A genotypic trade‐off between constitutive resistance to viral infection and host growth rate

Abstract

Genotypic trade‐offs are fundamental to the understanding of the evolution of life‐history traits. In particular, the evolution of optimal host defense and the maintenance of variation in defense against infectious disease is thought to be underpinned by such evolutionary trade‐offs. However, empirical demonstrations of these trade‐offs that satisfy the strict assumptions made by theoretical models are rare. Additionally, none of these trade‐offs have yet been shown to be robustly replicable using a variety of different experimental approaches to rule out confounding issues with particular experimental designs. Here, we use inbred isolines as a novel experimental approach to test whether a trade‐off between viral resistance and growth rate in Plodia interpunctella, previously demonstrated by multiple selection experiments, is robust and meets the strict criteria required to underpin theoretical work in this field. Critically, we demonstrate that this trade‐off is both genetic and constitutive. This finding helps support the large body of theory that relies on these assumptions, and makes this trade‐off for resistance unique in being replicated through multiple experimental approaches and definitively shown to be genetic and constitutive.

Experimental evolution of immunological specificity

“…The changes in priming specificity did not lead to any apparent trade-offs in adult short-term fecundity, which have been reported for primed immune responses against pathogens in other insect species (42, 43). This could be a consequence of our selection protocol, as we selected for larval phenotypes under ad libitum rearing conditions, or our fecundity readouts over a short time frame without specific testing for early and late life fecundity.…”

Resource quality determines the evolution of resistance and its genetic basis

“…However, the picture from our current study is more complicated, in addition to selecting for resistance through exposure to the virus (direct selection) there appears to be correlated responses to selection of diet (indirect selection). Previous results had suggested there may be a genetic basis for the trade-off in this system (Bartlett et al, 2018). To further investigate this potential, Plodia populations were directly selected for their development rate, and however, a trade-off between development and viral resistance was not consistently expressed.…”

“…Resistance mechanisms typically come at a price: either through the activation of induced defence mechanisms (Graham, Allen, & Read, 2005; Moret & Schmid‐Hempel, 2001; Sadd & Siva‐Jothy, 2006) or through the maintenance of a constitutively expressed defence when parasites are absent (Bartlett, Wilfert, & Boots, 2018; Boots & Begon, 1993; Fuxa & Richter, 1992; Kraaijeveld & Godfray, 1997; McKean, Yourth, Lazzaro, & Clark, 2008). A classic experimental example of such occurred when Drosophila evolved resistance to parasitoid attack, but the cost of resistance was only apparent when food was in limited supply, with an apparent trade‐off being between resistance and larval competitiveness for limited food resources (Kraaijeveld & Godfray, 1997).…”

Introduced parasite changes host phenotype, mating signal and hybridization risk: Philornis downsi effects on Darwin's finch song

“…[49,93 -96]), phylogenetic analysis (e.g. [97]), or the genetics of host resistance and immunity [98,99]. The findings of this study offer a new perspective for understanding evolutionary change from introduced parasites given that parasites can alter pre-mating signals and thus blur species boundaries.…”