Evolution of parasitic life in the ocean: paratenic hosts enhance lateral incorporation.

Cumulative evolution has been proposed to explain the high diversity of marine fish parasites. The process is based on the idea that marine parasites, being generalists, are able to follow new food web pathways and colonize novel hosts, subsequently undergoing speciation. Opportunities to colonize new hosts via different food chains might also arise from the ability to use paratenic hosts that maintain or increase transmission. However, caution is advised in the adoption of the term 'cumulative evolution' in evolutionary biology because of historical precedent. This term has previously been applied to the cultural evolution of tool design.