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RESEARCH PRODUCT

Abundance–variance and abundance–occupancy relationships in a marine host–parasite system: The importance of taxonomy and ecology of transmission

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Abundance-occupancy and abundance-variance relationships are two of the most general macroecological patterns capturing essential fundamentals of the structuring of species distributions and are widely documented for free-living animal and plant species populations at different spatial scales. However, empirical data for parasites have been gathered using appropriate sampling designs only recently. We performed analyses across species of the variation in infection parameters and patterns of aggregation of the most widespread parasites in the marine sparid fish Boops boops across seven localities of two marine biogeographical regions, the North East Atlantic and the Mediterranean. We used a large dataset of multiple population samples replicated over time for 20 parasite species and carried out assessments both intraspecifically and interspecifically, across taxonomic and ecological groupings. This taxonomically diverse complex of species representing five major metazoan higher taxa with differing transmission ecologies allowed us to assess the effect of taxonomic and ecological determinants on the abundance-occupancy and abundance-variance relationships in the model marine host-parasite system. The results revealed that: (i) a power function, relating spatial variance to mean abundance, represents a suitable model for the spatial distribution of the species; (ii) prevalence, abundance and the degree of spatial heterogeneity are true species characteristics and differ consistently between higher level taxonomic groupings; (iii) infection parameters and abundance-variance relationship are dependent on host specificity and regional distribution patterns of the parasites; and (iv) the observed infection parameters agree well with predictions from the epidemiological negative binomial abundance-occupancy model built on parameters of Taylor's power law both within and across species.