Evolution of intermediate latency strategies in seasonal parasites

TL;DR

This paper shows how seasonal host activity can influence parasite evolution by selecting for intermediate latency periods and multiple stable strategies.

Contribution

The study extends prior theory to show that seasonal host activity affects non-obligate killer parasites similarly to obligate ones.

Findings

Seasonal host activity can select for intermediate latency periods in non-obligate killer parasites.

Multiple evolutionarily stable strategies can be maintained due to host seasonality.

Host seasonal patterns act as a major selective force on parasite life-history evolution.

Abstract

Traditional mechanistic trade-offs between transmission and parasite latency period length are foundational for nearly all theories on the evolution of parasite life-history strategies. Prior theoretical studies demonstrate that seasonal host activity can generate a trade-off for obligate-host killer parasites that selects for intermediate latency periods in the absence of a mechanistic trade-off between transmission and latency period lengths. Extensions of these studies predict that host seasonal patterns can lead to evolutionary bistability for obligate-host killer parasites in which two evolutionarily stable strategies, a shorter and longer latency period, are possible. Here we demonstrate that these conclusions from previously published studies hold for non-obligate host killer parasites. That is, seasonal host activity can select for intermediate parasite latency periods for non-obligate killer parasites in the absence of a trade-off between transmission and latency period length and can maintain multiple evolutionarily stable parasite life-history strategies. These results reinforce the hypothesis that host seasonal activity can act as a major selective force on parasite life-history evolution by extending the narrower prior theory to encompass a greater range of disease systems.

Figures