Abstract
Ecologists have long sought recurring and predictable patterns in nature, not contingent on habitat type, local conditions or taxa involved, indicative of universal processes creating some order in natural systems. Are there such general laws in parasite ecology? Here, I propose 16 frequently reported patterns, manifesting across all host and parasite taxa, that I consider to represent general laws applying to the ecology of metazoan parasites. I also discuss briefly pseudo-laws, i.e., patterns that lack the strength or generality to qualify as laws. The proposed laws characterise repeatable patterns in the abundance, biomass, distribution, diversity and/or other basic traits of parasites, and the processes underpinning them, whether or not these are known. The different laws span several scales, from the patterns applying among host individuals at a local scale, to those observed globally across species or geographical areas. Each proposed law is subjectively categorised based on the quantity and quality of published empirical evidence supporting it, reflecting its strength and universality. Relationships between different laws are emphasised, to highlight the connections between their underlying mechanistic bases, as are the parallels with broader ecological laws documented for free-living organisms. Close examination suggests that many laws of parasite ecology are essentially manifestations of ecological laws applying to all organisms. Nevertheless, identifying regular, repeatable and nearly universal patterns in parasite ecology provides us with a powerful heuristic tool to forecast future host-parasite interactions in the fast-changing Anthropocene.