Mayr's view of Darwin: was Darwin wrong about speciation?

We commonly read or hear that Charles Darwin successfully convinced the world about evolution and natural selection, but did not answer the question posed by his most famous book, ‘On the Origin of Species …’. Since the 1940s, Ernst Mayr has been one of the people who argued for this point of view, claiming that Darwin was not able to answer the question of speciation because he failed to define species properly. Mayr undoubtedly had an important and largely positive influence on the study of evolution by stimulating much evolutionary work, and also by promoting a ‘polytypic species concept’ in which multiple, geographically separated forms may be considered as subspecies within a larger species entity. However, Mayr became seduced by the symmetry of a pair of interlocking ideas: (1) that coexistence of divergent populations was not possible without reproductive isolation and (2) reproductive isolation could not evolve in populations that coexist. These beliefs led Mayr in 1942 to reject evidence of the importance of intermediate stages in speciation, particularly introgression between hybridizing species, which demonstrates that complete reproductive isolation is not necessary, and the existence of ecological races, which shows that ecological divergence can be maintained below the level of species, in the face of gene flow. Mayr's train of thought led him to the view that Darwin misunderstood species, and that species were fundamentally different from subspecific varieties in nature. Julian Huxley, reviewing similar data at the same time, came to the opposite conclusion, and argued that these were the intermediate stages of speciation expected under Darwinism. Mayr's arguments were, however, more convincing than Huxley's, and this caused a delay in the acceptance of a more balanced view of speciation for many decades. It is only now, with new molecular evidence, that we are beginning to appreciate more fully the expected Darwinian intermediates between coexisting species. © The Author. Journal compilation © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 3–16.     

Pigmented basidiomycetous yeasts are a promising source of carotenoids and ubiquinone Q<Subscript>10</Subscript>

Strains of basidiomycetous yeasts isolated from different sources were studied in order to determine the content of carotenoid pigments and ubiquinone Q₁₀ for subsequent selection work to obtain producers of these substances. The high specific productivity of carotenoids (600–700 mg/g) was revealed in the representatives of the following species: Cystofilobasidium capitatum, Rhodosporidium diobovatum, R. sphaerocarpum, Rhodotorula glutinis, Rh. minuta, and Sporobolomyces roseus. The ratio of the major pigments (torulene, torularhodine, and β-carotene) in the representatives of different species was studied. Certain specific features of pigment formation in relation to the taxonomic position of the yeasts were determined. Eurybiont species with substantial ecological lability are the most active producers of carotenoids and ubiquinone Q₁₀ among the epiphytes. It is the first time a comparative analysis of the coenzyme Q₁₀ content in different taxa has been performed using several strains of the same species. The maximal coenzyme Q₁₀ production (1.84 mg/g of dry biomass) was found in the yeast species R. sphaerocarpum.     

Mapping Cod: Fisheries Science,Fish Harvesters’ Ecological Knowledge and Cod Migrations in the Northern Gulf of St. Lawrence

Some recent scholarship has focused on integrating local and/or traditional knowledge with conventional scientific information in fisheries management to improve the factual foundation of and strengthen support for management decisions. This article compares a sequence of historical and contemporary scientific texts and maps about the migrations and stock structure of cod in the Northern Gulf of St. Lawrence with texts and maps generated by the authors through the collection, aggregation and interpretation of commercial fish harvesters’ ecological knowledge. We find that the relationship between fisheries science and harvesters’ ecological knowledge is dynamic and has changed over time, and that both are ‘situated’ socially and ecologically. Overall, each paints an incomplete picture of cod movements and stock structure but the knowledge of harvesters provides a valuable complement to scientific information, particularly at the local scale, and has the potential to contribute to the identification of local cod stocks that are new to science and management. We end by considering how this case study informs the larger discussion about the challenges and potential benefits of the so-called integration project to bring together science and the ecological knowledge of fish harvesters.

“Berry Patch” As a Kind of Place—the Ethnoecology of Black Huckleberry in Northwestern Canada

The Gitksan and Wet’suwet’en of Northwestern British Columbia formerly used landscape burning to manage patches of black huckleberry (Vaccinium membranaceum), the most important plant resource of their seasonal round. In view of its significance one might postulate that managed sites would conform to a biophysical or ecological type to maximize return for effort. However, a survey of a number of traditionally managed sites indicated that managed sites are characterized by wide variation in biophysical attributes including elevation, aspect and moisture regime, while proximity to fishing sites, village sites, or sites for harvest of alpine resources proved to be a common factor in known historic berry patch sites. We conclude that characterization of the ideal site type for aboriginal V. membranaceum management must include the economy and social institutions of the local First Nations and requires an enhanced appreciation for the sophistication of the strategies and techniques employed in their management and utilization of the species.

城市绿地类型的划分及其在生态城市建设中的意义和作用

根据生境和绿地功能把城市绿地划分为10个类型,并阐述了这些类型的组建和管护问题。10个绿地类型包括保护区,植物园,城市公园,城市片林,街心花园、草坪和花坛,道路两旁绿化区,庭园绿地,房顶、墙壁、凉台和室内的绿化,村落生态经济园及生态农业景观。根据归属部门、管理级别、保护对象、管理对象及监控类型的不同,对保护区进行了进一步的划分。城市绿地分类系统的建立既能把城市建设与生物多样性保护相结合,也有助于生物多样性公约的实施,并在维护城市生态安全、美化城市环境、建立具有特色的生物多样性产业、开展生态旅游和生态教育培训、繁荣地方经济和提高当地人民生活水平等方面有重要意义。     

不同生态型东南景天对土壤中Cd的生长反应及吸收积累的差异性

 采用盆栽方法研究了两种生态型东南景天(Sedum alfredii)对土壤中不同含量Cd(即对照, 12.5, 25, 50, 100, 200, 300, 400 mg&;#8226;kg^－1)的生 长反应、吸收和积累Cd的差异性。结果表明,土壤添加重金属Cd后,矿山生态型东南景天生长正常,地上部和根系Cd含量随着土壤中Cd含量的 增加而增加,在400 mg&;#8226;kg^－1 Cd处理下含量分别高达2 900和500 mg&;#8226;kg^－1,其地上部显著大于根部;然而,土壤添加Cd后,非矿山生态型东 南景天的生长受到抑制,地上部和根部的生物量显著降低。当土壤Cd含量为50～100 mg&;#8226;kg^－1 时,非矿山生态型东南景天的地上部和根系Cd含 量随着土壤中Cd含量的增加而增加,而且根系Cd含量则大于地上部。当土壤Cd≤50 mg&;#8226;kg^－1时,矿山生态型东南景天根系Cd含量比非矿山生态 型高 ,但当土壤Cd≥100 mg&;#8226;kg^－1,两者之间无显著差异;然而,但在同一Cd处理水平下,矿山生态型东南景天地上部Cd含量总是高于非矿山 生态型。这些结果表明,矿山生态型东南景天有很强的忍耐和吸收土壤Cd的能力,再次证明其为一种Cd超积累植物。     

POPULATION QUANTITATIVE CHARACTERISTICS AND DYNAMICS OF RARE AND ENDANGERED TSUGA TCHEKIANGENSIS IN JIULONGSHAN NATURE RESERVE OF CHINA

 针对九龙山国家级自然保护区南方铁杉(Tsuga tchekiangensis)种群的分布特点, 设置了10个具有代表性的样地。以种群生命表及生存分析理论为基础, 编制了南方铁杉种群的静态生命表, 绘制了存活曲线、死亡率曲线、消失率曲线、生存率曲线、累计死亡率曲线、种群死亡密度曲线和危险率曲线, 分析了种群数量特征; 同时结合谱分析方法, 分析了南方铁杉种群数量的动态变化。结果表明: 1) 南方铁杉种群结构存在波动性, 幼年阶段的个体较丰富, 成年个体数量相对较少, 种群趋于Deevey Ⅱ型。2) 南方铁杉种群死亡率和消失率曲线变化趋势基本一致, 均出现两个高峰, 一个出现在第5龄级阶段, 另一个出现在第15龄级阶段。3) 南方铁杉种群的生存率单调下降, 累计死亡率单调上升, 生存率下降趋势前期高于后期, 累计死亡率则相反。4) 4个生存函数曲线表明, 南方铁杉具有前期稳定、中期锐减和后期衰退的特点。5) 种群动态的谱分析显示, 南方铁杉种群动态除受基波影响外, 还存在着明显的小周期波动, 谐波A3处周期的波动与南方铁杉的高生长有关; A6处周期的波动与外界环境变化有关; A8处周期的波动与南方铁杉进入生理衰退期有关。     

甘肃甘南藏族自治州生态环境现状与恢复对策

甘南藏族自治州生态环境状况,对于保障黄河、长江中下游地区生态安全具有重要作用。受多种因素影响,该地区生态环境受到严重破坏。在资料查阅、实地考察与访谈的基础上,阐述了甘南藏族自治州生态环境的现状,分析了产生这种现状的原因,最后提出了重建对策。     

Assessment of ecological status in U.K. rivers using diatoms

1. The European Union's Water Framework Directive requires all water bodies to achieve ‘good ecological status’ by 2015 and this paper describes a rationale for defining ‘good ecological status’ based on diatoms, a significant component of the biological quality element ‘macrophyte and phytobenthos’. 2. A database of benthic diatom samples collected over the past 20 years was assembled. New sampling, specifically for this project, was undertaken during 2004 to supplement these data. In total 1051 samples were included in the database with matching environmental data. 3. ‘Reference sites’, relatively unimpacted by human activity, were selected from this database by a series of screening steps and these sites were used to develop a site‐specific reference typology. 4. Environmental variables not related to the pressure gradient were used to predict the ‘expected’ Trophic Diatom Index (TDI) values at each site. Site‐specific TDI predictions were used to generate ecological quality ratios (EQRs) ranging from ≥1, where the diatom assemblage showed no impact, to (theoretically) 0, when the diatom assemblage was indicative of major anthropogenic activities. 5. The boundary between ‘high’ and ‘good’ status was defined as the 25th percentile of EQRs of all reference sites. The boundary between ‘good’ and ‘moderate’ status was set at the point at which nutrient‐sensitive and nutrient‐tolerant taxa were present in equal relative abundance. An ecological rationale for this threshold is outlined in the paper.     

Phytoplankton distribution along trophic gradients within and among reservoirs in Catalonia (Spain)

1. Longitudinal gradients in the epilimnetic waters of stratified reservoirs provide a useful database to study changing environmental conditions. The spatial distribution, assemblage structure and specific adaptations of phytoplankton assemblages can be analysed along these gradients over short time scales. 2. Four reservoirs with a similar typology, located along an altitudinal gradient in the same eco‐region, were sampled along their longitudinal axes. In total, 19 sampling stations provided a trophic spectrum, ranging from oligo‐mesotrophy to hypertrophy, which was quantified by calculating the trophic state index of each sampling station in the four reservoirs. 3. Several patterns in phytoplankton assemblage structure were detected. Total chlorophyll‐a (Chl‐a), biovolume, abundance and the relative biomass contribution of the main algal groups (chlorophytes, cyanobacteria, cryptophytes and diatoms) were highly correlated with their location along the trophic gradient. 4. We also adopted the functional classification of Reynolds et al. (2002) : this effectively summarized differences among phytoplankton assemblages under varying resource‐limiting combinations, especially nutrients and underwater light climate. 5. In terms of relationships with the trophic gradient, diatoms and cyanobacteria exhibited significant opposing trends in both their relative chlorophyll contribution to total Chl‐a and biovolume. Chlorophytes were more abundant at an intermediate position along the trophic spectrum. 6. The identified patterns are consistent with models of self‐organization of phytoplankton assemblages. In particular, light availability was a strong determinant of size and shape diversity, especially in hypertrophic conditions, where ‘R‐strategist’, needle shaped species, dominated the system. In contrast, under decreased availability of nutrients and higher light extinction coefficients (K_d), the system was co‐dominated by C‐ and S‐strategist species, having shapes with a higher surface/volume ratio.