Native Invertebrates Research Articles

Assessing the direct and indirect effects of bigheaded carp (Hypophthalmichthys spp.) on freshwater food webs: A meta‐analysis

Abstract The rapid growth of aquaculture over the last century has led to the widespread introduction of aquatic species to freshwater environments. Bighead carp (Cyprinidae: Hypophthalmichthys nobilis) and silver carp (Cyprinidae: Hypophthalmichthys molitrix), collectively referred to as bigheaded carp, are among the top finfishes produced in aquaculture. These filter feeders possess feeding structures that allow them to efficiently remove plankton and other particles from the water. Unfortunately, when introduced into the wild and outside their historical range, their feeding traits generally result in the exploitation and suppression of phytoplankton and zooplankton, reducing food resources for native invertebrates and vertebrates. We conducted a meta‐analysis of published experiments to examine how bigheaded carp directly and indirectly affect organisms in aquatic food webs to better understand their ecological role within ecosystems. Specifically, we addressed the following questions: (1) What is the overall magnitude and direction of bigheaded carp effects on different aquatic organisms? (2) Do bigheaded carp affect organisms in planktonic and benthic habitats? (3) Are effects similar between bighead carp and silver carp? (4) Are effects consistent among experimental arenas (i.e., mesocosm, ponds)? We detected direct and indirect effects of bigheaded carp across multiple trophic levels. Large zooplankton often exhibited the strongest negative effects, with taxa‐specific differences between carp species. The suppression of zooplankton cascaded down to primary producers, resulting in an increase in phytoplankton (i.e., indirect effect). However, we observed no compensatory increases in rotifers when large zooplankton were reduced. Growth rates of planktivorous native fishes were the slowest when stocked with bigheaded carp. Our results further indicated that egested waste from bigheaded carp appeared to subsidise (i.e., direct effect) some benthic invertebrates such as Chironomidae midges. Effects of carp on zooplankton were generally similar between mesocosms and ponds. Invasive bigheaded carp greatly restructure their surrounding food web, both positively and negatively, through a complex suite of direct and indirect effects. These changes manifested across multiple trophic levels and differing habitats. Our analysis provides a more complete understanding of how these invasive carps change their surroundings by exploiting food resources and transferring materials from planktonic to benthic habitats. Taken together, the suite of direct and indirect effects shows how an invasive species can create imbalances within aquatic ecosystems, often to the detriment of native taxa. Bigheaded carp are invasive in many countries across the globe because of their popularity in aquaculture. Our findings reaffirm the threat these planktivores pose to native freshwater organisms.

Introduced mice influence the large-bodied alpine invertebrate community

Invasive mammalian predators are a key threat to native fauna globally. Island ecosystems that developed in isolation from mammals are particularly threatened by introduced mammalian predators. This is the case in New Zealand, where introduced mammalian predators have caused the decline of native birds, lizards, and invertebrates. In alpine areas of New Zealand, predator control targets stoats, rats, and cats as they are recognised as the key threats to native birds. Mice, which are known predators of invertebrates at lower elevations, are not actively controlled. As a result, alpine invertebrates in New Zealand represent an ideal focus for a natural experiment to understand the effects of predator control efforts and invasive mice on native invertebrates that evolved in isolation from mammals. In the Fiordland region of New Zealand, we assessed the large-bodied alpine invertebrate community at eight different sites that vary in their occurrence of mice and control of higher-order predators. We found that the recent presence of mice influenced the invertebrate community: wētā (a group of native orthopterans) were less common at sites where mice were present, and the mean body size of invertebrates collected in pitfall traps was larger at sites where mice were absent compared to sites where they were present. Control of other predators (specifically rats and mustelids) did not influence invertebrate body size, abundance, or community composition. Our findings suggest that, as in lowland environments, mice are an important predator of large-bodied invertebrates in the alpine zone and should be incorporated into future predator management programmes.

Introduced species infiltrate recent stages of succession after glacial retreat on sub-Antarctic South Georgia

Biological invasions are one of the main drivers of global biodiversity decline. At the same time, glacial retreat induced by climate warming is occurring at an alarming rate across the globe, threatening unique taxa and ecosystems. However, we know little about how introduced species contribute to the dynamics of colonisation in newly-deglaciated forelands. To answer this question, detailed inventories of plant and invertebrate communities were undertaken during two summer field seasons in the forelands of three tidewater and three inland glaciers that are retreating on the sub-Antarctic Island of South Georgia. The vascular plant communities present included a large proportion of South Georgia’s native flora. As expected, plant richness and cover increased with time since deglaciation along a deglaciation chronosequence. Introduced plants were well represented in the study sites and two species (Poa annua and Cerastium fontanum) were amongst the earliest and most frequent colonisers of recently-deglaciated areas (occurring on more than 75% of transects surveyed). Introduced arthropods were also present around tidewater glaciers, including an important predatory species (Merizodus soledadinus) with known detrimental impacts on native invertebrate communities. Our study provides a rare and detailed picture of developing novel communities along a deglaciation chronosequence in the sub-Antarctic. Introduced species are able to track glacial retreat on South Georgia, indicating that further local colonisation and spread are inevitable as the region’s climate continues to warm.

Establishing a comprehensive invertebrate and vegetation inventory of Auckland Zoo, Aotearoa / New Zealand

Invertebrates are major contributors to biodiversity with important roles in ecosystem function but are often overlooked in conservation work in favour of larger, charismatic species. Invertebrates living outside of captive conditions may have the potential to affect zoo activities, and it has been suggested that zoos might contribute to invertebrate conservation programs by providing suitable habitat for these organisms. In this study, a survey of invertebrates living in non-fenced areas of Auckland Zoo was carried out to explore the relationship between the vegetation and invertebrate communities throughout the zoo grounds. A total of 6,133 invertebrate specimens were collected in pitfall traps over a ten-day period in January of 2018. Using morphospecies as surrogates for species, differences in invertebrate community structure in different non-fenced areas were assessed. No significant relationship between native vegetation and native invertebrates was detected.

Isotopic Overlap of Invasive and Native Consumers in the Food Web of Lake Trasimeno (Central Italy).

An advanced characterization of the trophic niche of non-indigenous species (NIS) may provide useful information on their ecological impact on invaded communities. Here, we used carbon and nitrogen stable isotopes to estimate pairwise niche overlaps between non-indigenous and native consumers in the winter food web of Lake Trasimeno (central Italy). Overall, a relatively low pairwise overlap of isotopic niches was observed between NIS and native species. The only exception was the Louisiana crayfish Procambarus clarkii, which showed a relatively high and diffuse overlap with other native invertebrates. Our findings highlighted a high niche divergence between non-indigenous and native species in Lake Trasimeno, suggesting a potentially low degree of interspecific competition that may facilitate coexistence and, in turn, limit the strength of impacts. The divergent results obtained for the Louisiana crayfish indicate that additional control measures for this invasive species are needed to mitigate its impact on the Lake Trasimeno system.

Lethality and Acetylcholinesterase Inhibition in a Native Invertebrate Species Exposed to Water Samples of an Impacted Stream (Reconquista River Basin, Argentina).

The study of multiple biomarkers in bioindicator species is a useful tool to evaluate water quality in addition to physicochemical analysis. The aim of this work was to study the toxicity of water samples from two sites with different anthropogenic impacts (R: near a residential area and FP: close to horticultural farms and industrial waste treatment plants) from Las Catonas sub-basin (Reconquista River basin) in the native gastropod Biomphalaria straminea. Some physicochemical parameters and chlorpyrifos concentration were measured in water samples. Snails were exposed in laboratory conditions 48h to the water samples and neurotoxicity, behavior, lethality and acetylcholinesterase, carboxylesterase, glutathione S-transferase, glutathione reductase and catalase activities were measured. In water from FP, chlorpyrifos was detected and conductivity and pH were higher than in R. Lethality (60%) and a decrease (30%) in acetylcholinesterase were observed in snails exposed to FP indicating that water contamination causes high toxicity in B. straminea.

Characterization of Cross-Species Transmission of Drosophila melanogaster Nora Virus.

Drosophila melanogaster Nora virus (DmNV) is a novel picorna-like virus first characterized in 2006. Since then, Nora virus has been detected in several non-Drosophila species, including insects in the Orders Hymenoptera, Lepidoptera, Coleoptera, and Orthoptera. The objective of this study was to determine if DmNV could infect individuals of other species of invertebrates besides D. melanogaster. The presence of DmNV in native invertebrates and commercially available stocks was determined. Laboratory-reared D. yakuba, D. mercatorum, Gryllodes sigillatus, Tenebrio molitor, Galleria mellonella, and Musca domestica were intentionally infected with DmNV. In addition, native invertebrates were collected and D. melanogaster stocks were purchased and screened for DmNV presence using reverse transcription-polymerase chain reaction (RT-PCR) before being intentionally infected for study. All Drosophila species and other invertebrates, except M. domestica, that were intentionally infected with DmNV ended up scoring positive for the virus via RT-PCR. DmNV infection was also detected in three native invertebrates (Spilosoma virginica, Diplopoda, and Odontotaenius disjunctus) and all commercially available stocks tested. These findings suggest that DmNV readily infects individuals of other species of invertebrates, while also appearing to be an endemic virus in both wild and laboratory D. melanogaster populations. The detection of DmNV in commercially available stocks presents a cautionary message for scientists using these stocks in studies of virology and immunology.

Predicting the Potential Suitable Area of the Invasive Ant Linepithema humile in China under Future Climatic Scenarios Based on Optimized MaxEnt

Linepithema humile (Mayr, 1868) (Hymenoptera: Formicidae) is one of “100 of the world’s worst invasive alien species” listed by the International Union for Conservation of Nature and Natural Resources (IUCN). Although native to South America, this ant has spread worldwide via international trade. Currently, L. humile has not been found in China, and if it invades China, it might pose a potential risk to the native invertebrates, vertebrates, plants, and human livelihoods. Based on 2432 global occurrence records and ten bioclimatic variables, the optimized MaxEnt model was used to predict the potential suitable areas of L. humile in China. We analyzed the important bioclimatic variables affecting the potential suitable areas, and determined the changes in potential suitable areas under future climatic scenarios. Our results indicated that the mean temperature of the coldest quarter (Bio11), precipitation of the coldest quarter (Bio19), mean temperature of the wettest quarter (Bio8), and precipitation of the warmest quarter (Bio18) were the most important bioclimatic variables. Under the current climatic scenarios, the potential suitable area of L. humile in China is 80.31 × 104 km2, which is mainly located in Fujian, Zhejiang, Hunan, Jiangxi, Guangxi, Yunnan, and Hubei. Under future climate scenarios over coming decades, the potential suitable areas of L. humile showed an overall increase and a shift to higher latitudes, which indicated the invasion risk of L. humile in China will increase under climate change. Our findings provide the theoretical guidance for the early warning and monitoring of L. humile in China.

Trophic niche of an invasive generalist consumer: Australian redclaw crayfish,Cherax quadricarinatus, in the Inkomati River Basin, South Africa

AbstractTrophic niche analysis can be used to assess ecological opportunities available to alien species in areas of introduction that might aid their establishment, define their functional role and inform on their potential impacts. This study assessed the trophic niche utilized by an invasive population of the Australian redclaw crayfish,Cherax quadricarinatus, in the Inkomati River Basin, South Africa. It evaluated the hypothesis that the euryphagous feeding strategy of redclaw crayfish may allow it to shift its niche width and niche position by altering its feeding strategy in response to fluctuations in resource availability. Gut content and stable isotope analyses were used to determine trophic niche and trophic interactions. Redclaw crayfish were shown to be omnivores and their diet consisted mainly of algae, plant material and invertebrates. Small‐sized individuals had a constricted niche width and fed primarily on invertebrates, whereas larger individuals expanded their niche width to include larger proportions of plant material. Crayfish caught from lotic environments had a higher proportion of invertebrates in their diet than crayfish from lentic environments, and the species exploited a wider niche in summer than in winter. These differences are likely related to differences in productivity amongst habitats and fluctuations in resource availability. There was significant niche overlap (>60%) between redclaw crayfish and Sidney's river crab (Potamonautes sidneyi), but not with other native invertebrates. Both species are omnivores and have similar functional roles, possibly making redclaw crayfish functionally redundant in this ecosystem. Even though both species mainly feed on resources (plant material and invertebrates) that are not normally limiting, the redclaw crayfish invasion might be an accelerator of ecosystem processes such as shredding and decomposition rates of plant material. There is, therefore, a need for further studies to examine potentially altered ecosystem functions caused by redclaw crayfish invasion in the Inkomati River system.

Marbled crayfish Procambarus virginalis invades a nature reserve: how to stop further introductions?

We hereby provide the first documented data on the occurrence of a viable Procambarus virginalis population in a nature reserve in Poland and the steps that were taken to prevent further introductions of the species in the country. To date, Poland represents the most north-eastward distribution area in Europe, where the species occurs in ecosystems with natural water temperature regimes. The ecological plasticity of P. virginalis and its obligate parthenogenetic reproduction make this crayfish an exceptional invader. The crayfish may have detrimental effects on the native invertebrates, amphibians, and fish, and alter the state of the entire ecosystem. Therefore, we investigated the presence of the species in the nature reserve of Pojezierze Łęczyńskie Landscape Park after a suspected P. virginalis individual was found by a local citizen. The nature reserve also includes an area designated to protect native amphibians and turtles. Our study revealed the presence of a thriving population of P. virginalis in the protected area and clear indications of its impact on native and invasive species, both in aquatic and terrestrial environments. If no action is taken, the species will likely expand to other water bodies across the country. An extensive sensibilization campaign allowed us to find additional invaded areas and significantly contribute to the effective ban of this and other invasive crayfish species from private and commercial online trade. Raising public awareness and banning invasive crayfish species trade is essential for successfully detecting and preventing further introductions.

Habitat complexity mediates spatiotemporal niche partitioning among native and invasive seed predators

Red imported fire ants dominate certain food webs in North America due to their omnivorous and aggressive feeding behavior. Structural habitat complexity can mediate effects of invasive predators on native insects, by either facilitating or tempering antagonistic interactions, with potential consequences at lower trophic levels. Along a gradient of habitat complexity, we evaluated how refuge affects the activity and foraging behavior of fire ants and native invertebrate seed predators using video surveillance, and then determined their consumption of pigweed seeds in seed removal assays. Fire ants dominated seed predation in our system, and structural complexity increased both their activity and seed removal, while reducing that of native seed predators. In structurally simple habitats with high sun exposure, fire ant activity was restricted to the evening when temperatures were milder, while native seed predators foraged during the heat of the day, possibly to avoid antagonistic interactions with fire ants. In relatively shaded, structurally complex habitat, the active foraging period for fire ants expanded earlier into the heat of the day, and almost totally overlapped with that of native seed predators. Our data suggest that structural refuge may facilitate antagonism and site/resource domination by fire ants.

Earthworm invasion shifts trophic niches of ground-dwelling invertebrates in a North American forest

Earthworms are invading soil communities worldwide, and their actions as decomposers and ecosystem engineers are vastly impacting many ecosystem functions. In the northern regions of North America, invasive earthworms are often functionally distinct from the native invertebrate fauna and, thus, typically occupy empty trophic niches in soil food webs. Nevertheless, they can affect the co-occurring soil invertebrate communities in multiple indirect ways. Particularly, the redistribution and removal of litter resources can affect feeding interactions of soil biota that channel up to higher trophic levels, such as predators, causing shifts across all components of the soil food web, which are hard to investigate. To study trophic shifts in earthworm-invaded soil communities, we used ground predators as model organisms since they occupy high trophic levels and connect different energy channels in soil food webs. We used stable isotope (13C and 15N) and fatty acid analyses as complementary tools to describe the trophic levels and basal resources of consumers that were impacted by earthworm invasion, specifically examining the trophic niches and resources available to ground-dwelling invertebrates of a northern aspen forest. The distinct trophic niches of invertebrate species were affected significantly by earthworm invasion. Shifts in neutral lipid fatty acid profiles as well as decreases in animal Δ13C and Δ15N signatures indicated changes in basal resources and trophic levels, respectively. Furthermore, we observed a trend of greater intra-specific and less inter-specific variation in fatty acid profiles of soil organisms following earthworm invasion. Notably, shifts in marker fatty acids of ground-dwelling invertebrates were opposite to the changes observed in soil microbial communities, suggesting de-coupling of soil microbial and ground arthropod food-web compartments. Overall, our study revealed a systemic effect of invasive earthworms on ground-dwelling invertebrates. Earthworms presumably consumed a considerable amount of resources, such as litter and, thus, incorporated them in the soil food web, which was, as a basal resource, not available in the food web free of earthworms. Overall, the ground-dwelling invertebrates have adapted (changed their trophic function) which could explain the balancing of potential environmental changes that are caused by invasive earthworms. This observation potentially explains why these species are dominant in the studied forest and resist earthworm invasion. Future studies should investigate if altered litter availability also causes shifts in soil biodiversity in invaded forests, which is assumed but rarely directly tested to date.

Effective and feasible mechanisms to support native invertebrate pollinators in agricultural landscapes: A meta‐analysis

AbstractPollinator declines have emerged as a major conservation concern across a wide diversity of systems and taxa worldwide. In response to these concerns, active efforts to conserve pollinators are increasingly considered in agricultural landscape design and management, natural area management, and public land decision‐making. An important conservation challenge is translating these efforts to feasible recommendations that agriculturalists across a diversity of systems and contexts can employ to support pollinator communities. In order to develop such a toolbox for agriculturalists, we conducted a meta‐analysis to examine feasible management practices, tools, or decisions, employed in agricultural landscapes, that directly impact pollinator forage and nest site resources. Our search terms netted a total of 743 unique references; from this, we developed a dataset of 209 unique records, derived from 89 unique references, for inclusion in our meta‐analysis. We found that across all treatments aimed at boosting pollinators, there were significant increases in bee abundance, bee species richness, and overall pollinator abundance and visitation rate. We also found specifically that across all study types, the following practices resulted in positive changes in pollinator community responses: reduced distance to natural areas, reduced regional intensity of human modification, increased quantity and quality of pollinator resources within a focal system, plantings adjacent to agricultural areas, and the use of nonconventional agricultural practices. The most consistent pollinator response to treatments was bee species richness, which was significantly increased by plantings adjacent to agricultural areas, distance from natural areas, and quantity and diversity of pollinator resources. Bee species richness also decreased with intensity of human modification. These findings are presented in a toolbox for agriculturalists, containing evidence‐based actions and outcomes to assist practitioners in decision‐making specific to pollinator habitat improvement that could be actionable in the near term.

Combined per‐capita and abundance effects of an invasive species on native invertebrate diversity and a key ecosystem process

Abstract Invasive alien species (IAS) are leading to the homogenisation of taxonomic and functional biodiversity, with negative consequences for key ecosystem processes in fresh water. Invasive signal crayfish (Pacifastacus leniusculus) is expected to disrupt detritus‐based food webs by affecting leaf breakdown and/or by decreasing invertebrate density and diversity through predation. The combination of per‐capita and abundance effects of P. leniusculus in invaded ecosystems is still largely unknown. A four‐week field experiment was established in Rabaçal and Tuela Rivers (NE Portugal) to assess effects of P. leniusculus on invertebrate taxonomic and functional diversity and leaf litter breakdown following a gradient of invasion. We controlled the presence and absence of crayfish by placing the animals and leaf litter inside cages at six sites (three sites per river) according to the crayfish in situ abundance (absent, low, high). Cages were covered with coarse‐ or fine‐mesh net to allow or prevent invertebrates from accessing the leaves. Results showed that higher crayfish in situ abundance led to a decrease in abundance, richness and Shannon diversity of invertebrates and to changes in the communities’ structures. Higher crayfish abundance led also to a decrease in invertebrate functional redundancy and an increase in the percentage of invertebrate taxa with resistance forms. Leaf litter breakdown increased with crayfish presence and decreased at sites with higher crayfish abundance. Overall, signal crayfish changed the community structure of invertebrates, with potential severe long‐term effects on native communities and leaf litter breakdown. Given the widespread distribution of signal crayfish (and other crayfish species), their ecological impacts should be assessed carefully, especially in pristine freshwater ecosystems such as those described here.

Contrasting effects of tree origin and urbanization on invertebrate abundance and tree phenology.

The ongoing wide-scale introduction of nonnative plants across the world may negatively influence native invertebrate fauna, due to a lack of coevolved traits related to the novel plants, e.g., unique phytochemicals or shifted phenology. Nonnative plants, specifically trees, are common in urban environments, areas that already pose novel habitats to plants and wildlife through a wide array of anthropogenic factors. For example, impervious surfaces contribute to increased ambient temperatures, the so-called urban heat island effect (UHI), which can affect local plant phenology. Yet, few studies have simultaneously studied the effects of urbanization and tree species origin on urban invertebrate communities. We measured the city-level UHI and phenology of nine native and seven nonnative tree species in five city-center parks in southern Sweden, as well as four common native species in a rural control forest. We quantified the abundance of invertebrates on a subset of native and nonnative tree species through shake sampling, sticky traps, and frass collection. In the urban environment, nonnative trees hosted significantly fewer invertebrates compared to native trees. Furthermore, the nonnative trees had a delayed phenology compared to native species, while the peak of caterpillars associated with the subset of trees surveyed for this measure was significantly earlier compared to that of the native species studied. The effect of tree species origin on urban invertebrate abundance was of a greater magnitude (effect size) than the effect of urbanization on invertebrate abundance in native tree hosts. Hence, the results indicate that the impact of nonnative vegetation may be a stronger driver of invertebrate declines in urban areas than other factors. As the effect of species origin on tree phenology was at a level comparable to the urban effect, increasing prevalence of nonnative vegetation can potentially obscure effects of urbanization on phenology in large-scale studies, as well as induce mismatches to invertebrate populations. Since parks harbor a large proportion of urban biodiversity, native trees play a crucial role in such habitats and should not be considered replaceable by nonnative species in terms of conservation value.

Invasive Plants Differentially Impact Forest Invertebrates, Providing Taxon-Specific Benefits by Enhancing Structural Complexity

Exotic plant species often negatively affect native herbivores due to the lack of palatability of the invading plant. Although often unsuitable as food, certain invasive species may provide non-nutritional ecological benefits through increased habitat structural complexity. To understand the potential for common invasive forest plant species of the eastern United States to benefit invertebrate communities, we examined the functional and taxonomic community composition of forest insects and spiders in long-term monitoring plots that contained invasive plant species. The extent of invasive plant species ground cover significantly altered spider community composition as categorized by hunting guild. Areas with higher invasive herbaceous and grass cover contained a higher abundance of space web-weaving and hunting spiders, respectively. Spider species richness and total invertebrate abundance also increased with greater invasive grass cover. Still, these trends were driven by just two invasive plant species, garlic mustard and Japanese stiltgrass, both of which have previously been shown to provide structural benefits to native invertebrate taxa. While these two species may improve the structural component of understory forest habitat, many invertebrate groups were not significantly correlated with other prevalent invasive plants and one species, mock strawberry, negatively affected the abundance of certain insect taxa. Particularly in forests with reduced native plant structure, invasive plant management must be conducted with consideration for holistic habitat quality, including both plant palatability and structure.

Biology, Ecology, and Management of the Invasive Longlegged Ant, Anoplolepis gracilipes.

The longlegged ant (Anoplolepis gracilipes) is one of the most damaging invasive tramp ants globally. It is generally found between latitudes 27°N and 27°S in Asia, although it has been introduced to other continents. Its native range remains debatable, but it is believed to be in Southeast Asia. Anoplolepis gracilipes invasion has many serious ecological consequences, especially for native invertebrate, vertebrate, and plant communities, altering ecosystem dynamics and functions. We examine and synthesize the literature about this species' origin and distribution, impacts on biodiversity and ecosystems, biology and ecology, chemical control, and potential biocontrol agents. We highlight emerging research needs on the origin and invasion history of this species, its reproductive mode, its relationship with myrmecophiles, and its host-microbial interactions, and we discuss future research directions.

A survey of benthic invertebrate communities in native and non-native seagrass beds in St. John, USVI

Halophila stipulacea, a seagrass native to the Indian Ocean, spread to the Caribbean in 2002. Few studies have explored the spatiotemporal distribution of H. stipulacea throughout the Caribbean and whether native invertebrates utilize this non-native seagrass as habitat. We surveyed the shallow, nearshore subtidal zones of four bays in St. John, US Virgin Islands over a two-year period to assess the abundance of both H. stipulacea and native seagrass species. We then surveyed macroinvertebrate communities in one bay with large areas of H. stipulacea, native seagrasses, and bare substrate to assess how macroinvertebrate species composition varied in these habitats. Our survey of the benthic macroinvertebrates revealed that: (1) native invertebrate species utilize H. stipulacea beds and (2) the density and richness of invertebrates was significantly higher in H. stipulacea beds compared to both native seagrass beds and bare substrate. Our results show that H. stipulacea is a common component of nearshore communities in St. John, USVI and that native invertebrates use H. stipulacea beds as habitat — results that agree with findings from other recent studies. While these findings indicate that native macroinvertebrate species can be abundant in non-native seagrass, further investigation, including experimental manipulations, preference tests, and surveys across broad spatial scales, are required to develop a robust understanding of the ecological impacts of this non-native grass.

Impact of round goby on native invertebrate communities - An experimental field study

This experimental field study provides first insights into the impact of a widely spread non-native fish species, round goby Neogobius melanostomus (Pallas 1814), on the diversity of native epifaunal macroinvertebrate communities in the Baltic Sea. A cage experiment was conducted in a macrophyte habitat in the Åland islands located in the northern Baltic Sea. Round gobies (13.5 ± 0.8 cm) affected macroinvertebrate biodiversity from a taxonomic and a trait-based point of view. Specifically, round goby decreased overall abundance, biomass and taxon richness of epifaunal invertebrates. Additionally, taxonomic and trait-based composition were affected, as the gobies reduced abundances of common bivalve (Cerastoderma spp. and Mytilus sp.) and gastropod species (Hydrobia spp.), and thereby modified the relative trait composition of the invertebrate assemblages. Round gobies consumed mainly larger epifaunal individuals leading to an overall decrease in invertebrate body size. Such alterations in taxonomic and trait-based diversity and composition of invertebrate communities through round goby predation may have implications for native fish species and other trophic levels in the respective food webs through food competition and trophic cascades. Round gobies might therefore affect ecosystem processes in invaded areas, and thus influence ecosystem functioning and services.

A Review and Secondary Analysis of Competition-Related Impacts of Nonindigenous Aquatic Plants in the Laurentian Great Lakes.

The Laurentian Great Lakes of North America are home to thousands of native fishes, invertebrates, plants, and other species that not only provide recreational and economic value to the region but also hold an important ecological value. However, there are also 55 nonindigenous species of aquatic plants that may be competing with native species and affecting this value. Here, we use a key regional database—the Great Lakes Aquatic Nonindigenous Species Information System (GLANSIS)—to describe the introduction of nonindigenous aquatic plants in the Great Lakes region and to examine patterns relating to their capacity to compete with native plants species. Specifically, we used an existing catalog of environmental impact assessments to qualitatively evaluate the potential for each nonindigenous plant species to outcompete native plant species for available resources. Despite an invasion record spanning nearly two centuries (1837–2020), a great deal remains unknown about the impact of competition by these species. Nonetheless, our synthesis of existing documentation reveals that many of these nonindigenous species have notable impacts on the native plant communities of the region in general and on species of concern in particular. Furthermore, we provide a thorough summary of the diverse adaptations that may contribute to giving these nonindigenous plants a competitive advantage. Adaptations that have been previously found to aid successful invasions were common in 98% of the nonindigenous aquatic plant species in the database.