How intraguild predation affects the host diversity-disease relationship in a multihost community

Abstract

Broad evidence has shown that host diversity can impede disease invasion and reduce the eventual prevalence, but little is known on how species interactions play in shaping this host diversity-disease relationship. Previous work has illustrated that intraguild predation (IGP), combined with parasite-mediated indirect effects, can have strong influences on parasitic infection. Following this line of thinking, we here examine the role of predatory interactions in the disease transmission within a multihost community. Through varying fractions of IGP in a competitive community, we show that, dependent on the fraction of predatory interactions, species richness can switch from enhancing to inhibiting disease establishment/prevalence. Without IGP interactions, high host species richness can likely weaken the 'dilution effect' and in some cases even enhance the disease establishment (and/or prevalence) due to the existence of alternative sources for infection, whereas IGP can generally heighten the negative diversity-disease relationship due to the reduction of encounter rate between prospective hosts and parasites. Although trait-mediated interactions (captured as the infection-induced changes in predation rate) only weakly affect disease prevalence, density-mediated interactions (captured as the additional infection-induced mortality) can pose a relatively strong influence on disease transmission. Our results thus underline the importance of considering species interactions when investigating the host diversity-disease relationship.

How Multiple Interaction Types Affect Disease Spread and Dilution in Ecological Networks

“…For instance, multihost pathogenic diseases can alter direct resource competition between two host species into apparent competition, where a disease outbreak in one host may facilitate pathogens to spill over to the other host species and thus foster the disease spreading across the community (Begon et al, 1999;O'Regan et al, 2015). Disease infections could modify trophic interactions among host species, inhibiting or boosting pathogen transmission under specific ecological context (Packer et al, 2003;Hatcher et al, 2006;Rohr et al, 2015;Su et al, 2020). Structural changes in mutualistic networks can also shape pathogen transmission, with increased connectance from mutualistic interactions diluting the likelihood of disease outbreak (Figueroa et al, 2020).…”

Phanerozoic parasitism and marine metazoan diversity: dilution versus amplification

“…At larger spatial scales of observation, one can find evidence for a positive relationship between diversity and parasitism [ 61 , 62 ]. Other factors like the transmission mode (density-dependent versus frequency transmitted or directly versus trophically transmitted) of the involved parasites [ 52 , 63 ] and the type of predation (intraguild versus non-intraguild predation) [ 64 , 65 ] have also been implicated to modulate the dilution effect, but are difficult to constrain for historical or fossil assemblages. Before we can analyze other factors, we document the dominant patterns on large timescales [ 66 ].…”