Hierarchical factors impacting the distribution of an invasive species: landscape context and propagule pressure

<p>Worldwide, invasive species are associated with severe ecological and economic impacts. As a group, reptiles are very successful invaders and in some areas where they have established they are responsible for the decline of native fauna and economic disruptions, whilst also posing a threat to human health. Due to its biogeographical isolation and unique evolutionary history, New Zealand is highly susceptible to invasive species. Importation of reptiles into New Zealand is illegal, however over a dozen species of exotic reptile are legally present in captivity and their risk of establishment is unknown. This study investigates their establishment potential and possible impacts by considering 1) the amount of trade and propagule pressure of species, 2) the degree of climate match between their native range and New Zealand, 3) areas that may be suitable for establishment based on physiological models of incubation and development, 4) their ability to transfer pathogens to native fauna and humans, and 5) overall establishment risk. The red-eared slider (Trachemys scripta elegans; RES) is the most common and easily obtained exotic reptile pet in New Zealand, with over 800 sales per annum. The RES is also the species most regularly released into the wild. Climate matching models in this study were developed to minimise false-negative predictions, to generate a suitability score irrespective of the prevalence of species records (allowing species to be easily compared to one another), and incorporated a weighted multimodel average prediction based on the relative importance of climatic variables to each species. These correlative models indicated that the blotched blue-tongue skink (Tiliqua nigrolutea) had the highest degree of climate match with parts of New Zealand, while the common blue-tongue skink (T. scincoides) had the highest proportion of land area predicted to be suitable for establishment. The other 10 species generally had both low climate match scores and limited areas within New Zealand predicted to be suitable. Mechanistic models focus upon environmental influences on physiological processes of a species, such as development and growth. Degree-day models, combined with soil measurements in potential reptile nesting sites in New Zealand, were utilised to determine if environmental conditions were suitable for the successful reproduction of oviparous exotic reptiles. These models predicted that the New Zealand environment meets the minimum thermal requirements for the incubation of eggs of RES, snake-neck turtles (Chelodina longicollis), and Reeves turtles (Chinemys reevesii). While prevalence of Salmonella in exotic reptiles is higher than that of native reptiles, it is considerably lower than that of exotic reptiles overseas. All serovars identified in this study had been previously reported both in humans and reptiles in New Zealand. The overall risk assessment for 12 species of exotic reptile kept in captivity in New Zealand indicates that blotched blue-tongue skinks and RES pose the highest establishment risk. Blotched blue-tongue skinks are allegedly only present in zoos. Therefore, based on propagule pressure, RES pose the highest establishment risk and efforts should focus on minimising release events and removing feral individuals from the New Zealand environment. In summary, at least eight species of exotic reptile legally traded within New Zealand are predicted to be capable of surviving in a portion of the New Zealand environment and at least three species have the potential to successfully breed in warmer microclimates. However, further research involving climatic tolerances and breeding potential (i.e., soil moisture content, juvenile survival, sex ratio, and predicted climate change) is recommended. Public education and possible regulations imposed on the New Zealand exotic reptile trade may prevent introductions of these species into the local environment and still allow selected species to be enjoyed by the New Zealand public. The methods developed in this study may be easily applied to other species and other geographic regions, allowing investigation into the establishment risk of alien species. This may help guide control and management efforts and help stem the tide of the growing problem of invasive species.</p>

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Are Introduced Alien Species More Predisposed to Invasion in Recipient Environments If They Provide a Wider Range of Services to Humans?

Diversity ◽

10.3390/d13110553 ◽

2021 ◽

Vol 13 (11) ◽

pp. 553

Author(s):

Kowiyou Yessoufou ◽

Annie Estelle Ambani

Keyword(s):

South Africa ◽

Invasive Species ◽

Alien Species ◽

Propagule Pressure ◽

Phylogenetic Signal ◽

Dna Barcode ◽

Alien Plants ◽

Invasion Success ◽

Alien Invasive Species ◽

Unexpected Finding

The drivers of invasion success of alien species remain, to some extent, a matter of debate. Here, we suggest that the services (the benefits humans obtain from a species) provided by alien plants could predict their invasion status, such that alien species providing more services would be more likely to be invasive than not. The rationale for this expectation is that alien species providing multiple services stand a better chance of being introduced in various numbers and multiple times outside their native range (propagule pressure theory). We investigated this hypothesis on alien woody species in South Africa. First, we defined 12 services provided by all the 210 known naturalized alien woody plants in South Africa. Then, we tested for a phylogenetic signal in these services using a DNA barcode-based phylogeny. Finally, we tested for potential links between the services and invasion status by fitting GLM models with appropriate error families. We found a phylogenetic signal in most services, suggesting that closely related species tend to provide similar services. Counter-intuitively, we consistently found that alien non-invasive species tend to provide more services, or even unique services, in comparison to alien invasive species. Although alternative scenarios are plausible to explain this unexpected finding, we speculate that harvesting alien plants for human benefits may limit their invasion ability. This warrants further investigation.

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Quantifying the propagule load associated with the construction of an Antarctic research station

Antarctic Science ◽

10.1017/s0954102009990162 ◽

2009 ◽

Vol 21 (5) ◽

pp. 471-475 ◽

Cited By ~ 37

Author(s):

Jennifer E. Lee ◽

Steven L. Chown

Keyword(s):

Invasive Species ◽

Biological Invasions ◽

Quantitative Assessment ◽

Propagule Pressure ◽

Research Effort ◽

Research Station ◽

Antarctic Research

AbstractAlthough the impacts of biological invasions are widely appreciated, a bias exists in research effort to post dispersal processes because of the difficulties of measuring propagule pressure. Here we quantify the propagule pressure associated with the construction of a research station in Antarctica. Based on quantitative assessment of different classes of cargo, we predict that over 5000 seeds will be entrained during the period of building the station. Seeds from 34 taxa were identified, including known invasive species.

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Propagule pressure and the establishment of emergent polyploid populations

Annals of Botany ◽

10.1093/aob/mcaa187 ◽

2020 ◽

Vol 127 (1) ◽

pp. 1-5

Author(s):

Donald A Levin

Keyword(s):

Invasive Species ◽

Seed Production ◽

Propagule Pressure ◽

Prime Factor ◽

Demographic Stochasticity ◽

Local Populations ◽

Population Survival ◽

Successful Colonization ◽

Number Of Seeds ◽

Diploid Populations

Abstract Background Whereas the incidence or rate of polyploid speciation in flowering plants is modest, the production of polyploid individuals within local populations is widespread. Explanations for this disparity primarily have focused on properties or interactions of polyploids that limit their persistence. Hypothesis The emergence of local polyploid populations within diploid populations is similar to the arrival of invasive species at new, suitable sites, with the exception that polyploids suffer interference from their progenitor(s). The most consistent predictor of successful colonization by invasive plants is propagule pressure, i.e. the number of seeds introduced. Therefore, insufficient propagule pressure, i.e. the formation of polyploid seeds within diploid populations, ostensibly is a prime factor limiting the establishment of newly emergent polyploids within local populations. Increasing propagule number reduces the effects of genetic, environmental and demographic stochasticity, which thwart population survival. As with invasive species, insufficient seed production within polyploid populations limits seed export, and thus reduces the chance of polyploid expansion. Conclusion The extent to which propagule pressure limits the establishment of local polyploid populations remains to be determined, because we know so little. The numbers of auto- or allopolyploid seed in diploid populations rarely have been ascertained, as have the numbers of newly emergent polyploid plants within diploid populations. Moreover, seed production by these polyploids has yet to be assessed.

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Anthropogenic hybridization at sea: three evolutionary questions relevant to invasive species management

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2019.0547 ◽

2020 ◽

Vol 375 (1806) ◽

pp. 20190547 ◽

Cited By ~ 1

Author(s):

Frédérique Viard ◽

Cynthia Riginos ◽

Nicolas Bierne

Keyword(s):

Invasive Species ◽

Gene Flow ◽

Reproductive Isolation ◽

Propagule Pressure ◽

Dispersal Ability ◽

Marine Animals ◽

Contact Zones ◽

High Fecundity ◽

High Dispersal ◽

Allopatric Divergence

Species introductions promote secondary contacts between taxa with long histories of allopatric divergence. Anthropogenic contact zones thus offer valuable contrasts to speciation studies in natural systems where past spatial isolations may have been brief or intermittent. Investigations of anthropogenic hybridization are rare for marine animals, which have high fecundity and high dispersal ability, characteristics that contrast to most terrestrial animals. Genomic studies indicate that gene flow can still occur after millions of years of divergence, as illustrated by invasive mussels and tunicates. In this context, we highlight three issues: (i) the effects of high propagule pressure and demographic asymmetries on introgression directionality, (ii) the role of hybridization in preventing introduced species spread, and (iii) the importance of postzygotic barriers in maintaining reproductive isolation. Anthropogenic contact zones offer evolutionary biologists unprecedented large scale hybridization experiments. In addition to breaking the highly effective reproductive isolating barrier of spatial segregation, they allow researchers to explore unusual demographic contexts with strong asymmetries. The outcomes are diverse, from introgression swamping to strong barriers to gene flow, and lead to local containment or widespread invasion. These outcomes should not be neglected in management policies of marine invasive species. This article is part of the theme issue ‘Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers’.

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Evaluating landscape characteristics of predicted hotspots for plant invasions

Invasive Plant Science and Management ◽

10.1017/inp.2020.21 ◽

2020 ◽

Vol 13 (3) ◽

pp. 163-175

Author(s):

Adrián Lázaro-Lobo ◽

Kristine O. Evans ◽

Gary N. Ervin

Keyword(s):

Land Use ◽

Invasive Species ◽

Propagule Pressure ◽

Landscape Heterogeneity ◽

Spatial Scales ◽

Plant Invasions ◽

Landscape Composition ◽

Environmental Predictors ◽

Distribution Models ◽

Landscape Characteristics

AbstractInvasive species are widely recognized as a major threat to global diversity and an important factor associated with global change. Species distribution models (SDMs) have been widely applied to determine the range that invasive species could potentially occupy, but most examples focus on predictive variables at a single spatial scale. In this study, we simultaneously considered a broad range of variables related to climate, topography, land cover, land use, and propagule pressure to predict what areas in the southeastern United States are more susceptible to invasion by 45 invasive terrestrial plant species. Using expert-verified occurrence points from EDDMapS, we modeled invasion susceptibility at 30-m resolution for each species using a maximum entropy (MaxEnt) modeling approach. We then analyzed how environmental predictors affected susceptibility to invasion at different spatial scales. Climatic and land-use variables, especially minimum temperature of coldest month and distance to developed areas, were good predictors of landscape susceptibility to invasion. For most of the species tested, human-disturbed systems such as developed areas and barren lands were more prone to be invaded than areas that experienced minimal human interference. As expected, we found that landscape heterogeneity and the presence of corridors for propagule dispersal significantly increased landscape susceptibility to invasion for most species. However, we also found a number of species for which the susceptibility to invasion increased in landscapes with large core areas and/or less-aggregated patches. These exceptions suggest that even though we found the expected general patterns for susceptibility to invasion among most species, the influence of landscape composition and configuration on invasion risk is species specific.

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Relative roles of climatic suitability and anthropogenic influence in determining the pattern of spread in a global invader

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1011723108 ◽

2010 ◽

Vol 108 (1) ◽

pp. 220-225 ◽

Cited By ~ 90

Author(s):

Núria Roura-Pascual ◽

Cang Hui ◽

Takayoshi Ikeda ◽

Gwénaël Leday ◽

David M. Richardson ◽

...

Keyword(s):

Invasive Species ◽

Biotic Resistance ◽

Propagule Pressure ◽

Distribution Patterns ◽

Global Scale ◽

Invasion Success ◽

Climatic Suitability ◽

Natural Ecosystems ◽

Widespread Species ◽

Human Modification

Because invasive species threaten the integrity of natural ecosystems, a major goal in ecology is to develop predictive models to determine which species may become widespread and where they may invade. Indeed, considerable progress has been made in understanding the factors that influence the local pattern of spread for specific invaders and the factors that are correlated with the number of introduced species that have become established in a given region. However, few studies have examined the relative importance of multiple drivers of invasion success for widespread species at global scales. Here, we use a dataset of >5,000 presence/absence records to examine the interplay between climatic suitability, biotic resistance by native taxa, human-aided dispersal, and human modification of habitats, in shaping the distribution of one of the world's most notorious invasive species, the Argentine ant (Linepithema humile). Climatic suitability and the extent of human modification of habitats are primarily responsible for the distribution of this global invader. However, we also found some evidence for biotic resistance by native communities. Somewhat surprisingly, and despite the often cited importance of propagule pressure as a crucial driver of invasions, metrics of the magnitude of international traded commodities among countries were not related to global distribution patterns. Together, our analyses on the global-scale distribution of this invasive species provide strong evidence for the interplay of biotic and abiotic determinants of spread and also highlight the challenges of limiting the spread and subsequent impact of highly invasive species.

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