Document Type

Article

Publication Title

Journal of Evolutionary Biology

Publication Date

7-2019

Keywords

fecundity compensation, genotype-by-environment interaction, life-history theory, residual reproductive value

Abstract

Infection can cause hosts to drastically alter their investment in key life‐history traits of reproduction and defence. Infected individuals are expected to increase investment in defence (e.g., by increasing immune function) and, due to trade‐offs, investment in other traits (e.g., current reproduction) should decrease. However, the terminal investment hypothesis postulates that decreased lifespan due to infection and the associated reduction in the expectation for future offspring will favour increased investment towards current reproduction. Variation in intrinsic condition will likely influence shifts in reproductive investment post‐infection, but this is often not considered in such assessments. For example, the extent of inbreeding can significantly impact an individual's lifetime fitness and may influence its reproductive behaviour following a threat of infection. Here, we investigated the effects of inbreeding status on an individual's reproductive investment upon infection, including the propensity to terminally invest. Male crickets (Gryllodes sigillatus) from four genetically distinct inbred lines and one outbred line were subjected to a treatment from an increasing spectrum of simulated infection cue intensities, using heat‐killed bacteria. We then measured reproductive effort (calling effort), survival and immune function (antibacterial activity, circulating haemocytes and haemocyte microaggregations). Inbred and outbred males diverged in how they responded to a low‐dose infection cue: relative to unmanipulated males, outbred males decreased calling effort, whereas inbred males increased calling effort. Moreover, we found that inbred males exhibited higher antibacterial activity and numbers of circulating haemocytes compared with outbred males. These results suggest that an individual's inbreeding status may have consequences for context‐dependent shifts in reproductive strategies, such as those triggered by infection.

Funding Source

This research was funded by a grant from the National Science Foundation to S.K.S., B.M.S., and J.H. (IOS 16–54028), grants from the Sigma Xi Research Honor Society, the Beta Lambda Chapter of the Phi Sigma Biological Honor Society, and Graduate Student Association of Illinois State University to K.R.D., and a grant from the Australian Research Council to J.H. (DP180101708). Research reported in this publication was also supported by the National Institute of General Medical Sciences of the National Institutes of Health under award number R15GM12968 to BMS.

Comments

This is the accepted manuscript of an article first published in Journal of Evolutionary Biology (2019): https://doi.org/10.1111/jeb.13478

Copyright held by European Society for Evolutionary Biology.

DOI

10.1111/jeb.13478

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