海洋生物中的隐藏生物多样性与物种形成：终生浮游生物悖论

隐种广泛存在于各类海洋生物中，尤其是底栖无脊椎动物．然而，海洋终生浮游生物由于具有较强的扩散能力，往往被视为生物多样性低、物种形成慢．本文就海洋终生浮游生物隐种与物种形成的研究作一综述．基于研究的38个种类，结果表明：1）海洋终生浮游生物普遍存在隐种。其物种形成要比想象得快；2）由于引种的广泛存在，形态种生物多样性无法反映海洋终生浮游生物真正的物种多样性；3）地理隔离有助于海洋终生浮游生物隐种的形成，但异域物种形成的作用仍值得商榷；4）生态物种形成很可能是海洋终生浮游生物物种形成的主流模式．海洋终生浮游生物强基因流下快速的物种形成有悖于生物进化常理，解决该悖论将有助于我们对海洋物种形成和生物多样性的理解．     

中山大学生命科学学院施苏华教授课题组提出并验证物种形成的新模型

<正>物种形成机制是进化生物学研究领域中的核心问题,是生物多样性形成的原始动力。过去七十年来,新达尔文主义的"金标准"是群体间地理隔离,或所谓的异域物种形成。但这一模型要求严苛的地理隔绝条件以杜绝基因流的存在,因此解释不了生物多样性的起源。虽然争议不断,但没有更好的模型取而代之。中山大学生命科学学院施苏华教授团队以马六甲海峡两侧(印度洋和西太平洋)海岸带生长的多种红树     

福建省生态学学科发展报告

福建省生态学科近两年来在红树林湿地、鸟类保护、海洋微型浮游生物研究、自然保护区群网建设、生物多样性流的概念和衡量指数等诸多领域取得了重要研究成果.     

淮南焦岗湖浮游生物群落及多样性分析

文章对焦岗湖浮游生物的种类、数量及分布进行调查,运用Shannon-Weiner指数(H)等生物多样性指数,对不同断面的生物多样性和优势度进行比较分析,研究浮游生物群落及水生生态系统,为湖泊资源合理开发利用提供理论依据.分析结果表明,湖区水体浮游植物群落以硅藻门、绿藻门为优势种群;在围网养鱼集中的区域(Ⅱ号断面)的浮游植物密度最大;浮游动物主要以小型原生动物为主,大型枝角类和桡足类数量较少;湖泊资源的开发对浮游生物的数量、分布及多样性有较明显的影响.     

海洋底栖生物生态学和生物多样性研究进展

综述了海洋底栖生物生态学和生物多样性研究的过去和现状,阐述了海洋底栖生物生态学和生物多样性学说的基本原理,剖析了我国海洋底栖生物生态学和生物多样性研究存在的不足及与国际研究的差距,提出了海洋底栖生物研究的前景和方向.     

赶走"海洋赤魔",保卫"海上花园"

海洋素有"蓝色宝库"之称,但有时由于某些环境因子的变化而改变颜色,在近岸海域更为常见.这和沿海的水深较浅,受大陆影响较大以及环境变化较快密切相关.赤潮就是海水变色的一种自然现象,这个现象是由某些微小的海洋浮游生物(称为赤潮生物)的爆发性增殖和高度密集所引起的.     

西北太平洋边缘海重要海洋动物分子系统地理学的研究进展

伴随溯祖理论(coalescent theory)的日益完善和分子生物学技术的不断创新,具有学科交叉性的分子系统地理学已成为国际上十分活跃的研究领域,其成果对现今的种内遗传格局、物种形成、生物多样性水平等研究有重要的启示。西北太平洋的边缘海约占世界边缘海的75%,其显著的历史地理过程和复杂的海洋水文环境为海洋生物遗传分化和物种系统地理格局的研究提供了良好的模型。本文对近年来西北太平洋边缘海重要海洋动物门类的分子系统地理学进行简要综述,以期加深对相关物种的遗传多样性水平及种群进化历史的认识,为海洋生物资源的合理开发利用和保护提供必要的理论指导;同时,本文还对分子系统地理学今后的研究重点及其所使用的技术手段进行更深层次地展望。     

用18SrRNA高通量测序分析马岭河生物多样性

用18S高通量测序技术于2022年5月对兴义市马岭河上、中、下游3个地点进行真核浮游生物的调查。调查得到样本涵盖真核浮游生物17个门,116种。其中,优势物种为绿藻。通过分析浮游生物群落、优势种、浮游生物丰度、多样性指数和均匀度指数,评价马岭河的水质状况,为研究喀斯特水体中生物多样性奠定基础。     

海洋底栖生物生态学和生物多样性研究进展

综述了海洋底栖生物生态学和生物多样性研究的过去和现状。阐述了海洋底栖生物生态学和生物多样性学说的基本原理，剖析了我国海洋底栖生物生态学和生物多样性研究存在的不足及与国际研究的差距，提出了海洋底栖生物研究的前景和方向．     

绘制土壤微生物蓝图:土壤微生物地理学

正生物地理学是研究生物多样性时空分布规律及成因的一门科学,主要回答三个问题:即:物种在何处分布,如何分布,为什么这样分布。可以做个形象的比喻,生物地理学研究的主要目标就是绘制动物、植物及微生物世界的蓝图。生物地理学的研究有助于我们深刻理解生物多样性的产生和维持机制(如物种形成、消失、扩散及相互作用等),并可预测生态系统功能的演变方向。早在18世纪末和19世纪初,德国著名地理学家洪堡在做了大量野外考察后,首先提出了植物地理学     

Cryptic genetic variation promotes rapid evolutionary adaptation in an RNA enzyme

Cryptic variation is caused by the robustness of phenotypes to mutations. Cryptic variation has no effect on phenotypes in a given genetic or environmental background, but it can have effects after mutations or environmental change. Because evolutionary adaptation by natural selection requires phenotypic variation, phenotypically revealed cryptic genetic variation may facilitate evolutionary adaptation. This is possible if the cryptic variation happens to be pre-adapted, or "exapted", to a new environment, and is thus advantageous once revealed. However, this facilitating role for cryptic variation has not been proven, partly because most pertinent work focuses on complex phenotypes of whole organisms whose genetic basis is incompletely understood. Here we show that populations of RNA enzymes with accumulated cryptic variation adapt more rapidly to a new substrate than a population without cryptic variation. A detailed analysis of our evolving RNA populations in genotype space shows that cryptic variation allows a population to explore new genotypes that become adaptive only in a new environment. Our observations show that cryptic variation contains new genotypes pre-adapted to a changed environment. Our results highlight the positive role that robustness and epistasis can have in adaptive evolution.     

Ecology: is speciation driven by species diversity?

Emerson and Kolm show that the proportion of species endemic to an island is positively related to its species richness and, assuming that endemism indexes speciation rate, they infer that greater species diversity accelerates diversification. Here we demonstrate that the same correlation between species richness and percentage endemism can arise even if within-island speciation is negligible, particularly when both endemism and species richness depend on attributes of islands (such as area) that influence the average age of resident populations. Island biogeography theory indicates that, where the average time to extinction is relatively long, diversity increases through colonization, irrespective of whether new species are formed; at the same time, islands on which populations persist for longer accumulate more endemic species as local populations differentiate and populations on neighbouring islands become extinct. We therefore suggest that species richness and endemism are correlated fortuitously owing to their mutual dependence on the life spans of populations on islands, which is unrelated to speciation itself.     

Host-plant adaptation drives the parallel evolution of reproductive isolation

Parallel evolution of similar traits in independent populations that inhabit ecologically similar environments strongly implicates natural selection as the cause of evolution. Parallel speciation is a special form of parallel evolution where traits that determine reproductive isolation evolve repeatedly, in closely related populations, as by-products of adaptation to ecological conditions. The outcome of such parallel evolution is that ecologically divergent pairs of populations exhibit greater levels of reproductive isolation than ecologically similar pairs of populations of a similar or younger age. The parallel evolution of reproductive isolation provides strong evidence for natural selection in the process of speciation, but only one conclusive example from nature is known. Populations of the walking-stick insect Timema cristinae that use different host-plant species have diverged in body size and shape, host preference, behaviour and the relative frequency of two highly cryptic colour-pattern morphs. Here we report that divergent selection for host adaptation, and not genetic drift, has promoted the parallel evolution of sexual isolation in this species. Our findings represent a clear demonstration that host-plant adaptation can play a crucial and repeatable role in the early stages of speciation.     

Sympatric speciation in palms on an oceanic island

The origin of species diversity has challenged biologists for over two centuries. Allopatric speciation, the divergence of species resulting from geographical isolation, is well documented. However, sympatric speciation, divergence without geographical isolation, is highly controversial. Claims of sympatric speciation must demonstrate species sympatry, sister relationships, reproductive isolation, and that an earlier allopatric phase is highly unlikely. Here we provide clear support for sympatric speciation in a case study of two species of palm (Arecaceae) on an oceanic island. A large dated phylogenetic tree shows that the two species of Howea, endemic to the remote Lord Howe Island, are sister taxa and diverged from each other well after the island was formed 6.9 million years ago. During fieldwork, we found a substantial disjunction in flowering time that is correlated with soil preference. In addition, a genome scan indicates that few genetic loci are more divergent between the two species than expected under neutrality, a finding consistent with models of sympatric speciation involving disruptive/divergent selection. This case study of sympatric speciation in plants provides an opportunity for refining theoretical models on the origin of species, and new impetus for exploring putative plant and animal examples on oceanic islands.     

Cladogenesis and morphological diversification in passerine birds

Morphological diversity tends to increase within evolving lineages over time, but the relative roles of gradual evolutionary change (anagenesis) and abrupt shifts associated with speciation events (cladogenesis, or 'punctuated equilibrium') have not been resolved for most groups of organisms. However, these two modes of evolution can be distinguished by the fact that morphological variance increases in proportion to time under anagenesis, and in proportion to the logarithm of the number of species under cladogenesis. Although species and time are themselves correlated, multiple regression analysis provides a statistical framework for partitioning their relative contributions. In this study, I use multiple regressions to evaluate the effects of time and species number on morphological diversity within clades of passerine birds. The results show clearly that number of species exerts a strong influence on morphological variance independent of time, but that time has no unique effect. Thus, morphological evolution in birds seems to be associated with cladogenesis. How lineage splitting promotes morphological diversification poses an important challenge to ecologists and evolutionary biologists.     

Species diversity enhances ecosystem functioning through interspecific facilitation.

Facilitation between species is thought to be a key mechanism by which biodiversity affects the rates of resource use that govern the efficiency and productivity of ecosystems; however, there is no direct empirical evidence to support this hypothesis. Here we show that increasing the species diversity of a functional group of aquatic organisms induces facilitative interactions, leading to non-additive changes in resource consumption. We increased the richness and evenness of suspension-feeding caddisfly larvae (Insecta, Trichoptera) in stream mesocosms and found that the increased topographical complexity of the benthic habitat alters patterns of near-bed flow such that the feeding success of individuals is enhanced. Species diversity reduces 'current shading' (that is, the deceleration of flow from upstream to downstream neighbours), allowing diverse assemblages to capture a greater fraction of suspended resources than is caught by any species monoculture. The fundamental nature of this form of hydrodynamic facilitation suggests that it is broadly applicable to freshwater and marine habitats; in addition, it has several analogues in terrestrial ecosystems where fluxes of energy and matter can be influenced by biophysical complexity. Thus, changes in species diversity may alter the probability of positive species interactions, resulting in disproportionately large changes in the functioning of ecosystems.     

Consistent patterns and the idiosyncratic effects of biodiversity in marine ecosystems

Revealing the consequences of species extinctions for ecosystem function has been a chief research goal and has been accompanied by enthusiastic debate. Studies carried out predominantly in terrestrial grassland and soil ecosystems have demonstrated that as the number of species in assembled communities increases, so too do certain ecosystem processes, such as productivity, whereas others such as decomposition can remain unaffected. Diversity can influence aspects of ecosystem function, but questions remain as to how generic the patterns observed are, and whether they are the product of diversity, as such, or of the functional roles and traits that characterize species in ecological systems. Here we demonstrate variable diversity effects for species representative of marine coastal systems at both global and regional scales. We provide evidence for an increase in complementary resource use as diversity increases and show strong evidence for diversity effects in naturally assembled communities at a regional scale. The variability among individual species responses is consistent with a positive but idiosyncratic pattern of ecosystem function with increased diversity.     

Large-scale processes and the Asian bias in species diversity of temperate plants

An important issue in the study of biodiversity is the extent to which global patterns of species richness reflect large-scale processes and historical contingencies. Ecological interactions in local assemblages may constrain the number of species that can coexist, but differences in diversity in similar habitats within different regions (diversity anomalies) suggest that this limit is not firm. Variation in rate of species production could influence regional and perhaps local diversity independently of the ecological capacity of an area to support coexisting species, thereby creating diversity anomalies. Temperate Zone genera of plants that are disjunct between similar environments in eastern Asia and eastern North America (EAS-ENA) have twice as many species in Asia as in North America. Because lineages of these genera in Asia and North America are mostly sister pairs, they share a common history of adaptation and ecological relationship before disjunction. Thus, the diversity anomaly in EAS-ENA genera is not an artefact of taxon or habitat sampling but reflects differences in the net diversification (speciation-extinction) of the lineages in each of the continents. Here we propose that the most probable cause of the EAS-ENA anomaly in diversity is the extreme physiographical heterogeneity of temperate eastern Asia, especially compared with eastern North America, which in conjunction with climate and sea-level change has provided abundant opportunities for evolutionary radiation through allopatric speciation.     

Predator diversity dampens trophic cascades

Food web complexity is thought to weaken the strength of terrestrial trophic cascades in which strong impacts of natural enemies on herbivores cascade to influence primary production indirectly. Predator diversity can enhance food web complexity because predators may feed on each other and on shared prey. In such cases, theory suggests that the impact of predation on herbivores relaxes and cascading effects on basal resources are dampened. Despite this view, no empirical studies have explicitly investigated the role of predator diversity in mediating primary productivity in a natural terrestrial system. Here we compare, in a coastal marsh community, impacts of arthropod predators on herbivores and plant productivity between a simple food web with a single predator species and a complex food web with a diverse predator assemblage. We show that enhancing predator diversity dampens enemy effects on herbivores and weakens trophic cascades. Consequently, changes in diversity at higher trophic levels can significantly alter ecosystem function in natural systems.     

Eutrophication causes speciation reversal in whitefish adaptive radiations

Species diversity can be lost through two different but potentially interacting extinction processes: demographic decline and speciation reversal through introgressive hybridization. To investigate the relative contribution of these processes, we analysed historical and contemporary data of replicate whitefish radiations from 17 pre-alpine European lakes and reconstructed changes in genetic species differentiation through time using historical samples. Here we provide evidence that species diversity evolved in response to ecological opportunity, and that eutrophication, by diminishing this opportunity, has driven extinctions through speciation reversal and demographic decline. Across the radiations, the magnitude of eutrophication explains the pattern of species loss and levels of genetic and functional distinctiveness among remaining species. We argue that extinction by speciation reversal may be more widespread than currently appreciated. Preventing such extinctions will require that conservation efforts not only target existing species but identify and protect the ecological and evolutionary processes that generate and maintain species.