Parasite Richness Research Articles

Sedimentary Ancient DNA (sedaDNA) Reveals Fungal Diversity and Environmental Drivers of Community Changes throughout the Holocene in the Present Boreal Lake Lielais Svētiņu (Eastern Latvia).

Fungi are ecologically important in several ecosystem processes, yet their community composition, ecophysiological roles, and responses to changing environmental factors in historical sediments are rarely studied. Here we explored ancient fungal DNA from lake Lielais Svētiņu sediment throughout the Holocene (10.5 kyr) using the ITS metabarcoding approach. Our data revealed diverse fungal taxa and smooth community changes during most of the Holocene with rapid changes occurring in the last few millennia. More precisely, plankton parasitic fungi became more diverse from the Late Holocene (2–4 kyr) which could be related to a shift towards a cooler climate. The Latest Holocene (~2 kyr) showed a distinct increase in the richness of plankton parasites, mycorrhizal, and plant pathogenic fungi which can be associated with an increased transfer rate of plant material into the lake and blooms of planktonic organisms influenced by increased, yet moderate, human impact. Thus, major community shifts in plankton parasites and mycorrhizal fungi could be utilized as potential paleo-variables that accompany host-substrate dynamics. Our work demonstrates that fungal aDNA with predicted ecophysiology and host specificity can be employed to reconstruct both aquatic and surrounding terrestrial ecosystems and to estimate the influence of environmental change.

Predictors of helminth parasite infection in female chacma baboons (Papio ursinus).

Helminth parasite infection can impose major consequences on host fitness. Several factors, including individual characteristics of hosts, environmental conditions, and patterns of coinfection, are thought to drive variation in parasite risk. Here, we report on four key drivers of parasite infection—phase of reproduction, steroid hormone profiles, rainfall, and patterns of coinfection—in a population of wild female chacma baboons (Papio ursinus) in South Africa. We collected data on reproductive state and hormone profiles over a 3-year span, and quantified helminth parasite burdens in 2955 fecal samples from 24 female baboons. On a host level, we found that baboons are sensitive to parasite infection during the costliest phases of the reproductive cycle: pregnant females harbored higher intensities of Protospirura eggs than cycling and lactating females; lactating and cycling females had a higher probability of Oesophagostomum infection than pregnant females; and cycling females exhibited lower Trichuris egg counts than pregnant and lactating females. Steroid hormones were associated with both immunoenhancing and immunosuppressive properties: females with high glucocorticoid concentrations exhibited high intensities of Trichuris eggs but were at low risk of Oesophagostomum infection; females with high estrogen and progestagen concentrations exhibited high helminth parasite richness; and females with high progestagen concentrations were at high risk of Oesophagostomum infection but exhibited low Protospirura egg counts. We observed an interaction between host reproductive state and progestagen concentrations in infection intensity of Protospirura: pregnant females exhibited higher intensities and non-pregnant females exhibited lower intensities of Protospirura eggs with increasing progestagen concentrations. At a population level, rainfall patterns were dominant drivers of parasite risk. Lastly, helminth parasites exhibited positive covariance, suggesting that infection probability increases if a host already harbors one or more parasite taxa. Together, our results provide a holistic perspective of factors that shape variation in parasite risk in a wild population of animals.

Biodiversity of anuran endoparasites from a transitional area between the Atlantic Forest and Cerrado biomes in Brazil: new records and remarks.

The richness of metazoan endoparasites associated with 25 anuran species from a transitional area between Cerrado and Atlantic Rain Forest from Brazil is here presented. We present and discuss the type-host and localities, the current taxonomic status, remarks on morphological features, biological cycle, and new records of these parasites. Nine hundred and seventy-eight anurans of four families (Bufonidae, Hylidae, Microhylidae, and Leptodactylidae) were collected during four expeditions in a private forested area from Northwest of São Paulo state. The richness of metazoan parasites was composed of nematodes (21), acanthocephalans (2), digeneans (18), monogeneans (1), cestodes (1), and oligochaetes (1), resulting in 44 taxa that are presented with their respective prevalence and the range of abundance in host populations. Among these parasites, nine were found in immature stages which usually complete their life cycle in fishes, snakes, birds or mammals, attesting the trophic relation of amphibians and their parasites within the regional vertebrate community. We reported 23 anuran species as new hosts resulting in 79 new associations between anurans and parasites. Gorgoderina diaster and Bursotrema tetracotyloides are reported for the first time in Brazil, and our finding of Clinostomum cf. complanatum represents the first in South American anurans.

Seasonal effects in gastrointestinal parasite prevalence, richness and intensity in vervet monkeys living in a semi‐arid environment

AbstractParasite and pathogen incidence and prevalence is driven by both periodic variation in environmental conditions and host characteristics. Given the increasing risk of zoonotic transmission to humans, and the close phylogenetic relationship between humans and non‐human primates, understanding this variation in parasite dynamics is becoming essential for epidemiologists and conservationists alike. The extreme seasonal temperatures coupled with declining annual rainfall and severe periodic drought of the semi‐arid Karoo poses distinct challenges to both hosts and pathogens and serves as a window into how animals confront climate change‐induced environmental changes. Here we quantified annual variation in gastrointestinal parasite prevalence, intensity and richness in three troops of wild vervet monkeys (Chlorocebus pygerythrus) and determined what climatic variables were driving these changes. Further, we assessed whether there is long‐term temporal dependence in intra‐individual faecal egg counts. We found variation in the prevalence of five genera of helminths identified in the study population, but little variation in parasite richness across the year. Such variation was driven primarily by precipitation and maximum daily temperature. Finally, we found structure in faecal egg counts, suggesting that contrary to previous findings, egg shedding of Trichostrongylus sp. and ?Protospirura sp. are not stochastic processes and may serve as an indicator of individual levels of infection in our population. Combined, these results provide the first report of seasonal effects in gastrointestinal parasites of vervet monkeys living in an extreme environment.

Epidemiological transitions in human evolution and the richness of viruses, helminths, and protozoa.

Background and objectivesIn absolute terms, humans are extremely highly parasitized compared to other primates. This may reflect that humans are outliers in traits correlated with parasite richness: population density, geographic range area, and study effort. The high degree of parasitism could also reflect amplified disease risk associated with agriculture and urbanization. Alternatively, controlling for other variables, cultural and psychological adaptations could have reduced parasitism in humans over evolutionary time.MethodologyWe predicted the number of parasites that would infect a nonhuman primate with human phenotypic characteristics and phylogenetic position, and then compared observed parasitism of humans in eight geopolitical countries to the predicted distributions. The analyses incorporated study effort, phylogeny, and drivers of parasitism in 33 primate species.ResultsAnalyses of individual countries were not supportive of either hypothesis. When analyzed collectively, however, human populations showed consistently lower than expected richness of protozoa and helminths, but higher richness of viruses. Thus, human evolutionary innovations and new parasite exposures may have impacted groups of parasites in different ways, with support for both hypotheses in the overall analysis.Conclusions and implicationsThe high level of parasitism observed in humans only applies to viruses, and was not extreme in any of our tests of individual countries. In contrast, we find consistent reductions in protozoa and helminths across countries, suggesting reduced parasitism by these groups during human evolution. We propose that hygienic and technological advances might have extinguished fecal-orally or indirectly transmitted parasites like helminths, whereas higher human densities and host-shifting potential of viruses have supported increased virus richness.Lay SummaryVastly more parasite species infect humans than any other primate host. Controlling for factors that influence parasite richness, such as the intensity of study effort and body mass, we find that humans may have more viruses, but fewer helminths and protozoa, than expected based on evolutionary analyses of parasitism in other primates.

Identification of Tapeworm Species in Genetically Characterised Grey Wolves Recolonising Central Europe.

Restored role of the grey wolf in ecological networks of newly recolonized areas can be studied via surveys of parasite communities of this predator. As helminths circulating in multi-host systems, the tapeworms directly reflect wolves' diet, while some species are also important from the One Health perspective. The Czech experienced centuries of wolves' absence, however, now it is situated on the crossroad of recolonising wolves' populations, which is opening questions of their role in ecological networks in this area and thus in sylvatic cycles of heteroxenous parasites. Five wolf carcasses from this area were obtained and genetic affinity to a particular population was inspected. Tapeworms isolated from wolves' intestines during necropsies were molecularly identified based on sequences of COI marker. Three wolf haplotypes (w1, w2, w14) correspond with the dominance of haplogroup 1 (w1, w2) within Central European lowland population and haplogroup 2 (w14) within the Carpathian population. Two Taenia spp. were revealed: T. krabbei in Central European population wolves and T. hydatigena in an individual from Carpathian population. The results serve as a base for future monitoring and studies of the recolonising wolf population and its impact on ecosystems in the studied area to contribute to the hypothesis about differentiation of parasite communities in particular wolf population and higher parasite diversity and richness in established populations in comparison to newly settled ones.

A Global Assessment of Parasite Diversity in Galaxiid Fishes

Free-living species often receive greater conservation attention than the parasites they support, with parasite conservation often being hindered by a lack of parasite biodiversity knowledge. This study aimed to determine the current state of knowledge regarding parasites of the Southern Hemisphere freshwater fish family Galaxiidae, in order to identify knowledge gaps to focus future research attention. Specifically, we assessed how galaxiid–parasite knowledge differs among geographic regions in relation to research effort (i.e., number of studies or fish individuals examined, extent of tissue examination, taxonomic resolution), in addition to ecological traits known to influence parasite richness. To date, ~50% of galaxiid species have been examined for parasites, though the majority of studies have focused on single parasite taxa rather than assessing the full diversity of macro- and microparasites. The highest number of parasites were observed from Argentinean galaxiids, and studies in all geographic regions were biased towards the highly abundant and most widely distributed galaxiid species, Galaxias maculatus. Parasite diversity generally increased with the number of studies and individual fish examined, however studies which examined parasites from all body tissues could overcome the effects of low study effort. In order to promote further understanding of galaxiid–parasite biodiversity, we provide a series of recommendations, including the use of molecular techniques to verify parasite identity, and highlight the future roles both fish biologists and parasitologists can play.

Helminth-fauna of Patagonian armadillos: comparative analysis of parasites geographical variation.

The similarity between parasites communities' decay with distance and its analysis may explain important ecological process such host dispersion. Patagonia is inhabited by two armadillo species, Chaetophractus villosus and Zaedyus pichiy. In this study we describe and analyze the variation on helminth fauna of these armadillos in Patagonia compared with northern localities described in previous studies. A total of 49 armadillos were collected in Patagonia. Quantitative descriptors of parasite ecology were calculated and community structure of helminths was analyzed following the central-satellite species hypothesis. The parasite richness in Patagonia decreases almost 50% in both armadillos. Zaedyus pichiy present the same central species in Patagonia as in northern localities. For C. villosus central-satellite species analysis could not be applied. The loss of some helminths in Z. pichiy could be the result of lower temperatures or the absence of intermediate arthropods hosts. But in C. villosus the absence of some helminths with Patagonian distribution could be explained by its recent dispersion in Patagonia. Trichohelix tuberculata still being the only helminth in C. villosus introduced population of Tierra del Fuego.

Community and infracommunities of metazoan parasites in Hemiodus unimaculatus (Hemiodontidae) from Jari River basin, a tributary of Amazon River (Brazil)

Abstract Parasites are an important part of biodiversity, and knowledge of species and their relationship with their hosts helps in monitoring an ecosystem over time. The aim of this study was to investigate the fauna of metazoan parasites in Hemiodus unimaculatus from the Jari River, in the eastern Amazon region, northern Brazil. Of the fish examined, 96.7% were parasitized by one or more species, and a total of 336 parasites such as Dactylogyridae gen. sp.1, Dactylogyridae gen. sp.2, Dactylogyridae gen. sp.3, Dactylogyridae gen. sp.4, Gyrodactilydae gen. sp., Urocleidoides sp.1, Urocleidoides sp.2, Urocleidoides sp.3, metacercariae of Digenea gen. sp., Procamallanus (Spirocamallanus) inopinatus, Contracaecum sp., Neoechinorhynchus sp. and Acarina gen. sp. The parasite community showed low Brillouin diversity (0.58 ± 0.29), low evenness (0.44 ± 0.21) and low species richness (7.40 ± 3.83). There was a predominance of ectoparasites, mainly monogeneans and digeneans. The parasites showed an aggregate dispersion, except for P. (S.) inopinatus, which had a random dispersion. The size of the hosts had no effect on diversity, species richness and abundance of parasites, but other factors structured the parasite community. This is the first study on the parasite community and infracommunities in H. unimaculatus.

Louse flies in Azorean and mainland populations of four Passeriformes species: A new perspective to parasite Island syndromes

Hippoboscid flies, also known as louse flies, are obligate blood-feeders ectoparasites of birds and mammals. By studying louse fly parasites of four Passeriformes species, Eurasian blackbird (Turdus merula), Eurasian blackcap (Sylvia atricapilla), common chaffinch (Fringilla coelebs) and European robin (Erithacus rubecula), with dissimilar time of colonization of Azores islands, we tested whether: (i) island host populations have lower parasite richness than the mainland one; (ii) island host populations undergo higher parasite prevalence, mean intensities and mean abundance than the mainland one; (iii) island parasite diversity are composed exclusively by specific parasites and (iv) parasite richness is positively correlated with the island area and proximity to the continent. For these purposes, 775 birds were sampled for presence of louse flies, by modified fumigation chamber method, from Azores Islands (São Miguel, Terceira and Flores) and Portugal mainland. Insular and mainland parasite assemblages were statistically compared. We record for the first time to Azores, Ornithomya fringillina and Icosta minor from Portugal mainland. Louse flies had highest prevalence and abundance from Azores Islands compared to those observed in mainland birds, especially blackbirds. The insular parasite diversity of Azores blackbirds, blackcaps and chaffinches was richer than the one observed in mainland population. None of the hippoboscid flies observed on the islands and mainland were host-specific. Thus, our findings provide an upgrade of parasite island syndromes knowledge, in the context of the ectoparasites, namely to the hippoboscid flies case.

Prevalence of Gastrointestinal Parasites in the Frugivorous and the Insectivorous Bats in Southcentral Nepal.

Bats are the only active flying placental mammals and are traditionally classified into mega- and microbats, which are, respectively, herbivorous and insectivorous in feeding habit. Though deforestation, habitat destruction, natural calamities, illegal hunting, and climate changes are the challenging threats for bats, the role of existing gastrointestinal (GI) parasites have not been evaluated yet in Nepal. Thus, the current study aims to determine the prevalence of GI parasites in bats from the Shaktikhor area at the Chitwan district of Southcentral Nepal. From July 2018 to February 2019, a total of 60 fecal samples of bats (30 from frugivorous bats and 30 from the insectivorous bats) were collected. These samples were preserved at 2.5% potassium dichromate solution. The fecal examination was carried out by the direct wet mount, concentrations, acid-fast staining, and sporulation techniques. Overall results showed the prevalence rate of 80% GI parasites. The parasites detected in the insectivorous bats were Ascarid spp., Capillarid sp., Cryptosporidium sp., Eimeria spp., Entamoeba sp., Giardia sp., Hymenolepis spp., Isospora sp., Oxyurid sp., Strongyle, and Strongyloides sp. In contrast, Eimeria sp., Entamoeba sp., and Hymenolepis sp. were detected in the frugivorous bats. Based on a wide diversity of parasite richness and parasitic concurrency measured by the prevalence rates, we suggest that GI parasitism might be a threatening factor in the insectivorous bats in the current study area.

Integrating climate and host richness as drivers of global parasite diversity

AbstractAimClimate and host richness are essential drivers of global gradients in parasite diversity, and the few existing studies on parasites have mostly investigated their effects separately. The advantages of combining these factors into a single analytical framework include unravelling the relative roles of abiotic and biotic drivers of parasite diversity. We compiled a dataset of helminths of amphibians to investigate the direct and indirect effects of temperature seasonality, annual precipitation, precipitation seasonality and host richness as drivers of parasite diversity at the global scale. Our analyses focus not only on the least studied group of vertebrates regarding macroecology of parasite diversity, but also the host group most sensitive to climatic conditions, especially temperature seasonality and water availability.LocationGlobal.Time period1955–2017.Major taxa studiedHelminth parasites of amphibians.MethodsWe used piecewise structural equation modelling on a global dataset of helminths of amphibians, comprising 613 populations of 319 anuran species and 94 populations of 43 salamander species from 10 zoogeographical realms.ResultsWe found that precipitation seasonality and host richness both affect parasite diversity positively, but the latter presented a stronger effect. Additionally, we found that both temperature seasonality and total precipitation indirectly affected parasite richness through their respective negative and positive effects on host richness.Main conclusionsFuture studies on global gradients in parasite diversity should include both direct and indirect effects of climatic factors as drivers of parasite diversity. Integrating multiple predictors into a single statistical framework that measures both direct and indirect effects increases our theoretical understanding of the relative importance of and interactions among different diversity drivers at the macroecological scale. The indirect effects of temperature seasonality and total precipitation on parasite diversity are an interesting new insight brought by our study, with implications for future studies dealing with host–parasite coextinctions due to climate change.

Effects of latitude, host body size, and host trophic guild on patterns of diversity of helminths associated with humans, wild and domestic mammals of Mexico.

Parasites are strictly associated with their hosts and present a great diversity of life histories, often resulting in different diversity patterns than those observed in free-living species. However, ecological approaches have detected that, in some cases, mammal-associated helminths respond similarly to non-parasitic species in terms of diversity patterns. Using 2200 recorded interactions, we analysed the diversity patterns of helminths (Acanthocephala, Nematoda and Platyhelminthes) harbored by humans, wild and domestic mammals of Mexico, depending on latitude, host body mass and trophic guild (carnivore, herbivore, insectivore, omnivore), considering helminth richness and average taxonomic distinctness, and host phylogenetic diversity and phylogenetic clustering. Latitude was positively correlated with the average taxonomic distinctness encompassing the three parasite phyla and nematodes. Northern latitudes had less taxonomically related parasite assemblages. Host body mass had a significant negative relationship with the average taxonomic distinctness of acanthocephalans and the richness of helminths associated to wild hosts. The omnivore hosts had greater parasite richness, while insectivores had a less taxonomically related parasite assemblage and herbivores had a more heterogeneous parasite assemblage. Our results highlight the importance of incorporating different dimensions of diversity, such as average taxonomic distinctness and to consider the composition of parasite assemblages to better understand their diversity patterns.

Spatial and seasonal variation in host community structure is weakly concordant with patterns of parasite composition

Abstract Parasites are known to respond strongly to changes in host diversity and may ultimately reflect changes in ecosystems. However, it remains unclear whether strong relationships between host and parasite richness also reflect those at the level of community composition. A complementary approach is to test for concordance between host and parasite composition to evaluate whether shifts in parasite community structure mirror patterns of their hosts and potentially the environment. I tested for concordance between patterns of community similarity in parasites, their fish hosts, and environmental factors sampled across three sites and four seasons within each of two river ecosystems. I constructed ordinations of parasites, fish, and environmental variables to establish their patterns of similarity in multivariate space and used Procrustes analysis to evaluate whether patterns in community structure were concordant. Spatial and seasonal patterns in fish and parasite community structure were concordant when analysing patterns in community composition (i.e. presence–absence), but not community abundance (i.e. numerical density). Patterns in fish communities were concordant with the physical river environment. However, despite finding concordance between fish and parasite communities and fish and their environment, parasites were concordant with the river environment in only one ecosystem. Re‐evaluating the relationship between host and parasite diversity under a community concordance framework showed that patterns among host and parasite community composition exist, but this relationship is weaker than expected. The looser connection between patterns in host and parasite community composition can be mediated by parasite life history and parasites responding both indirectly and directly to changes in host communities and the local environment.

Influence of land use and host species on parasite richness, prevalence and co-infection patterns

Tropical forests are experiencing increasing impacts from a multitude of anthropogenic activities such as logging and conversion to agricultural use. These perturbations are expected to have strong impacts on ecological interactions and on the transmission dynamics of infectious diseases. To date, no clear picture of the effects of deforestation on vector-borne disease transmission has emerged. This is associated with the challenge of studying complex systems where many vertebrate hosts and vectors co-exist. To overcome this problem, we focused on an innately simplified system – a small oceanic island (São Tomé, Gulf of Guinea). We analyzed the impacts of human land-use on host-parasite interactions by sampling the bird community (1735 samples from 30 species) in natural and anthropogenic land use at different elevations, and screened individuals for haemosporidian parasites from three genera (Plasmodium, Haemoproteus, Leucocytozoon). Overall, Plasmodium had the highest richness but the lowest prevalence, while Leucocytozoon diversity was the lowest despite having the highest prevalence. Interestingly, co-infections (i.e. intra-host diversity) involved primarily Leucocytozoon lineages (95%). We also found marked differences between bird species and habitats. Some bird species showed low prevalence but harbored high diversity of parasites, while others showed high prevalence but were infected with fewer lineages. These infection dynamics are most likely driven by host specificity of parasites and intrinsic characteristics of hosts. In addition, Plasmodium was more abundant in disturbed habitats and at lower elevations, while Leucocytozoon was more prevalent in forest areas and at higher elevations. These results likely reflect the ecological requirements of their vectors: mosquitoes and black flies, respectively.

CONDITION FACTOR AND ECOLOGY OF ENDOHELMINTHS IN <i>Metynnis lippincottianus</i> FROM THE CURIAí­Å¡ RIVER, IN EASTERN AMAZON (BRAZIL)

Fish are among the vertebrate groups most susceptible to parasitic infections due to environmental characteristics that can favor the development of parasites; also, position of the host in food web has been associated with the parasitism. The aim of this study was to investigate the ecology of parasites endohelminth in Metynnis lippincottianus from the Curiaú River, in eastern Amazon (Brazil), as well as to evaluate the parasite-host interactions. From 110 specimens of M. lippincottianus examined, 76.3% were infected by one or more parasite species, and a total of 146 parasites such as Procamallanus (Spirocamallanus) inopinatus (Nematoda), larvae of Contracaecum sp. (Nematoda) and Neoechinorhynchus pterodoridis (Acanthocephala) were collected in intestine. However, the dominance was of nematode species, and the parasites had uniform or random dispersion. The parasitic infracommunities showed low Shannon-Wiener diversity (0.2 ± 0.3), low evenness (0.2 ± 0.3) and low species richness of parasites (1.1 ± 0.8). The abundance of Contracaecum sp. presented a weak positive correlation with the weight of hosts, and relative condition factor was not affected by the parasitism. This first study about parasites of M. lippincottianus from Curiaí­­ River basin is the first report of N. pterodoridis for this host.

Parasite infection reflects host genetic diversity among non-native populations of pumpkinseed sunfish in Europe

Species introductions often coincide with loss of genetic diversity and natural enemies. Anthropogenic translocation of the North-American pumpkinseed Lepomis gibbosus (L., 1758) (Centrarchidae) and its further spread have resulted in recent species establishment in most European countries. This study determines genetic differentiation of non-native European pumpkinseed populations and identifies how their genetic structure relates to the distribution and abundance of parasite species. Microsatellite analysis indicated presence of three genetic lineages, which were well supported by discriminant analysis based on parasite abundance data. The first lineage clustered pumpkinseed populations from northern and southern France and showed high allelic richness, heterozygosity and parasite richness. The second included populations along the “Southern invasion corridor” connecting the rivers Rhine, Main and Danube. The fish exhibited low to high genetic and parasite diversity and generally high parasite abundance. The third lineage clustered populations with low genetic and parasite diversity, located in Portuguese reservoirs and water bodies along the upper Elbe. Parasite species richness was significantly associated with host microsatellite heterozygosity and allelic richness, a trend partially affected by richness of North-American parasites. Furthermore, our results indicate that parasite community composition may serve as a useful biological tool to discriminate non-native fish populations and their inter-relationships.

Ecto- parasitic infection in Nile tilapia (Oreochromis niloticus) fry during male reversal in Veracruz, México

The monogenean gyrodactylids and some ciliated protozoa species may cause ectoparasitic epidemics in tilapia hatcheries. An experimental framework was developed with fish reared during male reversal treatment. The infection dynamics were examined: mean intensity, prevalence, condition factor (K), fish growth and mortality. A total number of 3400 infected tilapia fish were transferred from high density (45 fish L-1) to a low-density tank (2 fish L-1). In the fish (0.012 ± 0.003 g) there were identified four ectoparasitic species; a worm, Gyrodactylus cichlidarum and 3 ciliated protozoa (Trichodina sp. Chilodonella sp. and Ambiphrya sp.). The infection dynamic examined during 31 days showed that the parasitic load and parasite richness for the different ecto-parasites demonstrated positive interspecific correlations, in spite of that, non-synergistic or antagonistic interactions were manifested. The condition factor K was strongly affected (p < 0.05) by G. cichlidarum during the course of infections. The growth and survival recovered after 31 days at low density.

The enemy release hypothesis and Callosciurus erythraeus in Argentina: combining community and biogeographical parasitological studies

The enemy release hypothesis (ERH) postulates that during the invasion process an introduced species is released from the natural enemies that regulate its populations, promoting its invasion success in the new environment. Callosciurus erythraeus is a sciurid native to Southeast Asia that has been successfully introduced into Argentina and other Asian and European countries. The aim of this study was to provide new parasitological data on this species and to compare it with studies in native and other introduced ranges under the framework of the ERH. We proposed two working hypotheses: (1) an analysis at the community level to compare the prevalence, abundance and identity of parasites of C. erythraeus and sympatric native mammals in the main invasion focus of Argentina, and (2) an analysis at the biogeographical level to compare parasite richness in native and introduced ranges of C. erythraeus and parasite prevalence and richness among introduced regions with different invasion success (using population density and spread as proxy variables). The community analyses indicated that C. erythraeus has lost its specific parasites in Argentina and that it has a lower level of parasitism than other native mammals. The biogreographical analyses indicated a lower macroparasite richness of C. erythraeus in introduced ranges compared to its native range. However, parasite richness in introduced ranges was not associated with population density and spread. The negative correlation between parasite prevalence and population parameters was mainly due to the low parasite prevalence of C. erythraeus in Argentina where this species shows high density and spread. The release of parasites of C. erythraeus in comparison to its native and other introduced ranges, the low acquisition of generalist parasites and the high population density and spread reached in Argentina are mostly in agreement with the expected outcomes based on the ERH. Further studies are needed to better understand the role of the ERH in the invasion success of this species.

Competition from sea to mountain: Interactions and aggregation in low-diversity monogenean and endohelminth communities in twospot livebearer Pseudoxiphophorus bimaculatus (Teleostei: Poeciliidae) populations in a neotropical river.

The role of interspecific interactions in structuring low‐diversity helminth communities is a controversial topic in parasite ecology research. Most parasitic communities of fish are species‐poor; thus, interspecific interactions are believed to be unimportant in structuring these communities.We explored the factors that might contribute to the richness and coexistence of helminth parasites of a poeciliid fish in a neotropical river.Repeatability of community structure was examined in parasitic communities among 11 populations of twospot livebearer Pseudoxiphophorus bimaculatus in the La Antigua River basin, Veracruz, Mexico. We examined the species saturation of parasitic communities and explored the patterns of species co‐occurrence. We also quantified the associations between parasitic species pairs and analyzed the correlations between helminth species abundance to look for repeated patterns among the study populations.Our results suggest that interspecific competition could occur in species‐poor communities, aggregation plays a role in determining local richness, and intraspecific aggregation allows the coexistence of species by reducing the overall intensity of interspecific competition.