The impact of urban development on butterflies within a city region

The effect of urban development on butterfly species' richness and species' incidence is tested for the Greater Manchester conurbation and two sample areas, mapped at finer scales, within the southern part of the conurbation. The tests include measures of bias for recording effort (number of visits). Species' richness is found to increase with percentage urban cover for Greater Manchester (tetrad scale) and decrease with urban cover for the two sample areas in South West Manchester (1 km scale) and the Mersey Valley (100 m scale). For Greater Manchester, the increase in species' richness with increased urban cover is largely explained by lower species' richness at higher altitude in the Pennines bounding the conurbation. For the two sample areas, decreasing species' richness associated with increasing urban cover corresponds with reductions in the areas of a number of semi-natural habitats, hostplants and nectar sources. Despite these statistically significant correlations, the impact of urban cover on species' richness is weak. The maximum loss rate identified anywhere within the region is 0.81 species per 10% change in urban cover for South West Manchester. This finding may reflect on the generally low species diversity of the region. However, these results could be influenced by recording and sampling artefacts, particularly the failure of mapping programmes to distinguish vagrant individuals from breeding populations and a bias of records to vagrants. This is supported by the higher correlations between species' incidence and nectar sources than between species' incidence and their hostplants. Adult butterflies are opportunistic nectar users and nectar sources are more widely spread and thus less influenced by urban development than are specific butterfly hostplants. The finding may also reflect on the capacity of most of the butterfly species to breed successfully on tiny areas of hostplant existing within extensively built-up areas. Moreover, the capacity of butterfly species to persist by using small fragments of hostplants would be enhanced by vagrancy. If this is indeed the case, it is a finding that would support the value of small patches in butterfly metapopulations, albeit ones comprising incomplete complements of resources required during the life cycle. The incidence of most species decreases with increase in urban cover. Multivariate analyses indicate that this is owing to corresponding declines in hostplant-habitats and nectar sources. Five species increase with urban cover, but none attain formal significance. Associations among hostplants and habitat variables in a principal components analysis suggest that, in three cases (Pieris brassicae, P. rapae, Celastrina argiolus), this is owing to increasing areas of their hostplants within urban environments.     

Targeting squares for survey: predicting species richness and incidence of species for a butterfly atlas

1. Predictions on species richness and incidence of species are made using data for three scales of mapping from the Greater Manchester butterfly atlas; for the whole of the conurbation (2 km×2 km scale) and for two sample areas centred on the Mersey Valley (1 km×1 km scale; 1 ha scale). Predictions are based on data for recording effort, altitude, biotopes, host-plants and nectar resources. 2. Data for Greater Manchester indicate that substantial shortfalls may occur in recording butterfly species for atlases despite the fact that butterflies are generally easily identified and well supported with recorders. Shortfalls tend to be larger for species with fewer records, indicating that some species may be more easily overlooked than others. 3. The results demonstrate that targeting squares for re-survey is necessary and feasible. The predictions have other valuable research applications, the most important of which is being able to assess the accuracy of distribution maps, to correct them, and to make projections of distribution changes. 4. Predictions may be enhanced by improvements to mapping in three ways: (i) Collecting data on recording effort. Variation in recording effort typically accounts for differences in species richness and incidence of species more than any other variable; (ii) Collecting data on biotopes and specific resources. The present results are promising and demonstrate that the collection of environmental data linked to a suitable sampling frame could facilitate knowledge of the distribution of species over extensive areas that remain under-recorded; and (iii) Distinguishing between breeding individuals and vagrants. Vagrancy is a problem associated both with species and scale. Although species vary substantially in their capacity to migrate beyond their habitats, the effect of vagrancy on distribution maps becomes an increasingly large problem as the grain of mapping (size of recording units) decreases. It is suggested that over-recording can be a problem, particularly when mapping is fine-grained.     

The remnants of restinga habitats in the brazilian Atlantic Forest of Rio de Janeiro state, Brazil: habitat loss and risk of disappearance.

"Restingas" (herbaceous/shrubby coastal sand-dune habitats) used to cover most of Rio de Janeiro State coast, and have suffered extensive degradation over the last five centuries. Using satellite images and field work, we identified the remaining restingas in the State, recording the factors that might cause their degradation. We used two mosaics of Landsat 7 scenes (spatial resolution 15 and 30 m) to map and evaluate preliminarly the remaining areas and conservation status. Each remnant area was checked in the field, degraded areas within it were mapped and subtracted from the remnants. We identified 21 restinga remnants totalling 105,285 ha. The largest and smallest restinga remnants were Jurubatiba (25,141 ha) and Itaipu (23 ha), respectively. We identified 14 causes of degradation. The most important were vegetation removal for housing developments, establishment of exotic plant species, change of original substrate, and selective removal of species of economic importance for the horticultural industry. All restingas had disturbed parts under strong pressure due to human activities. Due to intense habitat loss, and occurrence of endemic/threatened vertebrate species in restinga habitats, we strongly indicate the implementation of new conservation units to protect these fragile remnants. This habitat is steadily decreasing and most remnants lack legal protection. Therefore, under the current human pressure most of this unique habitat is likely to be lost from the State within the next few years.     

Measurement and mapping of avian diversity in southern Africa: implications for conservation planning

The potential and problems of using species diversity information, derived from the Southern African Bird Atlas Project (SABAP), are examined. Atlas data were analysed and the problem of uneven sampling effort was ameliorated through an application of an index of diversity. Maps of diversity for various suites of species are considered in relation to their implications for conservation planning. An approach to the identification of high-priority areas for conservation, based on an index of diversity, is described and called the Compatible Sets Approach. Birds in the grassland biome are used to illustrate the principles of the approach.     

The second Southern African Bird Atlas Project: Causes and consequences of geographical sampling bias

Using the Southern African Bird Atlas Project (SABAP2) as a case study, we examine the possible determinants of spatial bias in volunteer sampling effort and how well such biased data represent environmental gradients across the area covered by the atlas. For each province in South Africa, we used generalized linear mixed models to determine the combination of variables that explain spatial variation in sampling effort (number of visits per 5′ × 5′ grid cell, or “pentad”). The explanatory variables were distance to major road and exceptional birding locations or “sampling hubs,” percentage cover of protected, urban, and cultivated area, and the climate variables mean annual precipitation, winter temperatures, and summer temperatures. Further, we used the climate variables and plant biomes to define subsets of pentads representing environmental zones across South Africa, Lesotho, and Swaziland. For each environmental zone, we quantified sampling intensity, and we assessed sampling completeness with species accumulation curves fitted to the asymptotic Lomolino model. Sampling effort was highest close to sampling hubs, major roads, urban areas, and protected areas. Cultivated area and the climate variables were less important. Further, environmental zones were not evenly represented by current data and the zones varied in the amount of sampling required representing the species that are present. SABAP2 volunteers' preferences in birding locations cause spatial bias in the dataset that should be taken into account when analyzing these data. Large parts of South Africa remain underrepresented, which may restrict the kind of ecological questions that may be addressed. However, sampling bias may be improved by directing volunteers toward undersampled regions while taking into account volunteer preferences.     

Spatially-Explicit Estimation of Geographical Representation in Large-Scale Species Distribution Datasets

Much ecological research relies on existing multispecies distribution datasets. Such datasets, however, can vary considerably in quality, extent, resolution or taxonomic coverage. We provide a framework for a spatially-explicit evaluation of geographical representation within large-scale species distribution datasets, using the comparison of an occurrence atlas with a range atlas dataset as a working example. Specifically, we compared occurrence maps for 3773 taxa from the widely-used Atlas Florae Europaeae (AFE) with digitised range maps for 2049 taxa of the lesser-known Atlas of North European Vascular Plants. We calculated the level of agreement at a 50-km spatial resolution using average latitudinal and longitudinal species range, and area of occupancy. Agreement in species distribution was calculated and mapped using Jaccard similarity index and a reduced major axis (RMA) regression analysis of species richness between the entire atlases (5221 taxa in total) and between co-occurring species (601 taxa). We found no difference in distribution ranges or in the area of occupancy frequency distribution, indicating that atlases were sufficiently overlapping for a valid comparison. The similarity index map showed high levels of agreement for central, western, and northern Europe. The RMA regression confirmed that geographical representation of AFE was low in areas with a sparse data recording history (e.g., Russia, Belarus and the Ukraine). For co-occurring species in south-eastern Europe, however, the Atlas of North European Vascular Plants showed remarkably higher richness estimations. Geographical representation of atlas data can be much more heterogeneous than often assumed. Level of agreement between datasets can be used to evaluate geographical representation within datasets. Merging atlases into a single dataset is worthwhile in spite of methodological differences, and helps to fill gaps in our knowledge of species distribution ranges. Species distribution dataset mergers, such as the one exemplified here, can serve as a baseline towards comprehensive species distribution datasets.     

Ecological correlates of local extinction and colonisation in the British ladybird beetles (Coleoptera: Coccinellidae)

Five main drivers of population declines have been identified: climate change, habitat degradation, invasive alien species (IAS), overexploitation and pollution. Each of these drivers interacts with the others, and also with the intrinsic traits of individual species, to determine species’ distribution and range dynamics. We explored the relative importance of life-history and resource-use traits, climate, habitat, and the IAS Harmonia axyridis in driving local extinction and colonisation dynamics across 25 ladybird species (Coleoptera: Coccinellidae).Species were classified as continually present, continually absent, extinct, or colonising in each of 4,642 1-km² grid squares. The spatial distribution of local extinction and colonisation events (in the grid squares) across all species’ ranges were related to ecological traits, overlap with H. axyridis, climate, and habitat factors within generalised linear models (GLMs). GLMs were also used to relate species’ traits, range characteristics, and niche overlap with H. axyridis to extinction and colonisation rates summarised at the species level. Bayesian model averaging was used to account for model uncertainty, and produce reduced sets of models which were well-supported by data. Species with a high degree of niche overlap with H. axyridis suffered higher extinction rates in both analyses, while at the spatial scale extinctions were more likely and colonisations less likely in areas with a high proportion of urban land cover. In the spatial analysis, polymorphic species with large range sizes were more likely to colonise and less likely to go extinct, and sunny grid squares were more likely to be colonised. Large, multivoltine species and rainy grid squares were less likely to colonise or be colonised. In conclusion for ladybirds, extinction and colonisation dynamics are influenced by several factors. The only factor that both increased the local extinction likelihood and reduced colonisation likelihood was urban land cover, while ecological overlap with H. axyridis greatly increased extinction rates. Continued spread of H. axyridis is likely to adversely affect native species and urban areas may be particularly vulnerable.     

南京城市绿地地被植物应用的现状与建议

通过对南京城市公园、广场、道路、居民区、单位附属绿地等绿地地被植物种类及其应用的调查,表明地被植物在南京城市绿地的应用已得到重视,已用地被植物种类较为丰富,目前应用地被植物178种,隶属62科125属;分析了南京市应用地被植物存在的问题,提出了在南京城市绿地进一步科学应用地被植物的建议.     

Progressive bias in species status is symptomatic of fine-grained mapping units subject to repeated sampling

Atlas maps of butterflies invariably fail to distinguish the status of records, that is, whether they are observations of breeding populations or vagrant individuals. Yet, for conservation purposes, it is clearly important to know whether records relate to breeding populations in suitable habitats or not. The high mobility of butterfly adults carries two expectations. First, vagrants will frequently be recorded within grid squares, particularly when mapping is fine grained. Second, the frequency of vagrants is likely to be higher in mapping units comprising biotopes with few butterfly habitats, than in those rich in butterfly habitats, if only because there is a greater regional pool of potential vagrants for biotopes depleted in butterfly habitats. It follows that with repeated sampling of squares or biotopes differences in species breeding status will be cumulative between those rich and poor in butterfly habitats. In this paper, these predictions have been tested using data from 30, 1 ha grid squares on Alderley Edge Site of Special Scientific Interest (SSSI) (UK), half of which are in woodland (few butterfly habitats) and half with open habitats (non-woodland; rich in butterfly habitats). Butterflies have been recorded during 38 visits over 4 years. Within squares, vagrants have been distinguished from breeding species on the basis of the presence of larval hostplants and other suitable resources for seasonal maintenance. Owing to the occurrence of vagrants, number of breeding species was found to be significantly fewer than total species in mapping units. Vagrants were found to be significantly more abundant in woodland squares, which contain few species larval hostplants, than in squares dominated by open biotopes with many species larval hostplants. Repeated sampling resulted in a cumulative increase in the frequency of vagrant species. Furthermore, the relative frequency of vagrants increased at a greater rate in woodland squares compared to non-woodland squares. Suggestions are made as to how recording for atlases may be improved.     

How reliable are our vegetation analyses?

Abstract. Two sets of 40 relevés, made independently by two observers on the same 5m x 5m sample plots, were compared to estimate the sampling error and to assess the effect of this sampling error on (1) estimates of species richness and diversity (2) results of multivariate analyses, and (3) estimation of species turnover in repeated sampling. The relevés were made according to the standard Braun-Blanquet method. The sampling error was estimated for (1) recording of species in sample plots and (2) visual estimation of the degree of cover (or of the general population size). Despite the fact that the sample plots were searched thoroughly for 30 - 40 min, the number of overlooked species was high with a discrepancy of 13% between corresponding relevés. Regarding multivariate analysis, the error caused by missing species was at least as important as the error in visual estimation of species cover. The estimates of degree of cover using the Braun-Blanquet scale are sufficiently reliable for use in multivariate analysis when they are subjected to ordinal transformation. When average cover values are used, the patterns detected are based solely on dominants. Species richness and species diversity could be reliably estimated from the relevés, but the estimates of equitability are very unreliable. The classical relevé method remains one of the most efficient survey methods for recognition of vegetation types on the macro-community and landscape scales.     

Effects of urban land cover on the local species pool in Britain

Regression models were used to quantify the relationship between the amount of urban land and composition of local species pools. There was no evidence that urban land cover increases the richness of plant species, based on a survey of 785 2-km squares of which 157 had > 10% urban land cover. However, the number of alien plants is significantly higher in urban areas. Complete urbanization approximately doubles the proportion of alien species, and the proportion of aliens is twice as high in southern Britain as in the north. The flora of urban tetrads consists of ubiquitous native species and introduced species characteristic of waste ground, but woodland species are poorly represented. At the tetrad scale. enhanced dispersal by man is not the main factor for maintaining the urban flora; availability of urban habitats and high levels of disturbance are more important. The planned housing expansion to greenfield sites in Britain will increase the proportion of alien species, yet the majority of native species should persist in urban areas if existing woodland is preserved.     

Bias in Butterfly Distribution Maps: The Effects of Sampling Effort

Data from the Greater Manchester Butterfly Atlas (UK) reveal a highly significant and substantial impact of visits on both species' richness and species' incidence in squares. This effect has been demonstrated for three different zones mapped at different scales. The significant impact of number of visits persists when data are amalgamated for coarser scales. The findings demonstrate that it is essential for distribution mapping projects to record data on recording effort as well as on the target organisms. Suggestions are made as to how distribution mapping may be improved, including a geographically and environmentally representative structure of permanently monitored squares and closer links between distribution mapping and the Butterfly Monitoring Scheme (BMS), which primarily monitors changes in butterfly populations. The benefit to conservation will be data that can be better used to analyse the reasons for changes in ranges and distributions, fundamental for determining priorities and policy decisions.     

Geographic sampling bias in the South African Frog Atlas Project: implications for conservation planning

Quality conservation planning requires quality input data. However, the broad scale sampling strategies typically employed to obtain primary species distribution data are prone to geographic bias in the form of errors of omission. This study provides a quantitative measure of sampling bias to inform accuracy assessment of conservation plans based on the South African Frog Atlas Project. Significantly higher sampling intensity near to cities and roads is likely to result in overstated conservation priority and heightened conservation conflicts in urban areas. Particularly well sampled protected areas will also erroneously appear to contribute highly to amphibian biodiversity targets. Conversely, targeted sampling in the arid northwest and along mountain ranges is needed to ensure that these under-sampled regions are not excluded from conservation plans. The South African Frog Atlas Project offers a reasonably accurate picture of the broad scale west-to-east increase in amphibian richness and abundance, but geographic bias may limit its applicability for fine scale conservation planning. The Global Amphibian Assessment species distribution data offered a less biased alternative, but only at the cost of inflated commission error.     

The impact of giant panda foraging on bamboo dynamics in an isolated environment

Wildlife species are threatened by massive habitat destruction worldwide. Habitat fragmentation and isolation spatially constrain animals and in turn cause non-sustainable rates of animal foraging on plant populations. However, little empirical research has been done in large controlled settings to investigate foraging impacts. We conducted an experiment to characterize the impact of panda foraging on the sustainability of its food resource, bamboo, in an enclosed area of natural habitat (approximately 19 ha). We monitored bamboo density, age, and percent cover throughout the enclosure across a 3-year period. We documented marked declines in bamboo density and percent cover as a result of panda foraging, particularly in younger bamboo age classes. We constructed simultaneous autoregressive models to explain bamboo loss to panda foraging and subsequent bamboo recovery as a function of habitat conditions. Areas with high initial bamboo cover not only were prone to high rates of bamboo percent cover loss but also experienced high rates of subsequent bamboo recovery, as bamboo cover loss opened up the understory for new growth. Variograms of ordinary least squares model residuals revealed that the range of spatial autocorrelation in bamboo loss increased over time as available bamboo forage declined. The results have implications for understanding the impact of animal foraging on vegetation and also highlight the importance of preventing further habitat fragmentation and isolation.     

Do protected areas in urban and rural landscapes differ in species diversity?

Previous studies from Central Europe and North America showed that species richness is higher in urban than in rural landscapes. Do protected areas, which can be found in both city and countryside, reflect this species richness pattern? The impact of urban land-use might reduce conservation success and necessitate special management strategies. We compared species richness and species spatial turnover of selected animal and plant taxa (carabids, butterflies, snails, birds, lichens, mosses, vascular plants) in 30 protected areas in the city of Halle and 56 protected areas in the adjacent rural district of Saalkreis (Central Germany). Species were mapped by experienced biologists within a systematic species inventory. We corrected species numbers for the effects of landscape structure (e.g. size, shape and distance of habitats) which might influence species diversity beyond urbanisation effects. Butterflies, birds and lichens had significantly higher species numbers in the rural protected areas. Species spatial turnover was higher among urban areas than among rural areas or pairs of urban and rural areas for most taxa. Diversity in all taxa depended on the size of a protected area. We discussed these patterns in the context of the general urban-rural species diversity patterns. Our results indicate an increasing isolation of species assemblages with urbanisation and highlight that space for protected areas is even more limited in urban than rural areas. An effective conservation of urban species diversity should include both typical urban and semi-natural habitats to cover the full range of species living in cities.     

Habitat influences on urban avian assemblages

Urbanization is increasing across the globe and there is growing interest in urban ecology and a recognition that developed areas may be important for conservation. We review the factors influencing urban avian assemblages, focusing on habitat type and anthropogenic resource provision, and analyse data from a common bird monitoring scheme to assess some of these issues. The review suggests that (1) local factors are more important than regional ones in determining the species richness of urban avian assemblages, raising the potential for the management of urban sites to deliver conservation; (2) habitat fragmentation frequently influences urban avian assemblages, with the effects of patch size being greater than those of isolation, and (3) urban bird assemblages appear to respond positively to increasing the structural complexity, species richness of woody vegetation and supplementary feeding, and negatively to human disturbance. Data from Britain's Breeding Bird Survey, combined with habitat data obtained from aerial photographs, were used to assess a number of these issues at the resolution of 1‐km squares. Green‐space constituted 45% of these squares, and domestic gardens contributed 50% of this green‐space, though their contribution to large continuous patches of green‐space was negligible. There was no significant positive correlation between the densities of individual species in urban areas and surrounding rural areas. Rural species richness declined with increasing latitude, but urban species richness was not correlated with latitude. This contrast contributes to slightly higher avian species richness in rural squares in Southern England than urban ones. Occupancy and abundance were strongly positively correlated in urban avian assemblages, and some indicator species of conservation concern occurred in few urban areas and at low densities. Such species will require conservation action to be precisely targeted within urban areas. Of the urban indicators of conservation concern, only the House Sparrow Passer domesticus and Common Starling Sturnus vulgaris were more abundant in urban than rural areas. Moreover, the densities of these two species were strongly and positively correlated, indicating that they may be limited by shared resources, such as nest‐sites or supplementary food. There was little evidence that high densities of nest‐predating corvids were associated with reduced densities of their prey species. Species richness and the densities of individual species frequently declined with an increasing number of buildings. Current trends for the densification of many British urban areas are thus likely to be detrimental for many bird species.     

Threat spots and environmental determinants of red-listed plant,butterfly and bird species in boreal agricultural environments

The aims of this study were (1) to examine the geographic distribution of red-listed species of agricultural environments and identify their national threat spots (areas with high diversity of threatened species) in Finland and (2) to determine the main environmental variables related to the richness and occurrence patterns of red-listed species. Atlas data of 21 plant, 17 butterfly and 11 bird species recorded using 10 km grid squares were employed in the study. Generalized additive models (GAMs) were constructed separately for species richness and occurrence of individual species of the three species groups using climate and land cover predictor variables. The predictive accuracy of models, as measured using correlation between the observed and predicted values and AUC statistics, was generally good. Temperature-related variables were the most important determinants of species richness and occurrence of all three taxa. In addition, land cover variables had a strong effect on the distribution of species. Plants and butterflies were positively related to the cover of grasslands and birds to small-scale agricultural mosaic as well as to arable land. Spatial coincidence of threat spots of plants, butterflies and birds was limited, which emphasizes the importance of considering the potentially contrasting environmental requirements of different taxa in conservation planning. Further, it is obvious that the maintenance of various non-crop habitats and heterogeneous agricultural landscapes has an essential role in the preservation of red-listed species of boreal rural environments.     

Capybaras and ticks in the urban areas of Uberlândia,Minas Gerais,Brazil: ecological aspects for the epidemiology of tick-borne diseases

In Brazil capybara, the biggest existing rodent species, and associated tick species, Amblyomma cajennense and Amblyomma dubitatum, are undergoing an unplanned host and parasite population expansion in both urban and rural areas. However, scientific information about such issue, particularly in urban areas, is scanty. Such rodent and ticks are associated in some municipalities, particularly in southeastern Brazil, with the transmission of the highly lethal Rickettsia rickettsia caused spotted-fever. In this study ecological aspects related to the establishment and expansion of capybaras and ticks in urban areas of Uberlandia, Minas Gerais State, Brazil were evaluated. For this purpose, capybara and tick abundance in four urban areas and an ecological reserve was determined. Abundance of capybaras varied between areas and over the sampling period and these differences were related to human activities. A positive correlation was found between capybara and tick abundance, however, the tick species had an uneven distribution within the municipality and environmental factors rather than host availability were blamed for such. On the whole these observations show that capybara populations in urban areas are associated to high environmental infestation of ticks and the increased risk of bites and of pathogen transmission to humans. At the same time the uneven distribution of tick species might implicate in an unequal risk of tick-borne diseases within the same urban area.     

Bias in Butterfly Distribution Maps: The Influence of Hot Spots and Recorder's Home Range

We use data from the Mersey Valley zone (3×2km area; N = 600Iha squares) of the Greater Manchester butterfly atlas to investigate whether recorder visits are biased by access (viz. distance from recorder's home base) and by the locations of potential hot spots. In a multiple regression analysis, visits were found to correlate significantly both with distance from home base of the recorder and with the mean and maximum number of species found in squares. Sites close to the home base of the recorder were visited more frequently than those further afield and squares with more species were visited more frequently than those squares with fewer species. Visits were also made significantly more frequently to squares with greater numbers of butterfly resources (e.g. hostplants, nectar). Furthermore, recording is biased to and away from distinct land uses, which vary significantly in species richness. Reasons are given why these biases are to be expected at all scales. The message is that future distribution mapping should be based on rigorous sampling approaches.     

Urban plant ecology patterns and processes: a case study of the flora of the City of Plymouth, Devon, U. K.

Aim Using a large database that has been created over the past 5 years with the RECORDER package, presence/absence data for 829 species of vascular plants in the 103 1-km² squares that cover the city of Plymouth (pop. 243,373) have been analysed by two-way indicator species analysis (TWINSPAN ) and canonical correspondence analysis (CCA) to establish the major species assemblages and to examine their spatial distribution across the city in relation to variation in land use. Location The City of Plymouth. Methods Nine groupings of squares emerged and their distribution was mapped across the city. Interpretation of those groups and their variation in relation to the land use ordination axes showed that TWINSPAN groups lying along the first axis of variation correlated floristic variation with the process of urban development and the historical evolution of urban structure. The second axis appeared to be related to particular remnant semi-natural habitats within the city that could be regarded as ‘hot-spots’ for survival of many plant species. Species were categorized into four types on the basis of their recency and mode of arrival in the city and by using the historical flora of Plymouth produced by T. R. Archer-Briggs in 1880. Variations in the sources of species in relation to the TWINSPAN classification groups were then examined. A second ordination was also computed; this time with geological, altitudinal and distance variables. TWINSPAN groups were then superimposed on the ordinations using polygons to assist with biogeographical interpretation. Results and conclusions The results of both the multivariate analyses and distribution of species by source are then discussed in the context of previous research into urban plant ecology, particularly in Central Europe. The problems of inferring process from pattern in this meso-scale study are reviewed and suggestions are made for further research into urban ecology and biogeography in the city.