The importance of landscape and habitat properties in explaining instantaneous and long‐term distributions of large branchiopods in subtropical temporary pans

1. The notion that the spatial configuration of habitat patches has to be taken into account to understand the structure and dynamics of ecological communities is the starting point of metacommunity ecology. One way to assess metacommunity structure is to investigate the relative importance of environmental heterogeneity and spatial structure in explaining community patterns over different spatial and temporal scales. 2. We studied metacommunity structure of large branchiopod assemblages characteristic of subtropical temporary pans in SE Zimbabwe using two community data sets: a community snapshot and a long‐term data set covering 4 years. We assessed the relative importance of environmental heterogeneity and dispersal (inferred from patch occupancy patterns) as drivers of community structure. Furthermore, we contrasted metacommunity patterns in pans that occasionally connect to the river (floodplain pans) and pans that lack such connections altogether (endorheic pans) using redundancy models. 3. Echoes of species sorting and dispersal limitation emerge from our data set, suggesting that both local and regional processes contribute to explaining branchiopod assemblages in this system. Relative importance of local and regional factors depended on the type of data set considered. Overall, habitat characteristics that vary in time, such as conductivity, hydroperiod and vegetation cover, best explained the instantaneous species composition observed during a snapshot sampling while long‐term species composition appeared to be linked to more constant intrinsic habitat properties such as river connectivity and spatial location.     

地理距离和环境因子对阿拉善戈壁植物群落β多样性的影响

内蒙古阿拉善地区分布着超过20万km²的典型戈壁生态系统, 且这些戈壁生态系统正遭受着持续性气候变暖与极端天气的影响。然而, 土壤、气候、空间变量等因子对阿拉善戈壁大尺度植物β多样性及其关键组分的相对影响还没有得到系统研究。本文通过对阿拉善典型戈壁生境的276个样方进行植物群落组成调查, 并结合气候、土壤等数据, 探讨了地理距离和环境因子对阿拉善戈壁区植物群落β多样性及其组分的影响。研究表明: (1)在阿拉善戈壁区, 随着地理距离的增加, 植物群落β多样性及物种周转组分显著增加, 而且β多样性主要源于物种周转组分, 物种嵌套组分的贡献非常有限; (2)偏Mantel分析显示环境因子和地理距离对β多样性及其物种周转组分均有显著的单独作用; 方差分解结果进一步表明, 环境因子和地理距离共同解释了植物β多样性及其物种周转组分10.84%-17.67% (Bray-Curtis)和15.47%-24.81% (Sørensen)的变异, 但环境因子可以单独解释更多的变异(6.62%-9.97% (Bray-Curtis)和8.98%-14.51% (Sørensen))。在众多环境因子中, 气温日较差、土壤含水量和地表砾石盖度对植物群落β多样性和物种周转组分的贡献更大。以上结果表明, 环境过滤、扩散限制以及其他未知过程可能共同影响阿拉善戈壁区植物群落β多样性格局, 其中环境过滤可能具有更大的影响。     

哀牢山亚热带中山湿性常绿阔叶林树种beta多样性格局形成的驱动力

Beta多样性通常指群落在时间和空间上物种组成的差异, 包括物种周转组分和物种丰富度差异组分。驱动beta多样性格局形成的生态过程决定了群落的时空动态, 然而关于beta多样性及其两个组分格局形成的驱动力还存在较多争议。以往研究表明, beta多样性的格局存在取样尺度的依赖性, 驱动其形成的生态过程在不同取样尺度下的相对重要性也随之改变。本研究以哀牢山亚热带中山湿性常绿阔叶林20 ha动态监测样地为研究对象, 在不同取样尺度上, 将样方间的Bray-Curtis指数分解为物种周转组分和物种丰富度差异组分, 通过典范冗余分析和方差分解的方法揭示环境过滤和扩散限制对于beta多样性及其两个组分格局形成的相对重要性及其尺度依赖性。结果表明: (1) beta多样性、物种周转组分和物种丰富度差异组分均随取样尺度的增大而减小。在不同取样尺度下, 物种周转组分对于beta多样性的贡献始终占主导地位。(2)随着取样尺度的增大, 环境过滤驱动beta多样性格局形成的相对重要性逐渐增加, 而扩散限制的相对重要性逐渐降低。本研究进一步证实了取样尺度在beta多样性格局形成及其驱动力定量评价中的重要性, 今后的研究需要进一步解析上述尺度效应的形成机制。     

浙江遂昌马尾松林物种和谱系β多样性驱动因子分析

生境过滤和扩散限制是影响森林群落间物种组成差异(β多样性)的主要生态过程。为了探究生境过滤和扩散限制对亚热带马尾松(Pinus massoniana)群落物种和谱系β多样性的相对贡献,该文以浙江省遂昌县37个马尾松林样地为研究对象,结合物种和谱系β多样性分析,探讨了影响群落间物种组成差异主要生态机制; 通过计算群落内物种β多样性指数(Bray-Curtis指数)和谱系β多样性指数(Dnn指数和Dpw指数),分析土壤、地形等生境因子和地理距离与物种和谱系β多样性之间的相关性,并通过方差分解分析生境因子和地理距离对物种和谱系β多样性的相对作用大小; 此外,还进行了不同径级和生长型的上述相关性分析和方差分解。结果表明:(1)Bray-Curtis指数与土壤、地形因子和地理距离均显著正相关,Dnn指数仅与地理距离显著正相关,Dpw指数与土壤因子和地理距离均显著正相关。(2)环境因子对Bray-Curtis指数和Dpw指数的解释度均高于地理距离的解释度。(3)从物种多样性角度来说,生境因子对不同生长阶段Bray-Curtis指数的解释度均高于地理距离的解释度; 从谱系多样性角度来说,地理距离对幼树阶段的Dnn指数和Dpw指数的解释度更高,生境因子则对成树阶段的Dpw指数的解释度更高。由此可以推论,生境过滤是驱动该地区马尾松林物种和谱系β多样性的主要生态机制,扩散限制仅在幼树阶段对马尾松林谱系β多样性起主导作用。     

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.     

森林植被中优势种的形成和分布规律及其应用

一森林多是天然植被(人工林除外),它经历了千百年的演化,在改造环境和适应环境过程中,形成了物种与外界环境的高度吻合,最后形成了多种稳定的森林植被类型,因而研究森林植被中优势种的形成和分布规律,较之农田生态系统等人工植被具有更多的便利条件。森林树种的分布遵循着一定的规律,搞清     

Navigating the multiple meanings of β diversity: a roadmap for the practicing ecologist

A recent increase in studies of β diversity has yielded a confusing array of concepts, measures and methods. Here, we provide a roadmap of the most widely used and ecologically relevant approaches for analysis through a series of mission statements. We distinguish two types of β diversity: directional turnover along a gradient vs. non-directional variation. Different measures emphasize different properties of ecological data. Such properties include the degree of emphasis on presence/absence vs. relative abundance information and the inclusion vs. exclusion of joint absences. Judicious use of multiple measures in concert can uncover the underlying nature of patterns in β diversity for a given dataset. A case study of Indonesian coral assemblages shows the utility of a multi-faceted approach. We advocate careful consideration of relevant questions, matched by appropriate analyses. The rigorous application of null models will also help to reveal potential processes driving observed patterns in β diversity.     

The relative importance of local conditions and regional processes in structuring aquatic plant communities

1. The structure of biological communities reflects the influence of both local environmental conditions and processes such as dispersal that create patterns in species’ distribution across a region. 2. We extend explicit tests of the relative importance of local environmental conditions and regional spatial processes to aquatic plants, a group traditionally thought to be little limited by dispersal. We used partial canonical correspondence analysis and partial Mantel tests to analyse data from 98 lakes and ponds across Connecticut (northeastern United States). 3. We found that aquatic plant community structure reflects the influence of local conditions (pH, conductivity, water clarity, lake area, maximum depth) as well as regional processes. 4. Only 27% of variation in a presence/absence matrix was explained by environmental conditions and spatial processes such as dispersal. Of the total explained, 45% was related to environmental conditions and 40% to spatial processes. 5. Jaccard similarity declined with Euclidean distance between lakes, even after accounting for the increasing difference in environmental conditions, suggesting that dispersal limitation may influence community composition in the region. 6. The distribution of distances among lakes where species occurred was associated with dispersal‐related functional traits, providing additional evidence that dispersal ability varies among species in ways that affect community composition. 7. Although environmental and spatial variables explained a significant amount of variation in community structure, a substantial amount of stochasticity also affects these communities, probably associated with unpredictable colonisation and persistence of the plants.