Native and alien floras in urban habitats: a comparison across 32 cities of central Europe

Aim To determine relative effects of habitat type, climate and spatial pattern on species richness and composition of native and alien plant assemblages in central European cities. Location Central Europe, Belgium and the Netherlands. Methods The diversity of native and alien flora was analysed in 32 cities. In each city, plant species were recorded in seven 1‐ha plots that represented seven urban habitat types with specific disturbance regimes. Plants were classified into native species, archaeophytes (introduced before ad 1500) and neophytes (introduced later). Two sets of explanatory variables were obtained for each city: climatic data and all‐scale spatial variables generated by analysis of principal coordinates of neighbour matrices. For each group of species, the effect of habitat type, climate and spatial variables on variation in species composition was determined by variation partitioning. Responses of individual plant species to climatic variables were tested using a set of binomial regression models. Effects of climatic variables on the proportion of alien species were determined by linear regression. Results In all cities, 562 native plant species, 188 archaeophytes and 386 neophytes were recorded. Proportions of alien species varied among urban habitats. The proportion of native species decreased with increasing range and mean annual temperature, and increased with increasing precipitation. In contrast, proportions of archaeophytes and neophytes increased with mean annual temperature. However, spatial pattern explained a larger proportion of variation in species composition of the urban flora than climate. Archaeophytes were more uniformly distributed across the studied cities than the native species and neophytes. Urban habitats rich in native species also tended to be rich in archaeophytes and neophytes. Main conclusions Species richness and composition of central European urban floras are significantly affected by urban habitat types, climate and spatial pattern. Native species, archaeophytes and neophytes differ in their response to these factors.     

Local and regional patterns of species richness in Central European vegetation types along the pH/calcium gradient

We investigated the relationship between soil pH/calcium content and species richness of vascular plants in seven broadly defined Central European vegetation types, using Ellenberg indicator values for soil reaction and a phytosociological data set of 11,041 vegetation sample plots from the Czech Republic. The vegetation types included (A) broad-leaved deciduous forests, (B) meadows, (C) dry grasslands, (D) reed-bed and tall-sedge vegetation, (E) fens and transitional mires, (F) perennial synanthropic vegetation and (G) annual synanthropic vegetation. Relationships between local species richness (alpha diversity) and pH/calcium were positive for vegetation types A and C, negative for D and G, unimodal for E, and insignificant for B and F. Ellenberg soil reaction values explained 37% of variation in local species richness for vegetation type E, 24% for A, 13% for D, but only less than 4% for the others. Species pool size, i.e., the number of species that can potentially occur in a given habitat, was calculated for each plot using Beals index of sociological favourability applied to a large phytosociological database. For most vegetation types, the relationships between species pool size and pH/calcium were similar to the relationships between local species richness and pH/calcium, with the exception of meadows (weak unimodal) and perennial synanthropic vegetation (weak negative).These patterns suggest that for those types of Central European vegetation that developed independently of human influence in the Pleistocene or early Holocene (dry grasslands, deciduous forests), there are larger pools of calcicole than calcifuge species. This pattern is also found at the level of local species richness, where it is, however, less clearly pronounced, possibly due to the predominance of a few widespread and generalist calcifuges in acidic habitats. The unimodal pattern found in mires may result from similar underlying mechanisms, but in high pH environments mineral-rich spring waters probably decrease species richness by having toxic effects on plant growth. By contrast, vegetation types developed under direct human influence (meadows, synathropic vegetation) show weak negative or no relationships of local species richness or species pool to pH/calcium gradient. These results support the hypothesis ofPärtel (Ecology 83: 2361–2366, 2002) andEwald (Folia Geobot. 38: 357–366, 2003), that the modern calcicole/calcifuge disparity in the species pool of Central European flora has resulted from historical and evolutionary processes that took place on high pH soils. In the Pleistocene, calcareous soils dominated both the dry continental landscapes of Central Europe and glacial refugia of temperate flora, which were mostly situated in southern European mountain ranges with abundant limestone and dolomite. The negative pattern of species richness along the pH/calcium gradient found in reed-bed and tall-sedge vegetation, however, is not consistent with this historical explanation.     

Diversity and Biotic Homogenization of Urban Land-Snail Faunas in Relation to Habitat Types and Macroclimate in 32 Central European Cities

The effects of non-native species invasions on community diversity and biotic homogenization have been described for various taxa in urban environments, but not for land snails. Here we relate the diversity of native and non-native land-snail urban faunas to urban habitat types and macroclimate, and analyse homogenization effects of non-native species across cities and within the main urban habitat types. Land-snail species were recorded in seven 1-ha plots in 32 cities of ten countries of Central Europe and Benelux (224 plots in total). Each plot represented one urban habitat type characterized by different management and a specific disturbance regime. For each plot, we obtained January, July and mean annual temperature and annual precipitation. Snail species were classified into either native or non-native. The effects of habitat type and macroclimate on the number of native and non-native species were analysed using generalized estimating equations; the homogenization effect of non-native species based on the Jaccard similarity index and homogenization index. We recorded 67 native and 20 non-native species. Besides being more numerous, native species also had much higher beta diversity than non-natives. There were significant differences between the studied habitat types in the numbers of native and non-native species, both of which decreased from less to heavily urbanized habitats. Macroclimate was more important for the number of non-native than native species; however in both cases the effect of climate on diversity was overridden by the effect of urban habitat type. This is the first study on urban land snails documenting that non-native land-snail species significantly contribute to homogenization among whole cities, but both the homogenization and diversification effects occur when individual habitat types are compared among cities. This indicates that the spread of non-native snail species may cause biotic homogenization, but it depends on scale and habitat type.     

Estimating the age of fire in the Cape flora of South Africa from an orchid phylogeny

Fire may have been a crucial component in the evolution of the Cape flora of South Africa, a region characterized by outstanding levels of species richness and endemism. However, there is, to date, no critical assessment of the age of the modern fire regime in this biome. Here, we exploit the presence of two obligate post-fire flowering clades in the orchid genus Disa, in conjunction with a robust, well-sampled and dated molecular phylogeny, to estimate the age by which fire must have been present. Our results indicate that summer drought (winter rainfall), the fire regime and the fynbos vegetation are several million years older than currently suggested. Summer drought and the fynbos vegetation are estimated to date back to at least the Early Miocene (ca 19.5 Ma). The current fire regime may have been established during a period of global cooling that followed the mid-Miocene Climatic Optimum (ca 15 Ma), which led to the expansion of open habitats and increased aridification. The first appearance of Disa species in the grassland biome, as well as in the subalpine habitat, is in striking agreement with reliable geological and palaeontological evidence of the age of these ecosystems, thus corroborating the efficacy of our methods. These results change our understanding of the historical mechanisms underlying botanical evolution in southern Africa, and confirm the potential of using molecular phylogenies to date events for which other information is lacking or inconclusive.     

Observations on the Varanasi wall flora

Summary This study deals with the ecology of a man-made habitat, i.e., old walls and buildings of Varanasi, India. The wall flora of Varanasi includes 135 species of angiosperms, 1 species of pteridophyte, 4 species of bryophytes and one lichen. Abundant wall plants likeArthraxon lancifolius, Lindenbergia polyantha, Aristida funiculata and lichens are never seen off the walls. The vegetation of the three types of walls, viz., brick mortar, brick mud and mud walls, classified according to the materials of construction, show sharp differences, despite many common features. Analysis of the wall flora, according to Raunkiaer's life-form system, revealed a marked contrast from the adjoining ground flora in having a very high percentage of therophytes.It is concluded, that the distinctiveness of the wall flora is due to the unique topography, microclimate and xeric nature of the wall habitat. Differences in the physico-chemical nature of the three types of walls are responsible for the variation in their vegetation.     

Factors affecting the diversity of flora and vegetation in central European settlements

Published data on the number of plant species and/or communities were gathered for 77 European cities and 85 villages. The relationships between the floristic and vegetation diversity and some environmental variables were analysed. Species number in cities showed log linear increase with city size (expressed as the population size or city area). A linear increase in the species number with size was found in the village flora. The richness of both city and village flora was not significantly related to any climatic variable. On the contrary, the number of communities in both villages and cities was correlated not only with settlement size but also with altitude and mean annual temperature. The diversity of village vegetation was closely related to the climax type of the respective region. The features of human settlements that make it possible to consider them as landscape islands are discussed.     

Habitat size, flora, and fauna: Interactions in a tidal saltwater marsh

Anthropogenic habitat fragmentation is increasingly problematic in both terrestrial and aquatic systems. Fragmentation reduces the size of habitat patches, so examining the effect of patch size on community structure can provide insight into the potential effects of fragmentation. In this study, we examined the effect of habitat size on the density of Spartina alterniflora shoots in tidal saltwater marshes, as well as on the two predominant macrofaunal species, the marsh periwinkle Littoraria irrorata and fiddler crabs Uca spp. We estimated the density of shoots in three different marsh habitats, (1) large island marshes, (2) small island marshes, and (3) large fringing marshes, in Indian Field Creek, York River, Chesapeake Bay. We manipulated shoot density in each of the marsh types to distinguish between the effects of marsh grass density and marsh type on crab and Littoraria densities in the system. We found significant differences in grass density among the three marsh types as well as significant species-specific effects of grass density, marsh type, and distance from edge on faunal abundance. Decreasing the shoot density resulted in a decrease in Littoraria density in the large marshes. Littoraria density increased with distance from edge in the small marshes and in the first 5 m of the fringing marshes, then decreased with distance from edge after 5 m in the fringing marshes. Shoot density had a negative effect on crabs in both the large and small marshes. These results suggest that fragmentation would have a negative effect on the community structure by lowering the densities of both the flora and fauna.     

Evaluating the use of pairwise dissimilarity metrics in paleoanthropology

Questions of alpha taxonomy are best addressed by comparing unknown specimens to samples of the taxa to which they might belong. However, analysis of the hominin fossil record is riddled with methods that claim to evaluate whether pairs of individual fossils belong to the same species. Two such methods, log se_m and the related STET method, have been introduced and used in studies of fossil hominins. Both methods attempt to quantify morphological dissimilarity for a pair of fossils and then evaluate a null hypothesis of conspecificity using the assumption that pairs of fossils that fall beneath a predefined dissimilarity threshold are likely to belong to the same species, whereas pairs of fossils above that threshold are likely to belong to different species. In this contribution, we address (1) whether these particular methods do what they claim to do, and (2) whether such approaches can ever reliably address the question of conspecificity. We show that log se_m and STET do not reliably measure deviations from shape similarity, and that values of these measures for any pair of fossils are highly dependent upon the number of variables compared. To address these issues we develop a measure of shape dissimilarity, the Standard Deviation of Logged Ratios (s_LR). We suggest that while pairwise dissimilarity metrics that accurately measure deviations from isometry (e.g., s_LR) may be useful for addressing some questions that relate to morphological variation, no pairwise method can reliably answer the question of whether two fossils are conspecific.     

Spatial aspects of trait homogenization within the German flora

Aim Biotic homogenization, the replacement of local biota by non‐indigenous and locally expanding species, is among the major effects of species invasions. Almost all studies related to this topic are focused on the species level, on taxonomic homogenization. Homogenization effects on trait diversity (functional homogenization) may be very important for ecosystem functioning, but they are rarely analysed, especially not at different spatial scales within a single study. This paper aims to examine how the presence of alien species (species introduced since 1500 ad ) affects the distribution of ploidy levels in the German flora at different spatial scales. Location Germany. Methods We used a resampling method and the Morisita–Horn dissimilarity index to calculate dissimilarities of ploidy level within and between alien and indigenous plants at three different spatial scales in Germany: (1) the entire country as one location, (2) between grid cells, and (3) within grid cells of a lattice covering Germany. Results We found a significant differentiation effect within grid cells of c. 130 km², with alien plants increasing the variability of ploidy levels. The differentiation effect varies according to the scale used. At the coarsest scale (entire Germany), ploidy levels of alien plants tend to be more homogeneous in composition compared with those of native plants. At the intermediate scale (between grid cells), and even more pronounced at a small scale (within grid cells), ploidy levels are more heterogeneously distributed across Germany than those of native plant species. Main conclusions Homogenization of ploidy levels at a large scale (entire Germany) and differentiation at a small scale (within grid cells) is comparable with the patterns found in taxonomic homogenization analyses. This analysis is a first step towards understanding the impacts of plant invasions on a trait level. Differentiation and homogenization of ploidy levels might mirror the distribution of related ecological traits and therefore might have an impact on ecosystem functioning.     

The non-native vascular flora of the Falkland Islands

Summary

Non-native species form a significant, but under-recorded, component of the Falkland Islands vascular flora. With this in mind a comprehensive re vie w of the non-native flora of the Falkland Islands was undertaken for the first time since the publication of the definitive Flora in 1968. We have recorded 175 non-native taxa, from 46 families, from the Falkland Islands which are listed with accompanying notes on habitat, status and distribution. Twenty-nine of these are likely to be commonly encountered, though only Aira praecox, Cerastium fontanum, Rumex acetosella and Sagina procumbens are near ubiquitous throughout. The origins of much of the non-native flora are obscure, however most species seem to be of European descent, and a significant proportion of taxa seem to have become established after introductions for agricultural and horticultural purposes.     

The influence of habitat on the spatial variation in fish assemblage composition in an unimpacted tropical River of Ganga basin, India

Effects of local habitat variables on the structure of fish assemblage were evaluated from 50 sampling sites in a tropical River of Central India of the Ganges basin with limited anthropogenic disturbance covering premonsoon, monsoon and postmonsoon periods. Data were analyzed for 5,186 fish individuals of 24 freshwater fish species of conservation and fishery management interest. Out of the total fish species, seven belong to the ??endangered?? and 8 belong to the vulnerable category. A Cyprinid, Puntius sarana, was the most widely distributed species (frequency of occurrence 76%) out of the total species in this study. We used canonical correspondence analyses to determine the influence of environmental conditions on species occurrences and assemblage characteristics. Regarding the microhabitat, hydromorphological parameters (depth and current velocity) followed by temperature, turbidity and total dissolve solid were of significant for the structure of the fish community. Conductivity was another important factor that explained the major proportion of the variability affecting fish in their habitat choice. The other local habitat variables like overhanging vegetation and land use were of secondary but significantly important for the assemblage of the fishes. Our results suggests the importance of local environment influences on the fishes of conservation importance and their assemblage characteristics in an unimpacted river and provide a framework and reference conditions to support restoration efforts of relatively altered fish habitats in tropical rivers of India.     

乌鲁木齐地区典型灌木群落结构特征及其多样性研究

根据2013年对乌鲁木齐地区典型灌木群落野外50个样地调查的数据,结合双向指示种分析分类方法,从各群落基本特征、物种组成、区系特征、物种多样性等方面对乌鲁木齐地区典型灌木群落结构特征及其多样性进行了分析。结果表明:(1)被调查的50个样地灌木植被群落中共出现了169种植物(其中灌木植物36种,草本植物133种),隶属于118属,31科,其中以藜科、菊科、禾本科等干旱区的表征科居多。灌木物种的植物区系以地中海区、西亚至中亚分布和北温带分布为主。(2)采用TWINSPAN分类方法可将50个样方划分为10个灌木群落类型。乌鲁木齐地区典型灌木群落多样性指数偏低,黑果小檗+宽刺蔷薇+金丝桃叶绣线菊群落的多样性指数最大,群落之间水平差异显著;欧亚圆柏群落、宽刺蔷薇+矮锦鸡儿群落和铃铛刺+喀什菊群落次之;多枝柽柳群落和琵琶柴+喀什霸王群落最低。(3)属于灌丛植被类型的灌木群落,物种多样性指数为草本层灌木层;属于荒漠植被类型的灌木群落,物种多样性空间结构为灌木层草本层。     

Determinants of native and alien species richness in the urban flora of Rome

Until now, analytical studies on European urban floras have mostly concentrated on the central and north‐western parts of the continent. In this paper, factors determining species richness of urban flora were studied for the city of Rome, Italy, based on a comprehensive floristic survey carried out between 1985 and 1994, and updated in 2005. All species were recorded in grid cells of 1.6 km² and classified into native and alien (the latter divided into archaeophytes and neophytes). The grids were classified with respect to the prevailing habitat type, area available to vegetation, level of disturbance and geographical position within the city. Data were analysed using minimal adequate models. Total species number was determined by habitat and its interaction with position on the north‐west gradient; other variables explained much less variance. Holding other variables constant, the average species number per grid cell was highest in archaeological sites and parks, followed by woodlands and rivers, and grasslands and recent developments. Residential areas and the historical centre were poorest in species number. Towards the north of the city, species richness in corresponding habitats increases because of higher landscape heterogeneity and closer association with diaspore pools in the surroundings. Native species make up on average 84% of the total species numbers, and trends opposite to those for the total number of species were found for the proportional representation of aliens. The occurrence of alien and native species in the flora of Rome is driven by similar factors, but factors that increase representation of aliens decrease that of natives and vice versa. The representation of neophytes and native species in grid cells was easier to explain (74% of variation accounted for) than that of archaeophytes (27%); this result reflects that in terms of ecology and response to factors, archaeophytes take an intermediate position between native plants and neophytes. Proportional representation of neophytes decreased with increasing area available to vegetation, reflecting that semi‐natural vegetation is better developed where less fragmented.     

Microhabitat mosaics are key to the survival of an endangered ground beetle (<Emphasis Type="Italic">Carabus nitens</Emphasis>) in its post-industrial refugia

Biota dependant on early seral stages or frequently disturbed habitats belong to the most rapidly declining components of European biodiversity. This is also the case for Carabus nitens, which is threatened across Western and Central Europe. We studied one of the last remaining populations of this ground beetle in the Czech Republic, which inhabits post-extraction peat bogs. In line with findings from previous studies, we show that C. nitens prefers patches characterized by higher light intensity and lower vegetation cover. Abundance of females was positively correlated with the cover of plant species requiring higher temperature. In addition, we demonstrate its preference for periodically moist, but not wet or inundated plots, suggesting that the transition between dry heathland and wet peat bog might be the optimal habitat for this species. This hypothesis is further supported by results showing a positive correlation between the abundance of C. nitens and vegetation cover comprising of a mix of species typical for heathland, peat bog, and boreal habitats. Our results show that C. nitens mobility is comparable to other large wingless carabids. The maximum covered distance was ~?500 m in a month. To ensure the survival of this population, sites of recent peat extraction should be spared from reclamation and afforestation. In contrast, active measures should be taken to facilitate nutrient removal, disturbance of vegetation cover, and the creation of depressions with a humid microclimate. These actions will create a mosaic of heath, bog, and bare ground, which seems to be the preferred habitat of C. nitens at our study site.     

Lost and found: Short-term dynamics of the flora on 100 small islands in the White Sea

The aim was to uncover factors that influence short-term (decade) flora dynamics and species richness of northern marine islets characterized by poor flora and weak anthropogenic pressure. The study used presence–absence data of vascular plant species on 100 small uprising islets of the Kandalaksha Gulf of White Sea (Northern Karelia, Russia). We investigated the influence of islands' attributes on species richness and rates of flora dynamics. Two island types were analyzed separately: younger, stone-like and older, islet-like (which generally are larger and have higher diversity of habitats). Sampled islands were studied via classical biogeographical per island approach and metapopulation per species approach. Stone-like islands had noticeably poorer flora with higher rates of immigration and extinction when compared to those of islet-like islands. The species number for islet-like islands correlated positively with number of habitats, abundance of different habitat types and island area. Species richness of stone-like islands correlated positively only with number of habitat types. Plant species associated with birds, crowberry thickets and coastal rocks were the most stable, and the species of disturbed habitats were significantly less stable. Floristic changes that have occurred have been caused by the massive establishment of new species rather than the extinction of pre-existing taxa. Thus, most of these islands are still in the colonization (assortative) stage. While we found no relationship between island area and species number for stone-like islands, this relationship was seen on islet-like islands.     

Amphibians distribution and habitats in the southwestern region of Saudi Arabia

This study surveyed 205 wetland sites in the Southwestern Saudi Arabia. We found seven species of amphibians (Anura), which belong to four families: Bufonidae; which includes four species, Sclerophrys tihamica; S. Arabica, Duttaphrynus dhufarensis, and Bufotes viridis; Hylidae, represented by only one species, the tree frog Hyla savignyi; Ranidae, which represented by one species, Pelophylax ridibundus and finally the Dicroglossidae, represented by one species, Euphlyctis ehrenbergii. The reasonable amount of rain received in southwest Arabia, and habitat diversity contribute to the relative abundance of amphibians in the region. Five types of wetland habitats were found in the study area. Valley streams, irrigated farms, seasonal ponds, dam reservoir and lagoons of treated sewage water. The current study revealed the wide spread of amphibians in southwestern Saudi Arabia than what had been reported earlier and confirmed the presence of the Bufotes viridis at three new sites in Asir Heights. It also showed the wide spread of S. arabica in all types of habitats in the southwestern region of Saudi Arabia. Habitat degradation was evident in the region, which might lead to species loss.     

Pollen morphology of the shrub and arboreal flora of mangroves of Northeastern Brazil

The Brazilian coast, especially in the Northeastern one, possesses a vast area of mangrove which acts as the interface that links terrestrial ecosystems and estuaries. After an inventory of the shrub and tree species present in the mangroves of Northeastern Brazil, polliniferous material was collected for morphological study of the pollen grains, which were acetolysed, measured and analyzed using light and scanning electron microscopy. Fourteen species belonging to seven families were grouped as restricted and peripheral, according to their position into the mangrove vegetation. The restricted species are six: Avicennia germinans and A. schaueriana (Avicenniaceae), Rhizophora harrisonii, R. mangle and R. racemosa (Rhizophoraceae), Laguncularia racemosa (Combretaceae). The peripheral species are eight: Annona glabra (Annonaceae), Conocarpus erectus (Combretaceae), Dalbergia ecastophyllum, Inga subnuda, Sophora tomentosa (Leguminosae), Hibiscus pernambucensis, H. tiliaceus (Malvaceae) and Suriana maritima (Surianaceae). All species had their pollen grains described and illustrated in that first atlas of the pollen flora of the Brazilian mangroves.     

Hamiguitan Range: A sanctuary for native flora

Hamiguitan Range is one of the wildlife sanctuaries in the Philippines having unique biodiversity resources that are at risk due to forest degradation and conversion of forested land to agriculture, shifting cultivation, and over-collection. Thus, it is the main concern of this research to identify and assess the endemic and endangered flora of Hamiguitan Range. Field reconnaissance and transect walk showed five vegetation types namely: agro-ecosystem, dipterocarp, montane, typical mossy and mossy-pygmy forests. Inventory of plant species revealed 163 endemic species, 35 threatened species, and 33 rare species. Assessment of plants also showed seven species as new record in Mindanao and one species as new record in the Philippines. Noteworthy is the discovery of Nepenthes micramphora, a new species of pitcher plant found in the high altitudes of Hamiguitan Range. This species is also considered site endemic, rare, and threatened. The result of the study also showed that the five vegetation types of Mt. Hamiguitan harbor a number of endangered, endemic, and rare species of plants. Thus, the result of this study would serve as basis for the formulation of policies for the protection and conservation of these species and their habitats before these plants become extinct.     

Sandpits provide critical refuge for bees and wasps (Hymenoptera: Apocrita)

Evidence-based conservation allows the evaluation of both the collateral benefits and the drawbacks of a wide range of human activities, like quarrying. In this study, the community structure of bees and wasps (Hymenoptera:Apocrita) in Central European sandpits was investigated, focusing on the changes caused by quarrying cessation and technical reclamation, as well as on the changes caused by spontaneous succession leading to the increased availability of food resources but also to the loss of the number and size of available bare sand patches. The bees and wasps demonstrated an exceptional ability to colonize the newly emerging sand quarrying areas, and to survive in them unless these were quarried as intensively as to not allow the development of any early successional vegetation. Both active and closed sandpits were found to serve as important regional refuges for the persistence of many rare species. In total, 221 species were detected, 53 of those were red-listed, with two species thought to be regionally extinct. Typically, active quarrying was associated with the presence of Bembecinus tridens, Halictus subauratus, H. maculatus, and Andrena nigroaenea. The list of the species of conservation interest is provided, and so is the detailed analysis of the life-history traits of the species in relation to the presence of bare sand patches, vegetation cover, quarrying intensity, and time elapsed since the formation of each artificial habitat patch. Sandpits as refuges for xerothermophilous and psammophilous hymenopterans are usually completely and irreversibly lost if the current legislature enforcing the technical reclamation over spontaneous or assisted succession is applied in all or most of the post-mining areas.