Fish habitat preferences in large streams of southern France

1. Relationships between fish and their habitat over whole geographic regions, which are evident from studies of many streams and species, can improve understanding of lotic communities and provide reliable management tools. Nevertheless, most habitat preference studies have been based on single sites, and confined to small streams and to game species.
2. Regional habitat preference models, based on local velocity, depth and roughness, were developed for twenty-four species and their size classes commonly found in large European streams. Fish surveys were conducted in six large streams in southern France over an 8-year period. To limit the influences of habitat variables other than those studied, we estimated fish preferences within each survey and averaged this information across surveys. Preferences were fitted with confidence intervals and their sensitivity to field uncertainty was evaluated.
3. Most species and size classes had significant preferences for local habitat conditions which were consistent across the region. Habitat preferences predominant in the region overall were not always observed at any one site, but habitat conditions preferred on average in the region were never actually avoided locally. These results support the use of regional preference models for fish and the development of similar models for other lotic groups whose sensitivity to local habitat conditions has been reported elsewhere.     

Potential artefacts in morphometric analyses of fish: effects of formalin preservation on 0+ grayling

In 0+ grayling, 2 months of preservation in a 4% formalin solution usually caused decreases in various body lengths and fin areas and increases in various body widths. These effects of formalin were variable between two grayling populations and among three length classes of one population.     

毛竹林地上部分生物量遥感估算模型的可移植性

选择浙江省内临安、安吉、龙泉3个毛竹产区为研究区域,基于野外调查数据和Landsat 5 TM影像,分别建立3个区域的毛竹林生物量遥感估算模型,包括一元线性模型、一元非线性模型、逐步回归模型、多元线性模型和Erf-BP神经网络模型,并对3个区域的模型进行评价;最后,选择精度较好的模型进行移植并对其可移植性进行分析.结果表明:在3个区域,Eff-BP神经网络模型精度均最高,逐步回归模型和一元非线性模型次之.Erf-BP神经网络模型的可移植性最佳.模型类型和模型自变量对统计模型的可移植性有较大影响.     

木本植物水力学结构之导管长度研究进展

导管作为多数被子植物木质部水分运输的主要通道, 了解其结构及功能对研究被子植物水力学特性及植物对环境的适应性有着重要的作用。导管长度作为导管解剖特征之一, 对水分运输的安全性及有效性有着重要的影响。该文概述了导管长度测量及计算的方法, 导管长度在种内及种间的分布, 导管长度与导管直径的关系, 导管长度与导水率的关系及导管长度对建立栓塞脆弱曲线的影响, 并对未来导管长度的研究工作重点提出了建议: 1)改进灌注物质, 使灌注更加充分且更利于观察、提高计算精度、发展活体动态测量技术; 2)建立导管在植物不同器官及整体的分布网络以及不同生活型、不同地区的导管长度数据库; 3)对导管直径在导管方向的变化, 导管长度与其他导管特性之间的关系进行研究; 4)光学测量建立栓塞脆弱曲线技术的兴起, 可为解决离心机法建立栓塞脆弱曲线的真实与准确与否的争议提供新的方向。更深入地了解导管长度在植物水力功能中担负的角色, 可以为耐旱、抗旱品种选育提供理论基础。     

中国黑龙江水系茴鱼属一新纪录种(鲑形目,茴鱼科)

2006年10～11月,在黑龙江水系(中国境内)的乌苏里江、呼玛河、额木尔河等河流采集到茴鱼属鱼类标本,经鉴定为中国1新纪录种--下游黑龙江茴鱼Thymallus tugarinae.下游黑龙江茴鱼体色鲜艳,背部无或具少量黑色斑点,体侧具鲜艳橙色条纹,明显区别于属内其它物种.与同分布于黑龙江水系的黑龙江茴鱼T.grubii相比,两者在以下性状上存在明显区别:1)新纪录种体侧背部无或仅具少数黑色斑点,后者体侧具有大量黑色斑点;2)新纪录种背鳍鳍条数为23～26,后者为19～22;3)新纪录种体侧具多行间断开的鲜艳橙色条纹,后者无;4)新纪录种背鳍边缘红色带纹宽阔,后者狭窄;5)分布区不同,新纪录种仅分布于黑龙江中下游,后者仅分布于黑龙江中上游.     

Invertebrate hydraulic preferences and predicted impacts of changes in discharge in a large river

• 1 Instream habitat models are attractive tools for assessing the impacts of flow restoration on aquatic organisms, but have been rarely used for invertebrates due to the lack of knowledge of their hydraulic preferences.
• 2 In this study, we provide quantitative models of the hydraulic preferences for 66 invertebrate taxa found in the Upper Rhône River (France), and combine these preferences with a statistical habitat model (FSTress) to predict the effects of minimum flow restoration on invertebrate abundances in two bypassed sections of the river.
• 3 Many taxa show marked preferences for particular hydraulic conditions. Average preferred hydraulic conditions were significantly related to those observed in smaller streams (R² = 0.37).
• 4 Our model predicted that habitat values of 27 taxa should be enhanced by restoration operations, but also predicted a decrease of habitat values in the main channel for 12 limnophilic taxa. However, these taxa are expected to maintain populations by finding refuges in restored cut‐off channels and overall invertebrate diversity is predicted to increase in the two bypassed sections studied here.

     

Modelling the hydraulic preferences of benthic macroinvertebrates in small European streams

1. Relating processes occurring at a local scale to the natural variability of ecosystems at a larger scale requires the design of predictive models both to orientate stream management and to predict the effects of larger scale disturbances such as climate changes. Our study contributes to this effort by providing detailed models of the hydraulic preferences of 151 invertebrate taxa, mostly identified at the species level. We used an extensive data set comprising 580 invertebrate samples collected using a Surber net from nine sites of second and third order streams during one, two or three surveys at each site. We used nested non‐linear mixed models to relate taxon local densities to bed shear stresses estimated from FliesswasserStammTisch hemisphere numbers. 2. An average model by taxon, i.e. independent from surveys, globally explained 25% of the density variations of taxa within surveys. A quadratic relationship existed between the average preferences and the niche breadth of taxa, indicating that taxa preferring extreme hemisphere numbers had a reduced hydraulic niche breadth. A more complete model, where taxa preferences vary across surveys, globally explained 38% of the variation of taxa densities within surveys. Variations in preferences across surveys were weak for taxa preferring extreme hemisphere numbers. 3. There was a significant taxonomic effect on preferences computed from the complete model. By contrast, season, site, average hemisphere number within a survey and average density of taxa within a survey used as covariates did not consistently explain shifts in taxon hydraulic preferences across surveys. 4. The average hydraulic preferences of taxa obtained from the extensive data set were well correlated to those obtained from two additional independent data sets collected in other regions. The consistency of taxon preferences across regions supports the use of regional preference curves for estimating the impact of river management on invertebrate communities. By contrast, the hydraulic niche breadths of taxa computed from the different data sets were not related.     

Maxent模型复杂度对物种潜在分布区预测的影响

生态位模型在入侵生物学和保护生物学中具有广泛的应用, 其中Maxent模型最为流行, 被越来越多地应用在预测物种的现实分布和潜在分布的研究中。在Maxent模型中, 多数研究者采用默认参数来构建模型, 这些默认参数源自早期对266个物种的测试, 以预测物种的现实分布为目的。近期研究发现, Maxent模型采用复杂机械学习算法, 对采样偏差敏感, 易产生过度拟合, 模型转移能力仅在低阈值情况下较好。基于默认参数的Maxent模型不仅预测结果不可靠, 而且有时很难解释。在本研究中, 作者以入侵害虫茶翅蝽(Halyomorpha halys)为例, 采用经典模型构建方案(即构建本土模型然后将其转移至入侵地来评估), 利用ENMeval数据包来调整本土Maxent模型调控倍频和特征组合参数, 分析各种参数条件下模型的复杂度, 然后选取最低复杂度的模型参数(即为最优模型), 综合比较默认参数和调整参数后Maxent模型的响应曲线和预测结果, 探讨Maxent模型复杂度对预测结果的影响及Maxent模型构建时所需注意事项, 以期对物种潜在分布进行合理的预测, 促进Maxent模型在我国的合理运用和发展。作者认为, 环境变量的选择至关重要, 需要综合分析其对所模拟物种分布的限制作用和环境变量之间的空间相关性。构建Maxent模型前需对物种分布采样偏差及模型的构建区域进行合理地判断, 模型构建时需要比较不同参数下模型的预测结果和响应曲线, 选取复杂度较低的模型参数来最终建模。在茶翅蝽的分析中, Maxent模型的默认参数和最优模型参数不同, 与Maxent模型默认参数相比, 采用调整参数后所构建的模型预测效果较好, 响应曲线较为平滑, 模型转移能力较高, 能够较为合理反映物种对环境因子的响应和准确地模拟该物种的潜在分布。     

白菜EST-SSR标记的通用性

EST-SSR是从表达序列标签(expressedsequencetag,EST)中开发的新型简单序列重复(simplesequencerepeat,SSR)标记。根据白菜EST设计了15对SSR引物,对白菜、油菜、玉米、高粱、水稻和茶树等进行了PCR,研究了白菜的EST-SSR标记在不同物种间的通用性。所设计的引物对不同白菜品种、近缘种油菜和远缘种玉米、高粱、水稻和茶树的扩增成功率分别为100%、93.3%、80%、93.3%、93.3%和86.7%。在15对引物中,有11对在远缘种中都有扩增产物,而且一些引物可显示多态性,多态性引物分别占了可扩增引物的33.3%、28.6%、28.6%和61.5%。这些结果表明,白菜EST-SSR引物具有较高的通用性,这对于比较基因组学研究有重要意义。     

辽东栎林乔木种群龄级结构动态的量化分析

应用分形维数对样带内乔木种群的龄级结构进行研究, 探讨了植物种群龄级结构动态干扰条件下的敏感性, 进行了种群龄级结构的稳定、衰退、增长变化分析。研究结果表明:样带各地段辽东栎种群均为优势种群, 各龄级个体空间占据能力强于其它种群;大叶白蜡种群的龄级随海拔升高趋于丰富、五角枫种群的龄级趋于单一。所有乔木种群的龄级结构均为年轻的增长型, 种群增长性(V_pi)、干扰敏感性大小差异很大, 与龄级数量和空间分布呈负相关。