Populations Of Invasive Species Research Articles

A spatially discrete, integral projection model and its application to invasive carp

Natural resource managers and ecologists often desire an understanding of spatial dynamics such as migration, dispersion, and meta-population dynamics. Network-node models can capture these salient features. Additionally, the state-variable used with many species may be appropriately modeled as a continuous variable (e.g., length) and management activities sometimes can only target individuals of certain sizes. Integral projection models (IPMs) can capture this life history characteristic and allow for the examination of size-specific management. We combined an IPM with a network-node model to capture both of these salient features. We then demonstrated how this model could be used to understand and manage populations of invasive species focusing on grass carp as an example. Grass carp disrupt ecosystems outside of their native range and have spread around much of the world, including North America. The impacts of grass carp include adversely changing aquatic plant communities, which in turn affect a wide range of endpoints ranging from water quality to waterfowl recruitment. We specifically examined two theoretical systems using parameters from the literature. First, we modeled a lake with two tributaries and examined how modified sterile males could be used as a control tool. We found that modified sterile males may be a feasible control tool to limit population growth. Second, we modeled a series of river pools and examined how harvest and deterrents could be used to decrease the risk of expanding grass carp's range within a river system. Within this system, we also compared the impacts of size specific harvest and uniform harvest across all sizes. We found that targeting the largest, spawning populations may be more important than targeting the populations close to the invasion front for reducing the risk of spreading grass carp. We also demonstrate that size of harvested fish was important for controlling populations.

Invasive species of Asteraceae family in Kursk flora

The paper deals with biological features and quantitative characteristics of populations of some invasive species of the family Asteraceae in Kursk flora and their distribution. Kursk, being the industrial and administrative center of the Kursk Region, is characterized by a strong degree of flora transformation, as a result of the active transformation of the territory in recent years, which determines the suitable conditions for the introduction of invasive species and their wide distribution. In Kursk flora there are 43 invasive species, the proportion of Asteraceae is 21%. The paper presents biological features and characteristics of Xanthium albinum and Cyclachaena xanthiifolia populations. The following population indicators were studied: number of individuals, height and total projective cover. It was revealed that the populations of Xanthium albinum in different growing conditions show significant differences in the studied parameters. In the populations of Cyclachaena xanthiifolia fluctuations were observed in the number of individuals per 1 m. The reasons that determine the parameters of populations of invasive species is the degree of disturbance and shading. The study of urban vegetation is a necessary step in the development of measures to optimize the urban environment. The obtained materials will allow to evaluate the consequences of the introduction of these invasive species in the plant communities of Kursk and will provide a scientific basis for monitoring in order to prevent biological invasions.

Quantitative and Qualitative Dynamics of Interacting Populations

This research paper deals with the vast topic of population dynamics from both a quantitative view, the change in the number of individuals in a population, and a qualitative one, the variation or change in the phenotypes in evolutionary processes. In a broader sense, what regards the populations is also applicable to species. Quantitative dynamics are studied not only in an isolated population but also in the more interesting case of two or more populations interconnected in a simple trophic food chain in a prey–predator model, in the broadest sense of the term, thereby forming an ecosystem. However, the paper introduces the concept of ‘population control’. Two or more interconnected prey–predator populations regulate, in turn, their dynamics, even though unconsciously, exercising a control that has been defined as ‘natural’ and ‘endogenous’. The concept of ‘external’ control is also introduced, which is carried out by man through interventions aimed at increasing or reducing the size of one or more interconnected populations to arrive at minimum limits (populations of species in danger of extinction) or maximum ones (populations of invasive species) held to be advantageous to and congruous with the ecosystem. Also highlighted is the connection between qualitative and quantitative dynamics, in the sense that every mutation in the individuals of a population which increases the potency of the defence apparatus in prey, or the hunting apparatus in predators, necessarily modifies the rates of fecundity or extinction of that population, which necessarily affects the quantitative dynamics of all the interconnected populations. Taking as a basis, the Volterra–Lotka equations, Excel and Powersim simulations are presented for specific examples in which population dynamics is treated under the assumption of unlimited resources or resources that are limited but reproducible or limited until depletion. The case of environmental catastrophes that externally modify the dynamics of one or more populations is also touched upon. © 2018 John Wiley & Sons, Ltd.

The Legal International Wildlife Trade Favours Invasive Species Establishment: The Monk and Ring-Necked Parakeets in Spain

The international wildlife trade is a lucrative business. Although a huge variety of animal groups are trafficked, the Psittaciformes (parrots) are amongst the most traded avian groups. Deliberate or accidental releases of imported parrots have led to the establishment of feral populations in many countries. Far from their native habitats, parrots may cause economic and ecological damage, and may even favour the transmission of zoonotic diseases. Despite this, the links between numbers of imported individuals and the establishment of non-native populations is not well known. In this study, we analysed data on imports of two well-known invasive parrots, the Monk Parakeet Myiopsitamonachus and the Ring-necked Parakeet Psittacula krameri, in Spain. We contrasted this information with the growth of known naturalised populations of these species from 1975 to 2015 and compared the success of these two species with other Psittaciformes imported in similar numbers into the country. We show that more than 190,000 Monk Parakeets were imported from Uruguay and Argentina, and almost 63,000 Ring-necked Parakeets were legally brought into the country from Pakistan and Senegal. For both species, wild populations grew exponentially following peak importation periods in 2015 (18,980–21,455 Monk Parakeets and 3,005–3,115 Ring-necked Parakeets). Even though imports of the two species were banned in Spain in 2005, wild populations are now self-sustaining. We argue that these parrot populations started from accidental and deliberate bird escapes, especially from birds originally captured in the wild. Although lack of more precise data makes it difficult for us to propose clear statistical associations between imports and established bird populations, we nonetheless suggest that the international trade is with some certainty the main cause for the origin of naturalised populations of invasive species in Spain. Our conclusions are useful to help manage similar animal groups that are numerous in the wildlife trade, especially for wild-caught social species.—Lucrecia Souviron-Priego, Antonio Roman Munoz, Jesus Olivero, J. Mario Vargas & John E. Fa. (2018). The legal international wildlife trade favours invasive species establishment: the Monk and Ring-neked Parakeets in Spain. Ardeola, 65: 233–246.

Genetic diversity of populations of Bidens genera invasive and native species in Lithuania

Genetic diversity of populations of Bidens genera invasive and native species in Lithuania

Стан локальної популяції Tilia Platyphyllos Scop. та моделювання інвазійності адвентивного виду у парковій зоні міста Дніпро

Зважаючи на континентальний характер регіонального клімату Дніпропетровської області, можна очікувати, що його зміни у напрямку посилення рис аридності мають бути важливим чинником впливу на межі розповсюдження рослинних видів. Зроблено припущення, що деякі деревні рослинні види могли отримати переваги для виживання і розселення на території Степового Придніпров’я в умовах кліматичних змін останніх десятиліть. Досліджено локальні популяції інвазійних адвентивних деревних видів на території парку «Дружби народів», розташованого у лівобережній частині міста Дніпро. Виявлено популяцію насіннєвого походження липи широколистої ( Tilia platyphyllos Scop .) у насадженнях із свіжими гігротопами на лучно-чорноземних ґрунтах із високою трофністю. Розроблено математичну модель розвитку популяцій насіннєвого походження липи широколистої в антропогенно-трансформованих екотопах на території парку «Дружби народів» та прогнозовано збереження тенденції росту інвазійності липи широколистої за умов подальших змін клімату у регіоні.

Unexplained variability among spatial replicates in transient elasticity: implications for evolutionary ecology and management of invasive species

AbstractUnderstanding actual and potential selection on traits of invasive species requires an assessment of the sources of variation in demographic rates. While some of this variation is assignable to environmental, biotic or historical factors, unexplained demographic variation also may play an important role. Even when sites and populations are chosen as replicates, the residual variation in demographic rates can lead to unexplained divergence of asymptotic and transient population dynamics. This kind of divergence could be important for understanding long‐ and short‐ term differences among populations of invasive species, but little is known about it. We investigated the demography of a small invasive tree Psidium cattleianum Sabine in the rainforest of Hawaiʻi at four sites chosen for their ecological similarity. Specifically, we parameterized and analyzed integral projection models (IPM) to investigate projected variability among replicate populations in: (1) total population size and annual per capita population growth rate during the transient and asymptotic periods; (2) population structure initially and asymptotically; (3) three key parameters that characterize transient dynamics (the weighted distance of the structure at each time step from the asymptotic structure, the strength of the sub‐dominant relative to the dominant dynamics, and inherent cyclicity in the subdominant); and (4) proportional sensitivity (elasticity) of population growth rates (both asymptotic and transient) to perturbations of various components of the life cycle. We found substantial variability among replicate populations in all these aspects of the dynamics. We discuss potential consequences of variability across ecologically similar sites for management and evolutionary ecology in the exotic range of invasive species.

Consumption of Invasive Western Mosquitofish Fry by Adult Conspecifics and Native Crayfish

The absence of predators is often invoked to explain the ability of non-native species to successfully invade a habitat, however native species can control or regulate populations of invasive species through predation. To better understand the regulation of invasive Gambusia affinis (Western Mosquitofish), we conducted a laboratory experiment to examine the potential for native Cambarus thomai (Little Brown Mudbug) and adult conspecifics to consume Western Mosquitofish fry. On average, female Western Mosquitofish consumed nearly 3 times the number of fry in 24 h than males. Little Brown Mudbug, consumed some of the Western Mosquitofish fry, but the resulting mosquitofish mortality was not significantly higher than the control (which had 100% survivorship). Our results show that cannibalism is a potentially significant source of mortality in Western Mosquitofish, and thus may be a factor involved in the regulation of their population dynamics. However, native Little Brown Mudbug, while they do consume mosquitofish fry, are probably not a major source of mosquitofish mortality in nature.

Evaluation of a method for ballast water risk–release assessment using a protist surrogate

Understanding the risk–release relationship (the relationship between density of organisms released and associated risk of establishment of a population) of aquatic invasive species is important for setting policy standards to protect natural water bodies from species spread through human-mediated vectors, in particular ballast discharge. To test the viability of an experimental and analytical approach to investigate this relationship, we conducted a mesocosm-based experiment using a test organism, Melosira varians (a freshwater phytoplanktonic diatom native to the Great Lakes). Varying densities of the test organism were added to 19-l mesocosms of water from the Duluth-Superior Harbor at Superior, Wisconsin, in three consecutive trials over 4 months. Each mesocosm was sampled weekly for 4 weeks, and the size of the M. varians population and phytoplankton community was measured via assessments of cell densities. Population responses varied by initial M. varians density. Based on a logistic model, the inoculation density necessary for establishment of M. varians was approximately 12 cells/ml. These findings suggest mesocosm experiments coupled with logistic modeling have the potential to characterize risk–release relationships. Additional investigations using similar methods should be undertaken with a variety of test organisms and environmental conditions to further vet this method and extend understanding of risk–release relationships.

Have your cake and eat it too: greater dispersal ability and faster germination towards range edges of an invasive plant species in eastern Australia

The process of range expansion often selects for traits that maximize invasion success at range edges. For example, during range expansion, individuals with greater dispersal and colonization ability will be selected for towards range edges. For wind dispersed plants, however, there exists a fundamental trade-off between dispersal and colonization ability (germination success and growth) that is mediated by seed size; smaller seeds often have greater dispersal ability but poorer colonization ability. We investigated the nature of the dispersal/colonization trade-off by comparing dispersal ability (wing loading ratio: seed mass/wing area), germination success and growth related traits across multiple populations of a coastal exotic invasive plant species (Gladiolus gueinzii Kunze) along its entire introduced distribution in eastern Australia. We found that G. gueinzii had significantly greater dispersal ability towards its range edges which was mediated by a decrease in seed mass. However, this was not associated with a decrease in probability of germination or growth after 3 months. In fact, seeds from range edge populations had significantly faster germination times. Our results suggest that a shift towards greater dispersal ability does not have an associated negative effect on the colonization ability of G. gueinzii and may be a key factor in promoting further range expansion of this exotic invasive species.

Perspectives on invasive amphibians in Brazil.

Introduced species have the potential to become invasive and jeopardize entire ecosystems. The success of species establishing viable populations outside their original extent depends primarily on favorable climatic conditions in the invasive ranges. Species distribution modeling (SDM) can thus be used to estimate potential habitat suitability for populations of invasive species. Here we review the status of six amphibian species with invasive populations in Brazil (four domestic species and two imported species). We (i) modeled the current habitat suitability and future potential distribution of these six focal species, (ii) reported on the disease status of Eleutherodactylus johnstonei and Phyllodytes luteolus, and (iii) quantified the acoustic overlap of P. luteolus and Leptodactylus labyrinthicus with three co-occurring native species. Our models indicated that all six invasive species could potentially expand their ranges in Brazil within the next few decades. In addition, our SDMs predicted important expansions in available habitat for 2 out of 6 invasive species under future (2100) climatic conditions. We detected high acoustic niche overlap between invasive and native amphibian species, underscoring that acoustic interference might reduce mating success in local frogs. Despite the American bullfrog Lithobates catesbeianus being recognized as a potential reservoir for the frog-killing fungus Batrachochytrium dendrobatidis (Bd) in Brazil, we did not detect Bd in the recently introduced population of E. johnstonei and P. luteolus in the State of São Paulo. We emphasize that the number of invasive amphibian species in Brazil is increasing exponentially, highlighting the urgent need to monitor and control these populations and decrease potential impacts on the locally biodiverse wildlife.

When does invasive species removal lead to ecological recovery? Implications for management success

The primary goal of invasive species management is to eliminate or reduce populations of invasive species. Although management efforts are often motivated by broader goals such as to reduce the negative impacts of invasive species on ecosystems and society, there has been little assessment of the consistency between population-based (e.g., removing invaders) and broader goals (e.g., recovery of ecological systems) for invasive species management. To address this, we conducted a comprehensive review of studies (N = 151) that removed invasive species and assessed ecological recovery over time. We found positive or mixed outcomes in most cases, but 31% of the time ecological recovery did not occur or there were negative ecological outcomes, such as increases in non-target invasive species. Ecological recovery was more likely in areas with relatively little anthropogenic disturbance and few other invaders, and for the recovery of animal populations and communities compared to plant communities and ecosystem processes. Elements of management protocols, such as whether invaders were eradicated (completely removed) versus aggressively suppressed (≥90% removed), did not affect the likelihood of ecological recovery. Our findings highlight the importance of considering broader goals and unintended outcomes when designing and implementing invasive species management programs.

Local differentiation in the defensive morphology of an invasive zooplankton species is not genetically based

Evolutionary changes in functional traits represent one possible reason why exotic species spread to become invasive, but empirical studies of the mechanisms driving phenotypic differentiation between populations of invasive species are rare. This study tested whether differences in distal spine length among populations of the invasive cladoceran, Bythotrephes longimanus, could be explained by local adaptation or phenotypic plasticity. We collected Bythotrephes from six lakes and found that distal spine lengths and natural selection on distal spine length differed among populations, but were unrelated to the gape-limitation of the dominant fish predator in the lake from which they were collected. A common garden experiment revealed significant genetic and maternal variation for distal spine length, but phenotypic differences among populations were not genetically based. Phenotypic differences among lakes in this ecologically important trait are, therefore, the result of plasticity and not local adaptation, despite spatially variable selection on this heritable trait. The ability of Bythotrephes to plastically adjust distal spine length may explain the success of this species at invading lake ecosystems with diverse biotic environments.

Episodic Canopy Structural Transformations and Biological Invasion in a Hawaiian Forest.

The remaining native forests on the Hawaiian Islands have been recognized as threatened by changing climate, increasing insect outbreak, new deadly pathogens, and growing populations of canopy structure-altering invasive species. The objective of this study was to assess long-term, net changes to upper canopy structure in sub-montane forests on the eastern slope of Mauna Kea volcano, Hawai‘i, in the context of continuing climate events, insect outbreaks, and biological invasion. We used high-resolution multi-temporal Light Detection and Ranging (LiDAR) data to quantify near-decadal net changes in forest canopy height and gap distributions at a critical transition between alien invaded lowland and native sub-montane forest at the end of a recent drought and host-specific insect (Scotorythra paludicola) outbreak. We found that sub-montane forests have experienced a net loss in average canopy height, and therefore structure and aboveground carbon stock. Additionally, where invasive alien tree species co-dominate with native trees, the upper canopy structure became more homogeneous. Tracking the loss of forest canopy height and spatial variation with airborne LiDAR is a cost-effective way to monitor forest canopy health, and to track and quantify ecological impacts of invasive species through space and time.

Do prey handling predators really matter: Subtle effects of a Crowley-Martin functional response

Predator interference, or a decline in the per predator consumption rate as predator density increases, is generally considered a stabilizing mechanism in two-species predator-prey models. There is significant debate, as to whether prey handling predators, might interfere in the hunting process of prey searching predators, or whether these are mutually exclusive events. In the current manuscript, a three species food chain model, with strong top predator interference is considered. We prove that in terms of explosive instability/finite time blow up, sufficient interference by prey handling predators always tends to destabilize the system. The dynamics of a time delayed version, as well as the spatially explicit model are also explored. We use our results to comment on a certain paradox in ecological theory, as well as provide further insight into the nature of predator interference, and exploding populations of invasive species.

Mortality of overwintering emerald ash borer (Coleoptera: Buprestidae) associated with an extreme cold event in New York, United States of America

AbstractSevere mortality (93%) of overwintering larvae of emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), was recorded in March 2016 from green ash, Fraxinus pennsylvanica Marshall (Oleaceae), in Syracuse, New York, United States of America. In contrast, larvae collected from the same area in January exhibited <1% mortality. A strong cold front moved across New York from 13 to 15 February 2016 with temperatures plunging to nearly −40 °C in some areas. In many regions of New York where A. planipennis is established, temperatures dropped well below the reported supercooling point of overwintering larvae. To evaluate whether the extreme cold was linked to extensive mortality of larvae, trees were sampled from four areas that experienced a gradient of minimum temperatures on 14 February 2016. Overwintering mortality varied from ⩽5% to 93% among regions, with lowest survival in the coldest regions. When excised from their galleries, dead larvae were discoloured with brown spots or had black necrotic tissue in the spiracles or foregut. This is the first report of extensive cold-related mortality for this species in North America and highlights the stochastic nature of climatic extremes on invasive species populations.

Density-dependent colonization and natural disturbance limit the effectiveness of invasive lionfish culling efforts

Culling can be an effective management tool for reducing populations of invasive species to levels that minimize ecological effects. However, culling is labour-intensive, costly, and may have unintended ecological consequences. In the Caribbean, culling is widely used to control invasive Indo-Pacific lionfish, Pterois volitans and P. miles, but the effectiveness of infrequent culling in terms of reducing lionfish abundance and halting native prey decline is unclear. In a 21-month-long field experiment on natural reefs, we found that culling effectiveness changed after the passage of a hurricane part-way through the experiment. Before the hurricane, infrequent culling resulted in substantial reductions in lionfish density (60–79%, on average, albeit with large uncertainty) and slight increases in native prey species richness, but was insufficient to stem the decline in native prey biomass. Culling every 3 months (i.e., quarterly) and every 6 months (i.e., biannually) had similar effects on lionfish density and native prey fishes because of high rates of lionfish colonization among reefs. After the hurricane, lionfish densities were greater on all culled reefs compared to non-culled reefs, and prey biomass declined by 92%, and species richness by 71%, on biannually culled reefs. The two culling frequencies we examined therefore seem to offer a poor trade-off between the demonstrated conservation gains that can be achieved with frequent culling and the economy of time and money realized by infrequent culling. Moreover, stochastic events such as hurricanes can drastically limit the effectiveness of culling efforts.

Widespread and enduring demographic collapse of invasive common carp (Cyprinus carpio) in the Upper Mississippi River System

Populations of invasive species that undergo rapid expansions after establishment in a new system can also be subject to collapse. Although the dynamics of the establishment and expansion phases and their ecological effects are well documented, substantially fewer studies document collapses despite their importance for understanding invasion dynamics. Two long-term fish monitoring programs sample the fish assemblage of the Upper Mississippi River System. These data provide an opportunity to document the collapse of common carp (Cyprinus carpio), a globally invasive freshwater fish species. Here we describe their population trajectory over several decades and examine several hypotheses to explain the decline, including: boom-bust population dynamics; suppression by native predators; resource exhaustion; improvements in environmental conditions; and disease. The observed trends appear to be most consistent with the hypothesis that disease was the most important factor contributing to the collapse. In particular, cyprinid herpesviruses have been shown to affect common carp in a manner consistent with the observed decreases in catch rates and increases in size distributions. The apparent role of a viral agent in causing the decline of common carp across one of the largest river basins in North America suggests similar collapses may occur elsewhere.

A metatranscriptomic survey of the invasive yellow crazy ant, Anoplolepis gracilipes, identifies several potential viral and bacterial pathogens and mutualists

Thriving populations of invasive species often decline, but the mechanisms behind such declines are rarely elucidated. The microbial community living within insects can have significant impacts on host health and population dynamics and may be one such mechanism. Here, we use Illumina RNAseq and 16S amplicon sequencing to compare the bacterial communities, and investigate the presence of viruses, in queens of the invasive yellow crazy ant, Anoplolepis gracilipes, from populations in various stages of decline or expansion in Australia. Black queen cell virus and sequences with homology to the Dicistroviridae family of viruses were detected in queens from declining ant populations. This is the first instance of sequences with homology to a virus being found in A. gracilipes and may indicate a new virus. The overall bacterial communities were not statistically different between the population types and a number of potential mutualists were discovered. Several putative pathogens were also detected, including Candidatus Rhabdochlamydia, the entomopathogen Serratia marcescens and the reproductive parasite Candidatus Cardinium. These taxa are known to significantly affect host biology in other organisms. Our survey has identified several candidates that may be responsible for population declines of this invasive ant, and therefore may have potential as biological control agents.

Potential contribution to the invasion process of different reproductive strategies of two invasive roses

The type of reproductive system may be an important trait for the establishment and maintenance of populations of invasive plant species in new areas, as it can influence their demography and genetics. We studied the breeding system of two exotic invasive species, Rosa rubiginosa and R. canina, in a natural reserve in Argentina, using a combination of pollination experiments. We asked how the different reproductive modes of these species affect the quantity and quality of the fruits and seed produced. Our results show that both invasive rose species have an array of reproductive strategies, and that they are able to invade without pollinators, as they can produce seeds in the same quantity and quality through wind-pollination, self-pollination, and apomixis. Such lack of dependence on pollinators and pollination for reproduction should enhance colonization into new areas, suggesting the need of intensive monitoring of spread and dispersal. Considering that both species are successful invaders in the region, our results are in line with Baker’s rule, which posits that plants capable of uniparental reproduction are more likely to invade new areas.