海南岛石灰岩地区的外来植物

通过对海南岛石灰岩地区外来植物的实地调查,对该地区外来植物的种类、分布、来源、生活型、入侵生境、危害程度、引入途径以及与邻近地区的关系进行了统计分析.结果表明:该地区共有外来植物53种,隶属45属22科,约占该地区本地植物种类总数的4%,多为来源于热带美洲(77.4%)的草本植物(77.4%),这些外来植物大部分是通过人类活动有意(47.2%)或无意(35.8%)引入;主要分布在植被破坏严重的低海拔山坡、林缘、林隙和田间,有的外来植物在植被破坏较少的森林中以及在较高海拔也有分布;在自然条件大致相同的情况下,岛屿及沿海地区相对内陆地区似乎更易被外来种入侵,而且一个地区外来种总数及其占本地种比例与对外贸易有着密切关系.     

Contrasting responses of native and alien plant species to soil properties shed new light on the invasion of dune systems

在陆地生态系统中，沿海沙丘特别容易受到外来植物的入侵。许多研究将沙丘生境的入侵归因于人为因素，但对土壤性质和植物性状在植物 入侵中的作用却知之甚少。本研究考察了沙丘系统土壤特征与外来植物入侵的关系，重点研究了土壤养分、土壤盐分和植物功能特征之间的相互作 用。研究地点是马拉诺和格拉多泻湖(北亚得里亚海)的沙质堰洲岛。根据沙丘系统生态梯度上的主要生境(前沙丘、后沙丘和盐沼)，在10 个区域内选择100个地块(4 m × 4 m)。在每个地块中记录所有植物物种的发生和丰度，并收集一个土壤核。对每个土壤样品进行土壤质地、电导率(代表土壤盐 分)、有机碳和氮含量分析，并与本地和外来植物的种类数和覆盖度相关联。分析外来和本地物种主要的生殖功能和营养功能性状在生境中的变化。研究结果表明，土壤性质对外来物种库和本地物种库的影响不同，与植物整体多样性密切相关。在后沙丘(最易入侵)的生境中，高的土壤导电性限制了外来物种的数量，但土壤有机碳含量随着外来植物丰度的增加而增加，这也表明植物入侵与土壤之间存在潜在的反馈过程。只有在后沙丘生境中，随着环境条件的改善和植物竞争的加剧，本地植物和外来植物的功能性状谱有显著的趋同。本研究结果表明，在恶劣条件下，只有本地特有植物才能茁壮成长，而在中等条件下，土壤特性梯度与植物特性协同作用，抑制/促进外来植物丰富度。     

网格尺度下外来入侵植物对高黎贡山生态系统服务影响的空间分析

【目的】高黎贡山生物多样性资源丰富,蕴藏着极高的生态系统服务价值,是中国重要的西南生态安全屏障。在气候变化和人类活动等影响下,高黎贡山正面临越来越多的外来植物入侵。明确外来入侵植物分布特征与生态系统服务重要区的空间对应关系,能够为高黎贡山外来入侵植物防控及生态安全屏障建设提供科学支撑。【方法】利用当量因子法,在3 km×3 km网格单元尺度下评估高黎贡山生态系统服务价值并进行重要性分级分区;以文献资料分析和实地调查相结合分析高黎贡山区域外来入侵植物的空间分布格局;利用Arcgis 10.2软件分析空间对应关系。【结果】高黎贡山生态系统服务重要性分为5级,单位面积价值量最高的生态系统类型为水系、阔叶林、针叶林、灌木林和灌草丛。外来入侵植物为59种,入侵等级为Ⅰ~Ⅴ级的物种分别有12、17、8、11和11种。除1级重要区外,其他区域均分布有外来入侵植物,其中3级和4级重要区(主要为灌木林地和耕地)分布的外来入侵植物的种类和数量最多。【结论】外来植物入侵威胁高黎贡山生态系统服务供给,亟需开展外来入侵植物系统调查评估以识别高等级入侵植物实施外来入侵植物差别化管控;陆生外来入侵植物应该成为高黎贡山外来入侵植物研究的重点;人工灌木林地和耕地作为高黎贡山外来入侵植物集聚区应该重点关注开展外来入侵植物防控。     

外来植物入侵对生物多样性的影响及本地生物的进化响应

越来越多的证据表明,入侵植物能通过杂交和基冈渐渗等对本地种造成遗传侵蚀,甚至产生新的"基因型"来影响本地种的遗传多样性;通过生境片断化,改变本地种种群内和种群间的基因交流,造成近亲繁殖和遗传漂变,间接影响本地种的遗传多样性.另一方面,本地种能对入侵植物做出适应性进化响应,以减小或消除入侵植物的危害.本地种在与入侵植物的互作过程中产生了一系列的适应进化、物种形成以及灭绝事件,且这些事件不仅局限于地上生态系统,土壤牛物多样性同样受到影响,甚至也能发生进化响应.为更全面地了解外来植物入侵的生态后果和本地生物的适应潜力,本文综述了外来植物入侵对本地(地上和地下)生物(遗传)多样性的影响以及本地生物的进化响应.讨论了外来植物入侵导致的遗传和进化变化与其入侵性的关系,并提出了一些值得研究的课题.如土著种与外来种的协同进化、植物一土壤反馈调节途径和全球变化其他组分与生物入侵的关系等.     

天然林和人工林外来入侵和本地植物对比研究: 以弄岗国家级自然保护区为例

外来植物的入侵严重威胁了自然保护区的生物多样性。为探讨自然保护区内天然林和人工林林下外来植物入侵状况及其与本地优势植物的种间关系, 本研究以弄岗国家级自然保护区为研究区域, 结合保护区内4种生境72个样方的野外调查数据, 利用生态位宽度、生态位重叠和种间联结指数比较了不同生境中外来入侵草本植物的多样性和生态位宽度以及外来入侵草本植物与本土优势草本植物的生态位重叠和种间联结。结果表明: 弄岗国家级自然保护区4种生境共记录6种外来入侵草本植物, 隶属于3科6属, 其中菊科物种数量最多。外来入侵植物多样性呈现出秋枫(Bischofia javanica)人工林 > 麻竹(Dendrocalamus latiflorus)次生林 > 人面子(Dracontomelon duperreanum)人工林 > 广西澄广花(Orophea polycarpa)次生林的特征。除广西澄广花次生林生境的外来入侵草本植物丰富度与本土草本植物丰富度呈显著正相关外, 其余生境均无显著的相关关系。三叶鬼针草(Bidens pilosa)的生态位宽度最大, 为4种生境均有分布的外来入侵植物。4种生境的外来入侵植物与本土优势植物生态位重叠和种间联结程度均较低, 种间竞争较弱。本研究明确了弄岗国家级自然保护区天然林和人工林中外来入侵草本植物的分布及其与本土草本植物的种间关系。     

植物外来种入侵及其对生态系统的影响

对植物外来种的入侵及生态系统的影响进行综述与分析，植物入侵多种因子的影响，可分为外因和内因两类，植物外来种对生态系统的影响主要体现在生产力，土壤营养，水分，干扰体制，群落的结构和动态等方面，在管理外来种时，需对外来种的特性和影响因子进行系统的观察研究，采用机械法，化学方法和生物控制法等综合办法控制植物的入侵，引进植物引来种时，要对引进种的行为特性进行了调查研究，注意其安全性。     

“世界100种恶性外来入侵物种”在我国大陆的入侵现状

[目的] 明确世界自然保护联盟公布的“世界100种恶性外来入侵物种”在我国大陆发生分布现状,为我国制定外来入侵物种管控对象和分级管理对策提供依据。[方法] 基于在线数据库系统、文献报道以及外来入侵物种本底调查结果,采用分类统计方法,对物种的分类地位、原产地、在我国的入侵状态及其所在的生态系统进行分析。[结果] 世界100种恶性外来入侵物种已有82种在我国发生分布,包括本地种33种、外来入侵种32种、外来非入侵种16种,以及未明确入侵状态1种。其中,32种外来入侵种包括陆生无脊椎动物8种、哺乳动物2种、鱼类2种、两栖动物1种、爬行动物1种、水生无脊椎动物2种、陆生植物9种、水生植物4种、真菌1种、卵菌1种和病毒1种。以上物种主要分布在东南沿海地区和西南地区,而较少分布在西北地区和东北地区;约75%物种分布在农田、城镇、森林和湿地4类生态系统。[结论] 建议外来入侵物种管理部门重点关注尚未在国内发生分布的18种潜在外来入侵物种,并列入国家外来入侵物种相关管理对象,严防其传入与扩散;严密监控国内已发生且具有潜在危险的外来物种,防止其向可能入侵的生态系统边缘扩散;继续对在国内已发生的外来入侵种实施区域性分级控制管理措施。     

广州外来入侵植物

根据野外调查及相关文献资料,初步探讨了广州市外来入侵植物的种类组成、分布生境、生长特性、危害以及来源.结果表明:广州市现有外来人侵植物73种,隶属于27科59属,其中菊科(19种)、禾本科(8种)、豆科(7种)和苋科(7种)植物占了入侵植物总种数的56.2%.生活型分析发现,在广州有分布的外来入侵植物中,陆生草本植物最多(58种),其次为灌木(10种)、水生草本(3种),乔木种类最少(2种),它们主要生长在人类干扰比较频繁的低海拔地区.另外,基于对外来入侵植物目前在野外的生长和分布状况等生态学特性进行分析,可大致将它们对本地生物多样性危害程度分为3级,其中危害严重的有11种,危害中等的有25种,危害较轻的有37种.从原产地分析来看,61种来自于热带美洲地区,占广州外来入侵植物总种数的83.6%.与国内其他地区外来入侵植物进行比较发现,广州和广西共有种数最多,有62种,然而,对已经造成严重危害的外来植物种类,在数量上广州与香港、深圳和广西相同种类较多,分别有8种、7种和6种.对广州市目前外来植物的入侵风险(潜在威胁)的评估结果表明,对一些在其它地区已经造成严重危害的外来植物,应当加强监控,防止入侵扩散并造成重大生态灾难.还对广州市外来植物入侵的主要途径及防治策略做了简要分析和说明.     

外来入侵植物成灾的机制及防除对策

外来入侵植物是指自然或人为地由原生态系统中引入到新生境的植物 ,会给新生境或其中的物种带来威胁。紫茎泽兰从缅甸自然进入云南 ,其原产地是墨西哥 ;水葫芦从墨西哥引进用作饲料 ,而大米草是从英国南海岸引入用于促淤护堤。 3种外来入侵植物给我国当地的生产、生活等带来了极大的威胁 ,破坏了生态系统 ,影响了生物的多样性。对它们的治理费用昂贵。其繁殖力、适应性和抗逆性极强 ,竞争力也极强或本身拥有化感特性或特殊器官 ,同时又耐瘠、耐污 ,并且在本地还缺乏有力的竞争生物和天敌 ,是 3种外来入侵植物势不可挡 ,扩散蔓延的成灾机制。致力于外来入侵植物的国家能力建设和综合治理是 3种外来入侵植物的防除对策     

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。     

华南地区外来入侵和归化植物分析

为了解华南地区外来植物现状,通过野外调查和查阅文献等,确定华南地区有外来入侵和归化植物45科141属223种,以菊科(Asteraceae,38种)、豆科(Fabaceae,36种)、禾本科(Poaceae,19种)植物为主,其中草本植物和原产美洲的植物占优势,分别有204种(占总数的91.5%)和163种(占73.1%)。广东外来入侵植物有159种,归化植物23种;广西有入侵植物135种,归化植物16种;海南有入侵植物111种,归化种15种;香港有入侵植物105种,归化植物9种;澳门有入侵植物89种,归化种4种;华南5省区共有的外来入侵和归化植物为57种(55种为入侵植物,2种为归化植物)。广东是外来植物种类最多的地区,与其他4省区共有的外来入侵和归化植物种类也最多,说明广东同时是外来植物输入和输出大省。由于气候和生态生境的相似性,各省区都面临着其他植物从周边地区入侵的风险,因此在治理入侵植物时,应建立联合防控机制对外来入侵植物的联合监测和防控,以提升外来入侵植物的治理成效和降低其对人类健康和生态安全的威胁。     

Contrasting patterns in the invasions of European terrestrial and freshwater habitats by alien plants,insects and vertebrates

Aim To provide the first comparative overview on the current numbers of alien species that invade representative European terrestrial and freshwater habitats for a range of taxonomic groups. Location Europe. Methods Numbers of naturalized alien species of plants, insects, herptiles, birds and mammals occurring in 10 habitats defined according to the European Nature Information System (EUNIS) were obtained from 115 regional data sets. Only species introduced after ad 1500 were considered. Data were analysed by ANCOVA and regression trees to assess whether differences exist among taxonomic groups in terms of their habitat affinity, and whether the pattern of occurrence of alien species in European habitats interacts with macroecological factors such as insularity, latitude or area. Results The highest numbers of alien plant and insect species were found in human‐made, urban or cultivated habitats; if controlled for habitat area in the region, wetland and riparian habitats appeared to support relatively high numbers of alien plant species too. Invasions by vertebrates were more evenly distributed among habitats, with aquatic and riparian, woodland and cultivated land most invaded. Mires, bogs and fens, grassland, heathland and scrub were generally less invaded. Habitat and taxonomic group explained most variation in the proportions of alien species occurring in individual habitats related to the total number of alien species in a region, and the basic pattern determined by these factors was fine‐tuned by geographical variables, namely by the mainland–island contrast and latitude, and differed among taxonomic groups. Main conclusions There are two ecologically distinct groups of alien species (plants and insects versus vertebrates) with strikingly different habitat affinities. Invasions by these two contrasting groups are complementary in terms of habitat use, which makes an overall assessment of habitat invasions in Europe possible. Since numbers of naturalized species in habitats are correlated among taxa within these two groups, the data collected for one group of vertebrates, for example, could be used to estimate the habitat‐specific numbers of alien species for other vertebrate groups with reasonable precision, and the same holds true for insects and plants.     

Exotic plant invasion in the highly degraded upland landscape of Hong Kong, China

Plant communities in the continental tropics have suffered less from exotic plant invasions than their oceanic island counterparts. Most studies have focused on near-pristine communities. By contrast, we examine the resistance of semi-natural continental plant communities in Hong Kong, which have been suffering from chronic and massive human impacts. We compiled a list of all naturalized non-native species recorded in Hong Kong and then sampled the plant communities for exotic species along roadsides, a stream through semi-natural vegetation, and in semi-natural vegetation away from both roads and streams on Tai Mo Shan, Hong Kong’s highest peak (957 m). Similar surveys were repeated in other areas of Hong Kong. More than 162 naturalized exotic plant species have been recorded in Hong Kong. On Tai Mo Shan, 29 exotic species were recorded in roadside vegetation, with the diversity but not percentage cover declining significantly with altitude. Fifteen exotic species were found along the stream, including two not found along the roadside. Only six exotic species were found away from roads and streams, all in unshaded areas disturbed by feral cattle. In all surveys, no exotics were found in closed woody vegetation or in open areas without feral cattle, except for one species. The shade-tolerant tropical Asian tree Syzygium jambos was found invading along some streamsides without anthropogenic disturbance. Despite centuries of massive human impacts, exotic plant invasions in Hong Kong are still largely confined to habitats that suffer from chronic human disturbance. Feral cattle promote invasion where people are absent, but this problem still seems potentially reversible. Only Syzygium jambos is of possible current conservation concern.     

Risk Assessment and Invasion Characteristics of Alien Plants in and Around the Agro-Pastoral Ecotone of Northern China

Two risk assessment protocols were adopted to assess the risks posed by alien plants that naturalized or non-naturalized in the agro-pastoral ecotone of northern China (AGENC). In this study the Risk Assessment for Central Europe method revealed that more than two-thirds of the 19 naturalized and four-fifths of the 17 non-naturalized alien plants presented high or moderate risk, and all 36 alien plants were considered to be rejected for their potential agricultural and environmental risks under the Australian Weed Risk Assessment system. On the characteristics of plant invasions, more attention should be given to disturbed habitats rather than these relative natural or closed ecosystems, and also be prudent and careful of the alien plants that are introduced as useful plants from North or South America and unintentional introduction from Europe. Moreover, annuals needed special attention: three-quarters of the alien plants were annual species, only a few were biennial (8.3%), perennial (11.1%), liana and tree plants (2.8%). Plant invasions are not extremely serious in the AGENC, but there are several alien plants that have naturalized and spread themselves in the region. However, attention should be given in the future to predicting and preventing plant invasions in this fragile region.     

Contrasting patterns of naturalized plant richness in the Americas: Numbers are higher in the North but expected to rise sharply in the South

With increasing availability of plant distribution data, the information about global plant diversity is improving rapidly. Recently, Ulloa Ulloa et al. (2017) presented the first comprehensive overview of the native vascular flora of the Americas, yielding a total count of 124,993 native species. Of these, 51,241 occur in North America and 82,052 in South America. By combining these data with the information in the Global Naturalized Alien Flora (GloNAF) database of naturalized alien floras, we point out that for a complete picture of the regional and continental plant richness, the naturalized alien species need to be considered. Ignoring this novel component of regional floras can lead to an inaccurate picture of overall change in biodiversity in the Anthropocene. We show that North and South America might face contrasting challenges in terms of potential threats to biodiversity posed by alien plant species, because of the different past and present dynamics of invasions and predictions of future development. In total, there are 7,042 naturalized alien plants occurring in the Americas, with 6,122 recorded in North America and 2,677 in South America; if only introductions from other continents are considered additions to the native continental flora make up 6.9 and 1.4 %, respectively. Nevertheless, predictions of naturalized plant trajectories based on global trade dynamics and climate change suggest that considerable increases in naturalized plant numbers are expected in the next 20 years for emerging South American economies, which could reverse the present state.     

The invasion of Kangaroo Island by alien plants

The numbers of alien plant species naturalized on Kangaroo Is., South Australia, at different times were examined and compared with those from an adjacent part of the mainland, the Encounter Bay area. The establishment of new species appears to have been accelerating and the rate of acquisition is around 50% faster on the mainland than on the island. Flinders’ Chase, a National Park at the western end of Kangaroo Is., has been acquiring alien species more slowly than the rest of the island. Land use patterns are a more effective barrier to the invasion of alien plants than a 15 km stretch of sea.     

中国外来陆生草本植物: 多样性和生态学特性

构建包含基本生物学和生态学信息的外来物种数据库不仅对理解生物入侵分布格局至关重要, 同时也是制定外来种管理策略和解释生物入侵过程的重要一步。作者在前人研究的基础上构建了中国外来陆生草本植物数据库, 共收集到中国外来陆生草本植物800种, 分属37目72科; 其中约有60%集中在菊科、豆科、仙人掌科、禾本科、十字花科等10个优势科。中国外来陆生草本植物主要来源于美洲(407种, 占总数的47%), 主要分布在南亚热带—热带区(46%, 密度为4种/10⁴km²), 其次为温带湿润区(26%, 密度约2种/10⁴km²)和亚热带区(23%, 密度约2种/10⁴km²), 旱—寒区(5%, 密度小于1种/10⁴km²)分布较少。从生活型上看, 以多年生 (293种, 40%)和一年生 (272种, 37%)为主; 而从生境类型来看, 约有一半(46%)分布于“高养分高干扰”类型的生境。约有80%的物种属有意引入, 因此有意引入是陆生外来草本植物进入中国的主要途径。近2个世纪来, 外来陆生草本植物进入中国的速度快速增加, 约90%的物种在这个时期进入; 而近半个世纪以来, 外来陆生草本植物进入中国的速度快速增长, 约60%的物种在这个时期进入中国。本文所提供的中国外来陆生草本植物的生物学和生态学特征, 可以为管理层制定外来种相关管理和控制策略提供参考信息。     

Traits explain invasion of alien plants into tropical rainforests

• 1. The establishment of new botanic gardens in tropical regions highlights a need for weed risk assessment tools suitable for tropical ecosystems. The relevance of plant traits for invasion into tropical rainforests has not been well studied.
• 2. Working in and around four botanic gardens in Indonesia where 590 alien species have been planted, we estimated the effect of four plant traits, plus time since species introduction, on: (a) the naturalization probability and (b) abundance (density) of naturalized species in adjacent native tropical rainforests; and (c) the distance that naturalized alien plants have spread from the botanic gardens.
• 3. We found that specific leaf area (SLA) strongly differentiated 23 naturalized from 78 non‐naturalized alien species (randomly selected from 577 non‐naturalized species) in our study. These trends may indicate that aliens with high SLA, which had a higher probability of naturalization, benefit from at least two factors when establishing in tropical forests: high growth rates and occupation of forest gaps. Naturalized aliens had high SLA and tended to be short. However, plant height was not significantly related to species'' naturalization probability when considered alongside other traits.
• 4. Alien species that were present in the gardens for over 30 years and those with small seeds also had higher probabilities of becoming naturalized, indicating that garden plants can invade the understorey of closed canopy tropical rainforests, especially when invading species are shade tolerant and have sufficient time to establish.
• 5. On average, alien species that were not animal dispersed spread 78 m further into the forests and were more likely to naturalize than animal‐dispersed species. We did not detect relationships between the measured traits and estimated density of naturalized aliens in the adjacent forests.
• 6. Synthesis: Traits were able to differentiate alien species from botanic gardens that naturalized in native forest from those that did not; this is promising for developing trait‐based risk assessment in the tropics. To limit the risk of invasion and spread into adjacent native forests, we suggest tropical botanic gardens avoid planting alien species with fast carbon capture strategies and those that are shade tolerant.

     

Alien invasive neophytes of the Southeastern part of the Pannonian Plain

Floristic diversity in the Pannonian Plain is the result of mosaic habitat composition, characterized by steppes, saline meadows, and lowland forests along major rivers. In the last few centuries, the flora has become enriched by species introduced by human activities, such as colonization and industrialization. Presently it consists of nearly 1800 species. As a result of 30 years of field research as well as herbarium and literature searches, a list of invasive alien neophytes has been compiled and is presented here. The list includes 152 species, classified as either naturalized, casual, or unknown. One of the species is listed in Red Book of Serbian Flora. Eighty species are naturalized, and 61 are casual species. The majority of the introduced flora originates from North America (66) and the Old World (43). Most alien invasive species of the Southeastern part of the Pannonian Plain, were introduced accidentally by seed material or deliberately by nursery saplings. The annual and perennial herbaceous plants, which flower in the summer and summer-autumn periods, are represented in the greatest numbers. The alien flora was further analyzed with respect to taxonomy, life forms, pollination, and seed dispersal mode. The greatest number of alien species appears in anthropogenic and semi-natural habitats (59). In natural habitats, 45 invasive taxa were recorded, representing a conservation threat to biodiversity.     

Comparing naturalized alien plants and recipient habitats across an east–west gradient in the Mediterranean Basin

Aim To investigate alien plant species invasion levels in different habitats and alien species traits by comparing the naturalized flora in different areas of the same biogeographical region. Location Spain, Italy, Greece and Cyprus. Methods Comparison of floristic composition, species traits and recipient habitats of naturalized alien neophytes across an east–west gradient comprising four countries in the European Mediterranean basin. Results A total of 782 naturalized neophytes were recorded; only 30 species were present in all four countries. Although floristic similarity is low, the four alien floras share the same patterns of growth form (mostly herbs), life cycle (mostly perennials) and life form (mostly therophytes, hemicryptophytes and phanerophytes). The majority of the recipient habitats were artificial. Wetlands were the natural habitats, with the highest numbers of naturalized species. Floristic similarity analyses revealed: (1) the highest floristic similarity between Italy and Spain, both of which were more similar to Greece than to Cyprus; (2) two groups of floristic similarity between habitat categories in each country (Greece–Cyprus and Italy–Spain); (3) a higher degree of homogenization in the plant assemblages in different habitats in Greece and Cyprus and a lower degree of homogenization in those in Italy and Spain; and (4) a higher degree of homogenization in artificial and natural fresh‐water habitats than in the other natural habitats. Main conclusions The floristic similarity of naturalized neophytes between the four countries is low, although the overall analysis indicates that the western group (Italy–Spain) is separated from the eastern group (Greece–Cyprus). Similar patterns emerged regarding the life‐history traits and recipient habitats. The artificial habitats and the natural wet habitats are those that are invaded most and display the greatest homogenization in all four countries. Coastal habitats display a lower degree of homogenization but a high frequency of aliens. Dry shrubs and rocky habitats display a lower degree of homogenization and a low frequency of aliens.