The fitness effects of delayed switching to sex in a facultatively asexual insect

Abstract

Facultative reproductive strategies that incorporate both sexual and parthenogenetic reproduction should be optimal, yet are rarely observed in animals. Resolving this paradox requires an understanding of the economics of facultative asexuality. Recent work suggests that switching from parthenogenesis to sex can be costly and that females can resist mating to avoid switching. However, it remains unclear whether these costs and resistance behaviors are dependent on female age. We addressed these questions in the Cyclone Larry stick insect, Sipyloidea larryi, by pairing females with males (or with females as a control) in early life prior to the start of parthenogenetic reproduction, or in mid‐ or late life after a period of parthenogenetic oviposition. Young females were receptive to mating even though mating in early life caused reduced fecundity. Female resistance to mating increased with age, but reproductive switching in mid‐ or late life did not negatively affect female survival or offspring performance. Overall, mating enhanced female fitness because fertilized eggs had higher hatching success and resulted in more adult offspring than parthenogenetic eggs. However, female fecundity and offspring viability were also enhanced in females paired with other females, suggesting a socially mediated maternal effect. Our results provide little evidence that switching from parthenogenesis to sex at any age is costly for S. larryi females. However, age‐dependent effects of switching on some fitness components and female resistance behaviors suggest the possibility of context‐dependent effects that may only be apparent in natural populations.

Age‐dependent plasticity in reproductive investment, regeneration capacity and survival in a partially clonal animal (Hydra oligactis)

“…Asexual reproduction is thought to maintain a population of locally adapted clones (Ayre & Miller, 2004) and less costly than sexual reproduction (Rispe, Pierre, Simon, & Gouyon, 1998). For this reason, asexual reproduction can be advantageous for animals in good conditions and early in their life, since they can rapidly colonize resources for their own genotype, while later they can use more costly sexual reproduction to increase genotypic diversity (Burke & Bonduriansky, 2018).…”

“…This is in accordance with previous findings in other partially clonal species. For instance, female stick insects that mated in early life (prior to the start of parthenogenetic reproduction) produce fewer eggs, possibly because they were not fully mature at pairing (Burke & Bonduriansky, 2018). Age‐dependent sexual maturity is also known in some coral species (Kai & Sakai, 2008), while in Pelmatohydra robusta (likely synonymous to H. oligactis ; Schwentner & Bosch, 2015) a decreased sexual maturation time and increased fecundity with polyp age were reported previously by Noda (1982).…”

“…However, empirical studies of clonal animals detect a different pattern: clonal reproduction can be more emphasized in early life in individuals with good condition and growth is more important later (Glazier & Calow, 1992). An additional major life‐history decision in partially clonal species compared to non‐clonal ones is the switch from asexual to sexual reproduction, the timing of which can be flexible and might be triggered only when clonal reproduction is limited by exogenous factors (Burke & Bonduriansky, 2018; Harvell & Grosberg, 1988).…”

Effects of Delayed Mating on the Reproductive Performance of Henosepilachna vigintioctopunctata (F.) (Coleoptera: Coccinellidae)

“…In some species, delayed mating can increase adult longevity [25,43,81]. This is widely considered to be a result of the reduced energy expenditure associated with reproduction [82,83]. However, Omkar et al [34] and Bakker et al [84] showed that mating delays may be responsible for reducing adult longevity in Zygogramma bicolorata, Y. padellus (L.) (Lepidoptera: Yponomeutidae), and Anastrepha ludens Loew (Diptera: Tephritidae), possibly due to males deliberately harming females in order to stimulate a higher oviposition rate; the increased activity of females, including efforts spent in locating a mate prior to mating, i.e., crawling, flying, etc., and afterwards seeking a suitable oviposition medium; and, in males, the process of ejaculation consuming a portion of their energy.…”

The paradox of obligate sex: The roles of sexual conflict and mate scarcity in transitions to facultative and obligate asexuality

“…Indeed, cases of post‐copulatory parthenogenesis are extremely rare (e.g., see Arbuthnott, Crespi, & Schwander, ; Chang, Ting, Chang, Fang, & Chang, ), which suggests that coerced fertilization of eggs by sperm may further limit parthenogenetic reproduction. Fourth, fitness costs associated with switching from a parthenogenetic to sexual mode of reproduction could be an additional hurdle (Burke & Bonduriansky, ; Burke et al., ). Such constraints on parthenogenetic reproduction could therefore play key roles in preventing facultative mutants from invading obligately sexual populations.…”