Inbreeding parents should invest more resources in fewer offspring

Citation

Duthie AB, Lee AM & Reid JM (2016) Inbreeding parents should invest more resources in fewer offspring. Proceedings of the Royal Society B: Biological Sciences, 283 (1843), Art. No.: 20161845. https://doi.org/10.1098/rspb.2016.1845

Abstract
Inbreeding increases parent-offspring relatedness and commonly reduces offspring viability, shaping selection on reproductive interactions involving relatives and associated parental investment (PI). Nevertheless, theories predicting selection for inbreeding versus inbreeding avoidance and selection for optimal PI have only been considered separately, precluding prediction of optimal PI and associated reproductive strategy given inbreeding. We unify inbreeding and PI theory, demonstrating that optimal PI increases when a female’s inbreeding decreases the viability of her offspring. Inbreeding females should therefore produce fewer offspring due to the fundamental trade-off between off-spring number and PI. Accordingly, selection for inbreeding versus inbreeding avoidance changes when females can adjust PI with the degree that they inbreed. In contrast, optimal PI does not depend on whether a focal female is herself inbred. However, inbreeding causes optimal PI to increase given strict monogamy and associated biparental investment compared to female-only investment. Our model implies that understanding evolutionary dynamics of inbreeding strategy, inbreeding depression, and PI requires joint consideration of the expression of each in relation to the other. Overall, we demonstrate that existing PI and inbreeding theories represent special cases of a more general theory, implying that intrinsic links between inbreeding and PI affect evolution of behaviour and intra-familial conflict.

Keywords
Inbreeding; inclusive fitness; mate choice; parental investment; relatedness; reproductive strategy

Journal
Proceedings of the Royal Society B: Biological Sciences: Volume 283, Issue 1843

• Duthie-etal-RSProcB-2016.pdf