Proliferation Of Invasive Species Research Articles

Sentinel-2 versus PlanetScope Images for Goldenrod Invasive Plant Species Mapping

A proliferation of invasive species is displacing native species, occupying their habitats and degrading biodiversity. One of these is the invasive goldenrod (Solidago spp.), characterized by aggressive growth that results in habitat disruption as it outcompetes native plants. This invasiveness also leads to altered soil composition through the release of allelopathic chemicals, complicating control efforts and making it challenging to maintain ecological balance in affected areas. The research goal was to develop methods that allow the analysis of changes in heterogeneous habitats with high accuracy and repeatability. For this reason, we used open source classifiers Support Vector Machine (SVM), Random Forest (RF), and satellite images of Sentinel-2 (free) and PlanetScope (commercial) to assess their potential in goldenrod classification. Due to the fact that invasions begin with invasion footholds, created by small patches of invasive, autochthonous plants and different land cover patterns (asphalt, concrete, buildings) forming heterogeneous areas, we based our studies on field-verified polygons, which allowed the selection of randomized pixels for the training and validation of iterative classifications. The results confirmed that the optimal solution is the use of multitemporal Sentinel-2 images and the RF classifier, as this combination gave F1-score accuracy of 0.92–0.95 for polygons dominated by goldenrod and 0.85–0.89 for heterogeneous areas where goldenrod was in the minority (mix class; smaller share of goldenrod in canopy than autochthonous plants). The mean decrease in the accuracy analysis (MDA), indicating an informativeness of individual spectral bands, showed that Sentinel-2 bands coastal aerosol, NIR, green, SWIR, and red were comparably important, while in the case of PlanetScope data, the NIR and red were definitely the most important, and remaining bands were less informative, and yellow (B5) did not contribute significant information even during the flowering period, when the plant was covered with intensely yellow perianth, and red-edge, coastal aerosol, or green II were much more important. The maximum RF classification values of Sentinel-2 and PlanetScope images for goldenrod are similar (F1-score > 0.9), but the medians are lower for PlanetScope data, especially with the SVM algorithm.

Anglers as potential vectors of aquatic invasive species: Linking inland water bodies in the Great Lakes region of the US.

Unimpeded transfer and spread of invasive species throughout freshwater systems is of global concern, altering species compositions, disrupting ecosystem processes, and diverting economic resources. The magnitude and complexity of the problem is amplified by the global connectedness of human movements and the multiple modes of inter-basin transport of aquatic invasive species. Our objective was to trace the fishing behavior of anglers delineating potential pathways of transfer of invasive species throughout the vast inland waters of the Great Lakes of North America, which contain more than 21% of the world's surface freshwater and are among the most highly invaded aquatic ecosystems in the world. Combining a comprehensive survey and a spatial analysis of the movements of thousands of anglers in 12 states within the US portion of the Great Lakes Basin and the Upper Mississippi and Ohio River Basins, we estimated that 6.5 million licensed anglers in the study area embarked on an average of 30 fishing trips over the course of the year, and 70% of the individuals fished in more than one county. Geospatial linkages showed direct connections made by individuals traveling between 99% of the 894 counties where fishing occurred, and between 61 of the 66 sub-watersheds in a year. Estimated numbers of fishing trips to individual counties ranged from 1199-1.95 million; generally highest in counties bordering the Great Lakes. Of these, 79 had more than 10,000 estimated fishing trips originating from anglers living in other counties. Although angler movements are one mechanism of invasive species transfer, there likely is a high cumulative probability of invasive species transport by several million people fishing each year throughout this extensive freshwater network. A comprehensive georeferenced survey, coupled with a spatial analysis of fishing destinations, provides a potentially powerful tool to track, predict, curtail and control the transfer and proliferation of invasive species in freshwater.

Excessive presence of Nitrogen and Phosphorus in the Drini River and their impact on the Kune-Vain lagoon ecosystem: how anthropization can affect biodiversity

In the western part of Albania there are various examples of lagoons and wetlands ecosystems; the object of this manuscript is addressing the environmental conditions of The Kune-Vain Lagoon, located in proximity of the city of Lezhë and south of the Drini River and its delta and providing suggestions about its preservation: it has been calculated that about 10 million m3 of polluted water are released, in many ways, every year into the Drini River. Because of its biodiversity this land has both national and international protection status. However, the flux of contaminants and pollutants derived from anthropic activities is strongly affecting this transitional body of water which is located at the interface of the river and the Adriatic Sea. Due to human activities, mobile aqueous species of nitrogen (N) and phosphorous (P) have become an actual environmental issue because high levels of such chemical elements are linked to the eutrophication of the lagoon’s waters, causing the proliferation of invasive species (mostly microorganisms, plants and crustaceans). As mentioned above a very high quantity of N and P from anthropogenic sources can infiltrate the ecosystem in many ways, like from mining activity, liquid and solid wastes from the urban aera of Lezhë, from farms and livestock, from fires and more. But the main cause of this problem is associated with the use that people make with soils and lands: the increment of fallow uncultivated areas from abandoned agricultural sites contribute indeed to the surface runoff, erosion and subsequent transport of N and P chemical species to the actually cultivated territory in which cultivation and managements practices for forage and cereals are present; this leads to ulterior release of soil particles that are rich in N and P chemicals compounds into the aqueous phase of the land. A very big portion of those aforementioned particles have been and still are depositing in the main area of the Kune-Vain Lagoon. The Lagoon is part of the coastal area, thus it is very important for economy, industry and tourism and it also act as a ‘buffer zone’ between the sea and the agricultural areas because of its biological function as natural filter for nutrients overload through its characteristic vegetation. Nevertheless, the Kune-Vain lagoon waters show a clear tendency toward degradation and something must be done to prevent heavy ecological issues. It would be useful to constantly monitor the chemical composition and the state of the waters. Also, the employment of meanings of phytoremediation would represent a practical, cheap and environmental-friendly way to help the process of recovery toward better environmental conditions of the Kune-Vain Lagoon.

The non-native flora of Redberry Lake Biosphere Reserve, Canada

A checklist of alien plants of Redberry Lake Biosphere Reserve in the province of Saskatchewan, Canada is presented for the first time. By way of field surveys and herbarium research, 121 alien taxa (22.1% of the regional flora) were recorded. The most species rich families are Poaceae (24 taxa, 19.8%) and Asteraceae (22, 18.2%). Species richness is about evenly distributed across genera with Rumex, Artemisia and Poa (each contains 3 taxa or 2.5%) making up those with the greatest number of species. Concerning plant growth habits, the two dominant groups are forbs (94 taxa, 77.7%) and graminoids (23 taxa, 19%). Regarding habitat preferences, most alien plants occur in natural and seminatural habitats (48 taxa, 39.7%), ruderal places (43 taxa, 35.5%) and agricultural lands (30 taxa, 24.8%). In relation to the state of spread, invasive (63 taxa, 52%) and naturalised (48 taxa, 39.7%) species prevail. In terms of geographical origin, most alien plants are native to Eurasia–Africa (49 taxa, 40.5%) and Eurasia (34 taxa, 28.1%). The biosphere reserve is increasingly being invaded by alien plants whose introduction and distributions can be explained by intense agricultural pressure which resulted in extensive habitat alteration and proliferation of invasive species. URL: https://www.upjs.sk/pracoviska/botanicka-zahrada/odborne-aktivity/contents-abstracts/

Reconstitution of the Climate in the Municipality of Guimarães (Northern Portugal): A Regional Approach Based on Historical Information and the Record of Measured Data

Climate change is a global phenomenon that has become a focus of concern for society, mainly due to its impacts on daily lives. Despite being a global issue that affects the entire planet, these effects are not felt in the same way in all regions, so the analysis of processes from a regional or local perspective allows a better adaptation of populations to the new reality, as well as being used as a supporting tool for decision making when implementing mitigation measures. For the present analysis, a region in Northern Portugal was chosen, which is in the Mediterranean region, considered one of the hot spots for climate change. In this region of Entre Douro e Minho, more specifically in the municipality of Guimarães, the climate of the last centuries was reconstructed based on documentary information and recent data collected and modeled for the region under study. The results show a successive alternation of hot and dry periods with colder and wetter ones, where climate instability seems to be the dominant trend over the last thousand years. Currently, with the advent of a new period of climatic instability, which, unlike the periods verified previously, now have an anthropic origin, there is a tendency for a new period to occur, in which conditions will tend to be hotter and drier. Knowing this trend in advance allows informed decisions to be made to mitigate some problems that can be associated with these conditions, such as the increase in the risk of wildfires, the proliferation of invasive species, the decrease in agriculture and forests productivity, or even the occurrence of extreme weather events.

Climate and sea surface trends in the Galapagos Islands

The Galapagos Islands are a global hotspot of environmental change. However, despite their potentially major repercussions, little is known about current and expected changes in regional terrestrial climate variables and sea surface temperatures (SST). Here, by analysing existing meteorological observations and secondary datasets, we find that the Islands have warmed by about 0.6 °C since the early 1980s, while at the same time becoming drier. In fact, the onset of the wet season is currently delayed 20 days. This drying trend may reverse, however, given that future climate projections for the region suggest mean annual precipitation may increase between 20 and 70%. This would also be accompanied by more extreme wet and hot conditions. Further, we find that regional SST has increased by 1.2 °C over the last two decades. These changes will, in turn, translate into deterioration of marine ecosystems and coral, proliferation of invasive species, and damages to human water, food, and infrastructure systems. Future projections, however, may be overestimated due to the poor capacity of climatic models to capture Eastern-Pacific ENSO dynamics. Our findings emphasize the need to design resilient climate adaptation policies that will remain robust in the face of a wide range of uncertain and changing climatic futures.

Prosopis Species—An Invasive Species and a Potential Source of Browse for Livestock in Semi-Arid Areas of South Africa

Globally, there have been differing views on whether the proliferation of invasive species will be of benefit as a livestock feed source or it will have detrimental effects on the ecosystem. The infestation of invasive plants such as Prosopis species does not only affect the groundwater levels but also threatens the grazing capacity and species richness of most of the semi-arid areas around South Africa. Though Prosopis is invasive, it is however of good nutritive value and can serve as an alternative source of protein and minerals for livestock during the dry season. Bush encroachment by browsable invasive species can be controlled through biological methods by using organisms such as livestock. The utilisation of Prosopis through browse benefits livestock production and at the same time reduces its spread, thereby preventing possible environmental harm that may arise. Although several studies have been carried out globally on the assessment of the Prosopis species’ nutritive value and also on the threat of this invasive species to the environment, there is a need to update the state of knowledge on this species, particularly in the context of the semi-arid areas of South Africa where the dry season is characterised by less herbage of poor quality. It is therefore critical to understand whether Prosopis is a beneficial invader, or a detriment that needs to be eradicated. This review will contribute knowledge towards finding practical solutions to controlling Prosopis species and whether utilising Prosopis as a feed source will limit its spread and result in a vegetation structure where Prosopis becomes part of the ecosystem with limited detrimental impact. This means that the several components of the species such as nutritive value and the negative impact associated with this plant species along with the means to control its spreading must be well understood to recognise the plant species’ vital contribution to the ecosystem.

Distribution of alien invasive species in aquatic ecosystems of the southern Western Ghats, India

Abstract We present results of the first major attempt to record the distribution of aquatic alien species in the Western Ghats Biodiversity Hotspot using Geographical Information System. A total of 32 alien species, including four macrophytes (Salvinia molesta, Pistia stratiotes, Eichhornia crassipes and Cabomba furcata) and 28 fish were recorded from the southern part of the Western Ghats. Seven of these have established natural populations and are invasive, which includes Oreochromis mossambicus, O. niloticus (Cichlidae), Poecilia reticulata, Gambusia affinis (Poeciliidae), Pterygoplichthys pardalis (Loricariidae), Cyprinus carpio (Cyprinidae) and Clarias gariepinus (Clariidae). Oreochromis mossambicus is the most extensively distributed invasive fish in the region. Major reservoirs serve as a spawning hub for species such as C. gariepinus and C. carpio. Significant pathways for the establishment of most alien species in Western Ghats were aquarium trade and aquaculture. Given the increasing records of alien species and proliferation of invasive species in the southern region of the Western Ghats, urgent research and policy interventions are suggested, including the development of a comprehensive database on distribution, trade, invasion biology, as well as determining both short-term and longterm impacts on endemic fauna.

Recent onset of eutrophication in Lake Izabal, the largest water body in Guatemala

Recent human population growth has contributed to the degradation of environmental resources in Guatemala. Since 1900, the population of the country grew from 17 million inhabitants. The watershed of Lake Izabal, eastern Guatemala, also experienced rapid population growth, and with it, development of intensive agriculture in areas adjacent to the lake. These recent demographic and land-use changes altered anthropogenic nutrient inputs to the water body, through delivery of raw sewage, and agricultural practices that include excessive use of fertilizers. Currently, Lake Izabal is marked by frequent algal blooms and associated fish-kill events. It also hosts a number of invasive, and in some cases, exotic plant and animal species. We used data from a sediment core collected in the western end of the lake to link past anthropogenic activities in the watershed to the deterioration of water quality and shifts in aquatic ecosystem functioning. We measured total organic carbon (TOC), total nitrogen (TN), and δ13C and δ15N of organic matter in a 137Cs- and 14C-dated sediment core from the Polochic Delta in Lake Izabal to infer past limnological changes. The core chronology indicates that 505 cm of sediment accumulated in only the last 370 years (~ 1.4 cm a−1). TOC and TN concentrations increased since about 1950, a time during which the TOC:TN ratio decreased, indicating a relatively greater contribution of phytoplankton to the sediment organic matter. Stratigraphic shifts in δ13C and δ15N indicate recent increasing inputs of raw sewage and fertilizer to the lake during the same time period. Lake Izabal, like many other water bodies in Guatemala, is starting to undergo cultural eutrophication, which probably accounts for the frequent algal blooms, proliferation of invasive species (e.g. Hydrilla verticillata), and decline in fish abundance.

Lost in translation: the German literature on freshwater salinization.

Human activities have globally increased and altered the ion concentration of freshwater ecosystems. The proliferation of potash mines in Germany (especially intense in the early 1900s) constitutes a good example of it. The effluents and runoff coming from potash mines led to extreme salt concentrations (e.g. 72 g l-1 of total salt content, approx. 149 mS cm-1) in surrounding rivers and streams, causing ecosystem degradation (e.g. massive algal blooms and fish kills). This promoted scientific research that was mostly published in German, thereby being neglected by the wide scientific community. Here, the findings of the German literature on freshwater salinization are discussed in the light of current knowledge. German studies revealed that at similar ion concentrations potassium (K+) can be the most toxic ion to freshwater organisms, whereas calcium (Ca2+) could have a toxicity ameliorating effect. Also, they showed that salinization could lead to biodiversity loss, major shifts in the composition of aquatic communities (e.g. dominance of salt-tolerant algae, proliferation of invasive species) and alter organic matter processing. The biological degradation caused by freshwater salinization related to potash mining has important management implications, e.g. it could prevent many European rivers and streams from reaching the good ecological status demanded by the Water Framework Directive. Within this context, German publications show several examples of salinity thresholds and biological indices that could be useful to monitor and regulate salinization (i.e. developing legally enforced salinity and ion-specific standards). They also provide potential management techniques (i.e. brine collection and disposal) and some estimates of the economic costs of freshwater salinization. Overall, the German literature on freshwater salinization provides internationally relevant information that has rarely been cited by the English literature. We suggest that the global editorial and scientific community should take action to make important findings published in non-English literature more widely available.This article is part of the theme issue 'Salt in freshwaters: causes, ecological consequences and future prospects'.

Nitrogen fixation and diversity of benthic cyanobacterial mats on coral reefs in Cura\xe7ao

Benthic cyanobacterial mats (BCMs) have increased in abundance on coral reefs worldwide. However, their species diversity and role in nitrogen fixation are poorly understood. We assessed the cyanobacterial diversity of BCMs at four coral reef sites in Curaçao, Southern Caribbean. In addition, nitrogen fixation rates of six common mats were measured. Microscopic examinations showed 22 cyanobacterial species, all from the order Oscillatoriales. Species diversity was similar among sites despite differences in overall BCM abundance. Dominant mats were primarily composed of Hydrocoleum glutinosum, Oscillatoria bonnemaisonii or Lyngbya majuscula. However, some mats exhibited highly variable species composition despite consistent macroscopic appearance. 16S rRNA-based phylogeny revealed similar species as those identified by microscopy, with additional sequences of unicellular (Xenococcus and Chroococcidiopsis) and heterocystous (Rivularia and Calothrix) cyanobacteria. Vice versa, morphotypes of Tychonema, Schizothrix and Dichothrix were found by microscopy only. The detection of similar species at the same sites in a study conducted 40 years ago indicates that changes in environmental conditions over these years may have favored indigenous species to bloom, rather than facilitated the introduction and proliferation of invasive species. Nitrogen fixation rates of mats were 3–10 times higher in the light than in the dark. The highest areal nitrogen fixation rate (169.1 mg N m−2 d−1) was recorded in the cyanobacterial patch dominated by O. bonnemaisonii. A scale-up of nitrogen fixation at a site with 26% BCM cover at 7 m depth yielded an aerial rate of 13 mg N m−2 reef d−1, which exceeds rates reported in open ocean blooms of Trichodesmium in the Caribbean. Our results suggest that the Caribbean basin is not only a hotspot for planktonic nitrogen fixation, but also for benthic nitrogen fixation. Because BCMs fix vast amounts of nitrogen, their proliferation will strongly alter the nitrogen budget of coral reefs.

Primates in peril: the significance of Brazil, Madagascar, Indonesia and the Democratic Republic of the Congo for global primate conservation.

Primates occur in 90 countries, but four—Brazil, Madagascar, Indonesia, and the Democratic Republic of the Congo (DRC)—harbor 65% of the world’s primate species (439) and 60% of these primates are Threatened, Endangered, or Critically Endangered (IUCN Red List of Threatened Species 2017-3). Considering their importance for global primate conservation, we examine the anthropogenic pressures each country is facing that place their primate populations at risk. Habitat loss and fragmentation are main threats to primates in Brazil, Madagascar, and Indonesia. However, in DRC hunting for the commercial bushmeat trade is the primary threat. Encroachment on primate habitats driven by local and global market demands for food and non-food commodities hunting, illegal trade, the proliferation of invasive species, and human and domestic-animal borne infectious diseases cause habitat loss, population declines, and extirpation. Modeling agricultural expansion in the 21st century for the four countries under a worst-case-scenario, showed a primate range contraction of 78% for Brazil, 72% for Indonesia, 62% for Madagascar, and 32% for DRC. These pressures unfold in the context of expanding human populations with low levels of development. Weak governance across these four countries may limit effective primate conservation planning. We examine landscape and local approaches to effective primate conservation policies and assess the distribution of protected areas and primates in each country. Primates in Brazil and Madagascar have 38% of their range inside protected areas, 17% in Indonesia and 14% in DRC, suggesting that the great majority of primate populations remain vulnerable. We list the key challenges faced by the four countries to avert primate extinctions now and in the future. In the short term, effective law enforcement to stop illegal hunting and illegal forest destruction is absolutely key. Long-term success can only be achieved by focusing local and global public awareness, and actively engaging with international organizations, multinational businesses and consumer nations to reduce unsustainable demands on the environment. Finally, the four primate range countries need to ensure that integrated, sustainable land-use planning for economic development includes the maintenance of biodiversity and intact, functional natural ecosystems.

The Impossible Sustainability of the Bay of Brest? Fifty Years of Ecosystem Changes, Interdisciplinary Knowledge Construction and Key Questions at the Science-Policy-Community Interface

In this contribution, the study of the Bay of Brest ecosystem changes over the past 50 years is used to explore the construction of interdisciplinary knowledge and raise key questions that now need to be tackled at the science-policy-communities interface. The Bay of Brest is subject to a combination of several aspects of global change, including excessive nutrient inputs from watersheds and the proliferation of invasive species. These perturbations strongly interact, affecting positively or negatively the ecosystem functioning, with important impacts on human activities. We first relate a cascade of events over these five decades, linking farming activities, nitrogen and silicon biogeochemical cycles, hydrodynamics of the Bay, the proliferation of an exotic benthic suspension feeder, the development of the Great scallop fisheries and the high biodiversity in maerl beds. The cascade leads to today’s situation where toxic phytoplankton blooms become recurrent in the Bay, preventing the fishery of the great scallop and forcing the fishermen community to switch pray and alter the maerl habitat and the benthic biodiversity it hosts, despite the many scientific alerts and the protection of this habitat. In the second section, we relate the construction of the interdisciplinary knowledge without which scientists would never have been able to describe these changes in the Bay. Interdisciplinarity, first among natural sciences (NS) and then, between natural sciences and human and social sciences (HSS). We finally ask key questions at the science-policy interface regarding this unsustainable trend of the Bay: How is this possible, despite decades of joint work between scientists and fishermen? Is adaptive co-management a sufficient condition for a sustainable management of an ecosystem? How do the different groups (i.e. farmers, fishermen, scientists, environmentalists), with their diverse interests, take charge of this situation? What is the role of power in this difficult transformation to sustainability? Combining natural sciences with political science, anthropology and the political sociology of science, we hope to improve the contribution of HSS to integrated studies of social-ecological systems, creating the conditions to address these key questions at the science-policy interface to facilitate the transformation of the Bay of Brest ecosystem towards sustainability.

Differential response to fire by an introduced and an endemic species complicates endangered species conservation

Fire is a natural component of and serves as a tool for the restoration of forested ecosystems worldwide; however, disturbance due to fire also has been implicated in the proliferation of invasive species. How these fires affect occupancy and use of the forest by wildlife is of great concern, in particular, the differential response of non-native and native species. In the American Southwest, prior to European settlement, frequent wildfires helped to maintain forest structure. We examined the effect of a large wildfire on an introduced population of the Abert’s squirrel ( Sciurus aberti ) that has invaded the high elevations inhabited by the critically endangered Mt. Graham red squirrel ( Tamiasciurus hudsonicus grahamensis ). We found that introduced Abert’s squirrels were more common than native red squirrels in burned areas. Abert’s squirrels did not abandon burned areas but nested, foraged, and tended to have small home ranges in burned areas. This suggests that invasive Abert’s squirrels are better able to exploit burned areas than are native red squirrels and that fire can favor non-native species. This interaction between non-native species, native species, and fire adds new insight into the complexities of conservation and restoration of ecosystems and helps to inform conservation activities worldwide.

Seems like I Hardly See Them Around Anymore: Historical Geographies of Riparian Change along the Wind River

Riparian areas—and the cottonwoods, water birch, bull berry, and currants that flourish within them—hold special significance for Tribes of the Intermountain American West. These species have served ceremonial and practical purposes for generations. Yet cottonwoods have experienced well-documented declines over the past several decades, and serve as indicators of overall riparian change. Research generally attributes this shift to the development of water control infrastructure, altered flood regimes, invasive species, and grazing, and rightfully so. Less attention has been paid to the cultural and historical geographies underlying these vectors of change. This research focuses on the Wind River as a case study to examine the cultural and historical factors related to riparian change. Using remote sensing, interviews and document analysis, we specifically examine boundaries between tribal/non-tribal lands along the Wind River and (1) heterogeneous patterns of riparian change, (2) significant differences in settlement patterns and the development of water infrastructure, and (3) distinct differences in water governance and its power relationships. We conclude that riparian change is heterogeneous; differs temporally, spatially, and between cultural boundaries; and relates to a socio-ecological interplay of values, practices, and policies that underlie water control, flood regime change, and proliferation of invasive species. Ultimately this research suggests that examinations of riparian change would benefit from additional in depth analyses of cultural and historical geographies, and their temporal and spatial relationships. Furthermore, tribal sovereignty over land and water may have significant impacts on overall landscape mosaics, particularly regarding the maintenance of species that support traditional lifeways.

The role of human disturbance in island biogeography of arthropods and plants: an information theoretic approach

AbstractAimRecent progress in island biogeography indicates that classical island biogeography alone cannot encapsulate the complex and dynamic nature of island biogeographical processes. Factors such as habitat complexity and connectivity, and in the face of the Anthropocene, human disturbance and invasive species, may influence insular communities. The relative importance of these factors, however, may differ among groups of biota. Here we employed an information theoretic approach to investigate factors likely to explain patterns in species richness and assemblage composition of five different groups of arthropods (ants, beetles, flies, spiders and cockroaches) and native and exotic plants within an insular community.LocationCapricornia Cays located at the southern end of Great Barrier Reef, eastern Australia.MethodsArthropods were sampled from 14 cays using pitfall and Malaise traps and hand collecting. Plants were comprehensively surveyed on each island. We used univariate and multivariate generalized linear models with a model averaging technique, to calculate summed Akaike weights which quantified the relative importance of predictor variables in explaining variation in species richness and assemblage composition.ResultsWe found that infestation of the invasive ant Pheidole megacephala was negatively correlated with the species richness of ants, beetles and flies. Unlike species richness, only the assemblage composition of ants was related to P. megacephala infestation. Assemblage composition of other arthropod groups and plants was related to various factors, including island size (native plants), native plant species richness (beetles, flies and spiders) and presence of human disturbances (exotic plants and cockroaches).Main conclusionsThe information theoretic approach proved useful in determining the relative likelihood of factors influencing both univariate and multivariate data of insular fauna and flora. The results demonstrated that human disturbance and proliferation of invasive species can override other biogeographical processes. The relative importance of these factors, however, varied depending on the taxonomic groups studied.

Complex interactions in Lake Michigan’s rapidly changing ecosystem

For over 30 years, Lake Michigan’s food web has been in a constant state of transition from reductions in nutrient loading and proliferation of invasive species at multiple trophic levels. In particular, there has been concern about impacts from the invasive predatory cercopagids (Bythotrephes longimanus and Cercopagis pengoi) and expanding dreissenid mussel and round goby populations. This special issue brings together papers that explore the status of the Lake Michigan food web and the factors responsible for these changes, and suggests research paths that must be taken for understanding and predicting system behavior. This introductory paper describes the special issue origin, presents an overview of the papers, and draws overarching conclusions from the papers.

The Role of Impoundments, Temperature, and Discharge on Colonization of the Columbia River Basin, USA, by Nonindigenous American Shad

AbstractEcologists have become increasingly aware of the combined effects of habitat disturbance and climate change on the establishment and proliferation of invasive species. Long‐term data on the population of the invasive American ShadAlosa sapidissimain the U.S. portion of the Columbia River basin provide an opportunity to examine how habitat disturbances affect the abundance and spatial distribution of an invasive species in a heavily modified environment. After the establishment of American Shad in the Columbia River in the late 1800s, the drainage was transformed from its natural lotic state to a series of reservoirs, with concomitant changes to discharge and temperature regimes, which are confounded by climate change. As the Columbia River was dammed, American Shad extended its range and increased in abundance. A large and rapid increase in spawning population abundance (recruits per spawner = 63) followed completion of The Dalles Dam in 1957, which inundated Celilo Falls, a natural barrier to upriver American Shad migration. Regressions revealed that the annual percentage of American Shad migrating upstream from McNary Dam varied with water temperature and discharge (R2= 0.72), but not population density. When Atlantic coast rivers were dammed, however, American Shad lost spawning habitat and declined in abundance. Understanding the rapid colonization of the Columbia River by American Shad may reveal ways to help American Shad recolonize rivers where they are native. Understanding the roles of water temperature and discharge may allow us to project effects of climate change on the future distribution and abundance of American Shad in the Columbia River basin. Our results suggest that dam construction and alterations to the temperature and discharge regimes of the Columbia River have contributed to the increase in abundance and spatial distribution of American Shad. These changes might have improved the reproductive success of American Shad by providing access to additional spawning grounds and creating suitable juvenile rearing conditions.

Mechanistic models of animal migration behaviour – their diversity, structure and use

1. Migration is a widespread phenomenon in the animal kingdom, including many taxonomic groups and modes of locomotion. Developing an understanding of the proximate and ultimate causes for this behaviour not only addresses fundamental ecological questions but has relevance to many other fields, for example in relation to the spread of emerging zoonotic diseases, the proliferation of invasive species, aeronautical safety as well as the conservation of migrants. 2. Theoretical methods can make important contributions to our understanding of migration, by allowing us to integrate findings on this complex behaviour, identify caveats in our understanding and to guide future empirical research efforts. Various mechanistic models exist to date, but their applications seem to be scattered and far from evenly distributed across taxonomic units. 3. Therefore, we provide an overview of the major mechanistic modelling approaches used in the study of migration behaviour and characterize their fundamental features, assumptions and limitations and discuss their typical data requirements both for model parameterization and for scrutinizing model predictions. 4. Furthermore, we review 155 studies that have used mechanistic models to study animal migration and analyse them with regard to the approaches used and the focal species, and also explore their contribution to advancing current knowledge within six broad migration ecology research themes. 5. This identifies important gaps in our present knowledge, which should be tackled in future research using existing and to-be developed theoretical approaches.

Differentiating Migration and Dispersal Processes for Pond‐Breeding Amphibians

Abstract Understanding the movement of animals is critical to many aspects of conservation such as spread of emerging disease, proliferation of invasive species, changes in land‐use patterns, and responses to global climate change. Movement processes are especially important for amphibian management and conservation as species declines and extinctions worldwide become ever more apparent. To better integrate behavioral and ecological data on amphibian movements with our use of spatially explicit demographic models and guide effective conservation solutions, I present 1) a synopsis of the literature regarding behavior, ecology, and evolution of movement in pond‐breeding amphibians possessing biphasic life cycles to distinguish between migration and dispersal processes, 2) a working hypothesis of juvenile‐based dispersal, and 3) a discussion of conservation issues that follow from distinguishing the spatial and temporal movements of amphibians at different scales. I define amphibian migration as intrapopulational, round‐trip movements toward and away from aquatic breeding sites. Population‐level management, in general, can be focused on spatial scales of <1.0 km with attention focused on adult population and juveniles that remain near the natal wetland. I define amphibian dispersal as interpopulational, unidirectional movements from natal sites to other breeding sites. Metapopulation‐ or landscape‐level management can be focused on movements among populations at spatial scales >1.0–10.0 km and on importance of terrestrial connectivity. The ultimate goal of conservation for amphibians should be long‐term regional persistence by addressing management issues at both local and metapopulation scales.