广东省主要水系外来水生动物初步调查

【背景】广东省是我国遭受外来生物入侵最严重的地区之一,许多外来水生动物在广东省的河流均有分布,但有关其具体分布和数量缺乏系统研究。【方法】通过野外调查的方式对广东省鉴江、韩江、潭江、西江、北江、东江等水系的外来水生动物的分布和数量进行了初步调查,并对调查到的外来水生动物的生态学特征和入侵机制进行了初步研究。【结果】共调查到13种外来水生动物,包括巴西龟、尼罗罗非鱼、莫桑比克罗非鱼、奥利亚罗非鱼、下口鲶、革胡子鲶、食蚊鱼、麦瑞加拉鲮、露斯塔野鲮、斑点叉尾鮰、大口黑鲈等11种脊椎动物和福寿螺、克氏原螯虾2种无脊椎动物;其中以福寿螺、巴西龟和3种罗非鱼的分布最为广泛。【结论与意义】几种外来水生生物主要通过水产养殖、观赏渔业和生物防治引种入侵;典型的"R"策略者、对环境具有较强耐受力的生物、杂食性鱼类更容易成功入侵。     

深圳的外来植物

通过对深圳外来植物调查 ,报道了深圳 1 0 2种外来植物 ,约占深圳植物种类总数的 1 0 % ;并对深圳 1 0种危害较大的外来入侵植物进行了简要介绍。通过对深圳外来植物区系的种类组成、原产地、生长型、生境和危害程度的分析 ,结果表明 :(1 )外来植物的入侵对深圳的自然生态系统的影响较小 ,对人工林或人为干扰严重的生态系统的影响较大 ;(2 )来自新大陆热带地区的外来植物对深圳容易入侵并造成较大危害 ;(3 )草本和藤本植物具有较强的入侵能力 ,高大乔木的入侵能力小 ,造成的危害程度也较小。     

Aquatic plants are open flexible structures – a reply to Sukhodolov

1. Aquatic plant stands are flexible, mesh‐like open structures that undergo modification in shape and experience a cascade of declining flow velocities and micro‐scale Reynolds numbers with increasing distance into the stands. It is not possible to define or measure the frontal area of this open flexible plant structure. Total wetted area was used as a reference area for drag because it can be measured with high accuracy and it was the most suitable measure of plant size impeding the flow and absorbing light for photosynthetic production. What is important is that it is made absolutely clear which type of reference area that is used. 2. Numerous important relationships in biology are open to discussion because of differences in dimensions between variables. Relating dimensionless drag coefficients to dimensionless Reynolds numbers resolve such discussions, but defining Reynolds numbers cause other problems. Relating drag coefficients to macro‐scale Reynolds numbers would result in exactly the same form of relationship as to water velocity because macro‐scale Reynolds numbers changed in direct proportion to water velocity in the experiments, while kinematic viscosity and characteristic length within species remained constant.     

Anatomical patterns of aerenchyma in aquatic and wetland plants

A well-developed aerenchyma is a major characteristic of aquatic plants. However, because such tissues are also found in wetland and terrestrial plants, it is not always possible to use their presence or absence to distinguish aquatic species. Whereas patterns of aerenchyma in roots have been studied in detail, those of the shoots have not. We collected and tested 110 species of various aquatic and wetland plants, including ferns (5), basal angiosperms (5), monocots (65), and eudicots (35). Three common and two rare types of aerenchyma were observed in their roots (three schizogeny and two lysigeny), plus five types of schizogeny in their shoots. We re-confirmed that, although a well-developed aerenchyma is more common in most organs of aquatic plants than in wetland plants, this presence cannot be used as strict evidence for the aquatic quality of vascular plants. Here, aerenchyma patterns were stable at the genus level, and the consistency of pattern was stronger in the roots than in the shoots. Furthermore, significant trends were verified in several higher taxa, and those consistencies of patterns partially coincided with their phylogeny.     

广西的外来入侵植物

通过野外调查,结合相关文献资料,发现广西目前有外来入侵植物约74种,隶属于57属26科,其中,菊科的种类最多,有19种,其次是禾本科,有10种。草本植物最多,占总数的78.4 %。从来源看,大多来源于美洲。在广西,危害较为严重的外来入侵植物主要是紫茎泽兰、飞机草、银胶菊、凤眼莲等11种。此外,还进一步论述了外来植物在广西的基本特征和入侵成因,分析其在广西的发展状况,预测其可能入侵的区域,并提出了有关的防治对策。     

Underwater light attenuation inhibits native submerged plants and facilitates the invasive co-occurring plant Cabomba caroliniana

Aim

Decreasing in the diversity and distribution of native submerged plants have been widely observed in recent decades. Global underwater darkening, which is mainly caused by radiation dimming and a decrease in transparency due to, e.g. eutrophication, has emerged as a general trend that strongly hampers the growth of submerged plants in lakes by decreasing the light available for photosynthesis. However, few studies have attempted to compare the responses of native and invasive submerged plants to underwater darkening. In this study, we aimed to compare the effects of light attenuation on the growth and photosynthesis traits of native and invasive submerged plants.

Location

East China.

Method

Through field investigations and a mesocosm experiment, the responses of functional traits of two representative native [water thyme (Hydrilla verticillata), Eurasian watermilfoil (Myriophyllum spicatum)] and one invasive [Carolina fanwort (Cabomba caroliniana)] plant species to various environmental factors, notably to underwater light attenuation, were studied.

Results

Underwater photosynthetically active radiation (PAR) exerted a substantial effect on the relative coverage and abundance of the three studied submerged plants in their natural freshwater habitats. Invasive C. caroliniana showed relatively superior growth (total biomass and relative growth rate) and photosynthesis traits (maximum quantum yield of photosystem II F_v/F_m, chlorophyll a content, chlorophyll b content and the ratio of Chl a and b contents) compared to the two native plants under low underwater PAR conditions. In contrast, under high underwater PAR conditions, C. caroliniana showed the opposite response.

Main Conclusions

Light attenuation inhibits the growth of native submerged plants but facilitates the growth of invasive plant species. Restoration of freshwater lakes by reducing deterioration from underwater darkening (for instance, by reducing of external nutrients loading) may therefore constrain the growth and spread of the invasive C. caroliniana.     

西南喀斯特石漠化环境适生植物细根构型及其与细根和根际土壤养分计量特征的相关性

以西南喀斯特石漠化环境适生植物构树(Broussonetia papyrifera)、花椒(Zanthoxylum bungeanum)、刺梨(Rosa roxburghii)、火棘(Pyracantha fortuneana)为研究对象,采用挖掘法采集完整的细根根系,分析细根构型特征及其与细根和根际土壤C、N、P养分元素化学计量特征之间的相关性,探讨细根构型特征对石漠化贫瘠土壤生境的响应。结果表明:构树、花椒、刺梨、火棘细根构型均趋向于鱼尾形分支模式,细根拓扑指数分别为0.93、0.95、0.95和0.94。4种适生植物的细根连接长度较长,但细根根系分支率较小。构树、刺梨细根分支前后横截面积比不存在显著差异且分别为1.04、1.03,基本符合Leonardo da Vinci法则。细根构型与细根和根际土壤养分有一定的相关性。主成分分析结果表明,细根N含量及细根、根际土壤中与P相关的计量比均是影响细根构型的主要因子。进一步分析表明,4种适生植物通过减少细根次级分支、根系间的重叠、延长细根连接长度以获得充足的养分来应对环境的变化,提高对养分的吸收效率以及对喀斯特环境的生态适应性。研究结果...     

The number and kinds of embryo-bearing plants which have become aquatic: a survey

The extant embryo-bearing plants (mosses, ferns and seed plants) have an aquatic ancestor or ancestors. Today they dominate the terrestrial vegetation of the world. Embryo-bearing plants which now live in water have, for a second or even third time, re-invaded water. Aquatic species are found in 440 genera from 103 families of embryo-bearing plants. This survey attempts to find out how often the Event of evolving from land back to water has taken place among the living plants of today. Analysing the morphological and phylogenetic affinities of all aquatics at taxonomic levels from divisio to varieties of species indicate the Event has taken place, at least 222 times but it could have happened 271 or even more times (bryophytes 10–19 times, ferns seven times, seed plants 205–245 times). Aquatic plants have evolved from often very different genetic and ecological backgrounds. Also, they have evolved at different times; some old ones are aquatic at the level of order or family, while others, more recent, are isolated species in otherwise terrestrial genera or races within species. It is, nevertheless, wonderful that such a large variety of plants have evolved solutions to the single problem of remastering life in water.     

Distinctiveness magnifies the impact of biological invaders in aquatic ecosystems

There exist few empirical rules for the effects of introduced species, reflecting the context‐dependent nature of biological invasions. A promising approach toward developing generalizations is to explore hypotheses that incorporate characteristics of both the invader and the recipient system. We present the first general test of the hypothesis that an invader's impact is determined by the system's evolutionary experience with similar species. Through a meta‐analysis, we compared the taxonomic distinctiveness of high‐ and low‐impact invaders in several aquatic systems. We find that high‐impact invaders (i.e. those that displace native species) are more likely to belong to genera not already present in the system.     

湖南境内珍稀,濒危水生植物产地的考察

湖南茶陵湖里沼泽（北纬26°50'、东经113°40'）为一山地沼泽,面积0．15平方公里,海拔150米。对该沼泽的生境及水生植物进行了考察。采集到维管植物62种,其中,普通野稻（Oryza rufipogon）、长喙毛莨泽泻（Ranalisma rostrata）等为珍稀、濒危植物,总种数和珍稀、濒危植物种数多于我国大部分湖泊、沼泽。物种多样性程度之高与其水生生境的复杂性与稳定性有关。建议对这些珍稀、濒危水生植物及其生境采取保护措施。     

水生维管植物克隆繁殖方式的多样性

克隆繁殖是植物界的一种重要的繁殖方式 ,具有很大的多样性 ,特别是水生维管植物更是如此。通过对水生维管植物克隆繁殖方式的进行深入分析 ,不仅揭示了克隆繁殖在水生维管植物适应环境中的意义 ,而且也阐明了克隆繁殖方式作为水生维管植物的生存对策之一 ,在水生维管植物的生态和演化以及进化过程中的重要作用。     

中国归化植物组成特征及其时空分布格局分析

入侵植物是归化植物的子集, 归化是植物入侵的基本前提, 完整的归化植物清单有助于预测和预防植物入侵。该文基于实地调查和资料收集, 对中国归化植物种类及分布进行统计, 结果表明, 当前中国共有归化植物112科578属1 099种, 约70%为人为引入, 而美洲是其最大原产地, 植物生活型以草本为主, 分类学组成中菊科、禾本科、豆科最多。在空间尺度上, 物种多样性及密度均呈自东南沿海向西北内陆递减的趋势, 纬度和国内生产总值是其空间分布格局的主要驱动因素, 被殖民史、植物园分布及调查次数在一定程度上影响空间分布格局; 在时间尺度上, 归化植物物种多样性当前正处在快速增长阶段并可能持续20-30年, 社会经济发展、人为干扰、土地利用方式改变及全球变化是其主要驱动因素。该研究丰富了中国归化植物的本底资料, 有助于了解外来植物入侵的形式与威胁, 并为外来植物综合管控或本地生物多样性保护提供依据。     

再力花地下部水浸提液对几种水生植物幼苗的化感作用

采用砂培法研究了不同浓度再力花地下部水浸提液对荇菜、苦草、水田芥、芦苇和黄菖蒲幼苗的生长、光合速率、根系活力、叶绿素含量以及抗氧化保护酶活性的影响,并采用气相色谱-质谱(GC-MS)联用技术对再力花地下部水浸提液的化学成分进行了分析。结果表明:再力花地下部水浸提液对荇菜、苦草、水田芥、芦苇和黄菖蒲5种水生植物幼苗生长有明显的影响,其中使用50mg干重/mL再力花水浸提液处理5种水生植物幼苗,对其生长指标有着极显著的抑制作用(P<0.01),苦草、水田芥和黄菖蒲的净光合速率分别降低69.0%、63.7%和73.5%,荇菜、苦草、水田芥和黄菖蒲幼苗根系活力分别降低67.3%、65.4%、52.2%和46.7%,5种水生植物幼苗叶绿素含量分别下降59.7%、71.2%、35.2%、50.0%和76.5%。当处理浓度为5mg/mL时,对5种水生植物幼苗体内过氧化物酶(POD)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性有显著的促进作用;当浓度为50mg/mL时,对5种水生植物幼苗体内POD、SOD和CAT有显著的抑制作用,丙二醛(MDA)含量增加。分析显示,再力花地下部水浸提液中主要含有愈创木酚(78.93%)、邻苯二甲酸二丁基酯(7.13%)、邻苯二甲酸二乙氧基乙酯(1.48%)、香豆满(1.09%)、邻苯二甲酸二乙酯(0.98%)、松油醇(0.70%)、吲哚(0.65%)、二丁基羟基甲苯(0.64%),合计占到总量的91%以上。     

中国外来入侵物种的分布与传入路径分析

外来物种入侵已成为全球性的环境问题,本文采用文献调研,实地考察与专家咨询相结合的方式,调查了全国陆生,淡水水生生态系统中外来入侵微生物,无脊椎动物,两栖爬行类,鱼类,鸟类,哺乳类,杂草,树木和海洋生态系统中外来入侵物种的种类及分类地位,起源,引入路径和环境影响等内容。查明我国共有283种外来入侵物种,其中外来入侵微生物,水生植物,陆生植物,水生无脊椎动物,陆生无脊椎动物,两栖爬行类,鱼类,哺乳类分别为19种,18种,170种,25种,33种,3种,10种和5种,来源于美洲,欧洲,亚洲,非洲,大洋洲的外来入侵物种分别占55.1%,21.7%,9.9%.8.1%和0.6%。我国对外来物种的引进存在一定程度的盲目性;50.%的外来入侵植物是作为牧草或饲料,观赏植物,纤维植物,药用植物,蔬菜,草坪模特而引进的;25%的外来入侵动物是用于养殖,观赏,生物防治的引种,对外来物种只重引进,疏于管理,也可能导致外来物种逃逸到自然环境中,造成潜在的环境意传入的;76.3%的外来入侵动物是由于检查不严,随贸易物品或运输工具传入我国的。因此,我国既要加强检疫工作,又要对外来物种的有意引进进行严格管理,实行外来物种引进的风险评估制度。     

The potential for biological control of invasive alien aquatic weeds in Europe: a review

A retrospective analysis shows that invasive, alien, free-floating and emergent aquatic weeds in Europe are good targets for classical biological control, and that genus-specific chrysomelid and curculionid beetles offer the most potential. Ludwigia spp., Azolla filiculoides, Lemna minuta, Crassula helmsii and Hydrocotyle ranunculoides should be prioritised as targets. Fungal pathogens have been under-utilised as classical agents but, whilst they may have some potential against free-floating weeds, they appear to be poor candidates against submerged species, although the suitability of arthropod agents against these difficult targets still merits investigation. The use of indigenous pathogens as inundative agents (mycoherbicides) shows some promise.     

Geographic patterns and environmental correlates of taxonomic and phylogenetic diversity of aquatic plants in China

Studies on large-scale geographic patterns of aquatic plant diversity can promote research on the generality of macroecological patterns in different ecosystems. Here, we compiled a checklist of 889 aquatic angiosperms in China, including 738 helophytes (emergent and marshy plants) and 151 hydrophytes (submerged, free-floating, and floating-leaved plants). We explore the geographic patterns and environmental correlates of aquatic plant diversity based on six metrics including species richness (SR), weighted endemism (WE), phylogenetic diversity (PD), phylogenetic endemism (PE), the standardized effect size of phylogenetic diversity (PDses), and the standardized effect size of mean phylogenetic distance (MPDses). Our results show that the diversity of aquatic plants in China is extremely uneven, with high diversity in southeastern China and low diversity in northwestern China, and the geographic patterns of taxonomic and PD are generally consistent. The pattern of helophytes differs from that of hydrophytes. Notably, the wavy-shaped pattern of aquatic plant diversity (especially SR and PD for hydrophytes) across the latitude observed in this study is not consistent with those previously observed for aquatic plants in other continents. Climatic variables and water environmental variables are the main drivers of aquatic plant diversity in China; however, the effects of individual variables differ between helophytes and hydrophytes. Water environmental variables have a greater impact on PDses and MPDses of hydrophytes than those of helophytes. Overall, our work provides insight into understanding the large-scale patterns of aquatic plant diversity and is a critical addition to previous studies on the macroecological pattern of terrestrial organisms.     

Confronting introduced species: a form of xenophobia?

Critics from the fields of history, philosophy, sociology, gardening, and landscape architecture have recently attacked attempts to control introduced species as infected by nativism, racism, and xenophobia. Many appeals against introduced species, beginning in the 19^th century, focus on aesthetic issues. It is impossible to prove a particular aesthetic judgment is in no way underlain by xenophobia or racism. Certainly the Nazi drive to eliminate non-indigenous plants was related to the campaign to eliminate non-Aryan people, while the writings of some early 20^th century garden writers are laden with the language of contemporary nativism. Most judgments about the aesthetics of introduced species, however, cannot be clearly linked to such motives. Further, invasion biologists and conservationists today depict their motivation as preventing ecological or economic harm, as did their precursors a century ago. Because such harm is readily documented, this stated motivation is highly plausible, and attempts to impute baser motives are unconvincing if not tortuous. Critics of efforts to control invasions often ignore their ecological and economic impacts. These impacts, rather than aesthetic judgments or appeals to questionable concepts of naturalness, constitute a cogent, ethical basis for management of introduced species. Claims that modern introduced species activity targets all introduced species, not just invasive ones, and neglects benefits of certain introduced species have no basis in fact and becloud an urgent, important issue.     

Geographical patterns of species turnover in aquatic plant communities

1. A classic theory in biogeography predicts that high latitude communities are unstable. This may be because of decreased species richness or decreased environmental predictability and productivity towards the poles.
2. We studied latitudinal patterns in long-term community persistence of aquatic vascular plants in 112 Finnish lakes, situated within a 1000-km range from the northernmost to the southernmost lake.
3. Contrary to theoretical predictions, we found that the turnover rate of plant species in 45 years was inversely related to latitude. That is, plant communities in northern lakes were more persistent than communities in southern lakes. When we used multiple regression to find the best predictors of species turnover rate (TR), latitude was the only variable that was highly significantly related to species turnover rate. Area, species number, water transparency, pH and change in transparency did not notably explain the gradient observed.
4. The latitudinal trend was mainly because of lower species immigration rates at higher latitudes, whereas extinction rate did not so strongly decrease with increasing latitude. Immigrations and extinctions in the lakes were not in balance: the species numbers between the 1930s and 1980s increased more strongly in the southern than northern lakes.
5. We suggest that the inverse relationship between latitude and plant species TR in Finland is most probably caused by human influence on lakes, especially eutrophication and immigration of new species in southern latitudes. In addition, although species richness per lake did not decrease towards the north, the total species pool probably does, which means that in the north there are fewer species that can actually immigrate.     

Effects of weed control on species composition of aquatic plants and bank plants and macrofauna in ditches

For several years, the effect of ditch management measures on the species composition of aquatic and bank flora and macrofauna were studied in a polder with a peat soil. The mowing basket increased the presence of floating plants whereas the ditch-scoop increased filamentous algae and submerged plant species. Monospecific stands of aquatic plants had fewer macrofaunal species than stands with many plant species. Direct and indirect effects of management measures on the macrofauna composition were shown.     

Biomechanical responses of aquatic plants to aerial conditions

Background and Aims

Wetlands are impacted by changes in hydrological regimes that can lead to periods of low water levels. During these periods, aquatic plants experience a drastic change in the mechanical conditions that they encounter, from low gravitational and tensile hydrodynamic forces when exposed to flow under aquatic conditions, to high gravitational and bending forces under terrestrial conditions. The objective of this study was to test the capacity of aquatic plants to produce self-supporting growth forms when growing under aerial conditions by assessing their resistance to terrestrial mechanical conditions and the associated morpho-anatomical changes.

Methods

Plastic responses to aerial conditions were assessed by sampling Berula erecta, Hippuris vulgaris, Juncus articulatus, Lythrum salicaria, Mentha aquatica, Myosotis scorpioides, Nuphar lutea and Sparganium emersum under submerged and emergent conditions. The cross-sectional area and dry matter content (DMC) were measured in the plant organs that bear the mechanical forces, and their biomechanical properties in tension and bending were assessed.

Key Results

All of the species except for two had significantly higher stiffness in bending and thus an increased resistance to terrestrial mechanical conditions when growing under emergent conditions. This response was determined either by an increased allocation to strengthening tissues and thus a higher DMC, or by an increased cross-sectional area. These morpho-anatomical changes also resulted in increased strength and stiffness in tension.

Conclusions

The capacity of the studied species to colonize this fluctuating environment can be accounted for by a high degree of phenotypic plasticity in response to emersion. Further investigation is however needed to disentangle the finer mechanisms behind these responses (e.g. allometric relations, tissue make-up), their costs and adaptive value.