植菌昆虫与其共生真菌协同进化分子机制

昆虫菌业（fungiculture）是一种类似于人类种植业的昆虫种植体系,包括种植、耕作、收获和营养依赖4个过程,可分为高级的社会性昆虫如切叶蚂蚁、白蚁等和低级的非社会性昆虫如食菌小蠹虫、卷叶象甲、蜥蜴甲虫、树蜂等,它们均能种植并取食真菌。近年来随着组学及微生物组技术的发展,植菌昆虫与其共生真菌协同进化的分子机制研究方面取得了重要进展。系统发育分析阐明了植菌昆虫的起源与进化历程,并显示出与共生真菌系统发育的一致性;共生真菌细胞核数量也从双核增加到最多17个核,而染色体倍型也从单倍体增加为二倍体甚至多倍体;组学分析则揭示了植菌昆虫与其共生真菌在精氨酸、碳水化合物、木质素及几丁质合成或降解等方面显示出了高度的协同进化。本文系统综述了植菌昆虫及其共生真菌的系统进化、核进化及基因组进化进展,并探讨这种协同进化机制的生物学意义。     

The evolutionary ecology of symbiont-conferred resistance to parasitoids in aphids

Abstract Aphids may harbor a wide variety of facultative bacterial endosymbionts. These symbionts are transmitted maternally with high fidelity and they show horizontal trans-mission as well, albeit at rates too low to enable infectious spread. Such symbionts need to provide a net fitness benefit to their hosts to persist and spread. Several symbionts haveachieved this by evolving the ability to protect their hosts against parasitoids. Reviewing empirical work and some models, I explore the evolutionary ecology of symbiont-conferredresistance to parasitoids in order to understand how defensive symbiont frequencies are maintained at the intermediate levels observed in aphid populations. I further show thatdefensive symbionts alter the reciprocal selection between aphids and parasitoids by augmenting the heritable variation for resistance, by increasing the genetic specificity of thehost-parasitoid interaction, and by inducing environment-dependent trade-offs. These effects are conducive to very dynamic, symbiont-mediated coevolution that is driven by frequency-dependent selection. Finally I argue that defensive symbionts represent a problem for biological control of pest aphids, and I propose to mitigate this problem byexploiting the parasitoids＇ demonstrated ability to rapidly evolve counteradaptations to symbiont-conferred resistance.     

The evolutionary ecology of symbiont‐conferred resistance to parasitoids in aphids

Aphids may harbor a wide variety of facultative bacterial endosymbionts. These symbionts are transmitted maternally with high fidelity and they show horizontal transmission as well, albeit at rates too low to enable infectious spread. Such symbionts need to provide a net fitness benefit to their hosts to persist and spread. Several symbionts have achieved this by evolving the ability to protect their hosts against parasitoids. Reviewing empirical work and some models, I explore the evolutionary ecology of symbiont‐conferred resistance to parasitoids in order to understand how defensive symbiont frequencies are maintained at the intermediate levels observed in aphid populations. I further show that defensive symbionts alter the reciprocal selection between aphids and parasitoids by augmenting the heritable variation for resistance, by increasing the genetic specificity of the host–parasitoid interaction, and by inducing environment‐dependent trade‐offs. These effects are conducive to very dynamic, symbiont‐mediated coevolution that is driven by frequency‐dependent selection. Finally I argue that defensive symbionts represent a problem for biological control of pest aphids, and I propose to mitigate this problem by exploiting the parasitoids’ demonstrated ability to rapidly evolve counteradaptations to symbiont‐conferred resistance.     

The evolutionary ecology of deception

Through dishonest signals or actions, individuals often misinform others to their own benefit. We review recent literature to explore the evolutionary and ecological conditions for deception to be more likely to evolve and be maintained. We identify four conditions: (1) high misinformation potential through perceptual constraints of perceiver; (2) costs and benefits of responding to deception; (3) asymmetric power relationships between individuals and (4) exploitation of common goods. We discuss behavioural and physiological mechanisms that form a deception continuum from secrecy to overt signals. Deceptive tactics usually succeed by being rare and are often evolving under co‐evolutionary arms races, sometimes leading to the evolution of polymorphism. The degree of deception can also vary depending on the environmental conditions. Finally, we suggest a conceptual framework for studying deception and highlight important questions for future studies.     

The evolutionary ecology of corals

Corals display a wide range of complex life histories. The evolutionary consequences of factors such as clonality, indeterminate growth, asexual reproduction coupled with various (sexual) breeding systems, different levels of gene flow, and strongly overlapping generations have only just begun to be explored. We identify a series of problems and areas for new research that may be resolved b y the application of novel theoretical approaches (including nonequilibrium population genetic models and demographic models incorporating modular processes such as colony fission and polyp mortality), greater in situ experimentation, long-term monitoring of population dynamics and the use of new genetic techniques.     

The evolutionary ecology of metacommunities

Research on the interactions between evolutionary and ecological dynamics has largely focused on local spatial scales and on relatively simple ecological communities. However, recent work demonstrates that dispersal can drastically alter the interplay between ecological and evolutionary dynamics, often in unexpected ways. We argue that a dispersal-centered synthesis of metacommunity ecology and evolution is necessary to make further progress in this important area of research. We demonstrate that such an approach generates several novel outcomes and substantially enhances understanding of both ecological and evolutionary phenomena in three core research areas at the interface of ecology and evolution.     

The evolutionary ecology of Plasmodium

Plasmodium, the aetiological agent of malaria, imposes a substantial public health burden on human society and one that is likely to deteriorate. Hitherto, the recent Darwinian medicine movement has promoted the important role evolutionary biology can play in issues of public health. Recasting the malaria parasite two‐host life cycle within an evolutionary framework has generated considerable insight into how the parasite has adapted to life within both vertebrate and insect hosts. Coupled with the rapid advances in the molecular basis to host–parasite interactions, exploration of the evolutionary ecology of Plasmodium will enable identification of key steps in the life cycle and highlight fruitful avenues of research for developing malaria control strategies. In addition, elucidating the extent to which Plasmodium can respond to short‐ and long‐term changes in selection pressures, i.e. its adaptive capacity, is even more crucial in predicting how the burden of malaria will alter with our rapidly evolving ecology.     

Specificity of fungal associations of Pyroleae and Monotropa hypopitys during germination and seedling development

Mycoheterotrophic plants obtain organic carbon from associated mycorrhizal fungi, fully or partially. Angiosperms with this form of nutrition possess exceptionally small ‘dust seeds’ which after germination develop ‘seedlings’ that remain subterranean for several years, fully dependent on fungi for supply of carbon. Mycoheterotrophs which as adults have photosynthesis thus develop from full to partial mycoheterotrophy, or autotrophy, during ontogeny. Mycoheterotrophic plants may represent a gradient of variation in a parasitism–mutualism continuum, both among and within species. Previous studies on plant–fungal associations in mycoheterotrophs have focused on either germination or the adult life stages of the plant. Much less is known about the fungal associations during development of the subterranean seedlings. We investigated germination and seedling development and the diversity of fungi associated with germinating seeds and subterranean seedlings (juveniles) in five Monotropoideae (Ericaceae) species, the full mycoheterotroph Monotropa hypopitys and the putatively partial mycoheterotrophs Pyrola chlorantha, P. rotundifolia, Moneses uniflora and Chimaphila umbellata. Seedlings retrieved from seed sowing experiments in the field were used to examine diversity of fungal associates, using pyrosequencing analysis of ITS2 region for fungal identification. The investigated species varied with regard to germination, seedling development and diversity of associated fungi during juvenile ontogeny. Results suggest that fungal host specificity increases during juvenile ontogeny, most pronounced in the fully mycoheterotrophic species, but a narrowing of fungal associates was found also in two partially mycoheterotrophic species. We suggest that variation in specificity of associated fungi during seedling ontogeny in mycoheterotrophs represents ongoing evolution along a parasitism–mutualism continuum.     

The evolutionary ecology of the Lygaeidae

The Lygaeidae (sensu lato) are a highly successful family of true bugs found worldwide, yet many aspects of their ecology and evolution remain obscure or unknown. While a few species have attracted considerable attention as model species for the study of insect physiology, it is only relatively recently that biologists have begun to explore aspects of their behavior, life history evolution, and patterns of intra‐ and interspecific ecological interactions across more species. As a result though, a range of new phenotypes and opportunities for addressing current questions in evolutionary ecology has been uncovered. For example, researchers have revealed hitherto unexpectedly rich patterns of bacterial symbiosis, begun to explore the evolutionary function of the family's complex genitalia, and also found evidence of parthenogenesis. Here we review our current understanding of the biology and ecology of the group as a whole, focusing on several of the best‐studied characteristics of the group, including aposematism (i.e., the evolution of warning coloration), chemical communication, sexual selection (especially, postcopulatory sexual selection), sexual conflict, and patterns of host‐endosymbiont coevolution. Importantly, many of these aspects of lygaeid biology are likely to interact, offering new avenues for research, for instance into how the evolution of aposematism influences sexual selection. With the growing availability of genomic tools for previously “non‐model” organisms, combined with the relative ease of keeping many of the polyphagous species in the laboratory, we argue that these bugs offer many opportunities for behavioral and evolutionary ecologists.     

The evolutionary ecology of decorating behaviour

Many animals decorate themselves through the accumulation of environmental material on their exterior. Decoration has been studied across a range of different taxa, but there are substantial limits to current understanding. Decoration in non-humans appears to function predominantly in defence against predators and parasites, although an adaptive function is often assumed rather than comprehensively demonstrated. It seems predominantly an aquatic phenomenon—presumably because buoyancy helps reduce energetic costs associated with carrying the decorative material. In terrestrial examples, decorating is relatively common in the larval stages of insects. Insects are small and thus able to generate the power to carry a greater mass of material relative to their own body weight. In adult forms, the need to be lightweight for flight probably rules out decoration. We emphasize that both benefits and costs to decoration are rarely quantified, and that costs should include those associated with collecting as well as carrying the material.     

The evolutionary ecology of mast seeding

The past seven years have seen a revolution in understanding the causes of mast seeding In perennial plants. Before 1987, the two main theories were resource matching (i.e. plants vary their reproductive output to match variable resources) and predator satiation (i.e. losses to predators are reduced by varying the seed crop). Today, resource matching is restricted to a proximate role, and predator satiation is only one of many theories for the ultimate advantage of masting. Wind pollination, prediction of favourable years for seedling establishment, animal pollination, animal dispersal of fruits, high accessory costs of reproduction and large seed size have all been advanced as possible causes of masting. Of these, wind pollination, predator satiation and environmental prediction are important in a number of species, but the other theories have less support. In future, Important advances seem likely from quantifying synchrony within a population, and examining species with very constant reproduction between years.     

The evolutionary ecology of attachment organization

Life history theory’s principle of allocation suggests that because immature organisms cannot expend reproductive effort, the major trade-off facing juveniles will be the one between survival, on one hand, and growth and development, on the other. As a consequence, infants and children might be expected to possess psychobiological mechanisms for optimizing this trade-off. The main argument of this paper is that the attachment process serves this function and that individual differences in attachment organization (secure, insecure, and possibly others) may represent facultative adaptations to conditions of risk and uncertainty that were probably recurrent in the environment of human evolutionary adaptedness. An early version of this paper was presented in the symposium “Childhood in Life-history Perspective: Developing Views” organized by Gilda Morelli and Paula Ivey for the Annual Meeting of the Society for Cross-Cultural Research in Santa Fe, New Mexico, February 16–20, 1994. James S. Chisholm recently joined the Department of Anatomy and Human Biology at the University of Western Australia. Previously he taught in the Department of Anthropology at the University of New Mexico and in the Division of Human Development at the University of California, Davis. He is a biosocial anthropologist whose research interests lie in the fields of human behavioral biology, evolutionary ecology, and life history theory, where he focuses on infant social-emotional development and the development of reproductive strategies in adolescence and young adulthood. In addition to numerous articles he is the author ofNavajo Infancy: An Ethological Study of Child Development (Aldine de Gruyter, 1983).     

The evolutionary ecology of nut dispersal

A variety of nut-producing plants have mutualistic seed-dispersal interactions with animals (rodents and corvids) that scatter hoard their nuts in the soil. The goals of this review are to summarize the widespread horticultural, botanical, and ecological literature pertaining to nut dispersal inJuglans, Carya, Quercus, Fagus, Castanae, Castanopsis, Lithocarpus, Corylus, Aesculus, andPrunus; to examine the evolutionary histories of these mutualistic interactions; and to identify the traits of nut-bearing plants and nut-dispersing rodents and jays that influence the success of the mutualism. These interactions appear to have originated as early as the Paleocene, about 60 million years ago. Most nuts appear to have evolved from ancestors with wind-dispersed seeds, but the ancestral form of dispersal in almonds (Prunus spp.) was by frugivorous animals that ingested fruit. Nut-producing species have evolved a number of traits that facilitate nut dispersal by certain rodents and corvids while serving to exclude other animals that act as parasites of the mutualism. Nuts are nutritious food sources, often with high levels of lipids or proteins and a caloric value ranging from 5.7 to 153.5 kJ per propagule, 10–1000 times greater than most wind-dispersed seeds. These traits make nuts highly attractive food items for dispersers and nut predators. The course of nut development tends to reduce losses of nuts to insects, microbes, and nondispersing animals, but despite these measures predispersal and postdispersal nut mortality is generally high. Chemical defenses (e.g., tannins) in the cotyledons or the husk surrounding the nut discourage some nut predators. Masting of nuts (periodic, synchronous production of large nut crops) appears to reduce losses to insects and to increase the number of nuts dispersed by animals, and it may increase cross-pollination. Scatter hoarding by rodents and corvids removes nuts from other sources of nut predation, moves nuts away from source trees where density-dependent mortality is high (sometimes to habitats or microhabitats that favor seedling establishment), and buries nuts in the soil (which reduces rates of predation and helps to maintain nut viability). The large nutrient reserves of nuts not only attract animal dispersers but also permit seedlings to establish a large photosynthetic surface or extensive root system, making them especially competitive in low-light environments (e.g., deciduous forest) and semi-arid environments (e.g., dry mountains, Mediterranean climates). The most important postestablishment causes of seedling failure are drought, insufficient light, browsing by vertebrate herbivores, and competition with forbs and grasses. Because of the nutritional qualities of nuts and the synchronous production of large nut crops by a species throughout a region, nut trees can have pervasive impacts on other members of ecological communities. Nut-bearing trees have undergone dramatic changes in distribution during the last 16,000 years, following the glacial retreat from northern North America and Europe, and the current dispersers of nuts (i.e., squirrels, jays, and their relatives) appear to have been responsible for these movements.     

The evolutionary dynamics of batesian and muellerian mimicry: similarities and differences

ABSTRACT. 1. The continuous spectrum of palatability can be divided without difficulty into two halves: the distasteful forms in one half tend to become models and muellerian mimics, the palatable forms in the other half to become batesian mimics.
2. Most of the traditionally recognized differences between batesian and muellerian mimicry are valid and useful: negative versus positive frequency-dependence, detriment versus benefit to the model, convergent evolution versus advergent evolution. None the less in both kinds, mimicry usually evolves by means of a major mutation whose effects are later modified. 'Supergenes' tend to be discovered more in batesian mimics than in muellerian mimics. This results from a complex interaction between natural selection on the one hand, and the origin of clusters of genes of related function through tandem duplication on the other.
3. Adaptation is not simply the creation of the best of all possible worlds: what natural selection can do is limited by what is possible for the gene.     

The evolutionary ecology of the major histocompatibility complex

The major histocompatibility complex (MHC) has become a paradigm for how selection can act to maintain adaptively important genetic diversity in natural populations. Here, we review the contribution of studies on the MHC in non-model species to our understanding of how selection affects MHC diversity, emphasising how ecological and ethological processes influence the tempo and mode of evolution at the MHC, and conversely, how variability at the MHC affects individual fitness, population dynamics and viability. We focus on three main areas: the types of information that have been used to detect the action of selection on MHC genes; the relative contributions of parasite-mediated and sexual selection on the maintenance of MHC diversity; and possible future lines of research that may help resolve some of the unanswered issues associated with MHC evolution.