Causes and potential consequences of conditional host dispersal: the importance of spite in host populations

10 Jul 2018, 10:30
New Law School/--101 (University of Sydney)

New Law School/--101

University of Sydney

Oral Presentation Minisymposium: Host-parasite coevolution in space Host-parasite coevolution in space


Ryosuke Iritani (UC Berkeley)


Spatial structure owing to localized dispersal in hosts can have dramatic impacts upon the coevolutionary dynamics of hosts and parasites. The basic idea is that localized dispersal in hosts can lead to localized transmission, thereby selecting for costly resistance in hosts and lower virulence in parasites. Both of these evolutionary forces are grounded on the altruism (i.e., costly to the actor but benefitial to recipients). From the viewpoints of the hosts, however, they can also utilize the pathogens to harm their neighbors (biological weapon hypothesis), thereby gaining positive inclusive-fitness benefits overall. Despite this, few studies looked at the causes and consequences of host dispersal evolution. Here, using mathematical models of inclusive fitness theory, we show three understudied ideas. First, differential costs of dispersal between susceptible and infected individuals can modify the host population structure. Second, if hosts can condition their dispersal propensity depending on the sickness (susceptible or infected), then the evolutionary dynamics of such conditional host dispersal can generate evolutionary bistabilities such that dispersal propensity biases towards susceptible or infected individuals depending on the initial conditions of the host populations. Finally, we propose that such drastically different dispersal propensity could turn over the classic idea that spatial structure can often favour increased resistance: rather, differential costs of dispersal and/or conditional dispersal propensity in hosts could favour “spite” of the hosts, which has been largely ignored aspects in spatially structured host-parasite dynamics. We overall highlight the neglected but profound aspects of host dispersal.

Primary authors

Michael Boots (UC Berkeley) Ryosuke Iritani (UC Berkeley)

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