Using parasites to infer host population history: A new rationale for parasite conservation

Only one of the 5000 extant louse species (Phthiraptera) and no species of flea (Siphonaptera), parasitic helminth (Platyhelminthes), parasitic nematode (Nemata), mite, or tick (Acari) is listed as threatened by the IUCN, despite impassioned pleas for parasite conservation beginning more than a decade ago. Although they should be conserved for their own sake, past arguments, highlighting the intrinsic and utilitarian value of parasites, have not translated into increased attention by scientists or conservation managers, at least by the standard of listing for protection. Here, the use of estimated genealogies and population genetic patterns of parasites to illuminate their hosts' evolutionary and demographic history is advocated. Parasite DNA generally evolves more rapidly than their hosts', which renders it an underexploited resource for conservation biologists, particularly in cases where the hosts' genealogy or degree of population genetic structure is difficult to measure directly. Moreover, parasite gene flow may occur during host dispersal irrespective of host gene flow, revealing host movement through space and time. Parasite ecology and evolution may thus become another tool for the management of endangered vertebrate populations. This will result in the recognition of new host records, parasite species and cryptic lineages, which will help lift the veil of ignorance with respect to parasite biodiversity.