Parasite spillover rather than niche expansion explains infection of host brain by diplostomid eye flukes

Parasites often occupy specific sites within their host, which has important implications for host performance and parasite transmission. Nonetheless, parasitic infections can occur beyond their typical location within a host, significantly altering host-parasite interactions. Yet, the causes behind the atypical tissue tropism are poorly understood. Here, we focus on a ubiquitous group of diplostomid parasites that form diverse communities in fish eyes. We used targeted DNA metabarcoding (COX1, 250 bp) to evaluate potential mechanisms underlying atypical tissue tropism from predominantly eye to brain infection in two widespread fish species (Eurasian perch and common roach). We found that the most common eye-infecting species (Tylodelphys clavata, Diplostomum baeri) are present in the brains of perch but not in roach. The bipartite network comprising five species and 24 mitochondrial haplotypes revealed no brain-specific haplotypes, indicating an apparent lack of genetic divergence betw..., The data set was obtained by the metabarcoding characterisation of the diplostomids communties in the eyes and brain of Eurasian perch collected at seven lakes in souther Estonia. This files includes the bioinformatic pipeline to process the raw seqeunces (2 x 300 bp read length, Illumina Inc., San Diego, California, USA) and the R code for the down stream analysis., , # Parasite spillover rather than niche expansion explains infection of host brain by diplostomid eye flukes

[https://doi.org/10.5061/dryad.76hdr7t5p](https://doi.org/10.5061/dryad.76hdr7t5p)

## Description of data and file structure

This dataset includes the bioinformatic pipeline, R code (Diaz_Suarez_et_al_2024), and data files to run the statistical analysis and plotting of the MS entitled \"Parasite spillover rather than niche expansion explains infection of host brain by diplosomid eye flukes\". Raw sequences are available in GenBank on accession number PRJNA1078141. All used packages are indicated at the beginning of the R code file (library()).

The datasets included are the following:

**ASV_new_stric.csv** -> Strict mapping of ASv using the --search_exact function in VSEARCH

**TAX_brain_new.csv** -> taxonomic identification of ASV using SINTAX classifier

**Metadata_strict.csv** -> Metadata including the lake, infected tissue (eye, brain), infection type (eye, brain, ...