PT  - JOURNAL ARTICLE
AU  - Betts, A.
AU  - Gray, C.
AU  - Zelek, M.
AU  - MacLean, R. C.
AU  - King, K. C.
TI  - High parasite diversity accelerates host adaptation and diversification
AID  - 10.1126/science.aam9974
DP  - 2018 May 25
TA  - Science
PG  - 907--911
VI  - 360
IP  - 6391
4099  - http://science.sciencemag.org/content/360/6391/907.short
4100  - http://science.sciencemag.org/content/360/6391/907.full
SO  - Science2018 May 25; 360
AB  - Virtually all organisms are parasitized by multiple species, but our current understanding of host-parasite interactions is based on pairwise species interactions. Betts et al. address this by using the bacterium Pseudomonas aeruginosa and five different phage virus parasites. Increasing parasite diversity accelerated the rate of host evolution, driving both faster genomic evolution within populations and greater divergence between populations. Thus, different parasite loads prompt different evolutionary dynamics and profoundly shape host evolution by different mechanisms.Science, this issue p. 907Host-parasite species pairs are known to coevolve, but how multiple parasites coevolve with their host is unclear. By using experimental coevolution of a host bacterium and its viral parasites, we revealed that diverse parasite communities accelerated host evolution and altered coevolutionary dynamics to enhance host resistance and decrease parasite infectivity. Increases in parasite diversity drove shifts in the mode of selection from fluctuating (Red Queen) dynamics to predominately directional (arms race) dynamics. Arms race dynamics were characterized by selective sweeps of generalist resistance mutations in the genes for the host bacterium’s cell surface lipopolysaccharide (a bacteriophage receptor), which caused faster molecular evolution within host populations and greater genetic divergence among populations. These results indicate that exposure to multiple parasites influences the rate and type of host-parasite coevolution.