Über einige quantitative Wechselbeziehungen der Floren der Erde

Some quantitative correlations of the floras of the world Both the sequence of the 10 families comprising the most species of a flora, and the percentage contributed by these families to the whole species number of the flora, are very constant in different floras of the same floristic region. In contrast, in floras of different floristic regions the list of these 10 richest families, and also their share in the whole species number varies considerably. Therefore, these characters are useful in defining floristic regions. The taxonomic structure of any flora is scarcely influenced by the extent of its area. The De Candolle rule (the percentage of the species-richest families in the whole species number of the flora is the lower, the richer in species the flora) is not generally valid. The complicatness of the taxonomic structure is not only depending on the species number of the flora, but also on its age: The share of the richest families in the whole species number of the flora is rather low, where the flora development was not disturbed for a long time, and it is high, if there were catastrophes in the geological past. The possibilities of florogenetic deductions are demonstrated in the cases of the Mediterranean, Middle Asiatic, dan East Asiatic floras.     

Observations on the formation of Chinese desert floras

1. Based upon the analyses in the floristic elements of the three genera (Suaeda, Salsola and Zygophyllum) in different regions we can see that the genesis of our desert floras in these regions is very much diversified. The flora of Songaria is similar to that of the Middle Asia, while the Hosi Corridor seems to be a transitional area very close to Alashan and also related to the Tarim Basin in floristic elements. Thus, we may classify the desert floras into three parts: the flora of Songaria, of Alashan including the Hosi Corridor and of the Tarim Basin including the Tsaidam Basin. The ages and approaches in their formation are different. 2. There are plenty species but no or rare endemics in Songaria. In spring there are a number of ephemeral plants. The variation of aspect is evident. The vegetation cover is abundant. The floristic elements are developed from the flora of Middle Asia and it was formed in Quaternary period. 3. The floristic elements of the Tarim Basin are poor, but there are not few endemics and the distribution of the endemics is much limited. They are of the characteristics of relic species. Therefore it was formed in the Tertiary period and developed in Quaternary period. The elements are related to the Mediterranean flora. 4. There are a large number of endemics and many endemic monotypie genera in Alashan. They represent the flora formed in Tertiary period. Although it is of a special style, it relates both to the Middle-Asian and the Mediterranean flora. 5. The historic causes for the formation of the different floras lie chiefly on: (1) The rise of the Tibetan plateau and mountains strongly changed the climatic and edaphic conditions and in the long course of evolution some species survived or even developed, while the others deteriorated or even died out from the flora. (2) Because the circumstances of transgression or regression of the Tethys were different in these regions. (3) The mountain-making movement, the transgression and regression and the fluence of glaciation, all the mutation of these associated factors modified the climatic zonation and then the plant species changes followed, new species formed and migration of floristie elements occurred. (4) Songaria is the nearest region to the then Sibirian glacier, so the frozen injury to the flora might be the greatest. (5) In the Glacial period the descension of snow line in Songaria was greater than that of the Tarim Basin, so the frozen injurymight be greater.     

海南铜鼓岭与五指山种子植物属的比较研究

铜鼓岭位于海南省东北部,共有维管植物166科626属984种及变种。五指山位于海南岛中部山区,共有维管植物196科911属2146种及变种。前者共有单型科54科,单种属431属,分别占科和属总数的27.11%,68.74%;后者共有单型科35科,单种属496属,分别占科及属总数17.77%,54.5%。说明五指山物种组成比铜鼓岭的更丰富,但两个区系属内种系分化程度都较弱。区系分析表明:(1)铜鼓岭以泛热带分布占优势,热带亚洲分布次之,分别占该区非世界分布属总数的34.5%和17.8%;五指山以热带亚洲分布占优势,泛热带分布次之,分别占非世界分布属总数的37.5%和24.1%;两个区系热带性质强烈,但前者以泛热带分布为主,后者以热带亚洲成分为主。(2)铜鼓岭共有35种海南特有种,占海南536个海南特有种(变种)的6.53%;五指山共有284个海南特有种,五指山特有种16种,占海南特有种的52.99%,说明其在海南植物区系中比铜鼓岭更重要。     

A phytogeographical characterization of the vine flora of the Sonoran and Chihuahuan deserts

Aim This study presents a phytogeographical characterization of the vine flora of two lower North American desert regions as a biogeographical framework for further ecological inquiry into desert vines. Location The phytogeography of the vine flora of the Sonoran and Chihuahuan Deserts was c haracterized based on 263 known species. Methods Checklists of the vines of each desert were developed. Represented genera were then grouped into 10 phytogeographical elements based on worldwide distribution patterns. To compare the floristic composition of the desert floras, an index of species similarity was calculated. Results About a third more species of vines occur in the Sonoran Desert than in the Chihuahuan Desert. Based on the analysis, cosmopolitan genera are the only group more numerous in absolute terms in the Chihuahuan Desert than in the Sonoran Desert. Tropical elements are represented in about the same proportion in each desert as the number of species, however, nearly twice as many pantropical and neotropical genera are represented in the Sonoran Desert as in the Chihuahuan Desert. Proportionately, more genera of temperate elements occur in the Chihuahuan Desert than in the Sonoran desert, although the absolute number of genera is slightly higher in the latter. Main conclusions As these deserts are relatively recent ecological formations and as vines evolved in forest ecosystems, the composition of the desert vine floras is the result of the interaction between historical vegetation types, their constituent taxa and climatic and geological history. The main differences in the vining floras of the present‐day Sonoran and Chihuahuan Deserts appear to be the result of greater historical influence in the Sonoran Desert of (1) tropical vegetation types and (2) the emergence of the Gulf of California. The Chihuahuan Desert vine flora seems to be the result of (1) a more pronounced historical temperate vegetation, (2) the lack of an important isolating event, such as the creation of the Baja California peninsula, and (3) a cooler climate with shorter growing seasons.     

华东天目山脉、黄山山脉、大别山脉竹类植物区系分析,兼论区系的起源与扩散

华东天目山脉、黄山山脉、大别山脉竹类植物较为丰富,分别有10属/75种(含种下等级)、8/49、7/30.通过对属、种的分布型分析,前二者竹类植物区系属于典型的华东区系,起源的时间不迟于早第三纪的始新世;而大别山脉虽仍属华东区系的范畴,因渗入了不少华中区系的成分,已具有某些经向过渡性特征,且起源的时间较晚.这3个山脉的竹类植物区系均具有显著的亚热带性质.天目山脉不仅是刚竹属Phyllostachys和短穗竹属Brachystachyum的分化变异中心,也极有可能就是它们的起源中心,但它们自此地起源后的散布方式有所不同,刚竹属在我国亚热带为四周放射状顺序渐进,扩散的范围颇广;短穗竹属存在东西南北4条散布路线,但向各方扩散的距离相差甚远.这些山脉与华东其他地区竹类植物区系联系密切,与华中竹类植物区系也有一定的联系,但与华南、西南等地竹类植物区系联系微弱.从地理位置和区系组成来看,黄山山脉的竹类植物区系来源于天目山脉,大别山脉的竹类植物区系又来源于黄山山脉,前者都是在后者扩展的基础上融合了其他区系的一些成分后发展而成,大别山脉又是北方秦岭以东广大丘陵平原地区竹类植物区系的发祥地.     

Phytogeography of the bryophyte floras of oak forests and páramo of the Cordillera de Talamanca, Costa Rica

Aim Central America is a biogeographically interesting area because of its location between the rich and very different biota of North and South America. We aim to assess phytogeographical patterns in the bryophyte floras of oak forests and páramo of the Cordillera de Talamanca, Costa Rica. Location Tropical America, in particular the montane area of Cordillera de Talamanca, Costa Rica. Methods The analysis is based on a new critical inventory of the montane bryophyte flora of Cordillera de Talamanca. All species were assigned to phytogeographical elements on the basis of their currently known distribution. Absolute and percentage similarities were employed to evaluate floristic affinities. Results A total of 401 species [191 hepatics (liverworts), one hornwort, 209 mosses] are recorded; of these, 251 species (128 hepatics, one hornwort, 122 mosses) occur in oak forests. Ninety‐three per cent of all oak forest species are tropical in distribution, the remaining 7% are temperate (4%) and cosmopolitan (3%) species. The neotropical element includes almost 74% of the species, the wide tropical element (pantropical, amphi‐atlantic, amphi‐pacific) only 19%. A significant part of the neotropical species from oak forests are species with tropical Andean‐centred ranges (27%). As compared with bryophyte species, vascular plant genera in the study region are represented by fewer neotropical, more temperate and more amphi‐pacific taxa. Bryophyte floras of different microhabitats within the oak forest and epiphytic bryophyte floras on Quercus copeyensis in primary, early secondary and late secondary oak forest show a similar phytogeographical make‐up to the total oak forest bryophyte flora. Comparison of oak forest and páramo reveals a greater affinity of the páramo bryophyte flora to temperate regions and the great importance of the páramo element in páramo. Surprisingly, oak forests have more Central American endemics than páramo. Main conclusions (1) Providing first insights into the phytogeographical patterns of the bryophyte flora of oak forests and páramo, we are able to confirm general phytogeographical trends recorded from vascular plant genera of the study area although the latter were more rich in temperate taxa. (2) Andean‐centred species are a conspicuous element in the bryophyte flora of Cordillera de Talamanca, reflecting the close historical connection between the montane bryophyte floras of Costa Rica and South America. (3) High percentages of Central American endemics in the bryophyte flora of the oak forests suggest the importance of climatic changes associated with Pleistocene glaciations for allopatric speciation.     

Beta diversity of angiosperms in temperate floras of eastern Asia and eastern North America

The diversity of a region reflects both local diversity and the turnover of species (beta diversity) between areas. The angiosperm flora of eastern Asia (EAS) is roughly twice as rich as that of eastern North America (ENA), in spite of similar area and climate. Using province/state‐level angiosperm species floras, we calculated beta diversity as the slope of the relationship between the log of species similarity (S ) and either geographic distance or difference in climate. Distance‐based beta diversity was 2.6 times greater in the north–south direction in EAS than in ENA and 3.3 times greater in the east–west direction. When ln S was related to distance and climate difference in multiple regressions, both distance and climate PC1 were significant effects in the north–south direction, but only geographic distance had a significant, unique influence in the east–west direction. The general predominance of distance over environment in beta diversity suggests that history and geography have had a strong influence on the regional diversity of these temperate floras.     

The radiation of the Cape flora, southern Africa

The flora of the south-western tip of southern Africa, the Cape flora, with some 9000 species in an area of 90,000 km2 is much more speciose than can be expected from its area or latitude, and is comparable to that expected from the most diverse equatorial areas. The endemism of almost 70%, on the other hand, is comparable to that found on islands. This high endemism is accounted for by the ecological and geographical isolation of the Cape Floristic Region, but explanations for the high species richness are not so easily found. The high species richness is accentuated when its taxonomic distribution is investigated: almost half of the total species richness of the area is accounted for by 33 'Cape floral clades'. These are clades which may have initially diversified in the region, and of which at least half the species are still found in the Cape Floristic Region. Such a high contribution by a very small number of clades is typical of island floras, not of mainland floras. The start of the radiation of these clades has been dated by molecular clock techniques to between 18 million years ago (Mya) (Pelargonium) and 8 Mya (Phylica), but only six radiations have been dated to date. The fossil evidence for the dating of the radiation is shown to be largely speculative. The Cenozoic environmental history of southern Africa is reviewed in search of possible triggers for the radiations, climatic changes emerge as the most likely candidate. Due to a very poor fossil record, the climatic history has to be inferred from larger scale patterns, these suggest large-scale fluctuations between summer wet (Palaeocene, Early Miocene) and summer dry climates (Oligocene, Middle Miocene to present). The massive speciation in the Cape flora might be accounted for by the diverse limitations to gene flow (dissected landscapes, pollinator specialisation, long flowering times allowing much phenological specialisation), as well as a richly complex environment providing a diversity of selective forces (geographically variable climate, much altitude variation, different soil types, rocky terrain providing many micro-niches, and regular fires providing both intermediate disturbances, as well as different ways of surviving the fires). However, much of this is based on correlation, and there is a great need for (a) experimental testing of the proposed speciation mechanisms, (b) more molecular clock estimates of the age and pattern of the radiations, and (c) more fossil evidence bearing on the past climates.     

Biogeographical Divergence of the Flora of Yunnan,Southwestern China Initiated by the Uplift of Himalaya and Extrusion of Indochina Block

The floral composition of Yunnan is conspicuously linked to the biogeographical history of this extremely species-rich province in southwestern China. The floristic compositions of three representative regions in Yunnan were compared to reveal their variation with geography. From southern Yunnan, 4150 native species (including subspecies and varieties) from 1240 genera and 183 families of seed plants were recognized. From central Yunnan 3389 native species from 1095 genera and 167 families of seed plants were recognized. From northwestern Yunnan 6807 native species from 1296 genera and 166 families of seed plants were recognized. Although these three floras across Yunnan are similar in familial composition, similarities between the floras of southern and northwestern Yunnan are low at the generic and specific levels. The flora of northwestern Yunnan is dominated by families and genera with cosmopolitan and north temperate distributions, while the flora of southern Yunnan is dominated by tropical families and genera. Northwestern Yunnan is composed largely of temperate genera, of which the highest proportion has a north temperate distribution. In contrast, southern Yunnan has mainly tropical genera, of which most have a tropical Asian distribution. The flora of central Yunnan is a combination of southern and northwestern Yunnan. These three floras might be derived from a common Tertiary tropical or subtropical East Asian flora, but the geological history of each region has influenced its flora, and they have remained divergent since the late Tertiary. The flora of northwestern Yunnan has evolved with the uplift of the Himalayas and by gradual proliferation of mainly cosmopolitan and north temperate floristic elements, while the flora of southern Yunnan has evolved with extrusion of the Indochina block and the influence of mainly tropical Asian elements.     

Do climatically similar regions contain similar alien floras? A comparison between the mediterranean areas of central Chile and California

Aim Taxonomic comparisons of alien floras across climatically similar regions have been proposed as a powerful approach for increasing our understanding of plant invasions across scales. However, detailed comparisons between the alien biotas of climatically similar regions are scarce. This study aims to compare the taxonomic patterns of alien species richness in mediterranean‐type climate areas of central Chile and California, in order to better understand how climatically similar regions converge or diverge in terms of their alien flora. Location Central Chile and California, United States. Methods We compared the alien floras of the state of California in the United States and central Chile, considering within‐region variation and taxonomic composition up to the species level. To test for within‐region variation, administrative units and counties were grouped within seven latitudinal bands for each region. We tested for differences in the relative contributions of the various origins of the naturalized species to each region. We used a family naturalization index to establish which families had relatively higher numbers of naturalized species in each region. We evaluated the similarity, using cluster analyses with Jaccard’s similarity index, of alien taxa between regions and latitudinal bands using presence–absence matrices at the species, genus and family levels. We used principal components analysis to determine the presence of a compositional gradient including all latitudinal bands. Results We recorded 1212 alien plant species in California and 593 in central Chile, of which 491 are shared between the two regions. These figures include 25 species that are native to California and 37 that are native to Chile. A comparison between the alien floras of central Chile and California reveals three major trends: (1) higher naturalized species diversity for California than for Chile, at all taxonomic levels; (2) differences in the proportion of species according to origin, with America, Africa, Asia and Australia providing a larger number of species in California than in Chile; (3) segregation between regions in terms of taxonomic composition of their alien flora, and a rather weak differentiation within regions; and (4) a trend towards higher similarity between the alien floras of latitudinal bands associated with higher levels of human disturbances. Main conclusions The alien floras of central Chile and California are significantly different, but this difference diminishes in highly disturbed areas. Thus, the current high levels of species movement caused by globalization, together with increasing levels of anthropogenic disturbances, should reduce the differentiation of the alien floras in these regions, increasing overall biotic homogenization.     

A comparative study of the distribution of genus size in twenty angiosperm floras

The biodiversity of floras has until recently been measured solely in terms of their species number or species density, with little regard to the breadth of phylogenetic diversity represented by the species. The latter is partly a function of the size of the flora, and partly of the pattern of distribution of the species into higher taxa. To determine whether floras differ in this respect, this study compares the frequency distribution of genus size in 20 island and regional floras. Certain floras (Cape Region, S.W. Australia, New Zealand, Hawaii) are found to have high concentrations of genera containing many species. Others are notably lacking in large genera (Java, Jamaica, Nepal, Niger), though this group tend to be family-rich. In floras with high endemism (Cape, New Zealand, Fiji, Jamaica, Hawaii), the level of endemism is consistently higher in larger genera. Possible reasons for the observed differences between floras are geographic and temporal isolation, level of habitat diversity, climatic history, volcanic, orogenic and tectonic events. Clusters of large genera may indicate recent speciation, possibly following the last glaciation. Genus size may be an important consideration when limited conservation resources have to be targetted to retain the maximum phylogenetic diversity in a threatened flora.     

Phytogeography of Genu and Homag,two mountains with an Irano–Turanian flora in the Saharo–Sindian regional zone,south Iran

The Saharo–Sindian regional zone encompasses the flat and arid areas of North Africa, the Arabian Peninsula, southern Iran and the deserts of Pakistan and west India. There are some scattered mountains situated within this area, like Hoggar in Sahara, Saint Catherine in Sinai and Genu and Homag in southern Iran. These highlands serve as interglacial refugia for cold adapted plant species. In the present study, phytogeographical patterns and relationships of the flora of Genu and Homag mountains are described and discussed in relation to the phytogeography of the flora of low‐lying Hormoz Island. According to a chorological assesment of the flora, Genu and Homag mountains belong to the Irano–Turanian region with 59% of the species restricted to this area. In contrast, the surrounding lowland plains are part of the Saharo–Sindian area with a rather high proportion of widespread species (17%) and Somalia–Masai‐linking elements (20%). It is noteworthy that several Turanian enclaves also occur in the lowland zone. Furthermore, the distributional patterns imply that the mountainous Irano–Turkestanian region is an integrated area which is supposedly distinct from the Turanian lowland areas in the north and from the Saharo–Sindian lowland areas in the south. On the other hand, the expansive floras of Turanian and Saharo–Sindian regions are linked to each other. Endemic species in lowland areas in south Iran are mostly either frost sensitive vicariants of cold adapted Turanian species or of Saharo–Sindian origin, while the highland endemics in the area trace their origins to the Irano–Turkestanian region.     

Factors affecting range size differences for plant species on rock outcrops in eastern Australia

Abstract: Rock outcrops are considered as habitat or ecological islands discordant from the adjacent matrix. The floras of 24 aggregated outcrop regions within the New England Batholith of eastern Australia were sampled and investigations made into species range differences. A measure is developed to describe differences in species range sizes across floras (range saturation: RS). Range sizes increased in areas with higher incident radiation (higher available energy) and concordantly in regions with a greater proportion of hemi‐parasites, epiphytes and herbs (which were demonstrated to have large range sizes). Differences in species’ range sizes of granite outcrop occurring species on the New England Batholith of eastern Australia at different scales and extents are regressed against selected environmental variables and against local species richness and abundance. Although species’ range size has been linked in a number of systems with increased species richness and local species abundance, such correlations were not obtained in this investigation. Analyses of species’ range sizes could not be used to infer directly on processes that maintain species richness or abundance within the granitic outcrop flora of the New England Batholith.     

中国萨吾尔-塔尔巴哈台山地种的地理成分分析

划分出萨吾尔 -塔尔巴哈台山地植物种一级的分布区类型共 1 2种类型及 3种亚型。分析结果表明 ,南北向格局分布区类型中的种类数目占总种数的三分之一多 ,说明本区在近代与南北植物区系的交流较多 ,成为南北植物区系物种交流的重要通道及由于该地的低海拔成为一些山地物种的分布边界 ,但中低山及平原中旱生性质的种类的分布未受到本区地形的影响。     

湖北大洪山种子植物区系的研究

报道大洪山有种子植物１０５２种,隶属５１６属１４７科,在分析主要科的地理分布和全部属的分布区类型的基础上,认为温带属占主导地位,还讨论了该地区与我国其它１０个不同纬度山区植物区系的关系,并通过植物区系的属相似性系数的对比分析,讨论了该区系与华东,华中和华北植物区系的关系,得到大洪山属于华东植物区系的结论。     

The region effect on mesoscale plant species richness between eastern Asia and eastern North America

The greater number of plant species in temperate eastern Asia compared to eastern North America has been ascribed to both local environment and regional characteristics, but the relative contributions of each have not been resolved. In this analysis, we related species richness of flowering plants in mesoscale floras (<10⁴ km²) dominated by temperate forest vegetation to area, elevation, latitude, and several climate variables. When analyses were conducted separately within each region, area and, in eastern Asia, elevation, were the primary determinants of species richness. It appears that the number of species in mesic temperate floras within these regions is largely unrelated to the relatively narrow range of local climate factors associated with these floras. Analysis of covariance of the logarithm of species richness with the logarithm of area (b=0.148) and climate measurements as independent variables revealed a region effect, with species richness in eastern Asia exceeding that in eastern North America by 0.294 log₁₀ units, or a factor of 2.0. Similar regional differences in species richness were apparent in floras compiled from larger areas. Understanding differences in plant species richness between regions requires consideration of regional influences, whose effects should be tested in comparative analyses based on floristic surveys of ecologically characterized small areas.     

The Effect of Typhoons on the Diversity and Distribution Pattern of Aquatic Plants on Hainan Island,South China

Typhoons are an important meteorological feature of the tropical southwest Pacific. However, little is known about their effects on aquatic plants. Here, we describe the potential influence of typhoons on the diversity and distribution of aquatic plants on Hainan Island, South China. Using a combination of field survey and published data, 266 species or sub‐species belonging to 115 genera in 57 families were found across typhoon impacted regions of the island. Multiple regression analysis indicated that species richness of aquatic plants was correlated with typhoon incidence rather than the area of aquatic habitat within each region. Heavy rainfall, flooding, and strong winds are likely to create suitable habitats and increase the diversity of aquatic habitats in regions frequently affected by typhoons, which may explain the higher species richness found in those regions. Beta diversity and cluster analyses showed that distinct aquatic floras occurred in regions that were impacted by different typhoon pathways. By comparing the aquatic floras of the Philippines and the typhoon‐affected regions of Hainan, we suggest that typhoons have the potential to transport aquatic plants long distances, although there are a number of other potential explanations for the patterns observed in the aquatic flora of Hainan Island.     

广西扶绥东罗二叠纪长兴期海相层中的植物大化石

首次描述埋葬于长兴期海相地层中的一个高地植物群,计14属23种,包括4新种,2相似种和11未定种。概略论述植物群的性质及其埋葬特征和生态意义。以松柏植物和Taeniopteris等为代表的裸子植物在这一植物群中占61%,显示由古生代向中生代过渡的性质。这一植物群与华北同期的高地植物群在属种组成上很不相同,显示两地在区系性质上的差异。     

青藏高原高山区和泛北极地区种子植物多倍体比较

多倍化是植物快速适应极端环境胁迫的一种重要机制。青藏高原高山区和泛北极地区具有相似的极端低温环境, 且两地的植物曾有密切的交流和联系。然而, 多倍体物种对两地植物区系生物多样性的贡献是否相同仍不清楚。我们系统地收集两地已有染色体数目和倍性报道的种子植物物种名录, 共计1,770种, 其中青藏高原高山区774种, 泛北极地区996种; 同时也相应地收集了每个物种的生活型信息。分析显示青藏高原高山区多倍体植物的比例为20.9%, 泛北极地区多倍体植物比例为61.5%; 青藏高原高山区一年生草本、多年生草本和木本植物中多倍体的比例分别为20.7%、21.6%和12.8%, 泛北极地区一年生草本、多年生草本和木本植物中多倍体的比例分别为60.2%、65.5%和38.3%。这些结果表明泛北极地区比青藏高原高山区具有较高比例的多倍体物种。青藏高原高山植物区系在渐新世‒中新世之交开始兴起, 此时高原已达到一定高度, 而后的高寒环境相对稳定, 致使多倍体物种相对较少; 而泛北极地区植物区系在3-4 Ma兴起, 此后经历了冰期‒间冰期、海平面波动等反复剧烈的气候环境变化, 可能促进了大量的多倍化事件发生。本研究通过比较青藏高原高山区和泛北极地区植物多倍体物种的比例, 揭示了两地多倍体比例差异的可能原因, 将提高对多倍体适应极端环境的理解。     

Contrasting alien and native plant species–area relationships: the importance of spatial grain and extent

Aim The proportion of alien plant species in floras is increasingly being used to indicate the threat of invasions to native species and/or the homogenization of biodiversity. However, this indicator is only valuable if it is independent of the spatial extent and grain of observation. This study tested the equivalence of native and alien species–area relationships (SARs) in order to assess the support for scale invariance in the proportion of alien species in floras. Location England, UK. Methods Nested SARs were generated by assessing the richness of native and alien plant species drawn from the New atlas of the British and Irish flora for six areas comprising 100, 400, 900, 1600, 2500 and 3600 km² with each larger area containing all smaller areas. Five replicate sets of nested areas encompassing northern, southern, eastern, western and central regions were chosen. For each set of nested areas, the log‐transformed species richness was regressed on log‐transformed area to fit a power function to the SAR. Results Native and alien plant SARs reveal consistent differences in slope, highlighting that the proportion of alien species is a function of spatial grain. Aliens are more rare than natives and have higher spatial turnover leading to faster accumulation of species as area increases. However, equivalent samples drawn from a larger spatial extent reveal similar alien and native SARs. Main conclusions The significant differential scale dependence in native and alien species richness observed in this study reflects dissimilar influences of regional drivers such as habitat, but potentially also propagule pressure and introduction history, that leads to the relative rarity and high spatial turnover of alien species. Maps of invasion hotspots that identify areas where the proportion of the alien flora is particularly high should therefore be treated with considerable caution since patterns across most grains used for species monitoring will be scale dependent.