Hybridization Dynamics and Host-Parasite Interactions in Aquatic Species

Hybridization among aquatic taxa—from cyprinid fishes to amphibians and molluscs—reconfigures host genetic architecture and can alter susceptibility to native and novel parasites. Hybrid genomes may exhibit increased heterozygosity, leading to either enhanced resistance or, conversely, unexpected vulnerability depending on coevolutionary history. Introgression of parental alleles influences immune gene diversity, shaping the balance between resistance (the ability to limit parasite burden) and tolerance (the capacity to withstand infection). Environmental context—such as water temperature, salinity and community composition—modulates host–parasite encounters and determines whether hybrids act as sinks, bridges or filters for parasite transmission. In invaded or managed systems, hybrids can facilitate the spill-over of parasites from non-native to endemic species, with implications for conservation, aquaculture and disease emergence. Predator‐mediated selection further shapes hybrid fitness when predation risk compounds parasite challenge. Integrating genomic, ecological and epidemiological approaches underscores the global significance of hybrid zones in understanding disease dynamics, biodiversity maintenance and the evolutionary consequences of human-mediated species introductions.

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Hybridization Dynamics and Host-Parasite Interactions in Aquatic Species publication trend

The graph below shows the total number of articles in hybridization dynamics and host-parasite interactions in aquatic species across all publications each year (not limited to Nature Index journals).

Technical terms

Hybridization: Crossing between two genetically distinct species or populations, producing offspring with mixed ancestry.

Introgression: The incorporation of genes from one species into the gene pool of another through repeated backcrossing.

Host specificity: The degree to which a parasite can infect and reproduce in a limited range of host species.

Hybrid heterosis: Enhanced performance or vigor in hybrid offspring, often manifesting as increased growth or disease resistance.

Monogeneans: A group of flatworm parasites, typically ectoparasitic on fish gills and skin, with direct life cycles.

Parasite load: The number or biomass of parasites infecting a host, reflecting the intensity of infection.

References

1. Monogeneans in intergeneric hybrids of leuciscid fish: Is parasite infection driven by hybrid heterosis, genetic incompatibilities, or host-parasite coevolutionary interactions?. Frontiers in Zoology (2023).
2. Distribution of host-specific parasites in hybrids of phylogenetically related fish: the effects of genotype frequency and maternal ancestry?. Parasites & Vectors (2020).
3. Metazoan parasite communities: support for the biological invasion of Barbus barbus and its hybridization with the endemic Barbus meridionalis. Parasites & Vectors (2016).
4. Species integrity enhanced by a predation cost to hybrids in the wild. Biology Letters (2017).
5. Heterozygosity and parasite intensity: lung parasites in the water frog hybridization complex. Parasitology (2007).