Invasive species ecology

Risk analysis of species invasions links biology and economics, is increasingly mandated by international and national policies, and enables improved management of invasive species. Biological invasions proceed through a series of transition probabilities (i.e., introduction, establishment, spread, and impact), and each of these presents opportunities for management. Recent research advances have improved estimates of probability and associated uncertainty. Improvements have come from species-specific trait-based risk assessments (of estimates of introduction, establishment, spread, and impact probabilities, especially from pathways of commerce in living organisms), spatially explicit dispersal models (introduction and spread, especially from transportation pathways), and species distribution models (establishment, spread, and impact). Results of these forecasting models combined with improved and cheaper surveillance technologies and practices [e.g., environmental DNA (eDNA), drone...

Here in Hawaii, the only ones in the rat race are mongooses, along with Federal and State officials wanting to kill both rats and mongooses.  However, there is a big flaw in the recent Federal and State proposal for statewide eradication of Hawaii's rodents and mongooses, currently under review.  Here is the argument against eradication.

ABSTRACT: This study shows that disturbance allows the pavement ant to thrive on the Atlantic
Coast. Disturbance creates open, dry habitats similar to the habitats occupied by the pavement ant
in its native Eurasia. Disturbance tends to minimize competition by creating habitats too harsh or
transient for native species. While the pavement ant can encounter competition in these harsh conditions, we note that the pavement ant competes well in urban fields that are abundant in food
resources.

Invasive species pose threats to either human health or inflict ecological and/or economic damage. The silver-cheeked toadfish (Lagocephalus sceleratus), a Lessepsian species, is one of the most harmful species in the Mediterranean Sea, because of its potent neurotoxin, impacts on marine biodiversity, and the increased costs and labor they inflict on fishers. Since the catch and consumption of this pufferfish is prohibited by almost all countries bordering the Mediterranean, they have now expanded into the entire Mediterranean and Black Sea. We performed a comprehensive study of L. sceleratus covering ecological aspects, growth, reproduction, diet and trophic level based on samples from southwestern coasts of Turkey. The estimated growth parameters were L∞ = 88.7 cm, K = 0.27 year-1, C = 0.6 and WP = 0.1. Their sex-ratio was M/F = 1:0.69. Lagocephalus sceleratus appears to be a batch spawner with discontinuous oocyte recruitment and has different spawning seasons in the Eastern Medi...

The study examined the Air Pollution Tolerance Index (APTI) of seven different tree species growing around electricity generating houses within the Ahmadu Bello University (ABU) Main campus, Samaru. Four parameters, leaf relative water content (RWC), ascorbic acid content (AA), total chlorophyll (TCH) and pH of leaf extract were used to compute the APTI of the tree species. Results indicate the order of tolerance showing Azadirachta indica (9.8) < Carica papaya (11.5) < Albizia lebbeck (14.9) < Senna siamea (17.0) <Mangifera indica (17.8) <Khaya senegalensis (19.5) < Termonalia collii (20.9). Terminalia collii, the most tolerant could act as a possible sink for air pollutants around pollution emitting sources. On the other hand, A. indica, the most sensitive of the studied species could serve as a possible indicator of air pollution.

A population of a non-indigenous armoured catfish Pterygoplichthys aff. pardalis from the Dinh river basin (Khan Hoa province, Vietnam). We provide evidence that this is a fully naturalised self-reproducing population and present data on its reproduction. Batch spawning is noted. Possible threat presented by this population to the native habitat and its inhabitants is discussed along with its possible fate. We also analysed the patterns of the fish colouration, which is the main character used for the identification of the species of this genus. We provide evidence that morphometric traits and patterns of the body colouration do not form discrete clusters. Therefore, systematics of the genus should be revised and several species would likely be invalid.

We have developed a dynamic model to track the evolution of contaminant concentration in an aquatic organism as a function of season and ontogeny throughout its life cycle. We have focused our analysis on the round goby (Apollonia melanostoma), a globally distributed invasive forage fish. By integrating bioenergetics with a bioaccumulation model, we illustrate how life history characteristics interact to influence contaminant accumulation. We use uncertainty and sensitivity analyses to assess how the model output is affected by uncertainty and variability in model parameters. We then demonstrate the influence of important physiological characteristics on contaminant accumulation with two scenarios. First, we probe the influence of sexual dimorphism by comparing gender-specific accumulation of a standard polychlorinated biphenyl congener, PCB153, in male and female round gobies. We hypothesize that lipid loss in female gobies during spawning season leads to a decrease in the PCB body burden compared to male gobies. Second, we compare PCB accumulation in the round goby and in the mottled sculpin (Cottus bairdi), the native forage fish that the round goby displaced in southern Lake Michigan, to determine whether the invasive species has an intrinsically different bioaccumulation potential than the native one. Our non-intuitive findings from these simulations illustrate how the interaction of growth rate with other life history characteristics lead to unexpected bioaccumulation patterns. The model we present is a flexible tool that integrates complex and dynamic interactions among environmental parameters, thus providing a means to better assess the potential for chemical accumulation in human and wildlife populations, and aiding the development of ecological forecasts.

Ailanthus altissima (tree of heaven) is a non-native invasive tree spreading within central Appalachia. This dioecious, deciduous, and allelopathic species copiously produces samaras, capable of traveling at least 200 m through primary wind-dispersal. Removal of A. altissima individuals prior to timbering and other forest disturbances may help prevent spread into forest interiors. To aid in species management, this study investigated the use of remote sensing to identify the location and abundance of samaras in mixed mesophytic forests through supervised classifications. From empirical measurements, the estimated number of seeds per classified unit area was determined and the relationship between quantified propagule sources and individual seed primary dispersal was spatially modeled using a cellular automata model. The predicted seed dispersion pattern was compared to empirical seed trap measurements. Secondary seed dispersal, germination and seedling survival parameters were determined through field experiments. Specifically, I found that remote sensing can be successfully used to distinguish A. altissima samara clusters from surrounding closed canopy vegetation. The identified total area of classified A. altissima samara clusters was determined to be linearly related to total canopy seed yield, however model predictions of seed dispersal patterns generally predicted greater numbers of seeds per seed trap compared to measured outcomes. Seed dispersal predictions using all classified A. altissima samara clusters provided no positive relationships with observed values (Site II, p=0.2997; negative relationship at Site III, p=0.0053). Manually delineating seed sources through photo interpretation resulted in a positive relationship between model estimates and observed seed rain (Site II, p=0.0225), but may still contain commission errors (Site III, p=0.7002). Microsite survey observations of seed germination indicate the frequency of safe sites was high in disturbed environments (canopy gaps), but seedling survival was negligible in the year this study was performed. Measurements of secondary dispersal on land and water (hydrochory) indicate the species can be dispersed with multiple dispersal agents. Hydrochory was shown to be able to contribute greatly to the species’ long distance dispersal, as seeds can reach water bodies, stay viable for long periods of immersion, and can be dispersed downstream distances more than two orders of magnitude greater than primary dispersal. This was the first demonstration of hydrochory in this species. From these studies, it appears that polychory may contribute greatly to this species dispersal and I can infer the same polychory occurs in other terrestrial species, and may contribute to invasive success.

The American mink (Neovison vison) is a semi-aquatic, generalist carnivore released onto Tierra del Fuego (TDF) Island in the 1940s, subsequently spreading to adjacent islands in the archipelago with potential effects on native prey populations. Knowledge of this new predator’s trophic ecology is essential to identify threats, plan control strategies and conserve native fauna. We studied seasonal mink diet in TDF in different habitats. We identified undigested remains from 493 scats collected between May 2005 and March 2009 along marine coasts and freshwater shores (rivers and lakes). Small mammals and fish were the main mink prey in TDF (over 65% of diet items). Seasonal variations were not detected, but diet did vary significantly between marine and freshwater habitats, where more terrestrial items were consumed. Among mammals, mink consumed more small native rodents than exotic species. Native fish consumption was also important with greater representation of species from the families Nototheniidae and Galaxiidae in marine and freshwater habitats respectively. Birds were the third item in importance, but did not constitute a particularly large part of the mink’s diet on TDF. Overall, differences found in mink diet between habitats reflected their generalist/opportunistic feeding behaviour and did not differ greatly from observations in its native range or in other areas where it has been introduced. Our results establish the interactions between this novel predator and its prey and also illustrate the need to continue research on native prey populations to quantify mink impact on them and understand the ecological context of this biotic assemblage.

Ailanthus altissima is an invasive tree species which has colonized numerous ecosystems and affected
ecosystem processes worldwide. Despite its importance as an invasive species and the high economic
costs incurred from its spread, there is a lack of long-term management planning for its control. Although
mechanical disturbance is commonly applied, the effect that this treatment may have exhausting its
resprouting ability and also its joint effect with phytochemical treatments are poorly understood, especially
in Mediterranean environments. We tested three treatments (plus a control) aimed to reduce A.
altissima growth in Mediterranean forests throughout 5 years of study. The treatments (one cut stump,
double cut stump and cut stump with glyphosate application) were repeated annually. General plant
performance (biomass, height and resprout-type density) was measured yearly during the study. Water
potential and stomatal conductance were also measured at the end of the study to evaluate particular
ecophysiological factors which might affect the response of A. altissima to assayed treatments, together
with leaf area index. Our results show that only the cut stump with glyphosate application treatment
was able to reduce the long-term growth and spread of A. altissima. The treatments applied favoured
collar sprout growth in response to disturbance events (treatments) opposite to the control, where new
sprouts grew mainly from the root. Treated resprouts displayed ecophysiological changes depending
on the assayed treatment. To our knowledge, this is the only study testing the long-term effect of both
physical disturbance and phytochemical application on A. altissima growth. Our study further refines
our knowledge on the effects of repeating both commonly and newly used treatments, improving our
management techniques to reduce the presence and growth of this invasive tree.

Japanese beetle, Popillia japonica (Newman), is a severe invasive insect pest of turf, landscapes, and horticultural crops. It has successfully colonized much of the United States and has recently established in mainland Europe. The distribution and voltinism of P. japonica will undoubtedly change as a consequence of climate change, posing additional challenges to the management of this species. To assess these challenges, a process-oriented bioclimatic niche model for P. japonica was developed to examine its potential global distribution under current (1981-2010) and projected climatic conditions (2040-2059) using one emission scenario (representative concentration pathway [RCP] 8.5) and two global climate models, ACCESS1-0 and CNRM-CM5. Under current climatic conditions, the bioclimatic niche model agreed well with all credible distribution data. Model projections indicate a strong possibility of further range expansion throughout mainland Europe under both current and future climates. In North America, projected increases in temperature would enable northward range expansion across Canada while simultaneously shifting southern range limits in the United States. In Europe, the suitable range for P. japonica would increase by 23% by midcentury, especially across portions of the United Kingdom, Ireland, and Scandinavia. Under the RCP 8.5 scenario, cumulative growing degree-days increased, thereby reducing the probability of biannual life cycles in northern latitudes where they can occur, including Hokkaido, Japan, northeastern portions of the United States, and southern Ontario, Canada. The results of this study highlight several regions of increasing and emerging risk from P. japonica that should be considered routinely in ongoing biosecurity and pest management surveys.

After 1731 in the Zuiderzee in NL poles were protected against the ship worm by hammering in a protection shield of nails. Some of there poles were re-used in a creation of a Texel artitst. By this he, probably unaware. saved important information of the effort put into the fight against the destructive work of the invasive species Tedero navalis in the NL sea waters..

We explored differences in metabolic rates of the introduced snail Cornu aspersum collected from three distant coastal locations across a 1300 km latitudinal range in Chile and raised under common-garden conditions. We measured two proxies of metabolic rate: heart rate (f H) and CO 2 production (standard metabolic rate, SMR) in a flow-through respirometry system. Although both variables were significant-ly correlated (r 2 ¼ 0.49), suggesting that f H could be a predictor of SMR, the relationship between f H and SMR and also the CO 2 pulse (SMR/f H) varied across populations. Whereas SMR suggested an in-crease in energy metabolism towards high latitudes, supporting metabolic cold adaptation, f H indicated no trend (northern and southern populations exhibited the largest values). Our results suggest that, in invertebrates, energy metabolism cannot be inferred from heart rate. Our results show metabolic differ-entiation towards increased metabolic heat production in the southern location, warranting further analyses of functional differentiation in these introduced populations.

Aquatic invasive species are a major threat to native freshwater ecosystems and cause enormous ecological and economic damage worldwide.
Didymosphenia geminata (Lyngbye) M. Schmidt is an emerging invasive aquatic species that is spreading aggressively in Southern South America.
Using niche analysis and species distribution models (SDMs), we examined niche requirements of D. geminata using climatic, topographic, and
biological variables. We compared the realized niche of the species in the United States (US) with the niche in Chile. Within Chile, we also
examined the environmental conditions (environmental envelopes) of rivers with and without this alga, to assess whether this species has the
potential to colonize more rivers. Finally, we compared the SDMs from the US and Chile projected to Chile. Results showed that the potential
distribution of D. geminata varied significantly between US and Chile. The US-based model predicted a geographic distribution in Chile which
ranged from 32º to 55º S latitude while the Chile-based model predicted suitable habitats only from 36° to 48º S, and not so in the coastal ranges nor
in Southern Patagonia ( ̴ 52–55°S). In Chile, we found no differences in the environmental envelopes of the invaded and uninvaded rivers, thus
suggesting that this species has even more suitable habitats to invade. These results can be used for prioritizing survey sites in Southern Chile for an
early detection and management of D. geminata and for the conservation of native flora and fauna in freshwater ecosystems in Chile.

The invasion success of a species depends on its life history attributes, site conditions and stochastic events. Understanding this process is important for developing effective management. Using a series of field plots and nursery experiments, we examined the association of the Scalesia forest canopy cover and light availability with the presence, patterns of germination, growth and reproductive success of Rubus niveus, one of the most invasive plants in Galapagos. Increased cover of R. niveus was significantly correlated with low canopy cover; however, individual plants were also found to persist under very closed canopies. Rubus niveus seeds were able to germinate under four light treatments, however, significantly higher percentages of germination were obtained under medium (50 % and 75 %) light treatments. Plants growing under full light exhibited significantly greater growth rates and biomass production than plants growing under medium (70 %) or low (10 %) light conditions; only plants growing under full light conditions were able to reproduce sexually. These results suggest that light availability might be a key factor for the germination, growth, establishment and subsequent invasion of R. niveus in the Scalesia forest. RESUMEN El papel de la luz en el proceso de invasión de la mora Rubus niveus en un bosque de Scalesia en Galápagos. El éxito en el proceso de invasión de una especie depende de los atributos de su historia de vida, las condiciones del sitio que invade y los eventos estocásticos. El entendimiento de este proceso es importante para desarrollar un manejo eficiente. Usando una serie de parcelas en el campo y experimentos en vivero, examinamos la asociación de la cobertura del dosel del bosque de Scalesia y la disponibilidad de luz en la presencia, patrones de germinación, crecimiento y éxito reproductivo de Rubus niveus, una de las plantas más invasoras en las Islas Galápagos. Mayor cobertura de R. niveus se correlacionó significativamente con la disminución de la cobertura del dosel; sin embargo, también se encontró que plantas individuales sobrevivían bajo copas muy cerradas. Las semillas de R. niveus pudieron germinar bajo los cuatro tratamientos de luz; sin embargo, porcentajes de germinación significativamente más altos se obtuvieron bajo tratamientos de luz media (50 % y 75 %). Plantas creciendo a plena luz mostraron tasas de crecimiento y producción de biomasa significativamente mayores que las de plantas creciendo en condiciones de medio (70 %) o poca luz (10 %); solo las plantas que crecieron en condiciones de luz total pudieron reproducirse sexualmente. Estos resultados sugieren que la disponibilidad de luz podría ser un factor clave para la germinación, crecimiento, establecimiento y posterior invasión de R. niveus en el bosque de Scalesia.

The plantations of American cranberry introduced from the US in Hantsavichy district became a site for the research and development of a strategy to control accompanying invasive species in cranberry plantations. From 21 species, five species were characterized as aggressively invasive: Persicaria sagittata (L.) H. Gross (Truellum sagittatum (L.) Soják); Agrostis scabra Willd. (A. hyemalis auct. non (Walt.) Britt.); Aster lanceolatus Willd. х A. dumosum L.; Scirpus cyperinus (L.) Kunth., Ludwigia palustris (L.) Elliott and eight species were characterized as potentially invasive: Carex crawfordii Fernald); Lycopus uniflorus Michx. (L. virginicus auct. non L.); Lysimachia terrestris (L.) Britton; Myriophyllum farwellii Morong.; Penthorum sedoides L.; Solidago graminifolia (L.) Salisb. = Euthamia graminifolia (L.) Nutt. The remaining eight species do not appear to be invasive at this time. A database of the North American species that naturalized in Belarus at experimental and commercial plantations was compiled. Botanical descriptions with explanations of their invasiveness are included for each specie. Weed management with practical measures of control are also listed. This database along with the weed management recommendations will be beneficial for farms growing large-fruited cranberries, as well as for teachers and students of biological or agricultural. This work was funded by BRFFR (grants B16MC-019 and B19MC-038).
Spiridovich E.V., Vlasava N.B., Pavlovsky N.B., Lenkovetz T.I., Reshetnikov V.N., Dubovik D.V., Skuratovich A.N., Miller D., Naumcev Y.V., Moe P., Vinogradova Yu.K. Biological characterization and control measures of invasive plant species at American cranberry plantations in Belarus : Practical Guidelines // Ed. V.V. Titok, Corr member, DSci, Associate Professor, A.V. Pugachevsky, PhD, Associate Professor.  Minsk : "Publishing House "Four Quarters", 2021. – 76 p. – ISBN 978-985-581-475-8.

Several lines of evidence suggest that the effects of invasive speciesmay be greater in aquatic freshwaters than in terrestrial ecosystems.We argue that freshwaters are significantlymore invasible—from a number of poorly regulated sources—and also more susceptible to negative biodiversity, physical ecosystem, and socioeconomic impacts when invaded, than their terrestrial counterparts. Moreover, the nature
of freshwaters appears to result in impacts that are wide ranging and severe while being indirect, diffuse, and difficult to both detect and predict. For these reasons, we conclude that freshwater invasive species represent a special case,
when compared with terrestrial invasives, in which the likelihood of negative impacts, and their effects, is disproportionately severe. We suggest that future
approaches to research in this area should aim to audit the full array of impacts of a number of representative invasive species,with a view to building an evidence base
to support the global implementation of a precautionary approach to the release of aquatic freshwater non-native species.

Gunnera tinctoria invasions represent an often identified enigma: why should a spe- cies with a narrow ecological amplitude have the capacity to become such a significant invader? In Ireland, for instance, it is now recognised as one of the top thirteen invasive species. Consideration of its ecophysiology indicates that it should never be able to colonize areas subjected to even mild water deficits, although the impact of other environmental factors is unclear. Habitat-mapping of G. tinctoria in the west of Ireland indicates a preference for anthropogenic habitats. Rather surprisingly, coloniza- tion of organic soils, the dominant soil type in the region is poor. Analysis of G. tinctoria populations indicate that the invasive populations are genetically distinct and that gene flow may be an important factor contributing to invasive success. Stochastic evolutionary processes alone can explain the ob- served genetic variation, with no need for adaptive evolution. Genetic analysis, in conjunction with computer-based modelling, indicates that seed dispersal is the primary method for long distance propagule dispersal, despite the fact the initial belief that this species propagates solely asexually. However, few seeds germinate in the field, although they remain viable, with germination constrained by low soil temperatures. Projections of the impact of climate change on the future success of this species indicate that its distribution is likely to increase by the end of the century, with habitat-type playing the more significant role. Overall, these results indicated how little we know about what con- tributes to successful invasions and the significance of complex relationships among plant traits, habi- tat and climate.

Tolka Valley Park is a regional park located on both sides of the Tolka River between Finglas and Glasnevin. The Tolka River valley is rich in plant and animal life, a haven for biodiversity within the city, and local history. But the Tolka Valley Park is also situated over a former city landfill, which creates some unique challenges to its management and design. This paper examines the impacts that a man-made wetands can have on the biodiversity of an urban landscape.

Climate change, a timely topic, cannot be understood solely by analyzing modern-day ecosystems. Sediment stratigraphy from tidal marshes is an important source of paleoecological data, as these ecosystems experience high rates of deposition and preserve organic material well. Although Hudson River Valley marshes have been extensively researched, work has focused on the four areas protected by the Hudson
River National Estuarine Research Reserve (HRNERR). The marshlands of Haverstraw in Rockland County are comparable to the HRNERR sites in their capacity for biodiversity, carbon sequestration, and other important ecological functions. They are, however, understudied. This study uses loss-on-ignition and macrofossil analysis in combination with X-ray fluorescence spectroscopy to construct a high-resolution
paleoenvironmental record. Biotic and geochemical zones have been identified and correlated with archaeological and historical data to assess the influence of anthropogenic activity in the area. The organic:inorganic maxima evidenced likely correspond to a preindustrial period, characterized by burning events associated with increasing populations and concentrated settlement, as well as agricultural practices. Invasive species are prevalent, but certain key native species, notably Acorus americanus (American Sweet Flag), persist today. Exponential increases in heavy metal concentrations likely result from industry in the area but have declined following cessation of this activity and introduction of unleaded gasoline. Understanding historical human impacts is vital for predicting the ramifications of future development as well as establishing protocols for conservation and restoration.

Understanding the amount of impact and distribution of invasive species is important for both basic ecological research and making management decisions. Because of their extensive impacts in southern Patagonia, invasive North American beavers (Castor canadensis) are considered both a scientific and conservation priority. However, little is known about the landscape-scale effects of these exotic ecosystem engineers. Using satellite imagery, we estimated the impact of beavers in the Argentine portion of Tierra del Fuego Island and determined the habitat factors (vegetation cover, forest type, stream presence and topography) related to their presence using both non-parametric statistical and information-theoretic approaches. Results indicated that more than 31,000 ha (1.6 % of the study area) were impacted by beavers and that the presence, but not the amount, of beaver impacts were spatially clustered. Impacts were greater in the Mountain ecoregion (2.8 % of the ecoregion) and lower in the Steppe (0.1 %). The best model for predicting beaver presence included variables related to water availability (presence of peat-lands and streams), forage availability (forest type cover), and topography (slope and elevation). These findings support previous assertions that this invasion is the largest alteration to the sub-Antarctic forests in the Holocene. They also serve as a foundation for the development of maps based on habitat-and landscape-scale conditions to assist with the orientation of control, eradication, and restoration efforts currently being planned.

1. The North American signal crayfish Pacifastacus leniusculus has been widely introduced throughout Europe where it is expanding its range and in many areas replacing the native white-clawed crayfish Austropotamobius pallipes. There is concern with regards to the impact of this species replacement on benthic fish. Interspecific behavioural interactions and competition for shelter between the benthic fish, bullhead Cottus gobio and A. pallipes and P. leniusculus were measured to assess the comparative impact of native and non-native crayfish. 2. Both white-clawed crayfish and signal crayfish were dominant over bullhead. Bullheads moved away from approaches of crayfish, left shelters on entry of crayfish and rarely entered an occupied shelter. Signal crayfish made significantly more aggressive approaches towards bullheads than white-clawed crayfish. 3. Alone, bullheads spent most of their time by day under shelter (median 96%), reflecting a highly entrained behavioural response, which was relaxed by night (median 60%). Both crayfish species reduced shelter use by bullheads although the extent of shelter sharing by bullheads was higher in trials with white-clawed crayfish than with signal crayfish. 4. Sampling in the River Wharfe, northern England, where signal and white-clawed crayfish and bullhead currently exist, demonstrated a negative relationship between the densities of signal crayfish and bullhead, with high bullhead abundance where crayfish were absent or where white-clawed crayfish were present at low density. 5. Assuming that shelter is sometimes limited under natural conditions, crayfish are likely to displace bullheads from shelters, which may increase predation risk for bullheads. Although the effects of signal crayfish on bullhead shelter use were more intense, the pattern was highly evident for the native white-clawed crayfish. The higher fecundity and densities attained by signal crayfish may be more significant than differences in the behaviour of the two crayfish species in determining the impact of crayfish on bullheads.

Radio-telemetry was used to study the late autumn and winter movements of twenty adult signal crayfish Pacifasta-cus leniusculus (32.9–63.8 mm carapace length) an introduced exotic crayfish species, in the upland River Wharfe, northern England. The distances moved during the study varied greatly between individuals (0–328 m). Movements were generally sporadic; crayfish would remain in one position for several weeks and make occasional movements to new locations. Total distances travelled, linear range and ranging area did not differ significantly between males and females. The distance travelled in upstream and downstream directions did not differ significantly and there was no correlation between distance travelled and crayfish size. Several high flow events occurred during the study, but these did not cause any mortality or apparent displacement of crayfish downstream, suggesting that this is not a significant factor in downstream dispersal or mortality of adults of this invasive crayfish species in winter. A marked reduction in large-scale movements occurred in mid-December which coincided with a decline in water temperature. There was a less distinct pattern in local activity which was strongly correlated with water temperature and varied before and after mid-December.

Abstract
Background: There is little information about the early development of this invasive fish species in order to understand its early life history and developmental strategies towards invasion.
Material and Methods: Female Pterygoplichthys pardalis were induced to spawn using human chorionic gonadotropin (HCG) so as to study the developmental stages from fertilization until yolk
resorption.
Results: The females subjected to a single dose of HCG responded positively to treatment (97%) with higher fertilization success (88%) compared to the untreated females (21%). Nonetheless, the
HCG-induced fertilized eggs had a low hatching success (49%), while from the free-living embryos successfully hatched, a high number (90%) survived to become juveniles. Embryonic development in P. pardalis was completed 168 h and 30 min after fertilization, with the total yolk resorption completed on the 8
day post hatching, during which the suckermouth gradually shifted from rostral to ventral position to commence the loricariid algae-scraping feeding mode.
Conclusions: Pterygoplichthys pardalis does not undergo a true larval metamorphosis between the free-living embryo and the juvenile stage and a definitive adult phenotype is developed directly. These results provided basic, yet essential information on the early developmental features of this invasive species whose spawning and early developmental strategies were difficult to observe in the field. Implications of some ontogenetic features in this species with regards to invasion are also
discussed.
Keywords: Development, embryogenesis, invasion, larvae, morphology, Pterygoplichthys pardalis.

The wild boar is an invasive ecosystem
engineer in Argentina that has lacked sufficient basic
information to determine applied actions. The current
distribution, impacts and management of this species
were analyzed using the expert opinion surveys of
protected area managers. The boar is widely distributed and occupies most of Argentina’s terrestrial
ecoregions. Moreover, its populations are common,
and its abundance is growing in most of the protected
areas. Boars were recorded mostly in wetlands, forest
and shrublands. Managers also reported a wide range
of negative impacts, which included soil disturbance,
vegetation damage and animal predation. Several
control method types are used and in most protected
areas, more than one are applied, but hunting was the
most used technique. However, the effectiveness of
control methods was low, suggesting the need of an
urgent plan to define coordinated management actions
to minimize the negative impacts of this species and
also to prevent its expansion into new areas.

Exotic species are increasingly becoming an important consideration for biodiversity scientists and professionals. Invasion by exotics follows four stages
(Vankat and Roy 2002): 1) Introduction, when it becomes part of the regional species pool; 2) Dispersal, the movement of individuals into new areas of the region; 3) Colonization, the founding of a new population in the region; and 4) Establishment, a breeding thriving population is now present. A species must pass through filters as it moves from one stage of invasion to the next. One common filter is distance. Island biogeography predicts that successful immigration into a new habitat by potential colonists is inversely related to the distance that colonist must travel to arrive at the new habitat (MacArthur and Wilson 1967). This distance can be bridged as humans move species at high speeds and often under environmentally controlled situations around
the world. General ecological theory predicts that any mechanism that reduces isolation between the source
population and an uncolonized habitat should also stimulate movement of organisms from the source to the virgin habitat (Collinge 2000). Human transportation is one obvious factor that can reduce this isolation and promote colonization by exotic species, yet little is known about how easily some species travel as stowaways with humans

Common ash (Fraxinus excelsior) is a keystone tree species throughout temperate Europe whose future existence is threatened by an emerging invasive fungal disease. Ash dieback, which first appeared in Poland in the 1990s, has rapidly spread to most eastern, central and northern European countries. The causal agent of the disease, the ascomycete Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea), was recently described as a new species. Given that the disease lethally affects ash trees of all age classes, and that ash tree mortality levels are high, F. excelsior and the many organisms dependent on ash trees are under threat. Based on a literature survey, we provide an overview of the present knowledge on ash dieback, identify practical recommendations and point out research needs. The observation of relatively resistant individual ash trees (although at very low frequency) calls for a rapid germplasm collection effort to establish a breeding program for resistance or tolerance to the disease. Ash trees that appear to be tolerant to the pathogen should not be felled, unless they pose an unacceptable risk to people’s security. Given that the pathogen does not form propagules on wood, and given the importance of deadwood for biodiversity conservation, dead and dying ash trees should be left in the forest. Landscape pathology and genetic tools can be used to reconstruct the dispersal pathways of H. pseudoalbidus and to identify environmental features
associated with variation in disease severity, so as to better predict the further development of the epidemic. Observations on differences in susceptibility of various ash species are needed to locate the geographic origin of the pathogen and to identify Fraxinus species which might be used for resistance breeding or even replacement of F. excelsior. Conservation biologists, landscape managers, restoration ecologists, social scientists and tree geneticists need to engage with forest pathologists and the various stakeholders throughout the distributional range of F. excelsior so as to tackle this pressing conservation challenge.