genes and their machinery.     

Exoskeletal cuticle of cavernicolous and epigean terrestrial isopods: A review and perspectives

Comparative ultrastructural studies of the integument in terrestrial isopod crustaceans show that specific environmental adaptations of different eco-morphotypes are reflected in cuticle structure. The biphasic molting in isopods is a valuable experimental model for studies of cuticular matrix secretion and degradation in the same animal. The aim of this review is to show structural and functional adaptations of the tergal cuticle in terrestrial isopods inhabiting cave habitats. Exoskeletal cuticle thickness, the number of cuticular layers, epicuticle structure, mineralization, pigmentation and complexity of sensory structures are compared, with greater focus on the well-studied cave trichoniscid Titanethes albus. A large number of thinner cuticular layers in cave isopods compared to fewer thicker cuticular layers in related epigean species of similar body-sizes is explained as a specific adaptation to the cavernicolous life style. The epicuticle structure and composition are compared in relation to their potential waterproofing capacity in different environments. Cuticle mineralization is described from the functional point of view as well as from the aspect of different calcium storage sites and calcium dynamics during the molt cycle. We also discuss the nature and reduction of pigmentation in the cave environment and outline perspectives for future research.     

The biology and life history of arctic populations of the littoral mite Ameronothrus lineatus (Acari, Oribatida)

The present study attempts to elucidate possible microevolutionary adaptations of life-history traits of high-latitude populations of the holarctic, littoral oribatid mite Ameronothrus lineatus by comparing arctic and temperate populations. Additionally, the paper provides an overview of the limited research on general ecology and population biology of arctic populations. In the Arctic the larviparous A. lineatus has a 5-year life cycle (larva-to-larva), and adults survive a further 2–3 years. High survival to maturity is consistent with a low lifetime reproductive output of ca. 20 larvae. The life history can be regarded as an extreme version of the typical oribatid life history. However, several life-history features suggest specific adaptations of arctic populations. In particular, the pre-moult resting stage is synchronized with the warmest part of the arctic summer, which shortens this vulnerable part of development. High reproductive investment by females at relatively low temperatures may represent a physiological adaptation to the cool arctic summer. Finally, prolonged cold exposure positively affects reproduction and survival the following summer, suggesting adaptation of the species to the highly seasonal arctic environment. On the other hand, the ability of all life-cycle stages to overwinter, and a flexible life history with the species being able to take advantage of favourable climatic conditions to accelerate development and larviposition, seem to be ancestral features. Thus, the success of A. lineatus in arctic habitats is probably attributable to a combination of derived and ancestral life-history traits. Studies of conspecific temperate populations are required to elucidate further local adaptations of arctic populations.     

The biology and life history of arctic populations of the littoral mite Ameronothrus lineatus (Acari, Oribatida)

The present study attempts to elucidate possible microevolutionary adaptations of life-history traits of high-latitude populations of the holarctic, littoral oribatid mite Ameronothrus lineatus by comparing arctic and temperate populations. Additionally, the paper provides an overview of the limited research on general ecology and population biology of arctic populations. In the Arctic the larviparous A. lineatus has a 5-year life cycle (larva-to-larva), and adults survive a further 2-3 years. High survival to maturity is consistent with a low lifetime reproductive output of ca. 20 larvae. The life history can be regarded as an extreme version of the typical oribatid life history. However, several life-history features suggest specific adaptations of arctic populations. In particular, the pre-moult resting stage is synchronized with the warmest part of the arctic summer, which shortens this vulnerable part of development. High reproductive investment by females at relatively low temperatures may represent a physiological adaptation to the cool arctic summer. Finally, prolonged cold exposure positively affects reproduction and survival the following summer, suggesting adaptation of the species to the highly seasonal arctic environment. On the other hand, the ability of all life-cycle stages to overwinter, and a flexible life history with the species being able to take advantage of favourable climatic conditions to accelerate development and larviposition, seem to be ancestral features. Thus, the success of A. lineatus in arctic habitats is probably attributable to a combination of derived and ancestral life-history traits. Studies of conspecific temperate populations are required to elucidate further local adaptations of arctic populations.     

The Biology of Invasions: The Genetic Adaptation Paradox

One of the most relevant topics in the biology of invasion concerns the genetic changes that occur subsequent to a species invasion, an issue of particular focus among conservation biologists. Colonizing a novel environment presents a genetic challenge to invading species because such species surely have not experienced the selective pressures presented by the environment. Here we ask, by what mechanisms and processes do alien species genetically naïve to their new environment, become successful invaders? We attempt to resolve this paradox by considering the interplay between an invader’s ability to modify its new environment, and genetic modifications imposed by the new environment. We postulate that epigenetic adaptations, and adaptive mutations are likely play a role in enhancing invasion success.     

Invited review: molecular adaptations in mammalian hibernators: unique adaptations or generalized responses?

Hibernators are unique among mammals in their ability to attain, withstand, and reverse low body temperatures. Hibernators repeatedly cycle between body temperatures near zero during torpor and 37 degrees C during euthermy. How do these mammals maintain cardiac function, cell integrity, blood fluidity, and energetic balance during their prolonged periods at low body temperature and avoid damage when they rewarm? Hibernation is often considered an example of a unique adaptation for low-temperature function in mammals. Although such adaptation is apparent at the level of whole animal physiology, it is surprisingly difficult to demonstrate clear examples of adaptations at the cellular and biochemical levels that improve function in the cold and are unique to hibernators. Instead of adaptation for improved function in the cold, the key molecular adaptations of hibernation may be to exploit the cold to depress most aspects of biochemical function and then rewarm without damage to restore optimal function of all systems. These capabilities are likely due to novel regulation of biochemical pathways shared by all mammals, including humans.