Reproductive value and primary sex ratios under facultative asexual reproduction by both sexes in age-structured populations.

Abstract

Reproductive value (RV) and evolutionarily stable primary sex ratios are fundamentally linked, centrally important topics in evolutionary biology. Recent theoretical studies have advanced our understanding of (i) the relationship between the RV of juveniles of the two sexes under arbitrary transmission genetics, age structures, and fecundity schedules, and (ii) sex ratio evolution under facultative asexual reproduction. Here, we unite and build upon these two strands of work. We derive the relative RVs of daughters and sons in an age-structured population with arbitrary transmission genetics when both sexes can reproduce asexually and can produce offspring of either sex. We then apply this result to sex ratio evolution and derive a general expression for the primary sex ratio of the sexual pathway. A key finding is that the primary sex ratio of the sexual pathway is unaffected by asexual reproduction by either sex when asexually produced offspring are of the same sex as their parents. If asexual reproduction produces offspring of the opposite sex, the sex ratio of the sexual pathway is altered. The post-hatching population sex ratio results derived in earlier studies are recovered as special cases.