Current distribution and potential extent of the most invasive alien plant species on La Réunion (Indian Ocean,Mascarene islands)

Abstract La Réunion Island has the largest area of intact vegetation of the islands in the Mascarene archipelago. Biological invasions are the primary threat to biodiversity in the intact habitats of the island (those not already transformed by agriculture and urbanization). Our study aimed to identify areas to prioritize in managing invasive alien plants for biodiversity conservation. We used extensive surveys of 238 distinct untransformed areas on La Réunion to define the current distribution patterns of all invasive species. Using expert knowledge, we compiled maps of the current distribution of the 46 most widespread/important invasive plants at the habitat scale (identified according to vegetation structure). Data from 440 botanical relevés for the 20 most threatening invasive alien plant species across the island and climatic envelope models were used to derive climatic suitability surfaces; these were used to map potential distributions for these species. More than 10 species invade 16.7% of the remaining habitat. Five habitat types are invaded by 25 or more species, and eight have fewer than 10 invasive alien plant species. Cluster analysis based on presence/absence of species in the 18 habitat types produced eight groups of species that invade particular habitats. Potential distribution models show that some species have invaded large parts of their potential range (e.g. Fuchsia magellanica, Furcraea foetida, Hiptage benghalensis), whereas others have the potential to increase their range substantially (e.g. Clidemia hirta, Strobilanthes hamiltonianus, Ulex europaeus). Management implications are identified for both groups. Three broad groups of habitats were identified: (i) intact habitats with a low level of invasion (e.g. subalpine shrubland); (ii) moderately invaded habitats with varying levels of intactness (ranging from windward submountain rainforest to the Acacia heterophylla forest); and (iii) habitats with little remaining intact area and high levels of invasion (e.g. lowland rainforest). Different management interventions are appropriate for these three groups.     

黄河干流河岸带植物群落特征及其影响因子分析

作为河岸带生态系统的关键组成部分,河岸带植被为许多动植物提供了栖息地以及迁徙或扩散的廊道,并对非点源污染物有着缓冲和过滤作用。黄河是我国湿地的重要组成部分,也是生物多样性分布的关键地带。但是,目前黄河水资源的过度利用如农业灌溉和干流拦河水利工程的兴建在很大程度上改变了原有的水文情势,对河岸带植被发育带来了不利影响。另外,黄河两岸的加固硬化进一步破坏了河岸带植物的生存环境。然而,过去对于黄河河岸带植被仅有对个别河段的调查。为了解目前黄河河岸带植被现状,于2008年4-6月及2008年9-10月对黄河干流河岸带植被进行了两次系统调查,以期为黄河河岸带植被多样性的保护、河岸带的开发管理提供理论支持。对群落的物种组成、多样性进行了分析,并采用双向指示种分析法对黄河干流河岸带植被进行了数量分类。共采集到木本和草本植物169种,隶属于37科124属。区系分析表明黄河干流河岸带植被区系地理成分多样。空间分布方面,中游河段草本植物无论在种类数、密度、生物量上都较上游和下游河段丰富。TWINSPAN将植被划分为17个群落,论述了各群落的特征。环境分析表明,影响黄河干流河岸带植被空间分布的主要生态因子是海拔、年均气温、年均降雨量、年均径流量和平均最大流速。       

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

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

Contrasting habitat use of morphologically similar bat species with differing conservation status in south‐eastern Australia

The east‐coast free‐tailed bat Mormopterus norfolkensis Gray, 1839 is a threatened insectivorous bat that is poorly known and as such conservation management strategies are only broadly prescribed. Insectivorous bats that use human‐modified landscapes are often adapted to foraging in open microhabitats. However, few studies have explored whether open‐adapted bats select landscapes with more of these microhabitat features. We compared three morphologically similar and sympatric, molossid bats (genus Mormopterus) with different conservation status in terms of their association with vegetation, climate, landform and land‐use attributes at landscape and local habitat element scales. We predicted that these species would use similar landscape types, with semi‐cleared and low density urban landscapes used more than forested and heavily cleared landscapes. Additionally, we explored which environmental variables best explained the occurrence of each species by constructing post‐hoc models and habitat suitability maps. Contrary to predictions, we found that the three species varied in their habitat use with no one landscape type used more extensively than other types. Overall, M. norfolkensis was more likely to occur in low‐lying, non‐urban, riparian habitats with little vegetation cover. Mormopterus species 2 occupied similar habitats, but was more tolerant of urban landscapes. In contrast, Mormopterus species 4 occurred more often in cleared than forested landscapes, particularly dry landscapes with little vegetation cover. The extensive use of coastal floodplains by the threatened M. norfolkensis is significant because these habitats are under increasing pressure from human land‐uses and the predicted increase in urbanization is likely to further reduce the amount of suitable habitat.     

Flooding compromises compensatory capacity of an invasive plant: implications for biological control

Plant compensatory growth is proposed to be insidious to biological control and known to vary under different environmental conditions. However, the effects of microsite conditions on compensation capacity and its indirect impacts on biological control of plant invaders have received little attention. Alligator weed, Alternanthera phioxeroides, is an invasive plant worldwide, growing in both aquatic and terrestrial habitats that are often affected by flooding. Biological control insects have been successful in suppressing the plant in many aquatic habitats but have failed in terrestrial habitats. To evaluate the impact of flooding on compensation capacity, we conducted common garden and greenhouse experiments in which plants were grown under different moisture conditions (aquatic versus terrestrial). Our results show that plants were able to fully recover from continued herbivory in the terrestrial habitat, but failed in the aquatic habitat, indicating a flooding-regulated plant compensatory capacity. Also, the grazed plants increased below-ground growth and reproductive root bud formation in the terrestrial habitat, but there was no such difference in the aquatic habitat. Our findings suggest that the differing plant compensatory capacity, affected by flooding, may explain the different biological control efficacy of alligator weed in aquatic and terrestrial habitats. Understanding mechanisms in plant invader compensation in different microsite conditions is important for improving management efficiency.     

Abundance and habitat preferences of the southernmost population of mink: implications for managing a recent island invasion

Since 2001 invasive American mink has been known to populate Navarino Island, an island located in the pristine wilderness of the Cape Horn Biosphere Reserve, Chile, lacking native carnivorous mammals. As requested by scientists and managers, our study aims at understanding the population ecology of mink in order to respond to conservation concerns. We studied the abundance of mink in different semi-aquatic habitats using live trapping (n = 1,320 trap nights) and sign surveys (n = 68 sites). With generalized linear models we evaluated mink abundance in relation to small-scale habitat features including habitats engineered by invasive beavers (Castor canadensis). Mink have colonized the entire island and signs were found in 79% of the surveys in all types of semi-aquatic habitats. Yet, relative population abundance (0.75 mink/km of coastline) was still below densities measured in other invaded or native areas. The habitat model accuracies indicated that mink were generally less specific in habitat use, probably due to the missing limitations normally imposed by predators or competitors. The selected models predicted that mink prefer to use shrubland instead of open habitat, coastal areas with heterogeneous shores instead of flat beaches, and interestingly, that mink avoid habitats strongly modified by beavers. Our results indicate need for immediate mink control on Navarino Island. For this future management we suggest that rocky coastal shores should be considered as priority sites deserving special conservation efforts. Further research is needed with respect to the immigration of mink from adjacent islands and to examine facilitating or hampering relationships between the different invasive species present, especially if integrative management is sought.     

Non-intrusive systematic study reveals mutualistic interactions between threatened island endemic species and points to more impactful conservation

Oceanic islands harbour a disproportionately large share of extinct and endangered birds worldwide and up to about 6,800 highly threatened plants, stressing the urgency for conservation efforts there. However, effective conservation action can only be as sound as the ecological understanding on which it is based. Knowledge about the ecology of threatened birds and plants can be relatively sketchy even in well-studied oceanic islands and this can potentially misdirect or erode conservation actions’ effectiveness. We used camera traps to document vertebrate flower visitors of a threatened, mono-specific endemic oceanic island plant (Roussea simplex) that produces much nectar and which was abundant until the 1930s before declining severely despite its presence mostly within protected areas. We determined proportions of native and alien flower visitors in four populations and characterised their ecological role (e.g. florivore, nectar robber, pollinator) through observations and exclusion experiments alongside experiments to determine seed sets by agamospermy, autogamy, geitonogamy and xenogamy. Five native and three alien vertebrate species visited flowers (N = 5,085 camera trap-hours), 96.6% of visits being from birds. Among endemics, 74–96% of visits were by the Mauritius Bulbul (Hypsipetes olivaceus), a threatened bird able to effect pollination contrary to the other endemic birds. Roussea simplex is primarily xenogamous, producing 2,657 ± 480 seeds, and seed set dropped markedly when the bird was excluded (861.8 ± 91.0 SE, Kruskal-Wallis χ² = 14.2, p < 0.001). Natural seed set was very low (410.0 ± 85.3 SE) where the bird was locally extinct or very rare. Invasive alien rats (Rattus rattus) and long-tailed macaques (Macaca fascicularis) were important florivores or nectar robbers. Systematic non-intrusive study using camera traps combined with manipulative experiments revealed a mutualism between two relatively well-studied threatened endemic species as well as new threats from alien vertebrates acting as nectar robbers and florivores. Roussea simplex’s major decline within protected areas and its abundant and year round flowering and nectar production point to a major hitherto unrecorded drop in floral resource previously available to at least five endemic species, and particularly to its commonest flower visitor and principal pollinator, the threatened Mauritius Bulbul. These findings exemplify how systematic non-intrusive study of threatened species may radically change conservation managers’ priorities which in the current case should focus primarily on controlling alien rats and macaques and re-instating or reinforcing Bulbul-Roussea mutualism as each would be more impactful than addressing gecko-Roussea mutualism disruption by alien ants which so far was the only recorded threat thought to drive the rapid decline of Roussea simplex. Our study underscores that current conservation efforts should also pay particular attention to medium to longer-term changes in habitat or community composition which may not be obvious from merely considering extent and composition of current habitats.     

The restoration of gravelly floodplain vegetation and endemic plants to riparian habitat in a Japanese river

Aster kantoensis, an endangered and monocarpic perennial plant species, is endemic to the gravelly floodplain of a few rapid flowing rivers in eastern central Japan. In recent years, an extreme declining trend in the species has been accelerated due to the strong negative influence by invasion of an alien grass, Eragrostis curvula. A restoration project aimed at recovering the original condition of the floodplain in the Kinu River, central Japan, has been started. To determine the possibility of successful restoration as well as its habitat preferences, I carried out some seed sowing experiments. In April 2003, seeds collected from a seminatural habitat were sown (54,000 seeds) in the restoration site (1.2 ha), where flood frequency, substrate condition, and control of alien plants are combined to form different habitat conditions. Seedling survival, flowery, and seed production were subsequently monitored from 2003 to 2005. Seed cohorts completed their life cycles within 3 years, and mean fitness of 927 was achieved. Performance of A. kantoensis seedlings was generally greater for environmental variables of sandy-type substrate and/or with control of alien plants. In addition, there were significant negative correlations between percentage survival, percentage flowery, and seed production with vegetation cover and coverage of E. curvula. The results confirm that, if safe sites with sparse vegetation exist, irrespective of their substrate condition, as well as seed sources of river endemics in natural habitats, restoration of riparian vegetation including river endemics is possible. The aggressive alien species E. curvula should be taken into consideration.     

Patterns of population genetic diversity in riparian and aquatic plant species along rivers

Aim The downstream hydrochoric spread of seeds of aquatic and riparian plant species, without upstream compensation, can be expected to result in downstream accumulation of population genetic diversity. This idea has been termed the ‘unidirectional dispersal hypothesis’ and is the genetic equivalent of the more generally known ‘drift paradox’. Our aim was to test this unidirectional diversity hypothesis, and to present a general synthesis of the patterns of population genetic variation across different riparian and aquatic plant species along rivers. Location The Meuse River (Belgium) and rivers world‐wide. Methods First, we used amplified fragment length polymorphism markers to compare patterns of within‐ and between‐population genetic diversity among three riparian plant species (Sisymbrium austriacum, Erysimum cheiranthoides and Rorippa sylvestris), typically occurring in different habitats along a gradient perpendicular to the Meuse River. Second, we performed a meta‐analysis on studies reporting on the population genetic structure of riparian and aquatic plant species along rivers. Results Along the Meuse River, we found significant genetic differentiation among populations of all three riparian species, and significant isolation by distance for one of them (R. sylvestris). There was no clear association between the typical habitat of a species and its population genetic structure. None of the three species provided evidence for the unidirectional dispersal hypothesis. The meta‐analysis, based on 21 data records, did not support the unidirectional dispersal hypothesis either. Average weighted population genetic differentiation across species was significant. Main conclusions Important mechanisms of upstream seed dispersal, probably through zoochory, together with higher seed recruitment opportunities in upstream habitats due to density dependence of recruitment, may explain the absence of downstream accumulation of genetic diversity. Also, it seems difficult to find consistent patterns in genetic variation in species from aquatic and riparian habitats. We argue that this is due to the recurrent extinctions and colonizations characteristic of these habitats, resulting in complex genetic patterns. Our results strongly support previous suggestions that stream ecology should consistently embrace metapopulation theory to be able to understand patterns of genetic diversity, as well as species diversity.     

Invasion patterns in riparian habitats: The role of anthropogenic pressure in temperate streams

The riparian flora and the level of invasion in the rivers of the Cantabric watershed in Spain were studied in relation to the ecological status and the anthropogenic pressure. The level of invasion was also analyzed in different riparian habitats: forests, river bars and man-made slopes. For this purpose, 18 sites were sampled and a list of native and alien plant species was made along a 100-m strip at each site. The habitat/s where alien species were found and their abundance per habitat and in the total area were also indicated. Out of 112 alien taxa found, 51 were classified as invasive. Exotic plants native to America were the most common (35%). The level of invasion was significantly higher in the sampling sites subject to high levels of hydrological and morphological disturbances, proxies of the anthropogenic pressure. River bars and man-made slopes supported similar number of alien plant species, higher than forests. We suggest that disturbance in river banks should be minimized as much as possible in order to diminish the risk of invasion.     

Control of invasive species for the conservation of biodiversity in Mediterranean islands. The LIFE PonDerat project in the Pontine Archipelago,Italy

We present the EU LIFE PonDerat project, which is aimed at restoring the natural ecosystems of the Pontine Archipelago, a group of islands located off the western coast of Italy. The spread of invasive species is a major environmental threat on these islands, which are rich in rare habitats and endemic species and are important sites for the conservation of Mediterranean biodiversity. The project focuses on the conservation of species and habitats that are protected by EU laws but are currently threatened by introduced plants and animals. The main targets of the control measures are black rats, feral goats, mouflons and invasive plants of the genus Carpobrotus. Conservation measures focus on the shearwaters Puffinus yelkouan and Calonectris diomedea, which are endemic to the Mediterranean and are listed in Annex I of the European Bird Directive. Conservation measures also focus on island habitats of great biogeographical value, which are listed in Annex I of the European Habitats Directive and are seriously threatened by introduced herbivores and by invasive plants. The main outcome expected from this project is that the restoration of ecosystem functions will enhance the breeding success and population size of shearwaters and lead to the recovery of target habitats.     

Invasive river plants from Portuguese floodplains: What can species attributes tell us?

Biological traits of aquatic and riparian plants were compared among invasive and non-invasive groups of species from both native and exotic taxa in Portuguese fluvial systems. Twenty-six riparian and aquatic species were selected and their frequency of occurrence and foliar percentage cover was analysed at 401 sampling sites on the main catchments of Central and Southern Portugal. Canonical correspondence analysis and a hierarchical clustering were applied to the species traits data set. No typical invader profile emerged from the analyses. However, some specific attributes were clearly related to the alien and native plant invasiveness, such as vegetative reproduction, fragment viability and life span. The results of the present work could help with the early detection of invasive plant species in Portuguese fluvial corridors. Electronic Supplementary Material Electronic supplementary material is available for this article atand accessible for authorised users.     

Woody Plant Invasion in Relictual Grasslands

Invasion by alien plants is one of the greatest and most widely distributed causes of man-made changes in ecosystems. One of its most conspicuous variants is the invasion of natural grasslands by exotic trees, which not only means the addition of new taxa to the native biota, but also the introduction of completely new life-forms. In Argentina, the Pampean plain is one of the most highly altered regions and its natural vegetation is only partially conserved in the coastal dunes, swampy lowlands, mountainous areas, riparian habitats, field edges, roadside verges and railway tracksides. Nevertheless, all these habitats are undergoing severe invasions by woody aliens that jeopardize their conservation. We present a preliminary survey of the alien woody plants affecting the last remaining natural grasslands of the Argentine Pampas, the history of their colonization and the phase of the invasion process in which they presently occur. We construct an index of invasion severity to evaluate which woody exotic species should be considered invasive and therefore targeted for control, and to set priorities for the application of management practices according to the seriousness of the threat posed to biodiversity conservation.     

Contributo Allo Studio Della Temperatura Delle Infiorescenze Delle Palme E Aracee

Abstract

Prioritization of endemic, threatened species and the habitats where they live is a crucial point of conservation actions, particularly in areas with rich endemic floras. In this study, we have developed a new procedure to define the conservation priorities among endemic plants and habitats by evaluating eight criteria. Five criteria deal with the geographic and ecological range of the evaluated species, whereas the other three refer to threats. After the evaluation of each criterion, we combined the partial scores to obtain a priority index (PI). Finally, we characterized the EU habitat categories of conservation concern on the basis of the average PI value of the plants living in each habitat. We tested the method on a list of 260 endemic plants from a biodiversity hotspot (Sardinia) that had an average PI of 3.66 ± 0.16. Even if the habitat categories that are most rich in endemic plants were rocky habitats, and coastal/halophytic habitats, the most endangered habitat was coastal sand dunes (PI = 6.75 ± 1.15). The method herein presented is complementary with the application of IUCN criteria. This integrated approach is a concrete solution that adapts IUCN criteria and categories to local contexts.     

Dispersal via stream corridors structures populations of the endangered St. Francis’ satyr butterfly (Neonympha mitchellii francisci)

Habitat fragmentation may reduce gene flow and population viability of rare species. We tested whether riparian corridors enhanced gene flow and if human habitat modification between riparian corridors subsequently reduced dispersal and gene flow of a wetland butterfly, the US federally endangered St. Francis’ satyr butterfly (Neonympha mitchellii francisci). We surveyed nine populations throughout the taxon’s range using five polymorphic microsatellite loci. We found that genetic diversity of N. m. francisci was relatively high despite its restricted distribution, and that there is little evidence of population bottlenecks or extensive inbreeding within populations. We found substantial gene flow and detectable first generation migration, suggesting that N. m. francisci is unlikely to be currently endangered by genetic factors. Pairwise population differentiation and clustering indicate some structuring between populations on different drainages and suggest that dispersal probably occurs mainly via a stepping stone from the closest riparian corridors. However, genetic differentiation between geographically close populations suggests that isolation by distance is not solely responsible for population structure, and that management actions should be targeted at maintaining connectivity of riparian and upland habitats.     

Mapping of a rare plant species (Boronia deanei) using hyper‐resolution remote sensing and concurrent ground observation

Boronia deanei is one of many declared rare, and potentially threatened, species of the Australian flora that occur within freshwater swamps and riparian margins. However, a lack of knowledge regarding its ecological distribution and habitat requirements may result in vulnerability to current and planned anthropogenic activities. Identification of population boundaries, numbers and locations should be highly beneficial for developing appropriate conservation approaches. This study demonstrates (i) the potential of converging hyper‐resolution remote sensing imagery with targeted ground observations to identify individual population extents and densities and (ii) proposes methods of defining and mapping suitable habitat and potential extents for rare plant species in areas potentially exposed to multiple anthropogenic impacts.     

Invasive alien plants in Croatia as a threat to biodiversity of South-Eastern Europe: Distributional patterns and range size

During the analysis of alien and invasive flora of Europe, as a threat to biodiversity, data for Croatia were missing. The aim of our research was to analyse distributional patterns and range size of all invasive alien plants (64) for the state area (57,000 km²). They were detected on 49% of the state territory, averaging five taxa per 35 km². The greatest number of invasive plants (> 30 per grid cell) was recorded in the major urban centres, increasing in the south-east direction and reflecting positive correlation with temperature and negative with altitude. The most endangered areas are in the Mediterranean region, especially on islands. The number of invasive plants increased with habitat diversity and almost 75% of all sites with invasive plants are located within a few habitats with direct anthropogenic influence. The results should provide a reliable regional and global basis for strategic planning regarding invasive alien plants management.     

Invasion history, habitat preferences and phenology of the invasive ladybird Harmonia axyridis in Belgium

Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is native to Asia, and was widely introduced as a biocontrol agent of aphids and coccids in Europe and North America. In Europe, H. axyridis is considered to be an invasive alien species because of its potential to disrupt native ladybird communities. Since 1999, the Belgian Ladybird Working Group mapped all Belgian Coccinellidae and recorded data on substratum plants and habitat. The first feral H. axyridis population in Belgium was recorded in 2001, but the expansion rate is decreasing because it now colonised the whole country. Recorded occupancy in Belgium showed an average rate of increase of 189% between 2002 and 2006. In Belgium, H. axyridis occurred in a wide range of habitats, including those of high conservation value. However, habitat and land cover analysis showed that H. axyridis is more frequently found in urbanised landscapes than in semi-natural landscapes. A niche overlap analysis based on plant use data showed that the potential to affect native species is higher for generalist, deciduous and coniferous tree ladybird species than for heathland and wetland specialist species. Phenology data showed that H. axyridis is able to reproduce later in the year than native species. Based on recorded distribution, ecology and phenology, we discuss the potential of H. axyridis to disrupt native ladybird assemblages in Belgium.     

Combining larval habitat quality and metapopulation structure – the key for successful management of pre-alpine Euphydryas aurinia colonies

This study aims to analyse larval habitat preferences and landscape level population structure of the threatened Marsh Fritillary butterfly, Euphydryas aurinia, and discusses implications for the conservation and management of this strongly declining species in central Europe. Whereas current management strategies are mainly based on studies of habitat requirements of adult individuals, we intend to emphasise larval habitat quality and population processes at the landscape level as additional key factors. Microhabitat preference analysis of egg-laying females showed that eggs were predominantly laid on prominent large-sized host plant individuals. Additionally, when Succisa pratensis was used as a host plant (as opposed to Gentiana asclepiadea), host individuals in open vegetation structure were preferred. Optimal oviposition conditions were present in recently abandoned calcareous fen meadows and at the edges of such meadows currently in use. A two-year patch-occupancy study in the northern pre-alpine region of south-west Germany indicated that E. aurinia lives in a metapopulation. In a logistic-regression model, patch size, isolation, and habitat quality explained 82% of the observed patch-occupancy pattern in 2001. Our data suggest that a suitable conservation strategy must incorporate both the conservation of a network of suitable habitat patches, and efforts to maximise local habitat quality by ensuring that host plants can grow to a large size and are surrounded by sparse and low vegetation cover.     

Effects of forest-dune ecotone management on the endangered heath grasshopper, Chorthippus vagans (Orthoptera: Acrididae)

Dry, oligotrophic ecosystems are highly threatened in Europe due to massive changes in land use and eutrophication. The conservation of these xeric habitats has received much attention, whereas the ecotones between xeric habitats and other habitat types are often disregarded. One species which mainly inhabits the transition zone between pine forests and adjacent xeric habitats is the heath grasshopper, Chorthippus vagans. This species is endangered in large parts of Europe. One of the largest populations in northern Germany is found on a degraded inland dune near Hanover. This population is threatened by dense growth of deciduous trees and litter accumulation. We analyzed changes in the distribution of this population after the implementation of conservation measures (thinning out the forest and removal of leaf litter). Moreover, we examined dispersal distances of the species in order to assess its colonization potential. We also studied the microhabitat preferences of C. vagans to assess key factors influencing its local distribution. Our data show a substantial growth in population size, which might be a consequence of the conservation measures. New patches on the dune were colonized, promoting dispersal between the subpopulations. We propose that restoration of forest-dune ecotones should be considered more often in landscape planning and conservation management.