Host community assembly modifies the relationship between host and parasite richness

Abstract

1Host and parasite richness are generally positively correlated, but the stability of this 2 relationship during community assembly remains untested. The composition of host 3 communities can alter parasite transmission, and the relationship between host and parasite 4 richness is sensitive to parasite transmission. Thus, changes in composition during host 5 community assembly could strengthen or weaken the relationship between host and parasite 6 richness. Host community assembly, in turn, can be driven by many processes, including 7 resource enrichment. To test the hypothesis that host community assembly can alter the 8 relationship between host and parasite richness, we experimentally crossed host diversity and 9 resource supply to hosts, then allowed communities to assemble. As previously shown, initial 10 host diversity and resource supply determined the trajectory of host community assembly, 11 altering post-assembly host species richness, richness-independent host phylogenetic 12 diversity, and colonization by exotic host species. Throughout community assembly, host 13 richness predicted parasite richness. As predicted, this effect was moderated by exotic 14 abundance: communities dominated by exotic species exhibited a stronger positive 15 relationship between post-assembly host and parasite richness. Ultimately, these results 16 suggest that, by modulating parasite transmission, community assembly can modify the 17 relationship between host and parasite richness, providing a novel mechanism to explain 18 contingencies in this relationship. 19