Non-native parasite enhances susceptibility of host to native predators

Parasites often alter host physiology and behavior, which can enhance predation risk for infected hosts. Higher consumption of parasitized prey can in turn lead to a less parasitized prey population (the healthy herd hypothesis). Loxothylacus panopaei is a non-native castrating barnacle parasite on the mud crab Eurypanopeus depressus along the Atlantic coast. Through prey choice mesocosm experiments and a field tethering experiment, we investigated whether the predatory crab Callinectes sapidus and other predators preferentially feed on E. depressus infected with L. panopaei. We found that C. sapidus preferentially consumed infected E. depressus 3 to 1 over visibly uninfected E. depressus in the mesocosm experiments. Similarly, infected E. depressus were consumed 1.2 to 1 over uninfected conspecifics in field tethering trials. We evaluated a mechanism behind this skewed prey choice, specifically whether L. panopaei affects E. depressus movement, making infected prey more vulnerable to predator attack. Counter to our expectations, infected E. depressus ran faster during laboratory trials than uninfected E. depressus, suggesting that quick movement may not decrease predation risk and seems instead to make the prey more vulnerable. Ultimately, the preferential consumption of L. panopaei-infected prey by C. sapidus highlights how interactions between organisms could affect where novel parasites are able to thrive.     

Parasitism of the rhizocephalan <Emphasis Type="Italic">Briarosaccus callosus</Emphasis> on the crab <Emphasis Type="Italic">Paralomis verrilli</Emphasis> (Crustacea: Lithodidae) in the waters of southeast Sakhalin

The crab Paralomis verrilli in the waters of southeast Sakhalin is infected by the parasitic rhizocephalan barnacle Briarosaccus callosus. The prevalence of parasitic infection was on the average 4.36% (6.29% for females, 3.28% for males) and varied between samples from none up to 14.9%. The degree of prevalence was not related to the average carapace width and the sex ratio of crabs in samples. Sterilization of female P. verrilli was caused by the B. callosus infestation or its consequences. No more than two parasite externae per crab were found. Crabs with two externae made up 5.6% of all infected specimens. The infestation of crab hosts with two B. callosus externae negatively influenced the growth of the externae. A positive relationship was found between the width of the crab carapace and the length of the parasitic externae. The survival rate of P. verrilli with either one or two parasite B. callosus externae did not differ substantially. The proportion of crabs with externae and those with “scars” (12.2% in our case) can be taken as the index of survival of the parasitized crabs.     

Increase in density of genetically diverse invasive Asian shore crab (<Emphasis Type="Italic">Hemigrapsus sanguineus</Emphasis>) populations in the Gulf of Maine

Hemigrapsus sanguineus, the Asian shore crab, has rapidly replaced Carcinus maenas, the green crab, as the most abundant crab on rocky shores in the northwest Atlantic since its introduction to the United States (USA) in 1988. The northern edge of this progressing invasion is the Gulf of Maine, where Asian shore crabs are only abundant in the south. We compared H. sanguineus population densities to those from published 2005 surveys and quantified genetic variation using the cytochrome c oxidase subunit I gene. We found that the range of H. sanguineus had extended northward since 2005, that population density had increased substantially (at least 10-fold at all sites), and that Asian shore crabs had become the dominant intertidal crab species in New Hampshire and southern Maine. Despite the significant increase in population density of H. sanguineus, populations only increased by a factor of 14 in Maine compared to 70 in southern New England, possibly due to cooler temperatures in the Gulf of Maine. Genetically, populations were predominantly composed of a single haplotype of Japanese, Korean, or Taiwanese origin, although an additional seven haplotypes were found. Six of these haplotypes were of Asian origin, while two are newly described. Large increases in population sizes of genetically diverse individuals in Maine will likely have a large ecological impact, causing a reduction in populations of mussels, barnacles, snails, and other crabs, similar to what has occurred at southern sites with large populations of this invasive crab species.     

Reconstructing the range expansion and subsequent invasion of introduced European green crab along the west coast of the United States

The European green crab, Carcinus maenas, was first documented in San Francisco Bay in 1989, and has since spread north along the west coast of North America. The spread of this invasion has not been a smooth expansion, which has raised questions about the underlying causes of variation in recruitment. We modeled larval development and transport along the West Coast by employing an individual-based model that incorporated oceanographic model output of water temperature and ocean currents at fine spatial and temporal scales. The distance that larvae were advected depended primarily on the timing of larval release. However, the effect of seasonal ocean currents varied across latitude and years. Our results imply that the furthest northern transport from California occurs when larvae are released from Humboldt Bay during the fall of an El Niño year, making this a particularly risky time for invasion to Oregon and Washington estuaries. To precisely predict future spread and potential impacts of green crab, we recommend further empirical research to determine the precise timing of larval release and seasonal abundance of green crab larvae from North American west coast populations.     

Conspecific tolerance and heterospecific competition as mechanisms for overcoming resistance to invasion by an intertidal crab

The success of the invasive Asian shore crab, Hemigrapsus sanguineus, stems partly from its ability to exclude established crab species from preferred rocky and cobble intertidal habitat. Here, we assessed preference and competition for habitat types (cobble vs. sand) for H. sanguineus and two competitor species; the previous invasive green crab, Carcinus maenas, and the native rock crab, Cancer irroratus, in New England. In simple laboratory experiments, we paired similarly sized heterospecifics and conspecifics from each species, and also grouped combinations of C. maenas and H. sanguineus in a series of four-individual sets in order to dissect the outcome of intra- and inter-specific competition at different densities. Individually, all three species preferred cobble substrate. With paired conspecifics, H. sanguineus individuals would cohabitate in cobble, whereas C. maenas and C. irroratus individuals each excluded conspecifics from cobble. In heterospecific pairs, H. sanguineus excluded both C. maenas and C. irroratus from cobble. C. maenas and C. irroratus, were equally likely to exclude the other species, but rarely excluded H. sanguineus. In larger assemblages, H. sanguineus preferentially grouped under cobble, whereas C. maenas were more evenly distributed among habitat types. These observations demonstrate that conspecific tolerance and heterospecific competition can be effective, complementary mechanisms for overcoming invasion resistance. Such mechanisms help explain the well-studied success of H. sanguineus following its introduction into New England coastal habitats, and the resulting exclusion of preexisting crab species.     

Modelling the biological invasion of Carcinus maenas (the European green crab)

This paper proposes a system of integro-difference equations to model the spread of Carcinus maenas, commonly called the European green crab, that causes severe damage to coastal ecosystems. A model with juvenile and adult classes is first studied. Here, standard theory of monotone operators for integro-difference equations can be applied and yields explicit formulas for the asymptotic spreading speeds of the juvenile and adult crabs. A second model including an infected class is considered by introducing a castrating parasite Sacculina carcini as a biological control agent. The dynamics are complicated and simulations reveal the occurrence of periodic solutions and stacked fronts. In this case, only conjectures can be made for the asymptotic spreading speeds because of the lack of mathematical theory for non-monotone operators. This paper also emphasizes the need for mathematical studies of non-monotone operators in heterogeneous environments and the existence of stacked front solutions in biological invasion models.     

Tracking an invasion: community changes in hardwood forests following the arrival of <Emphasis Type="Italic">Amynthas agrestis</Emphasis> and <Emphasis Type="Italic">Amynthas tokioensis</Emphasis> in Wisconsin

Because Upper Midwest temperate forests lack native earthworms, the invasions of European and Asian earthworms can significantly alter soils and understory vegetation. Earthworms’ ability to increase leaf litter decay, alter nutrient cycling by mixing the organic layer with mineral soil, and decrease plant species richness leads to concern about the Asian ‘jumping earthworm’ (Amynthas agrestis and A. tokioensis) species that were recorded in the University of Wisconsin—Madison Arboretum in 2013. In 2015, we found A. agrestis and A. tokioensis in a distinct 8-ha region of a 23-ha hardwood forest surveyed in the Arboretum; by 2016 A. agrestis and A. tokioensis had spread over an additional 7 ha. Plots also contained the European earthworm species Lumbricus terrestris, L. rubellus, and Apporectodea spp., whose distributions decreased from 2015 to 2016. While leaf litter, plant species richness, and tree and shrub seedling abundance were generally reduced in areas with European earthworms, they were typically slightly increased in areas with A. agrestis and A. tokioensis versus those without. Although our results do not show substantial impacts of A. agrestis and A. tokioensis on vegetation in the initial years of invasion, the rapid replacement of European earthworms by A. agrestis and A. tokioensis suggests continued monitoring of these new invasive species is important to better understand their potential to change the Upper Midwest’s forests.     

Exploring the decline of oyster beds in Atlantic Canada shorelines: potential effects of crab predation on American oysters (<Emphasis Type="Italic">Crassostrea virginica</Emphasis>)

Atlantic Canada’s American oyster (Crassostrea virginica) beds, while economically and ecologically important, have been in decline over the past few decades. Predation by crabs, in particular by the European green crab (Carcinus maenas), has been proposed as one of the potential causes of such decline. Hence, this study examined oyster mortality levels in multiple beds across Prince Edward Island (PEI) and then experimentally assessed the contribution of green crab predation to oyster mortality. Results from surveys conducted in 10 estuaries across PEI in 2014 indicate that the probability of mortality for small oysters was significantly higher when green crabs were present then in areas without green crabs. This probability of mortality was significantly less when there was the presence of alternative prey like natural mussel beds (Mytilus edulis). The odds of oyster mortality were also higher when beds had rock crabs (Cancer irroratus) compared to beds with no rock crabs. Given the potential importance of green crab predation, its influence was assessed in 2015 using two field experiments with tethered oysters. Our results indicate that odds of small oyster mortality occurring were much higher in green crab inclusion cages than in the open environment and the exclusion cages. These results reaffirm that oysters up to ~40 mm SL are vulnerable to predation, and at least some of the mortality affecting these oysters can be causally attributed to green crab predation. Green crab predation rates upon small oysters are relevant given the economic benefits and ecosystem services provided by these bivalves. They highlight the need for the industry to consider mitigation measures and potentially adapt their oyster growing strategies.     

Health risks associated with wild animal translocation: a case of the European bison and an alien parasite

Introducing an animal into a new location could be hazardous in the form of disease transmission, especially with respect to infections that are often overlooked. Such introduced infectious agents, including parasitic ones, then pose potential danger to the native animal population. Within the conservation program, the European bison was introduced into many European countries. However, this largest European herbivore was recognized as a new host for an invasive parasitic nematode, Ashworthius sidemi, in Poland in 1998. Since then, the prevalence of this non-native parasite in Poland has increased not only in bison but also in other wild ruminants. In 2011 five European bison individuals were transported from Poland to the Czech Republic. In the current study, we examined the gastrointestinal tracts of two European bison and two red deer culled in the ?idlov game reserve. A. sidemi was identified in all investigated animals using both morphological and molecular methods; infection intensity was higher in bison than in deer. Our findings represent the first record of this invasive parasite in European bison at the Czech territory. The results of this study indicate changes in epidemiological patterns of Ashworthius infections in the climatic condition of Central Europe as well as the need to verify the reliability of ashworthiosis intravital diagnostics. One can expect A. sidemi to spread gradually in the Czech Republic and colonize other native ruminant hosts.     

Evidence of multiple introductions and genetic admixture of the Asian brush-clawed shore crab <Emphasis Type="Italic">Hemigrapsus takanoi</Emphasis> (Decapoda: Brachyura: Varunidae) along the Northern European coast

The Asian brush-clawed shore crab Hemigrapsus takanoi is a non-indigenous species along the Northern European coast. Although the history of range expansion of European H. takanoi has been well-documented, little is known about the genetic compositions of either the introduced European populations or the native Asian ones. We therefore collected H. takanoi broadly from their native Asian sites and introduced European ranges, and genotyped them by sequencing the mitochondrial 16S RNA gene and by analyzing nuclear microsatellite loci. Our results revealed that the H. takanoi Bay of Seine (France) populations consisted of a genetic admixture between populations in Japan and those in the Yellow Sea region. These French populations should be carefully monitored in the future, since the genetic admixture of multiple source populations may accelerate range expansion in non-indigenous organisms. Our results also suggested that shipping lines from East Asia were more probable vectors than historical juvenile oyster transportations from Japan for the foundation of present European H. takanoi populations. Interestingly, gene flow between populations in Japan and those in the Yellow Sea region (i.e., domestic invasion) was not observed despite the higher potential for artificial translocations via shipping lines in the native Asian range compared with those from Asia to Europe. The lack of domestic invasions implied that intra-specific priority effects of the resident H. takanoi populations played an important role in preventing the successful colonization of artificially-transferred individuals.     

Genome-wide single nucleotide polymorphisms (SNPs) for a model invasive ascidian <Emphasis Type="Italic">Botryllus schlosseri</Emphasis>

Invasive species cause huge damages to ecology, environment and economy globally. The comprehensive understanding of invasion mechanisms, particularly genetic bases of micro-evolutionary processes responsible for invasion success, is essential for reducing potential damages caused by invasive species. The golden star tunicate, Botryllus schlosseri, has become a model species in invasion biology, mainly owing to its high invasiveness nature and small well-sequenced genome. However, the genome-wide genetic markers have not been well developed in this highly invasive species, thus limiting the comprehensive understanding of genetic mechanisms of invasion success. Using restriction site-associated DNA (RAD) tag sequencing, here we developed a high-quality resource of 14,119 out of 158,821 SNPs for B. schlosseri. These SNPs were relatively evenly distributed at each chromosome. SNP annotations showed that the majority of SNPs (63.20%) were located at intergenic regions, and 21.51% and 14.58% were located at introns and exons, respectively. In addition, the potential use of the developed SNPs for population genomics studies was primarily assessed, such as the estimate of observed heterozygosity (H _O ), expected heterozygosity (H _E ), nucleotide diversity (π), Wright’s inbreeding coefficient (F _IS ) and effective population size (Ne). Our developed SNP resource would provide future studies the genome-wide genetic markers for genetic and genomic investigations, such as genetic bases of micro-evolutionary processes responsible for invasion success.     

Enhancement of local species richness in tundra by seed dispersal through guts of muskox and barnacle goose

The potential contribution of vertebrate-mediated seed rain to the maintenance of plant community richness in a High Arctic ecosystem was investigated. We analyzed viable seed content in dung of the four numerically most important terrestrial vertebrates in Northeast Greenland – muskox (Ovibos moschatus), barnacle goose (Branta leucopsis), Arctic fox (Alopex lagopus) and Arctic hare (Lepus arcticus). High numbers of plant propagules were found in the dung of muskox and barnacle goose. Seeds of many plant species were found in the faeces of one vertebrate species only. Propagule composition in barnacle goose droppings was relatively uniform over samples, with a high abundance of the nutritious bulbils of Polygonum viviparum (Bistorta vivipara), suggesting that geese have a narrow habitat preference and feed selectively. Propagule composition in muskox dung was diverse and heterogeneous among samples, suggesting a generalist approach in terms of food selection and the haphazard ingestion of plant propagules with foliage. The species composition of plant propagules in dung samples was different from that of the receiving plant communities (in terms of the Sørensen and Czekanowski dissimilarity indices), and dung deposition, especially by muskox, often brought new species to the receiving community. The results suggest that endozoochorous propagule dispersal in the Arctic has a great potential in the generation and maintenance of local species richness, albeit being little specialized. It is further suggested that endozoochory is an important means of long-distance dispersal and, thereby, of plant migration in response to climate change.     

Distribution and ecological relations among the alien crab, <Emphasis Type="Italic">Percnon gibbesi</Emphasis> (H. Milne-Edwards 1853) and autochthonous species,in and out of an SW Mediterranean MPA

The distribution of the allochthonous crab Percnon gibbesi and its relationships with other benthic invertebrate species was assessed inside the marine reserve of Cabo de Palos—Islas Hormigas (Mediterranean sea, Spain) and neighbouring non-protected sites. Although a significant spatial variability was detected at finer spatial scale, there was no influence of protection measures or insularity on the abundance of P. gibbesi. The presence of small holes, encrusting algae and low slope favour the colonization success of this crustacean, and the spatial distribution of these habitat features could explain the observed pattern. The abundance of P. gibbesi was similar to that of native crab species; however, a non-significant negative relationship between the abundance of P. gibbesi and native crabs (Pachygrapsus marmoratus and Eriphia verrucosa), urchins (Arbacia lixula and Paracentrotus lividus) and a snail (Phorcus turbinatus) was observed. This work highlights the importance of monitoring alien crab population densities taking structural habitat and other potentially influential factors into account and the likely effect of this alien species on the native ones.     

A comparison of reproductive patterns and adult dispersal in sympatric introduced and native marine crabs: implications for species characteristics of invaders

The introduction and translocation of nonindigenous marine species is widespread and can pose severe threats to biodiversity and ecosystem functioning. Predicting which species are potential invaders is of particular interest to ecologists. One approach is to identify characteristics that predispose a species to becoming a successful invader. Since its introduction in the 1980’s, the invasive Asian shore crab, Hemigrapsus sanguineus, has shown a remarkable ability to colonize rocky intertidal habitats along the east coast of the United States. In Long Island Sound H. sanguineus occurs sympatrically with the functionally equivalent, but non-invasive, native Atlantic mud crab, Panopeus herbstii. The presence of both species at the same site allowed us to make a detailed, simultaneous assessment of life history traits and adult dispersibility of co-occurring invading and native crab species. We investigated fecundity and maturation rates, length of breeding season and brood production for both species, and conducted field experiments using mark–recapture techniques to determine mobility patterns. Our results show that the nonindigenous Asian crab has a greater reproductive potential than the native mud crab as evidenced by a longer breeding season, multiple brood production and higher fecundity rates. Field experiments confirmed previous studies indicating H. sanguineus is a highly mobile crab, and further demonstrated that adult Asian crabs are more likely than mud crabs to disperse from their shelter/refuge sites. Recovery rates for native mud crabs were significantly higher than those for Asian crabs in three experimental trials, across sites and years. This work provides new information about life history characteristics of both species and supports the hypothesis that high reproductive potential combined with high adult dispersal ability may be important factors associated with the invasion/establishment success of the Asian shore crab. More study is needed, however, to determine the applicability of these findings to other highly successful marine invaders.     

A multi-scale approach to identify invasion drivers and invaders’ future dynamics

Climate, land use and disturbances are well known drivers of invasion. However, their relative influence may change across spatial scales, where climate is expected to be the main filter at broad scales; land use is expected to have more influence at intermediate scales, and disturbance, at fine ones. Understanding the underlying processes that drive invasion patterns at different spatial scales is thus crucial to be able to anticipate the future spread of invaders. Here, we quantified the relative importance of climate, land use, and disturbance on the distribution of the invasive trees Ailanthus altissima and Robinia pseudoacacia, across three nested spatial scales, namely global, country (Spain) and riverbank (three riparian riverbanks). To do so, for each species and scale, we built ensemble species distribution models. We also identified their range filling and inferred the most suitable areas in Spain for them to spread. In general, our study confirms that climate acts as an initial coarse filter of species distribution, whilst both climate and land use were important at the country scale; at the riverbank scale human-mediated disturbances gained importance. However, R. pseudoacacia and A. altissima showed differences in their degree of range filling, where A. altissima has a higher potential for range expansion in the near future. Overall, the integration of different scales into invasion studies shows a great potential to enrich our understanding of species-habitat relationships, and to help anticipate their future dynamics.     

Cryptic invasion of Italian pool frogs (<Emphasis Type="Italic">Pelophylax bergeri</Emphasis>) across Western Europe unraveled by multilocus phylogeography

Human introductions of exotic amphibians can have catastrophic effects on native species. However, they usually remain unnoticed without genetic tools when species are difficult to distinguish morphologically. In Western Europe, pool frogs (Pelophylax sp.) make a worrisome case: recent genetic data showed the presence of Italian (Pelophylax bergeri) mtDNA haplotypes within the range of the threatened European Pelophylax lessonae, two morphologically similar taxa. Here we conduct a multilocus phylogeographic and population genetic survey of European and Italian pool frogs (combining present and historic samples), to investigate the origin(s) and consequences of potential introductions. Results are unequivocal: we show that the alien P. bergeri have extensively invaded France and north-Alpine Switzerland, and have also deeply introgressed with P. lessonae, which has led to the complete replacement of most populations. Alien specimens have probably been translocated multiple times from Central Italy at least prior to the 1960s. Based on our dense sampling, only two areas, north and south of the Alps still host native pool frogs in Switzerland, the Joux Valley near the French border and the canton of Ticino, respectively. Importantly, we show that these last P. lessonae populations are remnants of a private genetic diversity specific to Western Europe, which vanished during the P. bergeri’s invasion. Our study emphasizes the risk of genetic pollution during invasion by human-introduced taxa and brings alarming concern regarding uncontrolled amphibian translocations. Moreover, it demonstrates the necessity for genetic surveys to detect and monitor these invasions, especially where species determination is problematic.     

Non-indigenous fish in the northern branch of the central European invasion corridor

The assessment of risks associated with non-indigenous species implies a detailed knowledge of their taxonomical composition and distribution within a certain region. The northern branch of the central European ‘invasion corridor’—a series of canals connecting different watersheds—has formed an important migratory route for Ponto-Caspian fish (i.e. fish from the Black Sea, the Sea of Azov and the Caspian Sea). However, the current status of non-indigenous fish species in this region is very scarce. This article presents a comprehensive overview of recent distribution data of non-indigenous fish species in the northern branch of the central European invasion corridor. Here, extensive data are integrated based on studies performed during 2003–2014 comprising reliable published and unpublished records from the last 12 years. Altogether, ten non-indigenous fish species were currently found in the northern branch of the central European invasion corridor, constituting 19 % of its freshwater fish diversity. Three species, including the Prussian carp (Carassius gibelio), the round goby (Neogobius melanostomus), and the Chinese sleeper (Perccottus glenii), are considered invasive species. Eight species may potentially invade this region in the near future. A comparison of the history of non-indigenous fish species introduction in the inland waters of the northern branch and other countries of the central European invasion corridor revealed similar introduction trends. Potential expansion of non-indigenous fish species across the central European invasion corridor has international implications that require awareness, cooperation, and government support from each individual country. Disclosure of recently operating vectors for non-indigenous fish introductions within the central European invasion corridor will help predict and prevent their further spread and establishment in this region.     

Molecular and morphological insights into the origin of the invasive greater white-toothed shrew (<Emphasis Type="Italic">Crocidura russula</Emphasis>) in Ireland

Identifying routes of invasion is a critical management strategy in controlling the spread of invasive species. This is challenging however in the absence of direct evidence. Therefore, indirect methodologies are used to infer possible invasion sources and routes, such as comparisons of genetic and morphological data from populations from invasive ranges and putative source areas. The greater white-toothed shrew (Crocidura russula) was first discovered in Ireland from skeletal remains in the pellets of birds of prey collected in 2007 and is it is now sufficiently established that the species has a detrimental impact on Ireland’s small mammal community. In this study, we address the uncertain origin(s) of the Irish population of C. russula. The cytochrome b gene of mitochondrial DNA was analysed from 143 individuals from throughout its range within a phylogenetic and approximate Bayesian computation framework. These analyses revealed that the Irish population stemmed from Europe as opposed to North Africa. Additionally, mandibles from 523 individuals from Ireland and 28 other European populations were subjected to multivariate and distance-based analyses, which demonstrated an association between the Irish population and those in France, Switzerland and Belgium. When the genetic and morphological analyses were considered together, an origin stemming from France was deemed the most likely scenario for the source of the invasive Irish population. This study has demonstrated the importance of utilising a multidisciplinary approach when attempting to identify the origins and invasion routes of invasive species.     

Trematodes (Plathelminthes) of <Emphasis Type="Italic">Clarias gariepinus</Emphasis> (Pisces: Clariidae) in Lake Tana,Ethiopia

All of the 166 Clarias gariepinus catfishes in Lake Tana, Ethiopia, were examined for trematode infestation in 2006—2009. Seven trematode species—Eumasenia bangweulensis, Astiotrema reniferum, Orientocreadium batrachoides, Paralecithodendrium chilostomum, Phyllodistomum bavuri, P. tana, and Cladorchiidae gen. sp.—as adult were found. The common catfish parasites were Eumasenia bangweulensis (20% prevalence and 1—62 intensity of invasion), Orientocreadium batrachoides (30% prevalence and 1–31 intensity of invasion), Phyllodistomum bavuri (24.8% prevalence and 1–8 intensity of invasion), Ph. tana (17.6% prevalence and 1–23 intensity of invasion), and Ph. bavuri. Astiotrema reniferum (three specimens were only found) was a rare species; Paralecithodendrium chilostomum was an accidental parasite of catfish. All these trematodes were first recorded in Ethiopia and Eastern Africa.     

A tale of three seas: consistency of natural history traits in a Caribbean–Atlantic barnacle introduced to Hawaii

Predictive models in invasion biology rely on knowledge of the life history and ecological role of invading species. However, species may change in key traits as they invade a new region, making prediction difficult. For marine invertebrate invaders there have been too few comparative studies to determine whether change in key traits is the exception or the rule. Here we examined populations of the intertidal barnacle Chthamalus proteus in three locations in its native range in the Caribbean and Atlantic, and in the Hawaiian Islands, where it has recently invaded, as a model system for such comparative studies. We measured body size, fecundity, population density and vertical distribution, compared habitat use and investigated aspects of the barnacle’s ecological role in Curaçao, Panama and Brazil and the main Hawaiian Islands. In terms of these measures, the barnacle has undergone little change in its invasion of Hawaii. Thus, if this barnacle had been studied in its native range, predictions about its spread in Hawaii could have been made. As little was known about this barnacle in either its native range or Hawaii, we also carried out studies of its larval life history, fecundity, growth, and mortality. Based on this work, we predict that this barnacle will continue to spread, aided by vessel traffic, throughout the Hawaiian Islands and elsewhere in the Pacific.