Symbiosis drove cellular evolution

Anthropocentric cultural bias led to conceptualizations of evolution as a tree with branches leading to a crown of vertebrates and higher plants. Gradually refined over the years it became part of common scientific culture to think of eukaryotic evolution as process by which cells, limited by surface to volume ratios and other factors, became specialized, leading to multi-cellularity and eventually to the crowned tree. Knowledge of other pathways of cellular evolution is available, but not broadly recognized. Molecular systematics, genetic analyses and ultrastructural comparisons have changed our outlook on evolution and the diversity of life. The discovery of a huge (average size 2.1 cm) unicellular, new, exceptionally complex, dinoflagellate-hosting soritid foraminiferan from the Heron-Wistori Channel, (GBR Australia) gave impetus to re-explore some old ideas on cellular evolution and place them in a contemporary context. In particular, it caused change in perspective of the evolution of the collective group known as larger foraminifera (LF). They exemplify the power by which symbiosis drove the evolution of a predisposed and malleable group of organisms. The factors that underlay foraminiferan predisposition to symbioses with algae are discussed. Each of the evolutionary lines of LF has developed, in its own way, amazing structural adaptations making them extremely complex giant cells.     

How Cancer Shapes Evolution and How Evolution Shapes Cancer

Evolutionary theories are critical for understanding cancer development at the level of species as well as at the level of cells and tissues, and for developing effective therapies. Animals have evolved potent tumor-suppressive mechanisms to prevent cancer development. These mechanisms were initially necessary for the evolution of multi-cellular organisms and became even more important as animals evolved large bodies and long lives. Indeed, the development and architecture of our tissues were evolutionarily constrained by the need to limit cancer. Cancer development within an individual is also an evolutionary process, which in many respects mirrors species evolution. Species evolve by mutation and selection acting on individuals in a population; tumors evolve by mutation and selection acting on cells in a tissue. The processes of mutation and selection are integral to the evolution of cancer at every step of multistage carcinogenesis, from tumor genesis to metastasis. Factors associated with cancer development, such as aging and carcinogens, have been shown to promote cancer evolution by impacting both mutation and selection processes. While there are therapies that can decimate a cancer cell population, unfortunately cancers can also evolve resistance to these therapies, leading to the resurgence of treatment-refractory disease. Understanding cancer from an evolutionary perspective can allow us to appreciate better why cancers predominantly occur in the elderly and why other conditions, from radiation exposure to smoking, are associated with increased cancers. Importantly, the application of evolutionary theory to cancer should engender new treatment strategies that could better control this dreaded disease.     

The history of development of evolutionary methods in St. Petersburg school of computer simulation in biology

The history of rise and development of evolutionary methods in Saint Petersburg school of biological modelling is traced and analyzed. Some pioneering works in simulation of ecological and evolutionary processes, performed in St.-Petersburg school became an exemplary ones for many followers in Russia and abroad. The individual-based approach became the crucial point in the history of the school as an adequate instrument for construction of models of biological evolution. This approach is natural for simulation of the evolution of life-history parameters and adaptive processes in populations and communities. In some cases simulated evolutionary process was used for solving a reverse problem, i. e., for estimation of uncertain life-history parameters of population. Evolutionary computations is one more aspect of this approach application in great many fields. The problems and vistas of ecological and evolutionary modelling in general are discussed.     

Neencephalization,hominization and behaviour

Neencephalization, i.e. enlargement of the neocortex of the brain, became representative of the higher mammals, including the primates, during the Tertiary. Consequently, the number of embryos per gestation became limited to one per gestation in nearly all cases. The intra-uterine time-span increased at the same time and also the ontogeny. As an effect of this, childhood and youth until adulthood became longer and sexual maturation was retarded to the same extent. Consequently the duration of one generation increased, and so, too, did the time-span that elapsed before a new combination of haploid gene-sets of the partners could (in view of the high death-rate before adulthood) realize the possibility of self reproduction.From paleodemographical data we know that this “effective duration of one generation” needed for Homo sapiens sapiens was about 35 years. This means, that for the process of evolution the number of new gene-combinations offered in the sequence of generations was very much lower, and at the same time the length of each generation became greater. As a significant compensation we find as an effect of neencephalization the ability to learn, realized through learned behaviour. Thus, the remarkably lower number of offspring could in fact “better” survive, using vertically transmitted experience in socialized groups instead of high losses through only personal trial and error with innate modes of behaviour.The possible tempo of evolutive processes must consequently have became slower, if in addition we consider the fact, that a smaller number of realizable mutations needed more time to became through selection representative of a taxon by distribution over slow gene-flow. Add to this the fact that most of our characteristics are directed multifactorially and pleiotropically. Hominid fossils represent thus in every case only local sectors of small populations. Their combinations of morphological traits represent in most cases limited sections. In view of this we must be careful not to confuse the issue by denominating morpho= as bio-taxa. In every case, we have to calculate for the human phase only about 3000 generation-sequences in 100,000 years. This indicates for the humane phase the time needed to reach the full state of a “species” with fully developed physiologically effective barriers separating them from related preceding or following taxa, must be calculated as being relatively large.     

A clinician's personal view of assisted reproductive technology over 35 years

This invited presentation is intended to cover clinical developments in the evolution of assisted reproductive technology (ART), a process which was attempted during the 1940's and 50's and culminated in the first fruition in 1978. The first in vitro fertilisation (IVF) child ensued following the partnership by a scientist with a focussed ambition (Nobel laureate Robert Edwards) joining with the gynaecologist who introduced laparoscopy to Britain in the late 60's (Patrick Steptoe). My journey commenced in 1976 as a clinician who became immersed in the embryological and endocrinological science, whence most progress in ART emanates, and continued into a medical directorship position from which this personal view is documented. Several clinical advances have been important developments in the understanding and management of sub-fertile patients. However evolution of the various laboratory sciences has been the major key essential to meeting both the immediate as well as the long-term needs for human reproduction. The future requires a much better understanding and control over gametogenesis and a laboratory process which much more closely duplicates intrinsic reproductive physiology, avoiding gamete and embryo exposure to the atmosphere.This invited presentation is intended to cover clinical developments in the evolution of assisted reproductive technology (ART), a process which was attempted during the 1940's and 50's and culminated in the first fruition in 1978. The first in vitro fertilisation (IVF) child ensued following the partnership by a scientist with a focussed ambition (Nobel laureate Robert Edwards) joining with the gynaecologist who introduced laparoscopy to Britain in the late 60's (Patrick Steptoe). My journey commenced in 1976 as a clinician who became immersed in the embryological and endocrinological science, whence most progress in ART emanates, and continued into a medical directorship position from which this personal view is documented. Several clinical advances have been important developments in the understanding and management of sub-fertile patients. However evolution of the various laboratory sciences has been the major key essential to meeting both the immediate as well as the long-term needs for human reproduction. The future requires a much better understanding and control over gametogenesis and a laboratory process which much more closely duplicates intrinsic reproductive physiology, avoiding gamete and embryo exposure to the atmosphere.     

Pre-biological evolution

Summary Some theoretical examples of possibilities for natural selection in a prebiotic organic medium at the molecular level are given. These examples, presented in the form of simple kinetic models, are based on the idea that the occurrence of autocatalysis and self-duplication broke through the limitations imposed by contacts by chance with rare but essential molecules in the surrounding medium. It is shown that many regulatory mechanisms and the development of organization are logical consequences of this selection process. Symbiogenetic associations might play a role in producing more efficiently duplicating systems. The peculiar circumstances prevailing during pre-biological evolution, including the chance of irregular duplications and the possibilities for the uptake of systems from the surrounding medium, suggest the accumulation in this phase of evolution of a vast amount of genetic information whose potentialities became manifest during the subsequent biological evolution.     

"Delayed" phase separation in a gelatin/dextran mixture studied by small-angle light scattering,turbidity, confocal laser scanning microscopy,and polarimetry

Small-angle light scattering, turbidity, and confocal laser scanning microscopy were used to study microstructure formation and evolution in a gelatin/dextran mixture. There was a time-delay of up to tens of minutes between reaching the quench temperature and the onset of phase separation, because demixing only occurred once a certain amount of ordering of the gelatin molecules, measured by polarimetry, was attained. The accompanying phenomenon of gelation retarded the development of the microstructure to different extents, depending on the quench temperature. At low temperatures, the structure was rapidly trapped in a nonequilibrium state with diffuse interfaces, characteristic of the early and intermediate stages of phase separation. At higher temperatures, coarsening continued for a certain amount of time before the structure was trapped. The duration of the coarsening period increased with increasing temperature and the interface between the phases became sharp, characteristic of the late stages of phase separation. Because the ordering process continued after the target quench temperature was reached, the effective quench depth continued to increase after the initial phase separation. At high quench temperatures, the system was able to respond to the thermodynamic requirements of the increasing effective quench depth by undergoing secondary phase separation to form a droplet morphology within the preexisting bicontinuous one.     

Haplotype evolution and linkage disequilibrium: A simulation study

We simulated the evolution of a three-site haplotype system, two restriction fragment length polymorphisms flanking one short tandem repeat polymorphism, under five different demographic scenarios, three with constant population size and two with population growth. The simulation was designed to observe the effects of population history, recombination fraction, and mutation rate on allele and haplotype frequencies, haplotype diversity, frequency of ancestral alleles, and linkage disequilibrium. The known ancestral haplotypes were often found at low frequencies and even became extinct after 5, 000 generations, especially with small effective population sizes. The original linkage disequilibrium was eroded and even reversed.     

The effects of the evolution of stoichiometry-related traits on population dynamics in plankton communities

Both ecological stoichiometry and the evolution of traits for energetic interactions such as prey protection and predatory efficiency are considered to be important aspects affecting population dynamics. However, no attempt has been made to examine the effect of the evolution of traits relating to stoichiometry. This study first examined the effects of the evolution of nutrient utilization traits (i.e., the minimum nutrient content of prey, the maximum nutrient uptake affinity of prey and the nutrient contents of predators) on population dynamics in a plankton community. When the evolution of these traits was assumed, the range of the nutrient loading conditions where the system became unstable was smaller than when the evolution was not assumed, but the range of the conditions for zooplankton extinction became larger. Furthermore, when the trade-offs (i.e. genetic correlation between the traits) were assumed, the system rarely became extinct and the range of the nutrient loading conditions where the system became stable became larger through evolution. Stable dynamics were caused by increasing uptake affinity through evolution, and zooplankton extinction was caused by decreasing the minimum content of limiting nutrients. Thus, our results suggest that the evolution of traits relating to stoichiometry can affect the dynamics of the systems, and the outcomes the dynamics change greatly depend on which traits can evolve.     

栝楼属(葫芦科)植物的系统演化与地理分布

依据世界范围栝楼属植物种类的形态学、孢粉学、细胞学、系统发育研究资料,对栝楼属植物的系统演化和现代地理分布的形成进行了总结。栝楼组在栝楼属中处于原始地位,大苞组、叶苞组属于较进化类群,该属内的部分类群是在二倍体的水平上经过多倍化形成的。栝楼属在第三纪时期广布于欧洲、北美洲、亚洲、大洋洲,到第三纪晚期演化进程加快,南亚和中国西南山地逐步成为该属的起源中心与分化中心;受第四纪冰川期影响,该属在欧洲的种类逐渐消失,东亚成为该属的现代分布中心。栝楼属作为中国本地起源种,是中国植物区系中的重要组成部分。     

The dentary of hadrosauroid dinosaurs: evolution through heterochrony

The near-global distribution of hadrosaurid dinosaurs during the Cretaceous has been attributed to mastication, a behaviour commonly recognized as a mammalian adaptation. Its occurrence in a non-mammalian lineage should be accompanied by the evolution of several morphological modifications associated with food acquisition and processing. This study investigated morphological variation in the dentary, a major element of the hadrosauroid lower jaw. Eighty-four hadrosauroid dentaries were subjected to geometric morphometric and statistical analyses to investigate their taxonomic, ontogenetic, and individual variation. Results suggest increased food acquisition and processing efficiency in saurolophids through a complex pattern of evolutionary and growth-related changes. The edentulous region grew longer relative to dentary length, allowing for food acquisition specialization anteriorly and processing posteriorly, and became ventrally directed, possibly associated with foraging low-growing vegetation, especially in younger individuals. The saurolophid coronoid process became anteriorly directed and relatively more elongate, with an expanded apex, increasing moment arm length, with muscles pulling the jaw more posteriorly, increasing mechanical advantage. During growth, all hadrosauroids underwent anteroposterior dental battery elongation by the addition of teeth, and edentulous region ventralization decreased. The dental battery became deeper in saurolophids by increasing the number of teeth per tooth family. The increased coronoid process anterior inclination and relative edentulous region elongation in saurolophids are hypothesized to have evolved through hypermorphosis and/or acceleration, peramorphic heterochronic processes; the development of an anteroposteriorly shorter but dorsoventrally taller saurolophid dentary, is probably due to post-displacement in dental battery elongation and edentulous region decreased ventral orientation, a paedomorphic heterochronic process.     

What are antibiotics? Archaic functions for modern activities

Secondary metabolites are proposed to have played important roles in the evolution of the reactions of living forms on earth, in effecting and modulating reactions during biochemical evolution by chemical and structural interaction with 'receptor' sites in primitive macromolecular templates. For example, in the evolution of the translation system, as the polymerizing reactions became more complex and proteins became involved, the low molecular-weight effectors were functionally replaced by polypeptides, but retained their ability to interact with receptor sites in nucleic acids and proteins. Many of these low molecular-weight effectors now play a different role, that of antagonists, by interacting with the original receptor sites in macromolecular structures; this explains their contemporary activity as antibiotics.     

Effects of Metabolic Inhibitors on the Rates of CO(2) Evolution in Light and in Darkness by Detached Spruce Twigs, Wheat, and Soybean Leaves

Detached spruce twigs, wheat and soybean leaves were infiltrated with various metabolic inhibitors, placed in a closed system in CO₂-free air and the amounts of CO₂ evolved in either light or darkness were determined with an infra-red CO₂ analyzer. In light, metabolic inhibitors always greatly suppressed evolution of CO₂, the magnitude of suppression varying between 50 to 80% of that without an inhibitor. This depressing effect became less pronounced with increasing oxygen. In darkness, metabolic inhibitors sometimes suppressed and sometimes stimulated CO₂ evolution. These observations have been taken as further support for a conclusion made earlier, that evolution of CO₂ in light and darkness is not the same process.     

Evidence of size-selective evolution in the fighting conch from prehistoric subsistence harvesting

Intensive size-selective harvesting can drive evolution of sexual maturity at smaller body size. Conversely, prehistoric, low-intensity subsistence harvesting is not considered an effective agent of size-selective evolution. Uniting archaeological, palaeontological and contemporary material, we show that size at sexual maturity in the edible conch Strombus pugilis declined significantly from pre-human (approx. 7 ka) to prehistoric times (approx. 1 ka) and again to the present day. Size at maturity also fell from early- to late-prehistoric periods, synchronous with an increase in harvesting intensity as other resources became depleted. A consequence of declining size at maturity is that early prehistoric harvesters would have received two-thirds more meat per conch than contemporary harvesters. After exploring the potential effects of selection biases, demographic shifts, environmental change and habitat alteration, these observations collectively implicate prehistoric subsistence harvesting as an agent of size-selective evolution with long-term detrimental consequences. We observe that contemporary populations that are protected from harvesting are slightly larger at maturity, suggesting that halting or even reversing thousands of years of size-selective evolution may be possible.     

Correlation of absorbance changes and thylakoid fusion with the induction of oxygen evolution in bean leaves greened by brief flashes

Dark-grown bean leaves (Phaseolus vulgaris) which had been greened for several days in a repetitive series of brief xenon flashes were studied during the initial induction period when O(2) evolution first appears. The induction of O(2) evolution requires actinic irradiation (e.g. 2 mw/cm(2) of red light) and goes to completion in about 8 minutes with a half-time just under 3 minutes. Absorbance measurements on the intact leaves showed that a change of a carotenoid pigment, monitored at 505 nm, was closely correlated with the rate of O(2) evolution during the induction period. Inhibitor studies, however, showed that the absorbance change persisted in the presence of a number of inhibitors which blocked O(2) evolution. Electron microscopy revealed that the primary thylakoids which were unfused in the flashed leaves before induction became fused in pairs or groups of three during the 8-minute induction period. It is postulated that the 505-nm absorbance change of the carotenoid pigment is correlated more directly with the fusion process than with O(2) evolution. Heat treatment (45 C for 5 min) or infiltration with 0.8 m tris, which prevented the fusion process, also prevented the absorbance change.If the leaves were preilluminated for 8 minutes with very weak red light (20 muw/cm(2)) which induced no O(2) evolution, absorbance change, or thylakoid fusion, there was an immediate burst of O(2) evolution at the onset of actinic irradiation and the induction period, as noted by O(2) evolution or by the 505-nm absorbance change, was reduced to 2 minutes (half-time of 40 seconds). It is concluded that the electron transport system in the flashed leaves is blocked at the Mn site between water and photosystem II and that the photoactivation of Mn into the thylakoid membranes occurs during the low light, photoactivation process. After the electron transport chain is thus repaired, ion-pumping mechanisms driven by actinic light may lead to steady-state photosynthesis as well as to thylakoid fusion.     

The relationship between the duration of food web evolution and the vulnerability to biological invasion

I conducted computer simulations of food web evolution and investigated the relationship between the duration of food web evolution and the vulnerability to biological invasion. Model food webs without evolution consisted of animal species with a limited number of prey species and producer species with small intrinsic growth rates. Because these species were not resistant to predation pressure, model food webs without evolution were vulnerable to invasion of powerful omnivores, which had a wide range of feeding preference and a high ecological efficiency. In model food webs without evolution, the number of animal species depending on producer species was small. Therefore, if a producer species invaded and disturbed the base of such food webs, few animal species became extinct. However, model food webs with a long time evolution had a structure that a small number of producer species supported a large number of animal species. When a producer species invaded and disturbed the base of such food webs in this state, many species became extinct by an indirect effect. The mean number of prey species of animal species and the mean intrinsic growth rate of producer species increased rapidly in the early stage of evolution. Therefore, in the early stage of food web evolution, food webs were temporarily resistant to invasion of powerful omnivores. However, this resistibility was not maintained for a long time. The result of this study strongly suggests that food webs change with time, and consequently the vulnerability to invasion changes with time.     

Interaction between natural and sexual selection during the evolution of mate recognition

The interaction between natural and sexual selection is central to many theories of how mate choice and reproductive isolation evolve, but their joint effect on the evolution of mate recognition has not, to my knowledge, been investigated in an evolutionary experiment. Natural and sexual selection were manipulated in interspecific hybrid populations of Drosophila to determine their effects on the evolution of a mate recognition system comprised of cuticular hydrocarbons (CHCs). The effect of natural selection in isolation indicated that CHCs were costly for males and females to produce. The effect of sexual selection in isolation indicated that females preferred males with a particular CHC composition. However, the interaction between natural and sexual selection had a greater effect on the evolution of the mate recognition system than either process in isolation. When natural and sexual selection were permitted to operate in combination, male CHCs became exaggerated to a greater extent than in the presence of sexual selection alone, and female CHCs evolved against the direction of natural selection. This experiment demonstrated that the interaction between natural and sexual selection is critical in determining the direction and magnitude of the evolutionary response of the mate recognition system.     

Unassigned Codons, Nonsense Suppression, and Anticodon Modifications in the Evolution of the Genetic Code

The origin of the genetic code is a central open problem regarding the early evolution of life. Here, we consider two undeveloped but important aspects of possible scenarios for the evolutionary pathway of the translation machinery: the role of unassigned codons in early stages of the code and the incorporation of tRNA anticodon modifications. As the first codons started to encode amino acids, the translation machinery likely was faced with a large number of unassigned codons. Current molecular scenarios for the evolution of the code usually assume the very rapid assignment of all codons before all 20 amino acids became encoded. We show that the phenomenon of nonsense suppression as observed in current organisms allows for a scenario in which many unassigned codons persisted throughout most of the evolutionary development of the code. In addition, we demonstrate that incorporation of anticodon modifications at a late stage is feasible. The wobble rules allow a set of 20 tRNAs fully lacking anticodon modifications to encode all 20 canonical amino acids. These observations have implications for the biochemical plausibility of early stages in the evolution of the genetic code predating tRNA anticodon modifications and allow for effective translation by a relatively small and simple early tRNA set.     

天然杂交与遗传渐渗对植物入侵性的影响

生物入侵给全球生态环境与社会经济都带来了严重危害, 对其入侵机制的研究非常重要。生物入侵是一个适应性进化的过程, 天然杂交与遗传渐渗可以改变外来物种对环境的适应性并提高其入侵能力, 使其进化成为入侵种。因此了解杂交-渐渗在促进生物入侵过程中的遗传作用, 将有助于我们采取有效措施来控制生物入侵及其危害。本文从杂交-渐渗对生物适应性进化和物种形成影响的角度, 阐明外来种如何通过杂交-渐渗在新的生境中改变其适应性、生存竞争能力和入侵能力。杂交-渐渗可以导致物种发生多倍体水平和同倍体水平的进化, 虽然二者的进化过程不尽相同, 但均能使杂种群体在遗传上产生较大变化, 进而影响杂种群体的适合度, 这一过程可能促使外来种在新的生境中的成功入侵进而转变为入侵种。随着转基因生物技术的迅速发展, 大量转基因作物进入环境释放和商品化种植, 具有特定功能的转基因可能通过杂交-渐渗进入野生近缘种群体, 也可能使之成为入侵性强的农田杂草, 带来难以预测的生态后果。总之, 生物入侵是一个复杂的进化和生态过程, 利用杂交-渐渗的理论来解释植物的入侵性, 仅从一个方面反映了入侵生物学的研究, 杂交-渐渗与其他理论的结合, 将从更深的层次来解释外来种的入侵机制。     

日本沼虾生精细胞核的形态变化及其在真虾部Caridea生殖进化中的地位

应用透射电镜（ＴＥＭ）技术研究了日本沼虾精子发生过程中细胞核的形态变异。生精细胞的核经历了由圆形或椭圆形变为浅碟状的一系列变化过程;其核膜由原来的完整变为不完整,成熟精子仅在精子尾部具有核膜;核内染色质由松散逐渐聚合分化,在成熟精子核内形成了泡状和丝状两种形态的核物质。精子具备泡状和丝状两种核物质是日本沼虾的重要特征之一。精核的形态可以作为十足类甲壳动物的重要分类依据;研究精子发生过程中细胞核的形