Data and code from: Biogeographic patterns and drivers of endolithic symbiosis in mussels across Atlantic Europe and North Africa

This dataset includes the file infestationdata.RData, which provides
records of mussel shell bioerosion, is stored in the column “infestation”.
The degree of endolithic association was evaluated according to the
classification in a previous study: Kaehler, S. (1999) Incidence and
distribution of phototrophic shell-degrading endoliths of the brown mussel
Perna perna. Mar. Biol., 135,
505-514. https://doi.org/10.1007/s002270050651 Shells
with clean, intact periostracum and distinct periostracal striations
(Group A); shells with central surface erosion, outer striations becoming
indistinct (Group B); shells with erosion extending beyond the central
portion, with grooves and pits appearing (Group C); shells heavily pitted,
deformed, with almost completely absent periostracal striations (Group D);
shells extremely pitted, brittle, and deformed, often with holes (Group
E). For each mussel, the valve showing the highest level of endolithic
bioerosion was used for classification. The dataset is structured to
facilitate quantitative analyses of spatial patterns in endolithic
infestation and can be reused for comparative biogeographic studies,
methodological benchmarking, or integration into broader meta‑analyses of
shell bioerosion and host-symbiont interactions. The accompanying R code
provides reproducible workflows for data handling and analysis. All data
were collected from wild mussels and do not involve protected species or
sensitive human information, and no legal or ethical restrictions apply to
their reuse.