Replacement Of Native Species Research Articles

(Not) sweeping invasive alien plants under the carpet: results from the use of mulching sheets for the control of invasive Carpobrotus spp.

Biological invasions represent a global threat to biodiversity. Particular attention should be made to the management of alien plants. The species from the Carpobrotus genus are well-known invasive plants native to South Africa, whose detrimental effects on native communities are widely documented. These impacts have become particularly important in terms of their invasive potential on small Mediterranean islands, where they often threaten particular ecosystems and endemic species. We report the experience from the efforts to eradicate this species from the island of Giannutri (Tuscan Archipelago, Italy)—an action included within the EU LIFE project “RESTO CON LIFE”—where the species occurred on about 14,000 m2 of coastal vegetation. The eradication employed an integrated approach with two control methods (manual removal and covering with mulching sheets) and involved mosaic rocky cliff coastal vegetation and disturbed areas with loose soil close to the cliffs. We present here the results obtained from five years of monitoring using permanent plots. Carpobrotus spp. exerted strong impacts on the invaded plant communities, with significant depletion and replacement of native species. Both of the control methods proved effective in the suppression of the mat formed by the invasive species and led to a positive response of native vegetation. Nevertheless, the recovery of native plant communities differed depending on the type of substratum, taking longer on rocky cliffs due to the harsher conditions. Improvements were driven by nitrophilous species in the plots treated with mulching sheets.

Forest conversion into pasture selects dung beetle traits at different biological scales depending on species pool composition.

The conversion of forests into open areas has large effects on the diversity and structure of native communities. The intensity of these effects may vary between regions, depending on the existence of native species adapted to open habitats in the regional pool or the time since habitat change.We assess the differences in species richness and functional diversity of dung beetle communities (Coleoptera: Scarabaeinae) between native forests and novel pasturelands of the Atlantic Forest and the Cerrado, two biomes with contrasting histories of human occupation in Brazil. We conducted standardized surveys in seven forest fragments and adjacent pastures in each region and measured 14 traits in individuals collected in each type of habitat at each particular site. We calculated functional richness, functional evenness, functional divergence, and community-weighted mean of traits for each area, and analyzed individual variation through nested variance decomposition and Trait Statistics.Communities were richer and more numerous at the Cerrado. We did not find any consistent relationship between functional diversity and forest conversion beyond the changes in species diversity. Although landscape changes were more recent at the Cerrado, the colonization of the new habitat by native species already adapted to open habitats lessens the functional loss in this biome. This indicates that habitat change's effects on trait diversity depend on the regional species pool rather than on time since land conversion.Forest conversion effects were primarily due to internal filtering. The effects of external filtering only appear at the intraspecific variance level, with contrasting differences between the Cerrado, where traits related to relocation behavior and size are selected, and the Atlantic Forest, where selection operates for traits related to relocation behavior and flight. These results evidence the importance of considering individual variance to address the responses of dung beetle communities to forest conversion.

How does invasion degree shape alpha and beta diversity of freshwater fish at a regional scale?

Freshwater ecosystems appear more vulnerable to biodiversity loss due to several anthropogenic disturbances and freshwater fish are particularly vulnerable to these impacts. We aimed to (1) identify the contribution of land use, spatial variables, and invasion degree in determining freshwater fish alpha (i.e., species richness) and beta (i.e., local contributions to beta diversity, LCBD) diversity, evaluating also the relationship between invasion degree and nestedness ( nes) and turnover ( sim) components of beta diversity. (2) Investigate the relationship between alpha diversity and LCBD, under the hypothesis that alpha diversity and LCBD correlate negatively and (3) investigate the relationship between species contributions to beta diversity (SCBD) and species occurrence, hypothesizing that non-native species show a lower contribution to beta diversity. The linear mixed models and the partition of R 2 retained the invasion degree as the most important variables explaining alpha and beta diversity, having a positive relationship with both diversity components. Furthermore, land use related to human impacts had a positive influence on alpha diversity, whereas it showed a negative effect on LCBD. Regression model further showed that invasion degree related positively with sim, but negatively with nes, suggesting that non-native species were involved in the replacement of native species in the fish community. Alpha diversity and LCBD showed a weak positive correlation, meaning that sites with low species richness have higher LCBD. SCBD scaled positively with species occurrence highlighting that rarer species contribute less to SCBD. Finally, native and exotic species contributed similarly to beta diversity. These results suggest that invasion degree plays a central role in shaping alpha and beta diversity in stream fish, more than land use features reflecting habitat alteration or other geospatial variables. Furthermore, it is important to evaluate separately the native and the non-native components of biotic communities to identify linkages between invasion dynamics and biodiversity loss.

Are invasive hymenopteran species replacing native mud dauber wasp-associated taxa on the Seychelles Archipelago?

Nest aggregations of mud dauber wasps increase substrate heterogeneity and provide suitable sites for colonization by other invertebrate species. The mud dauber wasp Sceliphron fuscum Klug, 1801 (Hymenoptera: Sphecidae) abundantly occurs throughout the Seychelles Archipelago, Republic of Seychelles. Here, we estimated the taxonomic richness of the hymenopteran assemblage associated with S. fuscum’s nest aggregations, using material collected from the Inner Seychelles in 2016. Furthermore, we examine available historical survey data in order to assess possible changes in this association over decades. We discovered that from 1936 to 1938, seven hymenopteran species were associated with the nest aggregations of S. fuscum on Mahé and Praslin islands, representing six native taxa and one invasive species. From the material collected in 2016, we found one native and three invasive hymenopteran species associated to S. fuscum nests. Our findings could indicate a replacement of native species associated with the mud dauber wasps’ nest aggregations by recently introduced alien taxa on the Seychelles Archipelago.

Invasive Sun Coral Species Challenges Decommissioning of Structures Offshore Brazil

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 30656, “Decommissioning of Subsea Structures in Brazil: Effect of Invasive Species and Genome Sequence of the Azooxanthellate Coral Tubastraea sp.,” by João Humberto Guandalini Batista, SPE, Repsol; Mauro Rebelo, Universidade Federal do Rio de Janeiro; and Giordano Soares-Souza, SENAI CETIQT, prepared for the 2020 Offshore Technology Conference, originally scheduled to be held in Houston, 4–7 May. The paper has not been peer reviewed. Copyright 2020 Offshore Technology Conference. Reproduced by permission. Decommissioning of offshore assets in Brazil is subject to high levels of uncertainty because of Tubastraea, an invasive species of sun coral. This species has a high capacity for dispersion and recruitment and has been associated with the replacement of native species in rocky shores, exerting a serious effect on native biodiversity. The complete paper explores the biology of the invasive species, aiming to identify methods to eliminate or diminish its spread. The authors write that data generated in this study will foster the development of effective technologies in coral-species management, whether species are invasive or threatened. Introduction Originally from the Coral Triangle in the Pacific Ocean—a highly diverse region with hundreds of coral species—Tubastraea was first observed in the Campos Basin in the 1980s. Tubastraea sp. have high fecundity and growth rates with the ability to reproduce asexually, establishing very dense populations. This fast reproduction allows larvae to outcompete native species in both natural and artificial substrates in the sea. Sun coral is extremely resistant to environmental change. It has been found in shallow waters, sometimes exposed to air, showing tolerance even to short periods of desiccation. Recently, new species have been identified in Brazilian waters, heightening concern over the proliferation of sun coral. In the past, the common understanding was that subspecies coccinea and tagusensis were those found in Brazilian waters. However, recent studies dedicated to the research of the Tubastraea genus raised suspicion of the presence of diaphana and aurea, with the possible occurrence of hybrids as well. The preference of Tubastraea is to live in structures that are static or mostly motionless, such as production platforms, subsea structures, and drilling rigs. This trait has made sun coral a major challenge for the local oil and gas industry. While in the Campos Basin, the main objective is to decrease dispersion of already bioencrusted production units and subsea structures, in the Santos Basin, the goal is to avoid colonization in structures in operation or those scheduled to be installed soon. To further complicate matters, drilling and intervention vessels and rigs are contracted to service both basins. They work in dynamic-positioning mode, stationary around the production units and subsea structures for lengths of time that exceed the reproduction cycle time of the sun coral, allowing larval dispersion.

Variability in climate-growth reaction of Robinia pseudoacacia in Eastern Europe indicates potential for acclimatisation to future climate

As a consequence of native tree species decline and distribution range contraction in Europe, acclimation of the non-native tree species at the edge of their distribution is gaining importance. Although non-native tree species may provide sustainable ecosystem services, as a potentially invasive species they may be a threat to local ecosystems as well. In Europe, black locust (Robinia pseudoacacia) a non-native species, seems to meet the condition of acclimation as a multi-generational process. The acclimatization, however, may have consequences not only for growth performance but also for the species' invasive potential. This study investigates the spatiotemporal pattern of secondary growth and climate sensitivity among six black locust stands along continentality gradient in Eastern Europe with the respect to bioclimatic conditions of the species distribution in Europe.Despite comparable bioclimatic conditions, climate sensitivity of black locust stands is highly variable, both temporally and spatially. The winter and spring temperatures are a key climatic driver of the growth pattern in southern and western Poland. Growth response to previous winter and current summer precipitation distinguished stands in western and eastern Poland. A significant increase in the mean annual temperature during the last 70 years likely triggered temporal instability of the black locusts’ climate signal. In general, drought conditions were found to be the main limiting factor at the edge sites within the black locust gradient. Thus, the climate sensitivity of black locust stands reflects rather site-specific microclimatic conditions then bioclimatically-based clustering pattern. Despite climate-related limiting factors, black locust seems to be characterized by high potential for acclimatization to Eastern European climatic conditions, suggesting high invasive potential. Thus, the replacement of native species by black locust or the conversion of local habitats into monocultures for biomass production should not be recommended, while species management should follow proactive measures to reduce the risk of uncontrolled spread of the species. Divergent growth reaction of black locust stands implies high plasticity of secondary growth and thus high probability of acclimatization to future climate. Given the expected range expansion to the East in Europe, we call for expanding dendroclimatic studies to the areas of future species expansion in order to test its climatic and edaphic limitations. This seems to be crucial for formulating non-native species management strategies in line with sustainable forestry, preventing the uncontrolled expansion of the species that threatens vulnerable habitats.

Using stable isotopes to analyse extinction risks and reintroduction opportunities of native species in invaded ecosystems

Invasive non-native species have pervasive impacts on native biodiversity, including population extirpations and species extinctions. Identifying reasons why a population of a native species is extirpated following an invasion often relies on literature-based results of anecdotal observations. The well-established schemes of existing risk assessments for invasive species assume that a species’ information (e.g. impacts or behavioural and biological traits) can be projected from one area to another to estimate the potential impact of a species in another environment. We used stable isotope data (δ13C, δ15N) from both invaded and uninvaded communities to predict such invasion impacts by reconstructing trophic relationships. This approach was tested on a community within a protected lake in Northern Spain where, following the introductions of non-native species, the last resident native species (the common tench Tinca tinca, the European eel Anguilla anguilla, and the whirligig beetle Gyrinus sp.) had been extirpated. Through the application of this novel approach, we found evidence that native species’ declines were related to direct predation by and resource overlap with non-native species, which occurred in conjunction with habitat modification. Using this approach, we outlined the mechanisms involved in the extirpation of native species in the post-invasion period. To compensate for losses of native species induced by invasions of non-native species, native species reintroductions might be an appropriate tool. For this, we further suggested and discussed a novel approach that predicts the outcome of arising interactions by superimposing stable isotope data from alternative sources to better estimate the success of native species´ reintroductions.

Invasão de ligustro no sub-bosque de um remanescente de floresta com araucária: uma abordagem demográfica

Espécies invasoras têm ocasionado a perda de biodiversidade no mundo todo por ocuparem o lugar de nativas. O presente estudo objetivou avaliar a regeneração natural ao longo do tempo em um fragmento florestal invadido por Ligustrum lucidum W.T. Aiton e Ligustrum sinense Lour. no sul do Brasil, a fim de quantificar essa invasão. Para isso, foram alocadas cinco transecções em um fragmento de Floresta Ombrófila Mista em Lages (SC), sendo cada transecção dividida em parcelas com diferentes setores de distâncias da borda e em subparcelas para avaliação do componente regenerativo. Em 2012, os regenerantes de espécies arbóreas que se encontravam nas subparcelas foram identificados, plaqueteados e divididos nas seguintes classes: classe 1 _ plantas com altura entre 10 cm e 1 m; classe 2 _ plantas com altura entre 1 e 3 m; classe 3 _ plantas com altura maior que 3 m e diâmetro medido à altura do peito (DAP) menor que 5 cm. Em 2014, esses indivíduos foram reavaliados, contabilizando os indivíduos mortos e recrutas e enquadrando os sobreviventes e recrutas nas atuais classes. Foram calculadas as taxas de mortalidade, recrutamento, mudanças de classe e mudança líquida. Os dados foram analisados por meio de uma análise de componentes principais (ACP) e tabela de contingência. Conclui-se que as espécies superaram a fase inicial do processo de invasão, demonstrando elevado incremento populacional na área estudada. Ainda, ficou evidenciado o particionamento espacial entre as espécies nativas e as exóticas, o que sugere a existência de competição interespecífica, cuja consequência pode ser a extinção local de representantes do grupo autóctone.

Climate change in the Bay of Biscay: Changes in spatial biodiversity patterns could be driven by the arrivals of southern species

Under climate change, future species assemblages will be driven by the movements and poleward shift of local species and the arrival of more thermophilic species from lower latitudes. To evaluate the impacts of climate change on marine communities in the Bay of Biscay, we used the hierarchical filters modelling approach. Models integrated 3 vertical depth layers and considered 2 Intergovernmental Panel on Climate Change (IPCC) scenarios (Representative Concentration Pathway, RCP2.6 and RCP8.5) and 2 periods (2041-2050 and 2091-2100) to simulate potential future species distributions. Results predicted potentially suitable future ranges for 163 species as well as future arrivals of non-indigenous southern species. We aggregated these results to map changes in species assemblages. Results revealed that coastal areas would undergo the highest species loss among the Bay of Biscay species, depending on their vertical habitat (benthic, demersal, benthopelagic or pelagic). Benthic and demersal species were projected to experience a westward shift, which would induce a deepening of those species. In contrast, pelagic species were projected to shift northward. The potential ecological niche for half of the studied species, mostly benthic and demersal, was projected to decrease under climate change. In addition, a high rate of southern species arrivals is expected (+28%). Assessment of community composition showed high species replacement within the 0-50 m isobath, driven by the replacement of native species by southern ones. This could lead to a major reorganization of trophic networks and have socio-economic impacts.

Two is better than one: combining gut content and stable isotope analyses to infer trophic interactions between native and invasive species

Two complementary approaches are commonly used for analysing trophic interactions that allow inferences about consumed and assimilated resources: gut content (GCA) and stable isotope (SIA) analyses. We used these methods to assess the trophic ecology of a native (Pontastacus leptodactylus) and an invasive species (Faxonius limosus) of crayfish in the Lower Danube (Romania) by calculating five frequently used metrics (i.e. trophic position, omnivory index, elemental imbalance for C:N ratio, trophic niche width and overlap). The SIA approach indicated significantly different trophic niche widths between the crayfish species and potential resource partitioning that triggered lower niche overlap, aspects not depicted by GCA. The latter approach suggested higher omnivory indices and elemental imbalance for macronutrients, potentially because of high incidences of basal resources with low nitrogen content in the foreguts of both species. Although, as indicated by GCA, the two species seem to feed largely on the same resources, SIA suggested that the ingested food items were assimilated with differing efficiencies. These findings are of importance for studies of invasion biology, where the replacement of native species by invasive taxa is underpinned by mechanisms that should be explored by using the most appropriate approach.

Comparative Analyses of Herbivory Rates and Leaf Phenology in Invasive and Native Shrubs in an East-Central Indiana Forest1

Exotic species that become invasive can have a strong impact on the success of native species because of traits that enhance their competitive abilities. This study investigates three potential trait differences between common invasive and native shrubs that could enhance the competitive success of invasives: resistance to herbivory, length of autumn leaf retention, and timing of spring leaf emergence. We measured herbivory per plant by leaf-chewing insects, autumn leaf color change and retention, and spring leaf-out in five native and five invasive shrub species in Wildman Woods near Richmond, Indiana, during the fall of 2014 and the spring of 2015. Although we found variation among species, native plants as a group had significantly greater percent leaf herbivory per plant compared to invasive plants, while invasive plants kept chlorophyll significantly later in autumn and had longer leaf retention. Invasive plants also leaf out slightly earlier than native species. Our findings in 2014 were very similar to previous unpublished work in the same area on several of the same species in 2002, 2004, and 2007, suggesting that these patterns are consistent between years. Overall, we found evidence that lower herbivory rates, longer leaf retention in fall, and perhaps earlier leaf-out in spring could improve the competitive abilities of invasive shrub species through increased season-long photosynthesis.

No evidence for a genetic impoverishment of the indigenous amphipod Gammarus roeselii (Gervais, 1835) due to the invasion of Dikerogammarus villosus (Sowinsky, 1894) in Lake Constance

The replacement of native species by invasive species is one of the most critical threats to the biodiversity of aquatic systems today. However, little is known about potential effects of species invasions on the genetic diversity of indigenous species in cases where the latter coexist with the invader. Here we present an example of the indigenous amphipod Gammarus roeselii, which has been partly replaced by the invasive Dikerogammarus villosus in Lake Constance (C-Europe) and now mostly exists in small, isolated populations. We compared the genetic diversity, population structure, indicators for bottlenecks and migrations rates of G. roeselii before and after the invasion event from samples collected between 1999 and 2013. We expected a genetic impoverishment in the reduced and segregated populations of G. roeselii. However, no genetic measure on G. roeselii differed temporally or spatially over the investigated period, which indicates that D. villosus has not yet had an impact on G. roeselii at the genetic scale. Hence, even though a decline in population size of G. roeselii was found in Lake Constance, our results on the genetic scale contribute to recent findings that the overall impact of D. villosus on native species is not as strong as often discussed.

Overcoming urban stream syndrome: Trophic flexibility confers resilience in a Hawaiian stream fish

Abstract Urbanisation is widely associated with a suite of physical, chemical and biological degradation of stream ecosystems, known as “urban stream syndrome.” It is unclear whether urban stream syndrome is applicable to oceanic islands, where marine dispersal of larvae enables diadromous species to continuously recolonise even highly degraded urban streams. The depauperate native fauna of oceanic island streams can be entirely composed of diadromous species, but urban streams food webs are often dominated by introduced predators, competitors and functional groups derived from continental systems. Despite these challenges, some native species appear to thrive in urbanised catchments. Here, we test for urban stream syndrome on oceanic islands by quantifying catchment land use, nutrient concentrations and fish community composition for 37 streams across the Hawaiian archipelago. To assess how native species adapt to food webs altered by species introductions, we quantified trophic responses by examining stomach contents, nitrogen stable isotopes and body condition of Awaous stamineus (an omnivorous goby) in each stream. Urbanisation was consistently associated with nitrogen pollution and replacement of native species with more tolerant exotics. Population densities of three of five native goby species declined sharply with urbanisation, whereas the two other native gobies species were resilient. The trophic position of the omnivore A. stamineus was elevated in urban streams compared to forested catchments, reflecting a shift in stomach contents from algae to greater reliance on exotic aquatic and terrestrial invertebrates. Comparable body condition and resilient population density of A. stamineus across the urbanisation gradient suggest that dietary flexibility buffers this species against environmental degradation. Our findings indicate that the concept of urban stream syndrome is applicable to oceanic islands, yet A. stamineus shows striking resilience. Flexibility in diet, life history and habitat use of this native goby appear to buffer it against the effects of urbanisation compared to most other amphidromous fishes in Hawaiian streams.

Leaching of carbon from native and non-native leaf litter of subtropical riparian forests

We evaluated the leaching of dissolved organic and inorganic carbon (DOC and DIC, respectively) from leaf litter of plant species of the native Atlantic Forest and of Pinus elliottii (Engelm.) and Eucalyptus grandis (Hill ex Maiden) forests. We carried out experiments in which leaves from each forest system (native, E. grandis, and P. elliottii) were placed in reactors with sterile water. After 1/4 h, 1 h, 4 h, 12 h, 24 h, and 48 h of incubation, we quantified the concentrations of DIC and DOC of each leachate. The greatest quantity of DIC was leached in the native forest system, whereas the greatest quantity of DOC was leached in the E. grandis forest system. With respect to the period of year, the greatest quantity of DIC was leached in autumn, whereas that of DOC was leached in the summer. Our results demonstrated that the replacement of native species in riparian zones, by non-native forest monocultures, could alter the chemical composition of the water. Finally, the results presented in this paper reinforce the need for a more careful look at ecological processes.

Закономерности процесса синантропизации растительного покрова городов южного Предуралья (Республика Башкортостан)

Increase of anthropogenic pressure on nature ecosystems leads to synanthropization of flora and vegetation. A replacement of native species in communities with synanthropic ones, including alien species, takes place as well as a change of native plant communities by synanthropic ones, decrease of biodiversity, simplification of structure, decrease in efficiency and stability of plant communities (Gorchakovskij, 1999). Synanthropization as an indicator of anthropogenic transformation of vegetation is a traditional object of studies (Sudnik-Wojcikowska, 1988; Abramova, 2010; Abramova, Mirkin, 2000; Abramova, Mikhailova, 2003; etc.). The ratio of synanthropic and native flora species for an assessment of synanthropization level is usually used. The assessment of synanthropization level is the most important element of monitoring as it helps to estimate a degree of ecosystems disturbance and to develop a system of their rational use and protection. Processes of synanthropization are most expressed in the towns. The towns are the heterotrophic ecosystems including uniform group of anthropogenically transformed communities formed on the residential, industrial, transport, agrarian, recreational territories where the florogenesis and the phytocoenogenesis are highly specific (Burda, 1991; Ilminskikh, 1993). The urban environment can have the leveling impact on climatic factors therefore the floras of towns in different nature zones quite often have the common features (Ilminskikh, 1993). An increase of a syntaxonomic variety due to destruction of native vegetation is compensated by increase of synanthropic syntaxa number from the synanthropic classes of vegetation, and also communities of aggressive alien species which are combined with species of local flora. The regularities of synanthropization of urban flora and vegetation are less studied (Kowarik, 1990; Burda, 1991; etc.). Due to a growth of urbanization process around the world the studying of anthropogenic transformation of ve­getation cover is required. The article is devoted to the analysis of regularities of synanthropization of plant cover in towns of the southern Cis-Urals belonging to the Southern industrial zone of Bashkortostan Republic. 3 towns — Sterlitamak, Salavat and Ishimbay representing different categories by their population size were chosen for an assessment of synanthropization level.

Greenhouse Gas Fluxes Vary Between Phragmites Australis and Native Vegetation Zones in Coastal Wetlands Along a Salinity Gradient

The replacement of native species by invasive Phragmites australis in coastal wetlands may impact ecosystem processes including fluxes of the greenhouse gases (GHGs) carbon dioxide (CO2) and methane (CH4). To investigate differences in daytime CH4 and CO2 fluxes as well as vegetation properties between Phragmites and native vegetation zones along a salinity gradient, fluxes were measured via cavity ringdown spectroscopy in 3 New England coastal marshes, ranging from oligohaline to polyhaline. While daytime CH4 emissions decreased predictably with increasing soil salinity, those from Phragmites zones were larger (15 to 1254 μmol m−2 h−1) than those from native vegetation (4–484 μmol m−2 h−1) across the salinity gradient. Phragmites zones displayed greater daytime CO2 uptake than native vegetation zones (−7 to −15 μmol m−2 s−1 vs. -2 to 0.9 μmol m−2 s−1) at mesohaline-polyhaline, but not oligohaline, sites. Results suggest that vegetation zone and salinity both impact net emission or uptake of daytime CO2 and CH4 (respectively). Future research is warranted to demonstrate Phragmites-mediated impacts on GHG fluxes, and additional measurements across seasonal and diel cycles will enable a more complete understanding of Phragmites' net impact on marsh radiative forcing.

Potential alteration of cross‐ecosystem resource subsidies by an invasive aquatic macroinvertebrate: implications for the terrestrial food web

Summary Biodiversity is globally threatened by the replacement of native species by invasive species and ensuing changes in ecosystem functioning. Although trophic linkages between aquatic and terrestrial ecosystems have received attention, effects of aquatic invasive species on the flow of resource subsidies have been considered only recently. We examined how the effects of one of the most invasive macroinvertebrate species in European waterways, the amphipod Dikerogammarus villosus, extend from streams to the terrestrial food web. We quantified aquatic emergence and the contribution of aquatic resources to the diets of two riparian spider taxa in relation to the density of D. villosus. Our results indicated that the effects of this invasive species carry over to the terrestrial system via cross‐ecosystem flow of resource subsidy. The contribution of aquatic resources to the diet of the terrestrial web‐building spider Tetragnatha decreased from 60% at low densities of D. villosus to 10% at a D. villosus density >5000 individuals m−2. This correlates with a decreasing emergence rate of merolimnic midges (species with an aquatic larval phase) from 12 to <3 mg dry biomass m−2 day−1 at the respective densities of D. villosus. The magnitude of biomass flow from the aquatic to the terrestrial ecosystem is most likely decreased by D. villosus, and this decrease extends to the diet of riparian web‐building spiders. Effects of this aquatic invader may also extend to a decoupling of the terrestrial ecosystem from the aquatic ecosystem in terms of subsidy flux.

What is the role of exotic medicinal plants in local medical systems? A study from the perspective of utilitarian redundancy

Medicinal plants are an important aspect of local medical systems. The composition of a medicinal plant collection is influenced by cultural and environmental factors. Additionally, the functionality of a local medical system can be threatened by the replacement of native species with exotic ones, as well as by cultural factors such as the erosion of knowledge. The objectives of this study are: 1) examine the composition of the medicinal plant collec- tion of two rural communities settled in the caatinga (savanna-like vegetation) of the state of Pernambuco (Brazil); 2) observe the role of exotic plants in the local medical systems; and 3) identify the profile of the species utilized according to the Utilitarian Redundancy Model. Similarities were observed between the medicinal floras of the communities studied, emphasizing the importance of the surrounding biome within the possibilities of species selection, although exotic species appear to contribute by increasing the diversity of species considered in the communities to be medicinal. The native species act broadly among the body systems recognized in the two communities, whereas exotic species act in specific body systems, for which there are few associated native species.

Distribution and spread of spiny-cheek crayfish Orconectes limosus (Rafinesque, 1817) in Belarus

The spiny-cheek crayfish Orconectes limosus was registered for the first time in the Neman River and its tributaries, in the Grodno region, Belarus in 1997. The crayfish spread upstream from Grodno over the next 14 years, migrating 177 km along the course of the Neman River. Today spiny-cheek crayfish are recorded in 8 rivers including the Neman, Narew and Western Bug basins. We never found native crayfish species together with spiny-cheek crayfish during our surveys, which may indicate replacement of native species by invasive O. limosus in the studied area.

Examination of the effects of largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus) on the ecosystem attributes of lake Kawahara-oike, Nagasaki, Japan

The introduction of largemouth bass (Micropterus salmoides) and bluegill sunfish (Lepomis macrochirus) into the freshwater ecosystems of Japan has resulted in the suppression and/or replacement of native species, generating considerable concerns among resource managers. The impacts of largemouth bass and bluegill on native fauna have been examined in aquaria and isolated farm ponds, but there is limited work examining the likelihood to fundamentally modifying Japan's lakes. The objective of the present study is to examine the direct and synergistic ecological effects of largemouth bass and bluegill on the biotic communities of Lake Kawahara-oike, Nagasaki, Japan, using an ecosystem (Ecopath) modeling approach. Specifically, we examine whether the two fish species have played a critical role in shaping the trophodynamics of the lake. We attempt to shed light on the trophic interactions between largemouth bass and bluegill and subsequently evaluate to what extent these interactions facilitate their establishment at the expense of native species. We also examine how these changes propagate through the Lake Kawahara-oike food web. Our study suggests that the introduction of bluegill has induced a range of changes at multiple trophic levels. The present analysis also provides evidence that largemouth bass was unable to exert significant top-down control on the growth rates of the bluegill population. Largemouth bass and bluegill appear to prevail over the native fish species populations and can apparently coexist in large numbers in invaded lakes. Future management strategies controlling invasive species are urgently required, if the integrity of native Japanese fish communities is to be protected.