Spread Of Non-native Species Research Articles

Rapid declines in freshwater gastropods in Pune city, India

ABSTRACT We studied freshwater gastropod fauna in a heavily urbanized region in tropical India, across a range of habitat types. A total of 16 species were found from a two-year survey, which is a decline of 27% compared to studies completed in the 1970s. Planorbidae was the most species rich family in the collection, with five species. Racesina luteola (Lamarck, 1822) was the most commonly occurring species in the collection. Three non-native species, including Pomacea diffusa (Blume, 1957), are also reported. Habitat type influenced species occurrences, although lentic and lotic habitats were largely similar in their fauna. Many species reported previously were missing from the current survey, along with an increased incidence of non-native species which were absent from earlier reports. This decline in species richness, particularly of native species, alongside an increased incidence and spread of non-native species in the region, highlights the impact of urbanization on the freshwater gastropod community.

Environmental DNA-Based Identification of Non-Native Fish in Beijing: Diversity, Geographical Distribution, and Interactions with Native Taxa.

Rapid urbanization and its associated human activities have facilitated the colonization and spread of non-native species, rendering urban ecosystems, particularly in megacities such as Beijing, highly susceptible to biological invasions. This study employed environmental DNA (eDNA) metabarcoding to evaluate the biodiversity and geographical distribution of non-native fish, as well as their interactions with native fish species, across three river basins in Beijing pertaining to the Daqing River, the North Canal, and the Ji Canal. Across all the 67 sampling sites, we identified 60 fish taxa, representing 11 orders, 23 families, and 40 genera, with an average of 33.0 taxa per site. Of these, 40 taxa were native, accounting for only 47.1% of the historically recorded native fish species. Additionally, we detected 20 non-native fish taxa, spanning 11 orders, 13 families, and 17 genera. Native fish exhibited geographical homogenization across the basins, while non-native taxa displayed varied geographical distributions. Non-metric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM) revealed no significant variation in the non-native communities across the river basins. Although most of the non-native taxa were widespread, some were restricted to specific sites or basins. The North Canal exhibited significantly lower non-native biodiversity compared with the Ji Canal across all alpha diversity indices. Simple linear regression analyses indicated positive correlations between the number of taxa and species richness for both native and non-native taxa. Interestingly, species co-occurrence analyses revealed predominantly positive interactions among both native and non-native species pairs, with only two negative relationships involving one native and two non-native taxa. This study provides insights into the biodiversity and geographical distribution of non-native fish in Beijing and establishes a baseline for future biomonitoring and conservation efforts. The findings underscore the need for further investigation into the mechanisms and dynamics of biological invasions within urban environments in Beijing.

Cities Shape the Diversity and Spread of Nonnative Species

Cities Shape the Diversity and Spread of Nonnative Species

Rapid Adaptation and Interspecific Introgression in the North American Crop Pest Helicoverpa zea.

Insect crop pests threaten global food security. This threat is amplified through the spread of nonnative species and through adaptation of native pests to control measures. Adaptations such as pesticide resistance can result from selection on variation within a population, or through gene flow from another population. We investigate these processes in an economically important noctuid crop pest, Helicoverpa zea, which has evolved resistance to a wide range of pesticides. Its sister species Helicoverpa armigera, first detected as an invasive species in Brazil in 2013, introduced the pyrethroid-resistance gene CYP337B3 to South American H. zea via adaptive introgression. To understand whether this could contribute to pesticide resistance in North America, we sequenced 237 H. zea genomes across 10 sample sites. We report H. armigera introgression into the North American H. zea population. Two individuals sampled in Texas in 2019 carry H. armigera haplotypes in a 4 Mbp region containing CYP337B3. Next, we identify signatures of selection in the panmictic population of nonadmixed H. zea, identifying a selective sweep at a second cytochrome P450 gene: CYP333B3. We estimate that its derived allele conferred a ∼5% fitness advantage and show that this estimate explains independently observed rare nonsynonymous CYP333B3 mutations approaching fixation over a ∼20-year period. We also detect putative signatures of selection at a kinesin gene associated with Bt resistance. Overall, we document two mechanisms of rapid adaptation: the introduction of fitness-enhancing alleles through interspecific introgression, and selection on intraspecific variation.

Competitive interaction in headwaters: slow upstream migration leads to trophic competition between native and non-native amphipods

The spread of non-native species is one of the outcomes of global change, threatening many native communities through predation and competition. Freshwater ecosystems are particularly affected by species turnover with non-native species. One species that has been established in Central Europe for many decades – or even a few centuries – is the amphipod crustacean Gammarus roeselii. Although G. roeselii is nowadays widespread in major river systems, there have been recent reports of its spread into smaller streams that are typically inhabited by the native species Gammarus fossarum. Due to their leaf shredding ability, G. fossarum takes up a key position in headwater streams. This raises the important question, to what extent G. roeselii can equivalently take over this function. To answer this question, we collected both species from nine different sites in a mid-mountain river system (Kinzig catchment, Hesse, Germany) and investigated their functional similarity using a combination of stable isotope analysis, gut content and functional morphology. The species hardly differed in morphological characteristics, only females showed differences in some traits. Gut content analysis indicated a broad dietary overlap, while stable isotopes showed a higher trophic position of G. roeselii. The observed functional overlap could intensify interspecific competition and allow the larger and more predaceous G. roeselii to replace G. fossarum in the future as a headwater keystone species. However, the differentiation in the stable isotopes also shows that co-existence can occur by occupying different trophic niches. Moreover, the wide range of inhabited sites and exploited resources demonstrate the omnivorous lifestyle of G. roeselii, which is likely to help the species succeed in rapidly changing environments.

Forest roads act as habitat corridors for Populus tremuloides in the boreal forest of eastern Canada

Edge habitats resulting from the construction and maintenance of forest roads favour pioneer, shade-intolerant and disturbance-adapted plant species. The effect of roads on the spread of non-native species has been frequently studied, but few studies have focused upon their effects on native tree species. We studied the effect of forest roads on the expansion dynamics of trembling aspen (Populus tremuloides Michx.) in a boreal forest landscape of eastern Canada. We determined whether roads act as a habitat and dispersal corridor for trembling aspen, and whether populations that established along roads act as a starting point for aspen expansion into adjacent stands. We evaluated the effect of forest roads on the distribution of trembling aspen by surveying the vegetation along 694 km of roads. In 19 stands, we compared the density and age of individuals in 100 m transects established parallel and perpendicular to roads, to determine the role of roads. Trembling aspen is abundant along the forest road network. Forest roads act sometimes as habitat corridors for trembling aspen, but their effects on its density extend only over a short distance (10 m) on each side of the roads. The forest roads did not act as a starting point for the expansion of trembling aspen into adjacent stands. Forest roads are particularly favourable habitats for trembling aspen. Although roads did not act as a starting point for aspen dispersal away from roads, these habitats would be vulnerable to invasion following a disturbance that would reduce the thickness of the organic layer.

Yeast vacuolar enzymes as novel hatching inhibitors for aquatic organisms, Daphnia magna and Danio rerio eggs

Concerns over the spread of non-native species in aquatic environments have led to the need for effective methods to prevent and control their spread while protecting native species. This study investigated the potential of yeast vacuolar enzymes as a natural hatching inhibitor for controlling aquatic organisms. Hatching experiments with Daphnia magna eggs demonstrated that exposure to yeast vacuole enzymes inhibited hatching in a concentration-dependent manner, suggesting their potential as an effective inhibitor of egg hatching in aquatic organisms. Interestingly, the protease used for comparative purposes did not inhibit hatching, but instead increased the mortality of hatched D. magna. Additionally, chorionic changes were observed in non-hatched D. magna eggs and zebrafish eggs exposed to yeast vacuole enzymes, suggesting that the enzyme can alter the chorion and interfere with hatching. These findings suggest that yeast vacuolar enzymes may be a promising and natural management tool for controlling the spread of harmful aquatic organisms, and further research is warranted to explore their potential for species-specific control.

First record of the non-native Osbornellusauronitens (Provancher, 1889) (Hemiptera, Cicadellidae, Deltocephalinae) in Italy.

Globalisation and international trade, in particular, are the major drivers of introduction and the spread of non-native species. To date, more than 30 species of non-native Hemiptera Auchenorrhyncha have been accidentally introduced into Europe. Some species are invasive with important repercussions primarily for agricultural activities, while almost no information exists on their impacts within natural ecosystems. Therefore, early detection of non-native species and their subsequent monitoring are extremely important actions to undertake. The North American Osbornellusauronitens (Provancher, 1889), firstly recorded for the Palearctic and Europe in Switzerland in 2016, is recorded in Italy for the first time on the basis of 77 specimens collected between August 2015 and October 2022.

Forest managers’ perspectives on environmental changes in the biosphere reserve Mura-Drava-Danube

Riparian forests are particularly vulnerable to environmental change and anthropogenic influences because they are highly dynamic ecosystems, thus proper adaptation measures are crucial. The implementation of these measures, however, strongly depends on the actors’ perceptions of the specific problems occurring in such forests. For understanding the constraints of specific interest groups toward different adaptation activities, information in this field is essential. By conducting a questionnaire survey we explore how different types of forest managers, i.e., forestry professionals, forest owners, and conservation managers, perceive the effects of environmental change on forest management in the recently established Transboundary Biosphere Reserve Mura-Drava-Danube. We show that these forest managers are highly aware of ongoing environmental changes and appraise deteriorating forest conditions, especially after observing changes themselves. Abiotic damage is expected to increase the most, followed by biotic damage, the spread of non-native species, and tree dieback. Nearly 80% of the survey respondents expect further changes and almost all of them intend to adapt their management of forests to mitigate or prepare for these changes. Nevertheless, we show differences in sensitivity to change and willingness to initiate adaptation actions by assessing adaptation thresholds: conservation managers appear generally more tolerant to changes, which results in higher thresholds to initiate management adaptation than forestry professionals and forest owners. Respondents’ selection of target tree species depends on management goals and therefore, we found further differences between forestry professionals and conservation managers. These aspects need to be carefully considered to foster cooperation or develop sustainable management frameworks and adaptation strategies.

Low genetic diversity among introduced axis deer: comments on the genetic paradox and invasive species

Abstract Human-mediated introductions and subsequent establishment and spread of nonnative species have the potential to create a founder effect in such populations, which typically results in low genetic diversity and potential for inbreeding. However, several exotic invasive species exhibit a “genetic paradox” in which they thrive and adapt to novel environments while also avoiding complications from low genetic diversity. Axis deer (Axis axis) were introduced into Texas, Hawaii, South America, Australia, and Croatia during the 19th and 20th centuries and successfully established large populations from a few founding individuals. Mitochondrial (Cytochrome-b, Cytb; displacement loop, D-loop) and nuclear (10 microsatellites) markers were used to assess genetic diversity within and between axis deer populations in Texas and Hawaii and then compared to other introduced (Australia and Croatia) and native (India) populations. Overall, mtDNA divergence was 0.54% (Cytb) and 1.55% (D-loop) indicating high mitochondrial similarity within the species. Further, each invasive population was composed of only one or two mtDNA haplotypes. Microsatellite allele diversity also was low within and between populations in Texas and Hawaii resulting in monomorphic loci and Hardy–Weinberg equilibrium violations in both populations. The low genetic diversity in native Indian axis deer and within and between invasive populations suggests that the introduced populations experienced founder effects following introduction, and yet overcame this potential handicap by undergoing successful establishment and expansion. Axis deer appear to be another successful invasive species characterized by the genetic paradox where they exhibit genetic profiles that suggest inbreeding effects should be imminent, yet display no signs of inbreeding and are highly successful adapting to novel environments.

Richness and resilience in the Pacific: DNA metabarcoding enables parallelized evaluation of biogeographic patterns.

Islands make up a large proportion of Earth's biodiversity, yet are also some of the most sensitive systems to environmental perturbation. Biogeographic theory predicts that geologic age, area, and isolation typically drive islands' diversity patterns, and thus potentially impact non-native spread and community homogenization across island systems. One limitation in testing such predictions has been the difficulty of performing comprehensive inventories of island biotas and distinguishing native from introduced taxa. Here, we use DNA metabarcoding and statistical modelling as a high throughput method to survey community-wide arthropod richness, the proportion of native and non-native species, and the incursion of non-natives into primary habitats on three archipelagos in the Pacific - the Ryukyus, the Marianas and Hawaii - which vary in age, isolation and area. Diversity patterns largely match expectations based on island biogeography theory, with the oldest and most geographically connected archipelago, the Ryukyus, showing the highest taxonomic richness and lowest proportion of introduced species. Moreover, we find evidence that forest habitats are more resilient to incursions of non-natives in the Ryukyus than in the less taxonomically rich archipelagos. Surprisingly, we do not find evidence for biotic homogenization across these three archipelagos: the assemblage of non-native species on each island is highly distinct. Our study demonstrates the potential of DNA metabarcoding to facilitate rapid estimation of biogeographic patterns, the spread of non-native species, and the resilience of ecosystems.

Effects of physical parameters on fish migration between a reservoir and its tributaries

Reservoirs interrupt natural riverine continuity, reduce the overall diversity of the environment, and enhance the spread of non-native fish species through suitable environments. Under favourable conditions, invasive species migrate to tributaries to benefit from local resource supplies. However, the changes in physical conditions in reservoirs that motivate fish species to migrate remain poorly understood. We analysed migration between a reservoir and its tributary in three non-native (asp Leuciscus aspius, ide Leuciscus idus, and bream Abramis brama) and two native (chub Squalius cephalus and pike Esox lucius) species equipped with radio tags. This 5-year study revealed that an increasing day length was the most general predictor of migration into the tributary in all observed species except E. lucius. Only L. aspius responded to the substantially increasing water level in the reservoir, while the migration of L. idus and S. cephalus was attenuated. Abramis brama and S. cephalus occurred more frequently in tributaries with an increase in temperature in the reservoir and vice versa, but if the difference in temperature between the reservoir and its tributary was small, then A. brama did not migrate. Our results showed that migration from the reservoir mainly followed the alterations of daylight, while responses to other parameters were species specific. The interindividual heterogeneity within the species was significant and was not caused by differences in length or sex. Our results contribute to the knowledge of how reservoirs can affect the spread of non-native species that adapt to rapid human-induced environmental changes.

Changes in Habitat Conditions of Invaded Forest Communities in Podunajská Nížina and the Impact of Non-Native Species on Biodiversity (SW Slovakia)

Abstract With the phytocenological research of riparian mixed forests and pannonic woods in the Podunajská nížina in 2018 and 2019, we obtained 113 phytocenological relevés of invaded and non-invaded stands. Using the Modified Permutation Test, we derived modified Ellenberg indication values (EIVs) in order to determine statistically significant differences and correlation relationships between diversity indices and EIVs. We recorded 15 invasive species in the stands, for example, Ailanthus altissima, Ambrosia artemisiifolia, Asclepias syriaca, Aster lanceolatus, Helianthus tuberosus, Impatiens parviflora, Negundo aceroides, Solidago canadensis, S. gigantea and Robinia pseudoacacia. We also confirmed the occurrence of species important for conservation: Epipactis helleborine agg., E. voethii, Cephalanthera longifolia, Clematis integrifolia and the like. We tested the statistical significance of EIVs as explanatory variables by redundancy analysis and Monte Carlo permutation test (stepwise selection, number of permutations 499, p < 0.05). In addition to the EIV continentality, the contribution of light, moisture, nutrients, soil reaction and temperature was higher than random. The model explains 20.21% of the variability pursuant to the coefficient of determination (R 2), with its adjusted (more accurate) variant (R 2 adj) capturing 15.70% of the variability of the model. Using the Kruskal–Wallis test, we confirmed the statistically significant differences (p*) in mean values between count of species, Shannon–Wiener index, Simpson dominance index and taxonomic diversity of invaded and non-invaded vegetation. For EIVs, we found significant differences in the mean values for moisture and soil reaction factors. In our model, count of species, Shannon–Wiener index, Simpson dominance index and taxonomic diversity index were positively correlated with invaded stands. Non-invaded stands showed statistically significant negative correlation with the EIVs moisture, soil reaction and nutrients. Biotic indices are appropriate and sensitive metrics for assessing the rate of community invasion. Lowland riparian forests are dynamic ecosystems through the structure of their stands and the dynamics of the nutrient and energy cycle of the river landscape. After disturbance (fire, wind, logging), the high degree of invasibility makes them vulnerable to the infiltration and spread of non-native species, which is a problem, especially in protected areas.

Influence of Mechanical Wounding and Compartmentalization Mechanism on the Suppression of Invasive Plant Species Using the Example of Cherry Laurel (Prunus laurocerasus)

Natural habitats increasingly face the introduction and spread of non-native species. Under the right conditions, non-native species can become invasive over time. This issue is now being addressed by many experts and researchers who are using and developing various approaches and methods to limit and eliminate or suppress problematic plant species. Many invasive plants are already spreading uncontrollably in urban and forestry areas, causing health hazards, environmental and economic damage and negatively impacting natural ecosystems. The use of chemical agents is generally limited, so our only option to control and suppress the problematic species is mechanical removal. In this research suppression by tree stem wounding, i.e., incomplete girdling, was used. This type of injury causes the plant to lose its vitality, become weaker after first year and then die within a few years. Using a research approach, we chronologically monitored the response of cherry laurel (Prunus laurocerasus L.) stem tissue to mechanical wounding of the incomplete girdling. Magnetic resonance imaging (MRI) and light microscopy were used for monitoring moisture content and anatomical changes in different periods after injury. The results of the study showed that cherry laurel, with an intense wound tissue response and other changes, is a species with good compartmentalization potential. The rapid and intense tissue response to injury requires high energy and nutrient consumption and consequently leads to a loss of vigour and mechanical stability, which may result in plant destruction. Results revealed that mechanical wounding by incomplete girdling is a successful method for suppression of non-native and invasive cherry laurel.

Nesting innovations allow population growth in an invasive population of rose-ringed parakeets.

Certain traits of recipient environments, such as the availability of limiting resources, strongly determine the establishment success and spread of non-native species. These limitations may be overcome through behavioral plasticity, allowing them to exploit alternative resources. Here, we show how a secondary cavity nester bird, the rose-ringed parakeet Psittacula krameri, innovates its nesting behavior as a response to the shortage of tree cavities for nesting in its invasive range in Tenerife (Canary Islands). We observed that some breeding pairs excavated their own nest cavities in palms, thus becoming primary cavity nester, whereas others occupied nests built with wood sticks by another invasive species, the monk parakeet Myiopsitta monachus. The use of these novel nesting strategies increased the number of breeding pairs by up to 52% over 6 years, contributing to a 128.8% increase of the whole population. Innovative nests were located at greater heights above ground and were more aggregated around conspecifics but did not result in greater breeding success than natural cavities. Occupation of monk parakeet colonies by rose-ringed parakeets also benefited the former species through a protective-nesting association against nest predators. Our results show how an invasive species innovate nesting behaviors and increase nest-site availability in the recipient environment, thus facilitating its population growth and invasion process. Potential behavioral innovations in other invasive rose-ringed parakeet populations may be overlooked, and should be considered for effective management plans.

Development and First Tests of a Lab-Scale Electric Field for Investigating Potential Effects of Electric Barriers on Aquatic Invasive Invertebrates

Canals and other connected waterway systems, including the Chicago Area Waterway System (CAWS), have often facilitated the spread of non-native species. Electric barriers have recently emerged as a method for preventing this spread and protecting uninvaded ecosystems from new invaders. The largest system of electric barriers in the world is in the CAWS and is operated primarily to prevent the spread of invasive Asian carp. It is not known whether these barriers are effective for other species, particularly invasive invertebrates. Here, we provide data regarding the efficacy of an electric field that operates at the same parameters as the electric barrier in the CAWS in affecting behaviors of two invertebrate species, the red swamp crayfish Procambarus clarkii and the amphipod Hyalella azteca. We constructed an electric field within a tank that operates at the same parameters as the existing CAWS barriers and determined the effects of the electric field on our test species. At the electric field parameters of the CAWS barriers, the vast majority of P. clarkii individuals showed altered movement with maintained equilibrium. For H. azteca, behavioral responses were less extreme than for P. clarkii, with a majority of individuals experiencing altered movement. By measuring the orientation of organisms to the electric field, we determined that the test organisms are affected by the electric field, especially at lower field strengths where they exhibited no or little other behavioral response. At lower field strengths, P. clarkii exhibited changes in orientation, but at higher field strengths, individuals were less able to orient themselves. H. azteca exhibited changes in orientation to the electric field at all field strengths. The results of this study suggest that the existing electric barriers may not slow or prevent spread of invasive invertebrates—including amphipods and crayfish—through passive movement attached boats/barges or through downstream drift, but that the barriers may prevent spread by active upstream movement. Overall, our work gives new data regarding the efficacy of electric fields in preventing the spread of invasive invertebrates and can inform management decisions regarding current and future electric barriers in the CAWS.

The evolutionary dynamics of biological invasions: A multi-approach perspective.

Biological invasions, the establishment and spread of non‐native species in new regions, can have extensive economic and environmental consequences. Increased global connectivity accelerates introduction rates, while climate and land‐cover changes may decrease the barriers to invasive populations spread. A detailed knowledge of the invasion history, including assessing source populations, routes of spread, number of independent introductions, and the effects of genetic bottlenecks and admixture on the establishment success, adaptive potential, and further spread, is crucial from an applied perspective to mitigate socioeconomic impacts of invasive species, as well as for addressing fundamental questions on the evolutionary dynamics of the invasion process. Recent advances in genomics together with the development of geographic information systems provide unprecedented large genetic and environmental datasets at global and local scales to link population genomics, landscape ecology, and species distribution modeling into a common framework to study the invasion process. Although the factors underlying population invasiveness have been extensively reviewed, analytical methods currently available to optimally combine molecular and environmental data for inferring invasive population demographic parameters and predicting further spreading are still under development. In this review, we focus on the few recent insect invasion studies that combine different datasets and approaches to show how integrating genetic, observational, ecological, and environmental data pave the way to a more integrative biological invasion science. We provide guidelines to study the evolutionary dynamics of invasions at each step of the invasion process, and conclude on the benefits of including all types of information and up‐to‐date analytical tools from different research areas into a single framework.

Diversity of Alien Macroinvertebrate Species in Serbian Waters

This article provides the first comprehensive list of alien macroinvertebrate species registered and/or established in aquatic ecosystems in Serbia as a potential threat to native biodiversity. The list comprised field investigations, articles, grey literature, and unpublished data. Twenty-nine species of macroinvertebrates have been recorded since 1942, with a domination of the Ponto-Caspian faunistic elements. The majority of recorded species have broad distribution and are naturalized in the waters of Serbia, while occasional or single findings of seven taxa indicate that these species have failed to form populations. Presented results clearly show that the Danube is the main corridor for the introduction and spread of non-native species into Serbia.

Protected Areas and Endemic Freshwater Fishes of the Cape Fold Ecoregion: Missing the Boat for Fish Conservation?

Freshwater systems and their associated biodiversity are among the most threatened ecosystems globally. The greatest threats to freshwater fishes are the introduction and spread of non-native species, pollution, habitat degradation and loss, and overexploitation. While many regions across the world contain extensive networks of protected areas, these are largely ineffective for protecting riverine systems and their biodiversity. This is because they were designed with the aim of prioritising conservation of terrestrial biodiversity, with limited or no consideration for aquatic systems. The Cape Fold Ecoregion, located within the Western and Eastern Cape Provinces of South Africa, is home to the highest percentage of threatened freshwater fishes in the country. The region has an extensive protected area network that protects a wide array of ecosystems, but limited information exists on the role of protected areas in conserving the endemic freshwater fish fauna of this region. This study evaluated the value of protected areas for protection of freshwater fishes in the Western Cape Province by setting species conservation targets and then intersecting species distribution data with protected area polygons. Conservation targets were set to protect the minimum viable population required for long-term persistence, with a minimum of 10 subpopulations as a target. This, along with other factors such as population viability and protected area effectiveness was used to determine whether a species was effectively protected by the current protected area network. Species were classified into one of four categories; (1) “well protected,” (2) “moderately protected,” (3) “poorly protected,” and (4) “not protected.” Our results indicate that the majority of native fishes are inadequately protected within the current protected area network in the province. This is mainly a result of the linear nature of riverine ecosystems that exposes them to impacts and threats that emanate from outside of the protected area. These limitations are not unique to the CFE, and our findings have broader implications as they highlight the need for integrating both the riverine and terrestrial ecosystems in the design, expansion and management of protected areas. This will enhance and maximise conservation and protection of riverine systems and their unique biodiversity.

Spatial and temporal diversity of non-native biofouling species associated with marinas in two Angolan bays

Artificial structures in coastal areas provide substrates which facilitate the spread of non-native species. Published records of introduced benthic species in the coastal waters of Angola are scarce, and so far these have numbered 29 non-native species and seven cryptogenic species. This study aimed to describe the spatial and temporal diversity of non-native biofouling species (Cnidaria, Annelida, Cirripedia, Bryozoa and Ascidiacea) in marinas in Luanda and Lobito bays. Settlement plates were employed for three months to enable development of the sessile community. We then identified all organisms retreived and compared the composition of introduced species between the sites and seasons (dry and wet). Species composition varied between seasons and sites, and 13 taxa (11 introduced) were recorded for the first time for Angolan waters, including nuisance species, such as the bryozoans Watersipora subtorquata and Amathia verticillata. Of the 35 taxa recorded, 21 were introduced species, 10 were not identified to species level, and only two species were native to the Angolan coast—corroborating the role of marinas and ports as main pathways for introductions, and the need for studies in Angola and on the tropical west coast of Africa in general. Our study expands, from 36 to 49, the number of introduced sessile animals recorded for the Angolan coast. Species known to cause harmful effects on coastal facilities elsewhere were among those most frequently recorded in the studied marinas. The findings indicate that monitoring initiatives and comparisons of biological communities between artificial and natural habitats are essential for the management of bioinvasions, to prevent both ecological and economic losses.