Biotic and abiotic factors determine species diversity–productivity relationships in mountain meadows

生物和非生物因素决定高山草甸物种多样性-生产力相互关系自然条件下物种多样性-生产力相互关系取决于生物和非生物因素,但其相对重要性及相互作用仍不清晰,特别是在未来的气候变化情景下。为此,我们在中国玉龙雪山3处不同海拔的高山草甸开展了模拟气候变暖和大气氮沉降的完全随机组块析因试验。除物种多样性外,我们根据株高、比叶面积、叶片碳、氮、磷含量计算了实验处理下草甸植物群落的功能多样性,并将其作为关键生物因素。此外,我们测量了气温、降雨以及土壤的化学属性作为潜在重要的非生物因素。我们利用广义线性混合模型研究了物种多样性和植物生产力对海拔、增温、施肥及其可能的交互作用的响应,同时评估了上述生物和非生物因素对物种多样性-生产力相互关系的影响。研究结果表明,物种多样性随海拔升高而降低并且在增温处理下有下降趋势且在中间海拔最为强烈。相对而言,植物生产力仅随海拔升高而下降。功能丰富度、最高气温、土壤pH对物种多样性-生产力相互关系表现出强烈的负交互作用,即物种多样性-生产力相互关系随着这些因素的增加从正相互关系变为中性关系,然后变为轻微的负相互关系。我们的研究指出短期增温对高山草甸物种多样性的负面影响,并强调生物和非生物因素决定了自然条件下物种多样性-生产力相互关系。     

地形和土壤特性对亚热带常绿阔叶林内植物功能性状的影响

植物功能性状与环境之间的关系是功能性状研究的核心问题.为了探讨地形和土壤特性的差异对亚热带常绿阔叶林植物功能性状的影响,并找到影响古田山亚热带常绿阔叶林植物形态和生理性状的主要环境驱动因子,我们于2008年和2009年夏天在古田山国家级自然保护区内24 ha大型监测样地测定了147个样方中115种常见木本植物的功能性状.所测性状包括3个生理生态性状(叶绿素含量、叶绿素荧光参数Fv/Fm和PIABS和枝条比导率)和4个形态性状(气孔密度、叶厚度、比叶面积和叶长/宽比).结合地形数据(平均海拔、凹凸度、坡度和坡向)和土壤数据(含水量、全氮含量、全磷含量、全碳含量和pH值),分析影响这些功能性状的主要驱动因子.排序结果显示,叶绿素含量随海拔和凹凸度的上升而下降,但与土壤中的氮含量和水分含量旱现正相关关系.由于古田山土壤呈酸性,土壤磷素缺乏,叶绿素荧光参数Fv/Fm和PIABS与土壤氮、磷含量呈现显著的负相关.枝条比导率与土壤含水量具有较为显著的正相关关系.比叶面积与海拔呈现正相关关系.研究结果表明,在小尺度上,海拔和凹凸度是影响亚热带常绿阔叶林植物功能性状晟关键的两个地形因子,而土壤含水量和伞氮含量是影响该地植物功能性状最主要的土壤因子.然而,由于土壤中磷的缺乏,诸如植物光合作用等一些重要的生理过程受到影响,使得某些性状与环境因子之间呈现出不同寻常的相关关系.     

Microhabitat associations and seedling bank dynamics in a neotropical forest

We conducted a rigorous test of tropical tree seedling microhabitat differentiation by examining microhabitat associations, survival and growth of established seedlings of ten tropical tree species representing a four-factor gradient in seed size. Eight microhabitat variables describing soil and light conditions were measured directly adjacent to each of 588 seedlings within twelve 10×100 m belt transects at Paracou, French Guiana, and at 264 reference points along the transects. From these measurements, we defined three principal components describing soil richness, soil softness and canopy openness. Six of ten species (in 9 of 30 total cases) were distributed non-randomly with respect to microhabitat along at least one principal component. However, few species demonstrated clear microhabitat specialization. All shifts in distribution relative to reference points were in the same direction (richer, softer soil). Furthermore, of 135 pairwise comparisons among the species, only 7 were significantly different. More than three-fourths of all seedlings (75.3%) survived over the 2-year monitoring period, but survival rates varied widely among species. In no case was the probability of survival influenced by any microhabitat parameter. Relative height growth rates for the seedlings over 2 years varied from –0.031 cm cm^–1 year^–1 (Dicorynia guianensis, Caesalpiniaceae) to 0.088 cm cm^–1 year^–1 (Virola michelii, Myristicaceae). In only 4 of 30 cases was height growth significantly associated with one of the three principal components. Because the conditions in this study were designed to maximize the chance of finding microhabitat differentiation among a group of species differing greatly in life history traits, the lack of microhabitat specialization it uncovered suggests that microhabitat partitioning among tropical tree species at the established seedling stage is unlikely to contribute greatly to coexistence among these species.     

Are ontogenetic shifts in foliar structure and resource acquisition spatially conditioned in tank‐bromeliads?

The phenotypic plasticity of plants has been explored as a function of either ontogeny (apparent plasticity) or environment (adaptive plasticity), although few studies have analyzed these factors together. In the present study, we take advantage of the dispersal of Aechmea mertensii bromeliads by Camponotus femoratus or Pachycondyla goeldii ants in shaded and sunny environments, respectively, to quantify ontogenetic changes in morphological, foliar, and functional traits, and to analyze ontogenetic and ant species effects on 14 traits. Most of the morphological (plant height, number of leaves), foliar (leaf thickness, leaf mass area, total water content, trichome density), and functional (leaf δ¹³C) traits differed as a function of ontogeny. Conversely, only leaf δ¹⁵N showed an adaptive phenotypic plasticity. On the other hand, plant width, tank width, longest leaf length, stomatal density, and leaf C concentration showed an adaptation to local environment with ontogeny. The exception was leaf N concentration, which showed no trend at all. Aechmea mertensii did not show an abrupt morphological modification such as in heteroblastic bromeliads, although it was characterized by strong, size‐related functional modifications for CO₂ acquisition. The adaptive phenotypic variation found between the two ant species indicates the spatially conditioned plasticity of A. mertensii in the context of insect‐assisted dispersal. However, ant‐mediated effects on phenotypic plasticity in A. mertensii are not obvious because ant species and light environment are confounding variables. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 299–312.     

A New Green Species of Frog,Genus Eleutherodactylus,from Bolivia and Perú (Amphibia,Anura, Leptodactylidae)

Eleutherodactylus olivaceus sp. n., a member of the E. unistrigatus group is described. The new species is known from montane rainforests of the Departamento Cochabamba, Bolivia, as well as from lowland rainforest of the Departamento Madre de Dios, Perú. E. olivaceus is mainly characterized by its predominantly olive green dorsal color and a papilla on the tip of the snout. Advertisement call and habitat of E. olivaceus are described. The occurrence of Eleutherodactylus mendax in Bolivia is briefly discussed.     

西藏横断山区溪流细菌beta多样性组分对气候和水体环境的响应

理解沿环境或空间梯度的群落组成变化(即beta多样性)一直是生态学和保护生物学的中心问题, 且beta多样性的形成机制及其对环境的响应已成为当前生物多样性研究的热点问题。本文以西藏横断山区怒江和澜沧江两个流域入江溪流中的细菌为研究对象, 使用Baselga的beta多样性分解方法, 基于Sørensen相异性指数将细菌的beta多样性分解为周转(turnover)和嵌套(nestedness)两个组分, 探究了细菌beta多样性及其分解组分随海拔距离的分布模式, 并且衡量了环境、气候和空间因子的相对重要性。结果表明, 两个流域中细菌的群落结构显著不同。两个流域的细菌总beta多样性和周转组分随海拔距离的增加而增加, 周转组分占总beta多样性的比例较大。气候和环境因子是两个流域中细菌总beta多样性及周转过程的重要预测因子, 并且所有的显著因子均为正相关, 其中环境因子中相关性最高的为海拔距离(R ²= 0.408, P < 0.001), 而气候因子中相关性最高的为年均温差(R ²= 0.417, P < 0.001)。方差分解结果暗示嵌套组分主要受空间扩散的影响; 总beta多样性和周转组分在环境较恶劣的澜沧江主要受环境过滤的影响, 而在环境较温和的怒江主要受空间扩散和环境过滤的共同影响。此外, 较为恶劣的环境条件会增加细菌的总beta多样性和周转率, 并且会形成更强的环境筛选作用去影响细菌群落的物种组成。我们的研究表明对西藏横断山区水体细菌多样性的保护需要从整个流域入手, 而非少量的生物多样性热点地区。     

‘Variations in phenological and functional traits in Thapsia garganica populations in Al Jebel Al Akhdar,Libya’

Thapsia garganica is a herbaceous perennial in the Apiaceae, distributed around the Mediterranean and traditionally used in North Africa as a remedy for arthritis, herpes, hair-fall, hypertension, rheumatic, eczema and scabies. T. garganica is the source of thapsigargin: known for killing cancer cells. Seven populations were studied in sites differing in aspect and elevation within Al Jebel Al Akhdar in Libya. We studied the within-population size distribution of individuals, the timing of the phenological events, and vegetative and reproductive traits.Thapsia garganica showed high flexibility of functional traits and shifts in the timing of phenological events in response to elevation and aspect (north- or south-facing slopes). Local soil properties, together with effects due to altitude and aspect, could be direct causes of the observed differences in terms of population size and phenological traits. The phenological patterns detected also provide insights into the species response to climate change. Despite this phenotypic flexibility, and good growth in sites at 300–700 m a. s. l. on south-facing slopes, most sites in this study have an unstable size-structure, with few small individuals. This raises concerns about the long-term persistence of the other populations of this species in Al Jebel Al Akhdar.     

Characterising functional trait diversity and trait–environment relationships in fish assemblages of boreal lakes

1. Characterisation of biodiversity is typically based on taxonomic approaches, while much less is known about other related aspects. Functional trait diversity is one such component of biodiversity that has not been addressed rigorously in ecological research until recently. We tested the congruence between taxonomic‐ and trait‐based approaches, and examined how spatial configuration, local abiotic environmental factors and biotic effects interact to influence taxonomic‐ and trait‐based characterisation of freshwater fish assemblages. 2. Fish assemblage data were compiled for 124 lakes in southern Finland. Variance partitioning in both linear regression analyses and redundancy analysis was used to quantify the relative contribution of spatial and environmental variables to taxonomic and functional trait diversity and structure. Additionally, a null model analysis was used to test for the potential effects of interspecific segregation and biotic interactions on the co‐occurrence of species. 3. The species pool was relatively poor. However, trait‐based classification of species indicated that most species belonged to unique functional entities, which suggested low redundancy in species composition. Correlation analysis indicated a very strong relationship between species richness (SR) and the number of unique trait combinations (UTC). Ecoregion‐level heterogeneity in SR and UTC were well represented in a relatively small group of randomly selected lakes (c. 30 lakes). Multiple regressions indicated moderate roles for abiotic environmental variables (i.e. lake surface area, depth, total phosphorous, colour and pH) in determining SR, UTC and the distribution of single trait categories, whereas geographical location was not generally influential. 4. Redundancy analysis revealed similar patterns to those of diversity analyses for taxonomic and associated trait‐based structure, emphasising the effect of abiotic environmental variables and the negligible effect of geographical position. 5. Co‐occurrence analysis indicated significant checkerboard distribution at the whole assemblage level, but interspecific segregation proved to be of relatively minor importance in the constrained analyses, where species pair combinations within trait category groups were evaluated. 6. Our results suggest that taxonomic‐ and trait‐based patterns of boreal lake fish assemblages are strongly interrelated. Environmental filtering through the effects of local abiotic variables seems to have the most prominent role in determining trait‐based assemblage patterns among lakes, which may also be secondarily shaped by biotic interactions. 7. From the applied perspective, it may not necessarily matter whether traditional taxonomic or more novel trait‐based approaches are used in characterising spatial patterns in boreal fish assemblages. However, trait‐based approaches may provide complementary information which cannot be directly revealed by taxonomic data.     

Photosynthesis and Leaf Structure in Domesticated Cassava (Euphorbiaceae) and a Close Wild Relative: Have Leaf Photosynthetic Parameters Evolved Under Domestication?

Broad patterns across wild plant species show that leaf composition and morphology vary predictably among habitats, richer habitats favoring resource‐acquisition strategies and poorer habitats favoring resource‐conservation strategies. Domestication is often accompanied by a shift to richer habitats, and might thus be expected to lead to a shift in leaf composition and morphology and hence in photosynthetic parameters. We compared leaf photosynthetic parameters in domesticated cassava (Manihot esculenta) and a close wild relative, using greenhouse‐grown plants. In domesticated cassava, CO₂ exchange rate expressed per unit mass and specific leaf area (SLA, m²/kg dry mass) were greater than in the wild relative, whereas leaf dry matter content (LDMC, dry mass/fresh mass) was lower in the domesticate. These results suggest that SLA and net photosynthetic rates may both have increased in the evolution of cassava under domestication, enabling more rapid growth in relatively resource‐rich and protected agricultural habitats. Previous comparisons of photosynthetic rates in domesticated plants and wild relatives have usually considered only leaf area‐based measures. Here, we discuss the interest of using mass‐based rates to study the evolution of ecological strategies under domestication.