Abstract
BackgroundRecently, human intervention enabled the introduction of Barbus barbus from the Rhône River basin into the Barbus meridionalis habitats of the Argens River. After an introduction event, parasite loss and lower infection can be expected in non-native hosts in contrast to native species. Still, native species might be endangered by hybridization with the incomer and the introduction of novel parasite species. In our study, we aimed to examine metazoan parasite communities in Barbus spp. populations in France, with a special emphasis on the potential threat posed by the introduction of novel parasite species by invasive B. barbus to local B. meridionalis. MethodsMetazoan parasite communities were examined in B. barbus, B. meridionalis and their hybrids in three river basins in France. Microsatellites were used for the species identification of individual fish. Parasite abundance, prevalence, and species richness were compared. Effects of different factors on parasite infection levels and species richness were tested using GLM.ResultsMetazoan parasites followed the expansion range of B. barbus and confirmed its introduction into the Argens River. Here, the significantly lower parasite number and lower levels of infection found in B. barbus in contrast to B. barbus from the Rhône River supports the enemy release hypothesis. Barbus barbus × B. meridionalis hybridization in the Argens River basin was confirmed using both microsatellites and metazoan parasites, as hybrids were infected by parasites of both parental taxa. Trend towards higher parasite diversity in hybrids when compared to parental taxa, and similarity between parasite communities from the Barbus hybrid zone suggest that hybrids might represent “bridges” for parasite infection between B. barbus and B. meridionalis. Risk of parasite transmission from less parasitized B. barbus to more parasitized B. meridionalis indicated from our study in the Argens River might be enhanced in time as higher infection levels in B. barbus from the Rhône River were revealed. Hybrid susceptibility to metazoan parasites varied among the populations and is probably driven by host-parasite interactions and environmental forces.ConclusionsScientific attention should be paid to the threatened status of the endemic B. meridionalis, which is endangered by hybridization with the invasive B. barbus, i.e. by genetic introgression and parasite transmission.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1867-9) contains supplementary material, which is available to authorized users.
Highlights
Human intervention enabled the introduction of Barbus barbus from the Rhône River basin into the Barbus meridionalis habitats of the Argens River
Genetic composition of Barbus spp. populations Based on microsatellite markers, STRUCTURE analysis confirmed the existence of one allopatric BB population in the Loire River basin (Site 1) and one allopatric B. meridionalis (BM) population in the Argens River basin (Site 14)
An h-index up to 0.11 was revealed in populations of the Rhône River basin. Using this value as an upper limit for B. barbus individuals, 25 B. barbus, 42 B. meridionalis and 81 hybrids were detected within the Argens River basin, where we considered Barbus populations with the occurrence of hybrids as sympatric populations
Summary
Human intervention enabled the introduction of Barbus barbus from the Rhône River basin into the Barbus meridionalis habitats of the Argens River. Native species might be endangered by hybridization with the incomer and the introduction of novel parasite species. We aimed to examine metazoan parasite communities in Barbus spp. populations in France, with a special emphasis on the potential threat posed by the introduction of novel parasite species by invasive B. barbus to local B. meridionalis. Many native species are endangered through hybridization with the closely related alien species [7,8,9]. Exposing susceptible local hosts to new parasite species carried by introduced individuals may result in accelerated mortality in native populations. The parasitic nematode Anguillicoloides crassus was imported to Europe probably as a result of the introduction of the Japanese eel Anguilla japonica and was, subsequently, disseminated in the populations of the European eel Anguilla anguilla (reviewed in [12]). While A. crassus is not highly pathogenic in the Japanese eel probably due to low-intensity infection rates [13], high infection and more serious pathology connected with high mortalities may be detected in wild European eels [14,15,16,17]
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