Non-native species are a major driver of environmental change. In this study we assessed the ecological impact of the “worst” non-native species and the associated scientific and media publications through time to understand what influences interest in these species. Ecological effect was based on a qualitative assessment reported in research publications and additional searches of the scientific and media attention were conducted to determine published articles and assess attention. We did not detect a relationship between the number of publications for a non-native species and the magnitude of the ecological effects of that species or the number of citations. Media coverage on non-native species was low, only evident for less than 50% of the non-native species assessed. Media coverage was initially related to the number of scientific publications, but was short-lived. In contrast, the attention to individual non-native species in the scientific literature was sustained through time and often continued to increase over time. Time between detection of the non-native species and the scientific/media attention were reduced with each successive introduction to a new geographic location. Tracking publications on non-native species indicated that media attention does seem to be associated with the production of scientific research while scientific attention was not related to the magnitude of the ecological effects.
Citation: Geraldi NR, Anton A, Lovelock CE, Duarte CM (2019) Are the ecological effects of the “worst” marine invasive species linked with scientific and media attention? PLoS ONE 14(4): e0215691. https://doi.org/10.1371/journal.pone.0215691
Editor: Judi Hewitt, University of Waikato, NEW ZEALAND
Received: January 17, 2019; Accepted: April 6, 2019; Published: April 18, 2019
Copyright: © 2019 Geraldi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data will be within the manuscript and its Supporting Information files.
Funding: This research was supported by the King Abdullah University of Science and Technology through baseline funding and funds and by the Tarek Ahmed Juffali Research Chair in Red Sea Ecology to C.M.D.
Competing interests: The authors have declared that no competing interests exist.
Society’s environmental perception of non-native species is complex, and includes multiple interacting social-ecological facets, including scientific research and cultural norms [1–3]. For example, economic drivers can influence public concern over environmental issues, as demonstrated for climate change , and the media can shape public opinion. Given the increasing audience that scientists can reach with social media and the dialogue that exists between scientists and the public , the influence of science communication and its magnification by the media on societal environmental perceptions is likely to increase.
A key factor that influences human perception of non-native species is the ecological effects of these species , which include the positive, neutral and negative impacts on native ecosystems. People’s perception of the effects of non-native species is complicated in that there is no comprehensive list of the truly disruptive non-native species based on their ecological effects globally, even though this is mandated in Aichi Biodiversity Target 9 of the Convention on Biological Diversity of the United Nations . One of the most useful references to identify the most detrimental non-native species is the IUCN’s “100 of the world’s worst invasive alien species”, which is also the Global Invasive Species Database [8,9]. This list is based on expert opinion and is widely used and cited (more than 2600 citations on Aug. 6th 2018; see methods for Google Scholar search details). The non-native species included on this list are referred to as the “worst” invasive species, terminology that we will also use in this study. The attention to this prominent list, by both researchers and the media, may be influencing people’s perception of non-native species. In this paper we investigated if researcher’s and society’s perception of invasive species are influenced by the reported ecological effects of non-native species on ecosystems and the media attention given to those species.
Here we assessed the ecological effects of some of the “worst” invasive species in marine ecosystems based on Luque et al. (2014) and follow the scientific and media attention given to them through time, to explore how scientific research and media interest follow the trajectory of non-native species, from detection to relevant publications. Specifically, we first compared the scientific interest in non-native species among three ecosystems (marine, freshwater, and terrestrial) and then compare these to other relevant ecological research topics (biodiversity and ocean acidification) to attain a general perspective on the scientific attention given to non-native species. Second, we reviewed marine non-native species, primarily from a list of the “worst” invasive species [8,9] (S2 Table), to assess their qualitative ecological impact and compare this with the number of scientific studies and citations. We then provide summaries about their invasion histories and include a terrestrial and freshwater non-native species in this analysis for comparison. Finally, we examined the dynamics of research and media attention (based on publications) on non-native species to characterize patterns and longevity in attention.
Broad indicators of scientific interest in invasive species were assessed by searching the Web of Science (WS) for articles that focused on the influence of non-native species in three ecosystems; marine, terrestrial and freshwater (see S1 Table for search terms and the number of references). We quantified the number of articles each year from the searches and compared the scientific interest on invasive species to other broad and relevant marine ecological topics, including effects on “biodiversity” and of “ocean acidification”, assessed through similar WS searches (S1 Table). To measure the trend through time we calculated the regression line for the articles per year, which was log transformed to compare to previous findings. The WS searches were performed on the 24th of September 2018.
Attention to individual non-native species was assessed by focusing on “100 of the World’s Worst Invasive Alien Species” [8,9]. The authors indicated that the species included in this list of the worst invasive species were selected for their serious impact on biological diversity and/or human activities but advised “absence from the list does not imply that a species poses a lesser threat, and their illustration of important issues of biological invasion. To ensure a wide variety of examples, only one species from each genus was selected” . This list was updated in 2014 , but with no change in the marine species included in the list. Lowe et al. (2000) continues to be referenced and was cited 2674 times, with 510 of these after 2016 (Google scholar search on Aug. 6th 2018).
Eleven marine species were identified on the “worst” invasive species list (S2 Table; Luque et al. 2014). We also included the non-native red lionfish (Pterois spp.) in the analyses given their recent and rapid invasion of the mid-western Atlantic Ocean, as well as two of the “worst” invasive species from terrestrial and freshwater systems for comparison with our marine non-natives: the terrestrial cane toad (Rhinella marina, formally Bufo marinus) and the freshwater zebra mussel (Dreissena polymorpha; S2 Table). To determine the temporal trends in scientific and media interest on individual non-native species we searched the WS and ProQuest’s ABI/INFORM collection (ABI/INFORM). The ABI/INFORM collection is an international English-language business research database that contains thousands of full text newspapers, magazines, wire feeds, trade journals and web based information starting in the 1970s. The species-specific ABI/INFORM and WS searches were performed from the 20th to the 26th of June 2016. Scientific journals and dissertations were excluded from the ABI/INFORM search to minimize overlap with WS search. Of the 14 species searched, only the results of eight species with appreciable media coverage were assessed, because the other species had almost no media coverage based on our searches.
The scientific interest in these eight individual species identified and the timeline of when they were labeled non-native or invasive were determined by two separate WS searches for each species. Although we do not know the exact definitions used by authors within publications, the following definitions are commonly used within scientific literature and for this reason we did two separate searches: The term ‘non-native’ is used to refer to species that have been moved outside their native geographic ranges via human actions while the term ‘invasive’ is used for established non-native species that are spreading in the new environment (sensu  and/or have a demonstrable ecological or economic impact sensu ). Thus, invasive species are a small subgroup of non-native species that are spreading fast and/or exert a clear ecological or economic impact. The first WS search included the following structure, “invader OR non-native OR exotic OR alien NOT invasive AND scientific name”. The second search consisted of “scientific name AND invasive”. Finally, to qualify the qualitative ecological effect of the six marine invasive species, a third WS search for each species was conducted using the following terms: (invader OR non-native OR exotic OR invasive OR alien AND scientific name) NEAR/5 (impact OR effect OR influence OR consequence*) AND (marine OR coastal OR sea OR estuar* OR ocean).
The reported ecological effect of the non-native species was determined based on the following ranking from null to broad ecosystem effects (adapted from : 0—No effect; 1—effects 1 species with little or no wider ecosystem impact; 2—effects multiple species, some wider ecosystem function or species of high conservation value; and 3—effects entire ecosystem processes and/or wider abiotic influences). A cumulative effect was made for each paper. Agreement among observers was checked by all observers ranking 3 of the same papers and observer ranks were identical. Only studies that included a quantitative comparison with and without the non-native species were included. To ensure the scientific and media search results were related to the focal non-native species and not another species or topics such as aquaculture or aquariums, references were individually inspected and articles not about the focal non-native species were removed (S1 and S2 Table for details). Three separate analysis were run to assess if there were relationships between focal species, attention, and ecological effects. To determine if the attention given to a species was related to the ecological effect a general linear model (glm) was run with the number of publications per species as the independent variable and the mean effect per species as the dependent variable. To assess if the number of publications per species was related to the mean number of citations a glm was run with the number of publications per species as the independent variable and the mean number of citations per year for each species as the dependent variable. Finally, to determine if there the ecological effect found by a study was related to the number of times a publication was cited, a glm was run with the ecological effect as the independent variable and the number of citations per year as the dependent variable. It is important to note that there is not a perfect procedure to standardize the number of citations for publications published in different years because the years since publication and number of citations is not linear. However, the accumulation of publication is relatively constant for the first 10 years, although the most citations often occur 2 years after publication . To incorporate the decline in citations after 10 years of publication, publications that were more than 10 years old were always divided by 10 instead of their actual years since publication. All analyses were run in R version 3.5.1 .
To elucidate patterns between introductions and attention, we matched the location of the study for scientific articles or the location of the focal non-native species for the media article with the year of introduction obtained from the Invasive Species Compendium (CABI; www.cabi.org). Because the exact year of introduction is usually unknown our calculations are referred to as the year of detection. CABI gives a detection year by country, but includes states/provinces for larger countries (i.e. USA and Australia). The detection location from CABI was then broadened to a region to encompass the location of the article. Matching detection location with article location was checked for accuracy based on the detection, distribution and spread given in CABI. Thus, our definition of region was dependent on the detection and spread given in CABI and the geographic distributions found in articles (region needed to encompass all articles associated with each species specific introduction), which varied from state (Florida for the Rhinella marina) to continent (e.g. Europe for Undaria pinnatifida). If the focal location of article could not be identified the location was categorized as general.
The attention span, whether scientific or mediatic, to each focal non-native species was measured by focusing on the 2 separate years with the greatest references and dividing the number of references in these peak years by the number of references in the following year. Peaks with less than 5 references were not included. The lag in attention between detection and peak articles, scientific and from the media, was then quantified for each species introduction by subtracting the years with the first and most references from the region-specific detection year. The lag in attention was calculated for both the media and the two scientific searches (e.g., using either the non-native or the invasive labels). Finally, we looked at how attention changed as a non-native species was successively introduced into new regions. This was accomplished by quantifying the time between detection and first article for each species for each region. The slope of time between detection and first article for each successive introduction was determined for each reference search and differences in the slope among scientific and media articles was tested with a Kruskal-Wallis test with each species as a replicate. Data are provided in S3–S6 Tables.
Results and discussion
Scientific attention to invasion ecology and comparisons among ecosystems
Research attention to the effects of non-native species has grown steeply at a rate of 15.7±0.9 (SE) %yr-1 (Fig 1), almost three times faster than the rate of increase of general ecological literature (7.7%yr-1) . More than 50% (56.1%) of the effort focused on terrestrial non-native species compared to 24.1% on freshwater and 19.8% on marine non-native species (Fig 1). The growth rate of research effort on the effects of non-native species has been similar for terrestrial (17.1±1.2%yr-1), freshwater (17.1±1.2%yr-1) and marine species (16.8±1.2%yr-1; Fig 1), but the latter increasing slightly from encompassing 14.1% of the papers published on the subject in 1995–2000 to 19.3% in 2012–2017 (Fig 1). The publication rate on the effects of non-native marine species was similar to growth in the research attention to biodiversity (18.4±0.8%yr-1), but less than ocean acidification (34.0±5.4%yr-1; Fig 1). However, the number of publications deviates from these rates in the last two to four years (2014–2017) depending on the search, indicating a leveling off or slight decrease in the number of publications per year for these topics. Compared to the 17% research effort marine non-native species received of the total research effort on non-native species (Fig 1), the list of the worst invasive species Lowe et al. (2000) includes mainly terrestrial species with only 11% of marine species (i.e. 75 terrestrial, 14 freshwater and 11 marine non-native species; S2 Table). This would suggest that future updates of this list could consider adding more marine and freshwater species to keep up with the scientific interest in evaluating the “worst” non-native species.
Scientific attention and findings on marine non-native species
Our qualitative review of the documented impacts of the “worst” non-native marine species indicates that the majority of ecological effects altered 1 species or multiple species (ranking of 1 or 2 which included 16 and 22 studies respectively). No effects were found for 11 of the 51 studies (rank of 0) and only 2 studies found an effect on the entire ecosystems (rank of 3). The mean effect of species ranged from 1 to 1.9 while the number of studies for each species ranged from 4 to 12 (Fig 2A). Given that there were less than 10 scientific publications for all but one of these species, continued research on these species is warranted to determine their long-term and region specific impacts. No relationship was detected between the scientific attention given to species (number of publications) and the mean ecological effect of the species (t-value = -1.55, df = 4, p-value = 0.884; Fig 2B). We did not detect a relationship between the scientific attention given to species (number of publications) and the number of citations (t-value = -0.2316, df = 4, p-value = 0.828; Fig 2C) or the ecological effect of each publication on the number of citations per year (t-value = 1.03, df = 54, p-value 0.306; Fig 2D). Although our results are based on only 6 species which limits the power of our analysis to detect significance, these findings suggest that scientific attention is not skewed towards species with greater ecological effects and that publications with greater effects are not cited more often than publications that found minimal effects of non-native species.
Qualitative assessment of the effects of the “worst” marine invasive species based on scientific research shown by the number of publication for each species with publications for each species being categorized by the effect (A), the number of publication for each species compared to the mean ecological effect (B) and mean number of citations per year (C) and the ecological effect compared with the number of citations per year of all publications (D). Species were ordered, from highest to lowest, by their mean effect (A) and the label color for each species indicates species data points in the other plots (C-D). The were no significant effects for the relationships shown in B-D (linear models, p-value>0.05).
Dynamics of attention by the media and the scientific community
We observed that the number of scientific papers on a non-native species was less likely to collapse abruptly once the peak attention was reached than that of the number of references by the media (Fig 3), pointing at a shorter attention span of the media, and therefore the public, compared to scientists. For example, 4 of the 8 species examined here received the greatest scientific attention in 2015, as indicated by scientific articles on them, while no media peaks were observed after 2014 (Fig 3). The year after the peak in scientific publications, scientific attention declined by only 19% (n = 12, SE = 6%; Fig 3) for invasive species references. Media attention was in contrast short-lived and coverage of invasive species declined by 61% the year after the peak (n = 7, SE = 13%; Fig 3), i.e. three times faster than that for scientific publications. Our case studies of the lionfish in the marine environment and the zebra mussel in freshwater departed from this pattern in showing sustained media attention for the past six and three years, respectively (Fig 3). Overall, these dynamics may be affected by the different turnover of media vs. scientific publications, with media reports released almost immediately while scientific publications typically requiring more than 1 year between study completion and publication in a scientific journal . Thus, media attention rises rapidly, but is short-lived, while attention to individual non-native species in the scientific literature is sustained and often continues to increase over time.
The first six plots are marine species and the bottom two are freshwater and terrestrial species respectively. The year of detection to a certain location are shown with vertical dashed lines and labeled with region. Detection locations before 1990 are shown on the left of each plot (General indicates region not identified). Bars and left axis show the media coverage of the species. Lines and right axis show the scientific literature citing the species as non-native (dashed line) or invasive (solid line). Media and scientific references are color coded to match the color of the region to which the label non-native or invasive occurred. Letters in the x-axis indicate attention peaks: media (m), non-native (e) and invasive (i).
The evaluation of the regional introductions of each species indicated that there was 8.5 years (median; mean = 36.9, n = 20, SE = 10.3) from the time when a species was detected to when it was reported as non-native in that region and 11 years (median; mean = 39.1, n = 20, SE = 10.4; Fig 3) from the time when a species was detected to when it was reported as invasive in that region within the scientific literature. The number of years between the detection of the non-native species and the first media reference was 10 years (median; mean = 36.0, n = 20, SE = 10.5, Fig 3). The maximum attention given to non-native species in the scientific literature was approximately 3 and 6 years after the first non-native and invasive references, respectively. The maximum media attention came on average 6 years after the initial coverage. These results suggest that media coverage followed research publications and the shorter lag between first and maximum coverage for the scientific literature on non-native species probably results from the species being labeled invasive after publication of multiple scientific articles. The rapid translation of scientific publications on invasive species to the media (median number of years between the first scientific publication and media reference was 0.5; mean = 0.2, n = 20, SE = 1.16) highlights the contrast between the immediacy of media articles compared to the slow scientific publication process . In addition, scientific articles seemed to positively correlate with media reports (Fig 3), therefore, the more scientific articles produced on a non-native species, the more media attention was given to that species.
Subsequent introductions and species labels
Non-native species are often introduced to multiple geographic regions, but evidence of ecological impacts in one region does not necessarily imply that the species will have similar impacts on a geographically distant region . However, it is unclear how scientists and the media react to subsequent introductions. For example, is an invasive species automatically labeled invasive when introduced in a new geographic region and how does the terminology change over time with each successive report of occurrence into a new geographic region? Our analyses show that regardless of the reference type (media or scientific references), the time between detection and attention decreased each subsequent time a species was introduced into a new region (Fig 4). On average, the time between detection and the first non-native scientific reference decreased by 65±17% at each successive introduction, while the time between detection and the first invasive scientific reference decreased by 78±17% at each successive introduction (Fig 4). In addition, three of the six marine invasive species in this study (Caulerpa taxifolia, Mnemiopsis leidyi and Pterois volitans) were termed invasive within one year of the species being detected in a new geographic region. Time between detection and the first media reference quickly decreased for each successive reported presence into a new region (52±26% of the time compared to the previous introduction, Fig 4). The decreasing time between detection and first reference for each successive introduction were not statistically different among scientific attention to non-native or invasive species or media attention (differences among slopes; Kruskal-Wallis test, p-value = 0.42). Given the time it takes to undertake ecological studies and to publish in the scientific literature, it is likely that researchers were much quicker to initiate research at each subsequent introduction to determine if the species alter ecosystems in the newly introduced region. The decreased time between successive detections and attention is probably a consequence of both enhanced ability to recognize previously documented invasive species and the enhanced promotion of a species from non-native to invasive regardless of local ecological impacts.
The number of years between detection and the first references for the media (top), scientific research when the species was associated with non-native (middle) and scientific research when the species was associated with invasive (bottom) in relation to chronologically ordered invaded regions for each species.
We focused on the “worst” marine non-native species to assess interactions among ecological impacts and the media and scientific attention. We did not find any indication that scientific publications or citations were associated with the magnitude of ecological effects reported in publications for individual species. These non-significant results could derive from low sample size, which in part reflects the scarce scientific and media attention given to non-native species. In general, the species were only promoted to an invasive status following scientific research on their ecological effects, and only then received media attention. However, many non-native species received little or no media attention. Once a species was labeled invasive, there was a clear trend to recognize this species and use the “invasive” label to describe that species more rapidly at each successive detection in a new geographic region.
The short-term media coverage, in general lasting from one to two years, likely results from two factors. First, the ecological impact of the invasive species loses novelty through time, and the non-natvie species are not news worthy anymore. Second, the effect of the non-native species may be low when compared to the initial predicted ecological impacts and, particularly, the exaggerated expectations of threats associated with media reports and the nicknames the species often receive (Table 1). In contrast, scientific interest was often sustained through time. Maintenance of scientific interest probably results from; 1) the precautionary principle, which necessitates robust evidence to determine the ecological effect of non-native species , 2) the slow publishing process in science, typically involving multiple years from funding to publication and 3) scientific interest in non-native species that goes beyond its ecological impacts and may include interest in other disciplines including evolutionary processes .
Although the time span of media attention was shorter than scientific interest, media coverage seemed to track scientific interest and was concomitant with the initial intensity of scientific publications, although it was almost non-existent for some of the “worst” marine non-native species. We concur that the amalgamation of scientific research and public perceptions, influenced through the media, exerts a strong influence on managerial actions , which may add fuel to the current debates surrounding invasion ecology (i.e., whether non-native species are harmful per se) and their management [2,5,21–23]. We illustrate the dynamics of scientific and media coverage and the ecological impacts of non-native species. The ability to look at the interaction between these factors and how they affect public opinion will be much improved as long-term datasets of social media, web searches, and impact metrics of research articles become available . This data, which continues to be accumulated, can help to understand the ecological perceptions of scientists, managers, and society as a whole.
S1 Table. The search terms used to obtain relevant references for invasive species in three ecosystems and comparison topics in marine ecosystems.
S2 Table. Invasive species assessed in this review with the number of references found in ABI/INFORM and WS searches.
The percent of the number references in the search that were appropriate, as indicated by the numbers, are given in parentheses.
S3 Table. The results of the WS searches for non-native species in terrestrial, freshwater and marine systems, as well as marine biodiversity and ocean acidification.
S4 Table. The results of the WS search for individual non-native species and the ecological effect from each publication.
S5 Table. The results of the WS search for individual non-native species and the focal region of the article.
This research was supported by the King Abdullah University of Science and Technology through baseline funding and funds and by the Tarek Ahmed Juffali Research Chair in Red Sea Ecology to C.M.D.
- 1. Essl F, Dullinger S, Rabitsch W, Hulme PE, Hülber K, Jarošík V, et al. Socioeconomic legacy yields an invasion debt. PNAS. 2011;108: 203–207. pmid:21173227
- 2. Jeschke JM, Bacher S, Blackburn TM, Dick JTA, Essl F, Evans T, et al. Defining the Impact of Non-Native Species. Conservation Biology. 2014;28: 1188–1194. pmid:24779412
- 3. Vaz AS, Kueffer C, Kull CA, Richardson DM, Schindler S, Muñoz-Pajares AJ, et al. The progress of interdisciplinarity in invasion science. Ambio. 2017;46: 428–442. pmid:28150137
- 4. Carmichael JT, Brulle RJ. Elite cues, media coverage, and public concern: an integrated path analysis of public opinion on climate change, 2001–2013. Environmental Politics. 2017;26: 232–252.
- 5. Courchamp F, Fournier A, Bellard C, Bertelsmeier C, Bonnaud E, Jeschke JM, et al. Invasion Biology: Specific Problems and Possible Solutions. Trends in Ecology & Evolution. 2017;32: 13–22. pmid:27889080
- 6. Shackleton RT, Richardson DM, Shackleton CM, Bennett B, Crowley SL, Dehnen-Schmutz K, et al. Explaining people’s perceptions of invasive alien species: A conceptual framework. Journal of Environmental Management. 2019;229: 10–26. pmid:30077400
- 7. Marques A, Pereira HM, Krug C, Leadley PW, Visconti P, Januchowski-Hartley SR, et al. A framework to identify enabling and urgent actions for the 2020 Aichi Targets. Basic and Applied Ecology. 2014;15: 633–638.
- 8. Lowe SJ, Browne M., Boudjelas S. 100 of the World’s Worst Invasive Alien Species. IUCN/SSC Invasive Species Specialist Group (ISSG), Auckland, New Zealand. IUCN/SSC Invasive Species Specialist Group (ISSG), Auckland, New Zealand; 2000.
- 9. Luque GM, Bellard C, Bertelsmeier C, Bonnaud E, Genovesi P, Simberloff D, et al. The 100th of the world’s worst invasive alien species. Biol Invasions. 2014;16: 981–985.
- 10. Blackburn TM, Pyšek P, Bacher S, Carlton JT, Duncan RP, Jarošík V, et al. A proposed unified framework for biological invasions. Trends in Ecology & Evolution. 2011;26: 333–339. pmid:21601306
- 11. Lockwood JL, Hoopes MF, Marchetti MP. Invasion Ecology. 2 edition. Chichester: Wiley-Blackwell; 2013.
- 12. Molnar JL, Gamboa RL, Revenga C, Spalding MD. Assessing the global threat of invasive species to marine biodiversity. Front Ecol Environ. 2008;6: 485–492.
- 13. Bani-Ahmad S. Sorting Search Results of Literature Digital Libraries: Recent Developments and Future Research Directions. Digital Libraries—Methods and Applications. 2011;
- 14. R Core Team. R: A Language and Environment for Statistical Computing [Internet]. Vienna, Austria: R Foundation for Statistical Computing; 2017. Available: https://www.R-project.org/
- 15. Andersen T, Carstensen J, Hernández-García E, Duarte CM. Ecological thresholds and regime shifts: approaches to identification. Trends in Ecology & Evolution. 2009;24: 49–57. pmid:18952317
- 16. Jefferson L, Fairhurst C, Cooper E, Hewitt C, Torgerson T, Cook L, et al. No difference found in time to publication by statistical significance of trial results: a methodological review. JRSM Open. 2016;7: 2054270416649283. pmid:27757242
- 17. Ricciardi A, Kipp R. Predicting the number of ecologically harmful exotic species in an aquatic system. Diversity and Distributions. 2008;14: 374–380.
- 18. Simberloff D, Martin J-L, Genovesi P, Maris V, Wardle DA, Aronson J, et al. Impacts of biological invasions: what’s what and the way forward. Trends in Ecology & Evolution. 2013;28: 58–66. pmid:22889499
- 19. Mooney HA, Cleland EE. The evolutionary impact of invasive species. PNAS. 2001;98: 5446–5451. pmid:11344292
- 20. Gozlan RE, Burnard D, Andreou D, Britton JR. Understanding the Threats Posed by Non-Native Species: Public vs. Conservation Managers. PLOS ONE. 2013;8: e53200. pmid:23341931
- 21. Heger T, Pahl AT, Botta-Dukát Z, Gherardi F, Hoppe C, Hoste I, et al. Conceptual Frameworks and Methods for Advancing Invasion Ecology. AMBIO. 2013;42: 527–540. pmid:23532717
- 22. Russell JC, Blackburn TM. The Rise of Invasive Species Denialism. Trends in Ecology & Evolution. 2017;32: 3–6. pmid:27887747
- 23. Crowley SL, Hinchliffe S, McDonald RA. Conflict in invasive species management. Front Ecol Environ. 2017;15: 133–141.
- 24. Davis E, Caffrey JM, Caughlan NE, Dick JTA, Lucy FE. Communications, outreach and citizen science: spreading the word about invasive alien species. Management of Biological Invasions. 2018;9.
- 25. Lever C. The Cane Toad: The History and Ecology of a Successful Colonist. Otley: Westbury Academic & Scientific Pub.; 2001.
- 26. Jolly CJ, Shine R, Greenlees MJ. The impact of invasive cane toads on native wildlife in southern Australia. Ecol Evol. 2015;5: 3879–3894. pmid:26445649
- 27. Letnic M, Webb JK, Shine R. Invasive cane toads (Bufo marinus) cause mass mortality of freshwater crocodiles (Crocodylus johnstoni) in tropical Australia. Biological Conservation. 2008;141: 1773–1782.
- 28. Hagman M, Shine R. Effects of invasive cane toads on Australian mosquitoes: Does the dark cloud have a silver lining? Biol Invasions. 2007;9: 445–452.
- 29. Lovell SJ, Stone SF, Fernandez L. The Economic Impacts of Aquatic Invasive Species: A Review of the Literature. Agricultural and Resource Economics Review; Durham. 2006;35: 195–208.
- 30. Higgins SN, Zanden MJV. What a difference a species makes: a meta–analysis of dreissenid mussel impacts on freshwater ecosystems. Ecological Monographs. 2010;80: 179–196.
- 31. Grosholz ED, Ruiz GM, Dean CA, Shirley KA, Maron JL, Connors PG. The Impacts of a Nonindigenous Marine Predator in a California Bay. Ecology. 2000;81: 1206–1224.
- 32. Kimbro DL, Grosholz ED, Baukus AJ, Nesbitt NJ, Travis NM, Attoe S, et al. Invasive species cause large-scale loss of native California oyster habitat by disrupting trophic cascades. Oecologia. 2009;160: 563–575. pmid:19352719
- 33. Matheson K, McKenzie CH, Gregory RS, Robichaud DA, Bradbury IR, Snelgrove PVR, et al. Linking eelgrass decline and impacts on associated fish communities to European green crab Carcinus maenas invasion. Mar Ecol-Prog Ser. 2016;548: 31–45.
- 34. Bertness MD, Coverdale TC. An invasive species facilitates the recovery of salt marsh ecosystems on Cape Cod. Ecology. 2013;94: 1937–1943. pmid:24279265
- 35. Hampton SL, Griffiths CL. Why Carcinus maenas cannot get a grip on South Africa’s wave-exposed coastline. Afr J Mar Sci. 2007;29: 123–126.
- 36. Lohrer AM, Whitlatch RB. Interactions among Aliens: Apparent Replacement of One Exotic Species by Another. Ecology. 2002;83: 719–732.
- 37. Bloch CP, Curry KD, Jahoda JC. Long-Term Effects of an Invasive Shore Crab on Cape Cod, Massachusetts. Northeastern Naturalist. 2015;22: 178–191.
- 38. Meinesz A, Hesse B. Introduction of the Tropical Alga Caulerpa-Taxifolia and Its Invasion of the Northwestern Mediterranean. Oceanol Acta. 1991;14: 415–426.
- 39. Ceccherelli G, Cinelli F. Short-term effects of nutrient enrichment of the sediment and interactions between the seagrass Cymodocea nodosa and the introduced green alga Caulerpa taxifolia in a Mediterranean bay. Journal of Experimental Marine Biology and Ecology. 1997;217: 165–177.
- 40. Marbà N, Díaz-Almela E, Duarte CM. Mediterranean seagrass (Posidonia oceanica) loss between 1842 and 2009. Biological Conservation. 2014;176: 183–190.
- 41. Glasby TM. Caulerpa taxifolia in seagrass meadows: killer or opportunistic weed? Biol Invasions. 2013;15: 1017–1035.
- 42. Iveša L, Jaklin A, Devescovi M. Vegetation patterns and spontaneous regression of Caulerpa taxifolia (Vahl) C. Agardh in Malinska (Northern Adriatic, Croatia). Aquatic Botany. 2006;85: 324–330.
- 43. Montefalcone M, Morri C, Parravicini V, Bianchi CN. A tale of two invaders: divergent spreading kinetics of the alien green algae Caulerpa taxifolia and Caulerpa cylindracea. Biol Invasions. 2015;17: 2717–2728.
- 44. Shiganova TA. Invasion of the Black Sea by the ctenophore Mnemiopsis leidyi and recent changes in pelagic community structure. Fisheries Oceanography. 1998;7: 305–310.
- 45. Daskalov GM, Grishin AN, Rodionov S, Mihneva V. Trophic cascades triggered by overfishing reveal possible mechanisms of ecosystem regime shifts. PNAS. 2007;104: 10518–10523. pmid:17548831
- 46. Shiganova T, Mirzoyan Z, Studenikina E, Volovik S, Siokou-Frangou I, Zervoudaki S, et al. Population development of the invader ctenophore Mnemiopsis leidyi, in the Black Sea and in other seas of the Mediterranean basin. Marine Biology. 2001;139: 431–445.
- 47. Fuentes VL, Angel DL, Bayha KM, Atienza D, Edelist D, Bordehore C, et al. Blooms of the invasive ctenophore, Mnemiopsis leidyi, span the Mediterranean Sea in 2009. Hydrobiologia. 2010;645: 23–37.
- 48. Haslob H, Clemmesen C, Schaber M, Hinrichsen H-H, Schmidt JO, Voss R, et al. Invading Mnemiopsis leidyi as a potential threat to Baltic fish. Mar Ecol-Prog Ser. 2007;349: 303–306.
- 49. Hamer HH, Malzahn AM, Boersma M. The invasive ctenophore Mnemiopsis leidyi: a threat to fish recruitment in the North Sea? J Plankton Res. 2011;33: 137–144.
- 50. Hockey PAR, Schurink C van E. The Invasive Biology of the Mussel Mytilus Galloprovincialis on the Southern African Coast. Transactions of the Royal Society of South Africa. 1992;48: 123–139.
- 51. Fields PA, Rudomin EL, Somero GN. Temperature sensitivities of cytosolic malate dehydrogenases from native and invasive species of marine mussels (genus Mytilus): sequence-function linkages and correlations with biogeographic distribution. J Exp Biol. 2006;209: 656–667. pmid:16449560
- 52. Branch GM, Nina Steffani C. Can we predict the effects of alien species? A case-history of the invasion of South Africa by Mytilus galloprovincialis (Lamarck). Journal of Experimental Marine Biology and Ecology. 2004;300: 189–215.
- 53. Erlandsson J, Pal P, McQuaid CD. Re-colonisation rate differs between co-existing indigenous and invasive intertidal mussels following major disturbance. Mar Ecol Prog Ser. 2006;320: 169–176.
- 54. Lockwood BL, Somero GN. Invasive and native blue mussels (genus Mytilus) on the California coast: The role of physiology in a biological invasion. J Exp Mar Biol Ecol. 2011;400: 167–174.
- 55. Saarman NP, Pogson GH. Introgression between invasive and native blue mussels (genus Mytilus) in the central California hybrid zone. Mol Ecol. 2015;24: 4723–4738. pmid:26230080
- 56. Bariche M, Torres M, Azzurro E. The Presence of the invasive Lionfish Pterois miles in the Mediterranean Sea. Mediterranean Marine Science. 2013;14: 292–294.
- 57. Albins MA, Hixon MA. Invasive Indo-Pacific lionfish Pterois volitans reduce recruitment of Atlantic coral-reef fishes. Mar Ecol Prog Ser. 2008;367: 233–238.
- 58. Anton A, Simpson MS, Vu I. Environmental and biotic correlates to lionfish invasion success in bahamian coral reefs. PLoS ONE. 2014;9: e106229. pmid:25184250
- 59. Green SJ, Akins JL, Maljković A, Côté IM. Invasive lionfish drive Atlantic coral reef fish declines. PLoS ONE. 2012;7: e32596. pmid:22412895
- 60. Thornber CS, Kinlan BP, Graham MH, Stachowicz JJ. Population ecology of the invasive kelp Undaria pinnatifida in California: environmental and biological controls on demography. Mar Ecol Prog Ser. 2004;268: 69–80.
- 61. Wotton DM, O’Brien C, Stuart MD, Fergus DJ. Eradication success down under: heat treatment of a sunken trawler to kill the invasive seaweed Undaria pinnatifida. Mar Pollut Bull. 2004;49: 844–849. pmid:15530528
- 62. Casas G, Scrosati R, Piriz ML. The Invasive Kelp Undaria Pinnatifida (Phaeophyceae, Laminariales) Reduces Native Seaweed Diversity in Nuevo Gulf (Patagonia, Argentina). Biological Invasions. 2004;6: 411–416.
- 63. South PM, Lilley SA, Tait LW, Alestra T, Hickford MJH, Thomsen MS, et al. Transient effects of an invasive kelp on the community structure and primary productivity of an intertidal assemblage. Mar Freshw Res. 2016;67: 103–112.
- 64. South PM, Thomsen MS. The ecological role of invading Undaria pinnatifida: an experimental test of the driver-passenger models. Mar Biol. 2016;163: 175.
- 65. Peteiro C, Sánchez N, Martínez B. Mariculture of the Asian kelp Undaria pinnatifida and the native kelp Saccharina latissima along the Atlantic coast of Southern Europe: An overview. Algal Research. 2016;15: 9–23.