A systematic review of context bias in invasion biology

Words matter: how ecologists discuss managed and non-managed bees and birds

Effectively promoting the stability and quality of ecosystem services involves the successful management of domesticated species and the control of introduced species. In the pollinator literature, interest and concern regarding pollinator species and pollinator health dramatically increased in recent years. Concurrently, the use of loaded terms when discussing domesticated and non-native species may have increased. As a result, pollinator ecology has inherited both the confusion associated with invasion biology’s lack of a standardized terminology to describe native, managed, or introduced species as well as loaded terms with very strong positive or negative connotations. The recent explosion of research on native bees and alternative pollinators, coupled with the use of loaded language, has led to a perceived divide between native bee and managed bee researchers. In comparison, the bird literature discusses the study of managed (poultry) and non-managed (all other birds) species without an apparent conflict with regard to the use of terms with strong connotations or sentiment. Here, we analyze word usage when discussing non-managed and managed bee and bird species in 3614 ecological and evolutionary biology papers published between 1990 and 2019. Using time series analyses, we demonstrate how the use of specific descriptor terms (such as wild, introduced, and exotic) changed over time. We then conducted co-citation network analyses to determine whether papers that share references have similar terminology and sentiment. We predicted a negative language bias towards introduced species and positive language bias towards native species. We found an association between the term invasive and bumble bees and we observed significant increases in the usage of more ambiguous terms to describe non-managed species, such as wild. We detected a negative sentiment associated with the research area of pathogen spillover in bumble bees, which corroborates the subjectivity that language carries. We recommend using terms that acknowledge the role of human activities on pathogen spillover and biological invasions. Avoiding the usage of loaded terms when discussing managed and non-managed species will advance our understanding and promote effective and productive communication across scientists, general public, policy makers and other stake holders in our society.

Impacts of Moso bamboo (Phyllostachys pubescens) invasion on species diversity and aboveground biomass of secondary coniferous and broad-leaved mixed forest

In recent decades, Moso bamboo has been largely increasing in the subtropical area of China, raising ecological concerns about its invasion into other native forest ecosystems. One concern is whether the invasion of Moso bamboo significantly simplifies forest community composition and structure and declines biomass. This study adopted the space-for-time method to investigate a secondary coniferous and broad-leaved mixed forest (SF) being invaded by an adjacent Moso bamboo forest (MB) in the Wuxie forest reserve, Zhejiang Province. Three plots were established in each SF, MB, and transitional forest. The results showed that the species composition and species dominance of the arborous layer changed significantly (P < 0.05), which was indicated by the significantly decreased species richness (Margalef index, Shannon-Wiener index, and Simpson index) and evenness (Pielou evenness index). In contrast, the species richness of the shrub and herbaceous layers had two divergent indications (increasing or unchanged), and the evenness remained unchanged. The total and arborous-layer aboveground biomass of the forest community has had no noticeable change (P < 0.05). However, the biomass of the shrub and herbaceous layers showed an increasing trend (shrub significant but herbaceous not), but they only occupied a small proportion (∼1%) of the total biomass. Finally, the aboveground biomass and the diversity index had no significant correlation in each layer and overall stands. We hope that the findings could provide a theoretical basis for the invasion mechanism and ecological consequences of the Moso bamboo invasion.

Ecological Review of the Ciona Species Complex

AbstractThe set of four closely related solitary ascidians Ciona spp. were once considered a single cosmopolitan species, Ciona intestinalis, but are now recognized as genetically and morphologically distinct species. The possibility of ecological differences between the species was not widely considered in studies preceding the schism of Ciona spp. Consequently, there may be an over-generalization of the ecology of Ciona spp., with potential implications for the broad range of studies targeting these species, encompassing the evolution, development, genomics, and invasion biology of Ciona spp. We completed a comprehensive review of the ecology of Ciona spp. to establish the similarities and differences between the widely distributed Ciona robusta and C. intestinalis (and what little is known of the two other species, Ciona sp. C and Ciona sp. D). When necessary, we used study locations and the species' geographic ranges to infer the species in each study in the review. As expected, ecological similarities are the norm between the two species, spanning both abiotic and biotic interactions. However, there are also important differences that have potential implications for other aspects of the biology of Ciona spp. For example, differences in temperature and salinity tolerances likely correspond with the disparities in the geographic distribution of the species. Asymmetries in topics studied in each species diminish our ability to fully compare several aspects of the ecology of Ciona spp. and are priority areas for future research. We anticipate that our clarification of common and unique aspects of each species' ecology will help to provide context for future research in many aspects of the biology of Ciona spp.

Surprisingly high economic costs of biological invasions in protected areas

Biological invasions are one of the main threats to biodiversity within protected areas (PAs) worldwide. Meanwhile, the resilience of PAs to invasions remains largely unknown. Consequently, providing a better understanding of how they are impacted by invasions is critical for informing policy responses and optimally allocating resources to prevention and control strategies. Here we use the InvaCost database to address this gap from three perspectives: (i) characterizing the total reported costs of invasive alien species (IAS) in PAs; (ii) comparing mean observed costs of IAS in PAs and non-PAs; and (iii) evaluating factors affecting mean observed costs of IAS in PAs. Our results first show that, overall, the reported economic costs of IAS in PAs amounted to US$ 22.24 billion between 1975 and 2020, of which US$ 930.61 million were observed costs (already incurred) and US$ 21.31 billion were potential costs (extrapolated or predicted). Expectedly, most of the observed costs were reported for management (73%) but damages were still much higher than expected for PAs (24%); in addition, the vast majority of management costs were reported for reactive, post-invasion actions (84% of management costs, focused on eradication and control). Second, differences between costs in PAs and non-PAs varied among continents and environments. We found significantly higher IAS costs in terrestrial PA environments compared to non-PAs, while regionally, Europe incurred higher costs in PAs and Africa and Temperate Asia incurred higher costs in non-PAs. Third, characterization of drivers of IAS costs within PAs showed an effect of environments (higher costs in terrestrial environments), continents (higher in Africa and South America), taxa (higher in invertebrates and vertebrates than plants) and Human Development Index (higher in more developed countries). Globally, our findings indicate that, counterintuitively, PAs are subject to very high costs from biological invasions. This highlights the need for more resources to be invested in the management of IAS to achieve the role of PAs in ensuring the long term conservation of nature. Accordingly, more spatially-balanced and integrative studies involving both scientists and stakeholders are required.

A review of the critics of invasion biology

Herein, I review existing criticisms of the field of invasion biology. Firstly, I identifiy problems of conceptual weaknesses, including disagreements regarding: (i) definitions of invasive, impact, and pristine conditions, and (ii) ecological assumptions such as species equilibrium, niche saturation, and climax communities. Secondly, I discuss methodological problems include the misuse of correlations, biases in impact reviews and risk assessment, and difficulties in predicting the effects of species introductions or eradications. Finally, I analyse the social conflict regarding invasive species management and differences in moral and philosophical foundations. I discuss the recent emergence of alternatives to traditional invasion biology approaches, including the concept of novel ecosystems, conciliation biology, and compassionate conservation. Understanding different value systems will be the first step to reconciling the different perspectives related to this controversial topic.

Rethinking the native range concept

A species is not native outside its native range, but native range is not precisely defined. The invasion literature contains wide discussion of the core concepts such as naturalization, invasiveness, and ecological impact, but the concept of native range has received so little attention that a formal definition does not exist. I considered, among other impediments to a formal definition of native range, the sometimes arbitrariness of the spatial and temporal limits assigned to native range. Broad questions that remain include whether invasion theory can be used to define the native range for species without non-native ranges.

Native Bamboo Invasions into Subtropical Forests Alter Microbial Communities in Litter and Soil

Both exotic and native plant invasions can have profound impacts on ecosystems. While many studies have examined the effects of exotic plant invasions on soil properties, relatively few have tested the effects of native plant invasions on soil microbial communities. Furthermore, we know little about the effects of native plant invasions on microbial communities in litter. In subtropical forests in southern China, we sampled litter at three decomposition stages and top soil in three forest sands representing three stages of the invasion (not invaded, moderately and heavily invaded) by the Moso bamboo (Phyllostachys edulis (Carriere) J. Houzeau), a native species in China. We measured chemical properties (concentrations of C, N, P, Mg, Al, K, Ca, Mn, Cu, and Zn, and concentrations of cellulose and lignin) and microbial communities in litter and/or soil. The bamboo invasion, in general, decreased the element concentrations in litter and soil and also decreased total microbial abundance and diversity. Considering bacteria and fungi separately, the bamboo invasion decreased fungal diversity in litter and soil, but had little impact on bacterial diversity, suggesting that fungi are more sensitive and vulnerable to the bamboo invasion than bacteria. We conclude that native Moso bamboo invasions into subtropical forests may lead to a complex biogeochemical process in the litter–soil system, which may threaten local forest ecosystems by affecting microbial communities and, thus, litter decomposition and nutrient cycling.

Disconnects between Communicated Impact and Ecological Impact of Biological Invasions

Although scientists strive to accurately communicate their research, disconnects can arise between results and rhetoric. Some have regarded invasion scientists as particularly prone to using value-laden language incommensurate with the scientific facts or results. We addressed how authors used 10 near synonyms (words for which usage is similar but not completely overlapping) of the negative-value word invasive. We asked whether study findings (effect sizes) or other factors predicted language use. The use of negative-value words such as invasive was not associated with study findings but, instead, with contextual factors. For example, plant and invertebrate biologists used more negative language to describe nonnatives than did those studying vertebrates. The authors also tended to use more negative language in recently published papers than in older studies. Although many have called for impartial language when communicating research, some scientists use language imbued with value that may be inappropriate. Such use may affect how the public perceives scientific findings.

Invasive plants negatively impact native, but not exotic, animals

Despite our growing understanding of the impacts of invasive plants on ecosystem structure and function, important gaps remain, including whether native and exotic species respond differently to plant invasion. This would elucidate basic ecological interactions and inform management. We performed a meta-analytic review of the effects of invasive plants on native and exotic resident animals. We found that invasive plants reduced the abundance of native, but not exotic, animals. This varied by animal phyla, with invasive plants reducing the abundance of native annelids and chordates, but not mollusks or arthropods. We found dissimilar impacts among "wet" and "dry" ecosystems, but not among animal trophic levels. Additionally, the impact of invasive plants increased over time, but this did not vary with animal nativity. Our review found that no studies considered resident nativity differences, and most did not identify animals to species. We call for more rigorous studies of invaded community impacts across taxa, and most importantly, explicit consideration of resident biogeographic origin. We provide an important first insight into how native and exotic species respond differently to invasion, the consequences of which may facilitate cascading trophic disruptions further exacerbating global change consequences to ecosystem structure and function.

Biological control of pests and a social model of animal welfare

This paper considers the sociocultural implications of biological pest control that sit at the cusp of managing an invasive species for conservation or productivity (i.e. a 'natural enemy') and socially driven 'manipulating life' arguments. We consider the role of perceived humaneness or, more accurately, animal welfare as it relates to managing invasive species from a scientific and social perspective. In order to highlight and articulate particular nuances and standards across different pest control contexts, we use three case examples (feral cats, wild rabbits, and invasive cane toads) and explore where biological pest control and animal welfare interests intersect. The paper summarises key scientific welfare concerns and then extends the literature to also examine key social characteristics of each pest management scenario, including lay perceptions of animal welfare, the sociocultural context that pests exist within, and overarching psychological factors contributing to public sentiment, including perceived risks. The subsequent descriptive model presented is useful in articulating core sociocultural beliefs relative to each case and how these antecedent associations and attitudes about an animal influence subsequent beliefs about a pest management strategy and ultimately acceptance of the management approach. The model can inform invasive species management policies and highlight key sociocultural factors likely to influence public responses. The model also informs interdisciplinary science designed to develop acceptable and socially responsible biocontrol strategies that consider public perceptions of animal welfare and cultural appropriateness.

Invasive species denialism: Sorting out facts, beliefs, and definitions

In the last decades, thousands of investigations confirmed the detrimental effects of species translocated by man outside of their native ranges (nonindigenous species, or NIS). However, results concluding that many NIS have null, neutral, or positive impacts on the biota and on human interests are as common in the scientific literature as those that point at baneful impacts. Recently, several scholars confronted the stand that origin per se is not a reliable indicator of negative effects, suggesting that such conclusions are the expression of scientific denialism, often led by spurious purposes, and that their numbers are increasing. When assessed in the context of the growing interest in introduced species, the proportion of academic publications claiming that NIS pose no threats to the environment and to social and economic interests is extremely low, and has not increased since 1990. The widely prevailing notion that many NIS are effectively or potentially harmful does not conflict with the fact that most have mixed (negative, neutral, and positive) impacts. When based on solid grounds, reports of positive or neutral impacts should not be labeled as manipulative or misleading unless proven otherwise, even if they may hamper interest in- and funding of research and control bioinvasion programs.

Responses of the native species Sparganium angustifolium and the invasive species Egeria densa to warming and interspecific competition

Climate change, especially warming temperatures, may increase invasion and modify the ecological impacts of invasive species by enhancing their ability to compete. To test the effects of warming on invasive plants, a mesocosm experiment was conducted to study competition between the invasive plant Egeria densa and the native hygrophyte Sparganium angustifolium under simulated warming conditions in a greenhouse. These two species were grown in monoculture (no competitor control) or mixed culture (competitor control) for two months under different temperature conditions (warming treatment or no-warming treatment). In S. angustifolium, the higher temperatures led to a shorter root length and significantly increased the aboveground traits of ramets, the total biomass, and the RGR (relative growth rate) but had no effect on the aboveground traits of genets. Growth in mixed culture significantly decreased the S. angustifolium ramet height under warmer conditions and significantly reduced the ramet root length, ramet number, genet biomass, root-to-shoot ratio and RGR of S. angustifolium under natural temperature conditions. All the morphological, biomass and growth traits of E. densa except for the root-to-shoot ratio were significantly increased by the warmer temperatures and decreased by growth in mixed culture. The RCI and RII of E. densa in both the no-warming and warmer environments were two and three times greater than those of S. angustifolium, whereas the ACI values for the two species were similar. Thus, S. angustifolium was a better competitor than E. densa under both temperature conditions. These results suggest that although the superior competitive ability of native species can inhibit E. densa growth, the performance of this species will be enhanced under future climate warming in cold regions.