Modelling bioenergetic and population-level impacts of invasive bigheaded carps (Hypophthalmichthys spp.) on native paddlefish (Polyodon spathula) in backwaters of the lower Mississippi River

1. While invasions of large rivers by exotic fish species are well documented, assessing actual or potential impacts on native species is a challenge. Rapid assessments may be possible through the application of a combination of bioenergetic and population dynamic models.
2. Paddlefish (Polyodon spathula) is a native species in the central USA with a history of population decline due to waterway development and overharvesting for roe. It is not known whether paddlefish are impacted by resource competition from invasive bigheaded carp populations, including silver (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis), which have expanded dramatically in the Mississippi River.
3. We used bioenergetic models to project the potential impact of invasive silver and bighead carp on zooplankton density and paddlefish somatic growth in backwater habitat. Bioenergetic outputs were translated to impacts on fecundity, becoming inputs for 50-year metapopulation simulations of backwater habitat connected to the main-stem Mississippi River by episodic flood events.
4. Competition with carp reduced growth and increased the risk of population decline for paddlefish. Impacts increased disproportionately with increased carp abundance and were further exacerbated in scenarios with increased diet overlap or decreased zooplankton abundance.
5. We also analysed paddlefish condition data collected at sites near the lower Mississippi River with varying histories of carp invasion. These data give credence to the bioenergetic model output; paddlefish had reduced body condition at sites with long-established, high-density carp populations.
6. We conclude that invasive bigheaded carps have great potential to reduce paddlefish growth, fecundity, and abundance. The pairing of bioenergetics and population models is likely to be broadly useful in assessing the risks posed by other invasive species.

     

The genetic characteristics of invasive Largemouth Bass in southern Brazil

Largemouth Bass (Micropterus salmoides) have been introduced on a global scale for sport fishing but represent a conservation concern given their documented negative impacts on native faunal diversity and abundance. Recent research using molecular data to characterize invasive Largemouth Bass populations elsewhere has demonstrated that populations are typically characterized by limited genetic diversity, or represent a combination of Largemouth Bass and Florida Bass (Micropterus floridanus). To test whether these traits were consistent with invasive populations in Brazil, we generated mitochondrial sequence data from four established populations of Largemouth Bass collected in southern Brazil as well as a local aquaculture facility to confirm species identity and quantify levels of genetic diversity. We identified the exclusive presence of Largemouth Bass in the region and observed limited levels of haplotype (haplotype diversity = 0.0684, SE = 0.038) and nucleotide diversity (0.0003, SE = 0.0002) which suggested the presence of a founder effect associated with introduction. Each of the four populations were dominated by a single haplotype that was identical to one recovered from a nearby aquaculture facility, which identified this facility as a potential introduction source.     

Different climatic envelopes among invasive populations may lead to underestimations of current and future biological invasions

Aim We explore the impact of calibrating ecological niche models (ENMs) using (1) native range (NR) data versus (2) entire range (ER) data (native and invasive) on projections of current and future distributions of three Hieracium species. Location H. aurantiacum, H. murorum and H. pilosella are native to Europe and invasive in Australia, New Zealand and North America. Methods Differences among the native and invasive realized climatic niches of each species were quantified. Eight ENMs in BIOMOD were calibrated with (1) NR and (2) ER data. Current European, North American and Australian distributions were projected. Future Australian distributions were modelled using four climate change scenarios for 2030. Results The invasive climatic niche of H. murorum is primarily a subset of that expressed in its native range. Invasive populations of H. aurantiacum and H. pilosella occupy different climatic niches to those realized in their native ranges. Furthermore, geographically separate invasive populations of these two species have distinct climatic niches. ENMs calibrated on the realized niche of native regions projected smaller distributions than models incorporating data from species’ entire ranges, and failed to correctly predict many known invasive populations. Under future climate scenarios, projected distributions decreased by similar percentages, regardless of the data used to calibrate ENMs; however, the overall sizes of projected distributions varied substantially. Main conclusions This study provides quantitative evidence that invasive populations of Hieracium species can occur in areas with different climatic conditions than experienced in their native ranges. For these, and similar species, calibration of ENMs based on NR data only will misrepresent their potential invasive distribution. These errors will propagate when estimating climate change impacts. Thus, incorporating data from species’ entire distributions may result in a more thorough assessment of current and future ranges, and provides a closer approximation of the elusive fundamental niche.     

Will climate change promote future invasions?

Biological invasion is increasingly recognized as one of the greatest threats to biodiversity. Using ensemble forecasts from species distribution models to project future suitable areas of the 100 of the world's worst invasive species defined by the International Union for the Conservation of Nature, we show that both climate and land use changes will likely cause drastic species range shifts. Looking at potential spatial aggregation of invasive species, we identify three future hotspots of invasion in Europe, northeastern North America, and Oceania. We also emphasize that some regions could lose a significant number of invasive alien species, creating opportunities for ecosystem restoration. From the list of 100, scenarios of potential range distributions show a consistent shrinking for invasive amphibians and birds, while for aquatic and terrestrial invertebrates distributions are projected to substantially increase in most cases. Given the harmful impacts these invasive species currently have on ecosystems, these species will likely dramatically influence the future of biodiversity.     

Prunus serotina in Italy: a challenging candidate for the national list of priority invasive alien species

Abstract

In accordance with the European regulation on Invasive Alien Species (IAS), the black cherry tree (Prunus serotina Ehrh.) has recently been indicated as one of the 96 species proposed for the development of the national list of priority invasive alien species in Italy. The species, native to North America, is recognised as one of the most harmful IAS in Europe, given its high spread potential and the associated ecological and economic impacts reported in its alien range. Although P. serotina is recognised as a pest within the EU, plants are still available on the market, confirming intentional introduction as a current potential pathway for this species arrival into new areas. Since a comprehensive overview of the main features characterizing the invasive potential of this species is still lacking, we aim to underpin the high priority status of P. serotina as a IAS of main concern in Italy by outlining the main biological features, pathways and impacts of the black cherry in its secondary range. Management measures to be potentially included in specific action plans are also summarised.     

The invasion by the Yellow-legged hornet: A systematic review

The Yellow-legged hornet (Vespa velutina nigrithorax), native to regions of Southeast Asia, was accidentally introduced in Europe, South Korea, and Japan, where is has often become invasive. Due to its potential negative impacts at ecologic, economic and social levels, this hornet was included in the “Union list” of the EU legislation for invasive alien species. This means that measures are urgently needed to prevent further introductions, as well as to early-detect and control spread to avoid new populations. In this study we aim to identify the main reported drivers of distribution, ecological preferences, impacts, and methods for preventing introduction, controlling, and managing this invasive species. The supporting information was obtained from a comprehensive literature search. Then, a literature review was performed to classify the records gathered and to extract the relevant information following an adapted Drivers-Pressures-State-Impacts-Responses framework. The achieved results show a growing interest of researchers on V. velutina nigrithorax through time due to its quick spread and impacts on new ecosystems. They also revealed that there is much information on the State of invasions, whereas more knowledge is needed regarding the Drivers of those invasions. Biological traits such as life history traits, morphology, and the sting venom properties are some of the most studied topics regarding V. velutina nigrithorax. In the future, research should focus on the topics that lack information, analyse other Response solutions that meet the intended measures by the EU legislation, and use new methodology to study the impacts caused by this invader under new perspectives.     

Increased Topsoil Mineral Nutrient Concentrations Under exotic invasive plants in Belgium

Exotic invasive plants can alter ecosystem processes. For the first time in Europe, we have analysed the impacts of exotic invasive plants on topsoil chemical properties. At eight sites invaded by five exotic invasive species (Fallopia japonica, Heracleum mantegazzianum, Solidago gigantea, Prunus serotina and Rosa rugosa), soil mineral element composition was compared between invaded patches and adjacent, uninvaded vegetation. We found increased concentrations of exchangeable essential nutrients under the canopy of exotic invasive plants, most strikingly so for K and Mn (32% and 34% increase, respectively). This result fits in well with previous reports of enhanced N dynamics in invaded sites, partly due to higher net primary productivity in exotic invasive plants compared to native vegetation. Sonia Vanderhoeven and Nicolas Dassonville - Equally contributing authors.     

The invasion and potential impact of the Asian House Gecko (Hemidactylus frenatus) in Australia

Hemidactylus frenatus is an Asian gecko that has spread pantropically to become one the world's most widespread reptiles. It has been established in Australia for approximately 50 years, but the last two decades have seen massive range expansion across settled areas of northern and eastern Australia; and this spread continues at pace. Disturbingly, H. frenatus is increasingly being detected in natural habitats in Australia, in some cases at high densities. Despite rampant spread, there has been little concern regarding the potential impact of this species on native geckos or natural systems more broadly. This is surprising given that Australia is a centre of gecko origin and diversity, and that H. frenatus has had well documented detrimental impacts on geckos in other parts of its introduced range. Here I review the biology and global distribution of H. frenatus, plot its spread in Australia over the five decades since establishment, and review the research on invasive populations of this species overseas and in Australia to assess potential impacts. I argue that Australia should be more concerned about H. Frenatus because: (i) it is spreading rapidly across northern, eastern and central Australia; (ii) it can invade natural habitats; (iii) it is a very strong competitor and may out‐compete Australian geckos in some situations; and (iv) it carries novel parasites that may impact native reptile species. Hemidactylus frenatus is here to stay and represents a potential threat to Australia's diversity and ecology. A key question is the degree to which it will invade natural habitats and what its impacts will be in these. Research is required to assess the current and potential impacts of H. frenatus in Australia so as to determine how these can be managed and the level of investment warranted.     

Geographic trend in sexual size dimorphism and body size of Osteopilus septentrionalis (Cuban treefrog): implications for invasion of the southeastern United States

We collected Osteopilus septentrionalis from Central Florida for analysis of sexual size dimorphism and compared our data to published information from populations across the native and introduced range of the species. We found significant sexual size dimorphism (females larger), with the degree of dimorphism decreasing with increasing degrees north latitude, a trend largely driven by a pronounced decrease in female mean snout to vent length. Potential explanations for this trend include reduced growth rates, increased time to maturity, and reduced life expectancy, all of which may be tied to climatic variation. A trend of decreasing female mean size toward the northernmost extent of the current introduced range of this species may be indicative of diminished impacts and invasive success. Geographical variation in morphology and its associated implications should be evaluated when considering the potential impacts of invasive species.     

Impacts of freshwater aquaculture on fish communities: A whole‐ecosystem experimental approach

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Predicting the impacts of an introduced species from its invasion history: an empirical approach applied to zebra mussel invasions

1. Quantitative models of impact are lacking for the vast majority of known invasive species, particularly in aquatic ecosystems. Consequently, managers lack predictive tools to help them prioritise invasion threats and decide where they can most effectively allocate limited resources. Predictive tools would also enhance the accuracy of water quality assessments, so that impacts caused by an invader are not erroneously attributed to other anthropogenic stressors. 2. The invasion history of a species is a valuable guide for predicting the consequences of its introduction into a new environment. Regression analysis of data from multiple invaded sites can generate empirical models of impact, as is shown here for the zebra mussel Dreissena polymorpha. Dreissena's impacts on benthic invertebrate abundance and diversity follow predictable patterns that are robust across a range of habitat types and geographic regions. Similar empirical models could be developed for other invaders with a documented invasion history. 3. Because an invader's impact is correlated with its abundance, a surrogate model may be generated (when impact data are unavailable) by relating the invader's abundance to environmental variables. Such a model could help anticipate which habitats will be most affected by invasion. Lack of precision should not be a deterrent to developing predictive models where none exist. Crude predictions can be refined as additional data become available. Empirical modelling is a highly informative and inexpensive, but underused, approach in the management of aquatic invasive species.     

First observations of intersex development in paddlefish Polyodon spathula

This study reports the first cases of intersex (abnormal development of both male and female reproductive tissues in a gonad) paddlefish Polyodon spathula, an Acipenseriform species of large rivers in the central U.S. and in aquaculture worldwide. Despite a large, multi-decadal data set in Oklahoma, Montana, and North Dakota, intersex development was not observed until 2019, when two individuals were harvested from the Grand Lake/Neosho River stock in Oklahoma. This suggests that intersex development in mid-water, zooplanktivorous paddlefish is rarer than in bottom-dwelling sturgeons for which intersex development is regularly observed. Although contaminants are implicated in causing intersex development in other Acipenseriformes, more investigation is needed.     

Suitable areas for the invasion expansion of Xylocopa bees in South America

The introduction of exotic species into native ecosystems can be a cause for concern when those species are invasive. Invasive species cause ecological problems and have socio-cultural impacts on human health and the economy; for example, invasive bees may negatively impact their introduced ecosystem by spreading diseases or outcompeting native pollinators. Xylocopa spp. bees are diverse and distributed throughout the Neotropics. However, Xylocopa augusti (Lepeletier, 1841) and Xylocopa splendidula (Lepeletier, 1841) are not native to Mediterranean Chile. This study aimed to evaluate the invasive potential of these exotic species and predict the potential macroecological effects of their invasions. We also aimed to pinpoint possible distributions for these species throughout South America. We correlated biogeographic occurrence data with climatic variables for each species to model their potential distribution in both current and future scenarios. The models provide strong evidence that both species are changing their distributions: their ranges are expanding towards western South America, particularly Bolivia, Chile and Peru. We demonstrate an increase in niche overlap between these species and show there are new geographic areas vulnerable to the establishment of these invasive bees under current and future climate conditions. These data suggest that these bees may adapt their geographic distribution as the climate changes and pose a threat to native pollinators in new geographic areas.     

Turning back the tide? Local-scale impacts of climate change may have positive effects by restoring natural riverine habitat and reducing invasive fish density

1. Global biodiversity is increasingly threatened by habitat loss, climate change, and biological invasion. However, predictions of impacts on native fauna are hampered by an inadequate knowledge of how these factors interact and how climate change will affect the distribution, abundance, and behaviour of both native and invasive species, not least as most predictions are based on the long-term effects of temperature alone.
2. Here, we present a case study illustrating how local-scale climate change impacts (increased temperature, reduced rainfall, shifts in peak rainfall) affected the hydrology of a channelised lowland European river (reduced flow, reduction in flood events, increased siltation, macrophyte growth), allowing native fish species to recolonise the bankside zone and reducing the density of invasive round goby Neogobius melanostomus by removing its preferred habitat.
3. While most studies predict long-term negative impacts on global fish populations, some suggest potential direct and indirect benefits at a local scale. We are of the opinion that, at a local scale, climate change impacts on fish will be more nuanced and complex than long-term predictions suggest, resulting in both positive and negative effects, with consolation prizes in the face of larger losses. While impacts on fish will differ between regions and/or continents, depending on the specific impacts of climate change, identification of positive effects will be essential in clarifying long-range forecasts and identifying management procedures for mitigating overall negative impacts.

     

Review article: The catastrophic impact of invasive mammalian predators on birds of the UK Overseas Territories: a review and synthesis

The UK has sovereignty over 16 Overseas Territories, which hold some of the world’s great seabird colonies and collectively support more endemic and globally threatened bird species than the whole of mainland Europe. Invasive alien mammalian predators have spread throughout most of the Territories, primarily since European expansion in the 16th century. Here we review and synthesize the scale of their impacts, historical and current, actions to reduce and reverse these impacts, and priorities for conservation. Mammalian predators have caused a catastrophic wave of extinctions and reductions in seabird colony size that mark the UKOTs as a major centre of global extinction. Mammal‐induced declines of threatened endemics and seabird colonies continue, with four Critically Endangered endemics on Gough Island (Tristan da Cunha), St Helena and Montserrat directly threatened by invasive alien House Mice Mus musculus, Feral Cats Felis catus and rats Rattus spp. Action to reduce these threats and restore islands has been modest in comparison with other developed countries, although some notable successes have occurred and a large number of ambitious eradication and conservation plans are in preparation. Priority islands for conservation action against mammalian predators include Gough (which according to one published prioritization scheme is the highest‐ranked island in the world for mammal eradication), St Helena and Montserrat, but also on Tristan da Cunha, Pitcairn and the Falkland Islands. Technical, financial and political will is required to push forward and fund the eradication of invasive mammalian predators on these islands, which would significantly reduce extinction risk for a number of globally threatened species.     

A modelling approach to estimate the effect of exotic pollinators on exotic weed population dynamics: bumblebees and broom in Australia

The role of mutualisms in contributing to species invasions is rarely considered, inhibiting effective risk analysis and management options. Potential ecological consequences of invasion of non‐native pollinators include increased pollination and seed set of invasive plants, with subsequent impacts on population growth rates and rates of spread. We outline a quantitative approach for evaluating the impact of a proposed introduction of an invasive pollinator on existing weed population dynamics and demonstrate the use of this approach on a relatively data‐rich case study: the impacts on Cytisus scoparius (Scotch broom) from proposed introduction of Bombus terrestris. Three models have been used to assess population growth (matrix model), spread speed (integrodifference equation), and equilibrium occupancy (lattice model) for C. scoparius. We use available demographic data for an Australian population to parameterize two of these models. Increased seed set due to more efficient pollination resulted in a higher population growth rate in the density‐independent matrix model, whereas simulations of enhanced pollination scenarios had a negligible effect on equilibrium weed occupancy in the lattice model. This is attributed to strong microsite limitation of recruitment in invasive C. scoparius populations observed in Australia and incorporated in the lattice model. A lack of information regarding secondary ant dispersal of C. scoparius prevents us from parameterizing the integrodifference equation model for Australia, but studies of invasive populations in California suggest that spread speed will also increase with higher seed set. For microsite‐limited C. scoparius populations, increased seed set has minimal effects on equilibrium site occupancy. However, for density‐independent rapidly invading populations, increased seed set is likely to lead to higher growth rates and spread speeds. The impacts of introduced pollinators on native flora and fauna and the potential for promoting range expansion in pollinator‐limited ‘sleeper weeds’ also remain substantial risks.     

Predicting socio‐economic and biodiversity impacts of invasive species: Red Imported Fire Ant in the developing western Pacific

Effective biosecurity and pest management are fundamental to sustainable development. Invasive ants pose significant risks to the environment and economy, which are well‐managed by biosecurity agencies in developed countries. However, a comprehensive view of the potential impacts of invasive ants in developing Pacific Island Countries and Territories (PICTs) is lacking. We quantified the potential costs of the Red Imported Fire Ant (Solenopsis invicta Buren) across multiple sectors using an extrapolation analysis. Overall, we estimated that the impacts of Red Imported Fire Ant on developing PICTs could amount to over USD 329 million annually, corresponding to approximately 0.7% of combined GDP. Over half of the costs were predicted to result from impacts on the agriculture sector, a major source of employment and subsistence. We found that over 350 highly threatened species could be at risk from Red Imported Fire Ant. We would expect countries with Least Developed Country status and relatively low GDP to be least able to respond to an incursion of these ants, and as a result the costs could be higher than we have extrapolated. Red Imported Fire Ant could therefore potentially have considerable impact on the on‐going development of the region.     

Ecological impacts of non-indigenous invasive fungi as forest pathogens

Non-indigenous pathogenic fungi increasingly threaten North American tree species. Ecosystems may be fundamentally changed when abundant tree species are functionally eliminated, as occurred with American chestnut (Castanea dentata (Marsh.) Borkh.). Conversely, changes may be more subtle but still significant and long lasting when populations are lost, or all trees in the larger size classes are killed. Proposed approaches for characterizing the magnitude of ecological impacts use characteristics of both the non-indigenous pathogen and the host species. Impacts are most significant when highly successful invading pathogens attack foundation species, setting in motion a long-lasting cascade of effects on the host and associated species. Such impacts have generally not been well documented at the ecosystem level. Several North American forest tree species have been functionally eliminated or severely reduced by non-indigenous pathogens. Historical invasions, such as that of chestnut blight (Cryphonectria parasitica (Murr.) Bar), caused very significant ecological impacts that will never be completely understood because of lack of quantitative data. Beech bark disease, caused by a combination of an introduced scale insect (Cryptococcus fagisuga Lindinger) and a fungus (Neonectria faginata (Lohman et al.) Castl. & Rossman), is still advancing and provides opportunities for studying ecosystem-level impacts when a major tree species is removed or markedly reduced in abundance from the overstorey. Butternut canker, caused by the fungus, Sirococcus clavigignenti-juglandacearum N.B. Nair, Kostichka & Kuntz, has spread throughout the host range, endangering species’ survival. Other non-indigenous invasive fungi such as Cronartium ribicola J.C. Fisch and Phytophthora lateralis Tucker & Milbrath continue to move into new populations, causing high mortality and associated restructuring of these ecosystems. Global trade and environmental change trends will ensure new challenges by non-indigenous fungal pathogens, presenting an urgent need for improved understanding of long-term impacts across ecological systems.     

Research priorities for wind energy and migratory wildlife

With upcoming global wind-energy build-out estimated in millions of units, cumulative environmental impacts must be considered and understood to promote responsible expansion of this renewable energy source. In June 2009, 30 wildlife scientists convened in Racine, Wisconsin, USA to identify key research priorities concerning wind energy's potential impacts on migratory wildlife (birds and bats). This working group suggested 4 areas where improved science is most needed to evaluate the impacts of wind-energy development on migrating animals more accurately than can be accomplished today: 1) standardized protocols and definitions; 2) new methods and models for assessing and forecasting risk; 3) documenting lethal and sub-lethal effects at existing wind facilities; and 4) improved facility-site access, data access, and data management for researchers. Focused research based on these priorities will both quantify potential risks associated with wind-energy development and help derive science-based, peer-reviewed, best-management practices for existing and future wind projects. © 2011 The Wildlife Society.