Determinants of female fecundity in a simultaneous hermaphrodite: the role of polyandry and food availability

Janicke, Tim; Sandner, Peter; Schärer, Lukas

doi:10.1007/s10682-010-9402-5

Cited by 25 publications

(33 citation statements)

References 81 publications

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“…In our study, we controlled for age effects and manipulated the feeding status of the potential mating partners by exposing them to two different food levels. This manipulation affected the body size of the mating partners and has previously been shown to influence the number of offspring produced by the female sex function in M. lignano (Janicke et al 2011). Specifically, well-fed mating partners were considerably larger and presumably more fecund in their female sex function compared to unfed mating partners.…”

Section: Discussionmentioning

confidence: 98%

“…Second, given that our food level manipulation induced variation in the body size among mating partners it might also have affected the size of the sperm storage organ, which may have caused a lower sperm storage capacity in unfed compared to well-fed mating partners. However, the sperm storage organ of M. lignano is relatively flexible in size (Vizoso et al 2010), and the body size of a recipient is usually not correlated with the number of sperm stored (Janicke et al 2011). This makes it unlikely that unfed worms were more constrained in their sperm-storage capacity compared to well-fed worms.…”

Section: Discussionmentioning

confidence: 99%

“…Specifically, we manipulated experimentally the feeding status of potential mating partners and tested whether focal individuals bias their mating effort towards well-fed or unfed mating partners. Manipulating the feeding status in our study species, the hermaphroditic flatworm Macrostomum lignano, has been previously shown to have a strong effect on both female fecundity (Janicke et al 2011) and body size . Specifically, worms that have relatively more access to food are significantly more fecund in their female sex function and grow to a larger size.…”

Section: Introductionmentioning

confidence: 99%

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Strategic mating effort in a simultaneous hermaphrodite

Janicke

Kesselring

Schärer

2012

Behav Ecol Sociobiol

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Sexual selection theory for simultaneously hermaphroditic animals predicts an overall preference for inseminating partners that have a relatively higher female fecundity. Previous work on the link between male mating decisions and female fecundity has primarily focused on the effect of the partners' body size using existing variation in this trait within a study population. On the assumption that the body size is positively correlated with female fecundity, sperm donors should preferentially inseminate relatively larger individuals to obtain a higher fitness gain through their male sex function. However, empirical evidence for such size-dependent mate choice in simultaneous hermaphrodites is equivocal, possibly because of confounding variables. We studied the mating behavior of the simultaneously hermaphroditic flatworm Macrostomum lignano and tested for a strategic mating effort in response to the feeding status of the partner. We experimentally manipulated the feeding status of potential mating partners in order to generate variation in female fecundity among them and tested whether this affected the copulation number and the number of sperm that the focal worm managed to store in the partner's sperm storage organ. We found that the manipulation of the feeding status had a strong effect on the body size of the potential mating partners and that focal worms copulated more frequently with, and stored more sperm in well-fed partners compared to unfed partners. Our results suggest that M. lignano adjusts its mating effort in response to the feeding status of the mating partner.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Strategic mating effort in a simultaneous hermaphrodite

Janicke

Kesselring

Schärer

2012

Behav Ecol Sociobiol

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“…Here it is worthwhile to note that sperm depletion due to passive sperm loss and/or sperm usage for fertilization might be particularly important in M. lignano as worms usually store relatively few sperm in their sperm storage organ (e.g., on average 29 sperm; Janicke et al. ).…”

Section: Discussionmentioning

confidence: 99%

Sex Allocation Adjustment to Mating Group Size in a Simultaneous Hermaphrodite

et al. 2013

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Sex allocation theory is considered as a touchstone of evolutionary biology, providing some of the best supported examples for Darwinian adaptation. In particular, Hamilton's local mate competition theory has been shown to generate precise predictions for extraordinary sex ratios observed in many separate-sexed organisms. In analogy to local mate competition, Charnov's mating group size model predicts how sex allocation in simultaneous hermaphrodites is affected by the mating group size (i.e., the number of mating partners plus one). Until now, studies have not directly explored the relationship between mating group size and sex allocation, which we here achieve in the simultaneously hermaphroditic flatworm Macrostomum lignano. Using transgenic focal worms with ubiquitous expression of green-fluorescent protein (GFP), we assessed the number of wild-type mating partners carrying GFP+ sperm from these focal worms when raised in different social group sizes. This allowed us to test directly how mating group size was related to the sex allocation of focal worms. We find that the proportion of male investment initially increases with increasing mating group size, but then saturates as predicted by theory. To our knowledge, this is the first direct test of the mating group size model in a simultaneously hermaphroditic animal. K E Y W O R D S :Local mate competition, Macrostomum lignano, mating group size, phenotypic plasticity, sperm competition.

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“…Most importantly, all individuals were fed ad libitum over the entire experiment, which might have relaxed the strength of selection against deleterious alleles that might be particularly important for the female sex function. This is because female reproductive success in simultaneous hermaphrodites (as in separate‐sexed organisms) is expected to be primarily limited by the resources available for egg production rather than by the availability of mates (e.g., Janicke et al ; reviewed in Charnov ). Consequently, the strength of sex‐specific inbreeding depression observed in our experiment does not necessarily reflect the one that can be observed in nature.…”

Section: Discussionmentioning

confidence: 99%

Sex-Specific Inbreeding Depression Depends on the Strength of Male-Male Competition

et al. 2013

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Inbreeding depression has become a central theme in evolutionary biology and is considered to be a driving force for the evolution of reproductive morphology, physiology, behavior, and mating systems. Despite the overwhelming body of empirical work on the reproductive consequences of inbreeding, relatively little is known on whether inbreeding depresses male and female fitness to the same extent. However, sex-specific inbreeding depression has been argued to affect the evolution of selfing rates in simultaneous hermaphrodites and provides a powerful approach to test whether selection is stronger in males than in females, which is predicted to be the consequence of sexual selection. We tested for sex-specific inbreeding depression in the simultaneously hermaphroditic freshwater snail Physa acuta by comparing the reproductive performance of both sex functions between selfed and outcrossed focal individuals under different levels of male-male competition. We found that inbreeding impaired both male and female reproductive success and that the magnitude of male inbreeding depression exceeded female inbreeding depression when the opportunity for sperm competition was highest. Our study provides the first evidence for sex-specific inbreeding depression in a hermaphroditic animal and highlights the importance of considering the level of male-male competition when assessing sex differences in inbreeding depression. K E Y W O R D S :Female fecundity, inbreeding depression, paternity success, Physa acuta, sexual selection, sperm competition.

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Determinants of female fecundity in a simultaneous hermaphrodite: the role of polyandry and food availability

Cited by 25 publications

References 81 publications

Strategic mating effort in a simultaneous hermaphrodite

Strategic mating effort in a simultaneous hermaphrodite

Sex Allocation Adjustment to Mating Group Size in a Simultaneous Hermaphrodite

Sex-Specific Inbreeding Depression Depends on the Strength of Male-Male Competition

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