Abundance-occupancy relationships drive core-satellite structure in helminth metacommunities of a Neotropical cichlid

Understanding how parasite communities are structured across spatial scales is a central challenge in parasite ecology. A widespread macroecological pattern is the positive relationship between local abundance and regional occurrence (abundance-occupancy relationship), yet its role in shaping parasite assemblages remains incompletely understood. In this study, we analysed helminth communities of 247 specimens of the Neotropical cichlid Vieja fenestrata (Günther) (with a size range of 38-194 mm) across 13 localities in two river basins in Mexico, integrating local (component community) and regional (metacommunity) scales. We evaluated (i) the relationship between local abundance and regional occurrence, (ii) the presence of core-satellite structure, and (iii) the contribution of spatial processes to community organisation. A total of 16 helminth taxa were recorded. Most species exhibited low prevalence and restricted distributions, whereas a small subset of taxa reached high prevalence and occurred across multiple localities. The relationship between abundance and prevalence revealed a clear positive association, supporting the existence of an abundance-occupancy pattern. This pattern was accompanied by a well-defined core-satellite structure, with a few widespread and abundant species coexisting with many rare and spatially restricted taxa. Spatial analyses indicated high heterogeneity among component communities and only weak structuring across environmental gradients, suggesting that local ecological filtering and transmission dynamics play a stronger role than broad-scale spatial segregation. Our results demonstrate that helminth communities in V. fenestrata are structured by macroecological processes that link local infection dynamics to regional distribution patterns. The core-satellite organisation arises from the abundance-occupancy relationship, highlighting the importance of integrating metacommunity theory into parasite ecology.