Evidence for inter-population variation in waiting times in a self-fertilizing flatworm

Giannakara, Athina; Ramm, Steven A.

doi:10.1080/07924259.2020.1732485

Cited by 9 publications

(11 citation statements)

References 54 publications

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“…22 may only self in isolation. In contrast, M. hystrix-thought to be a preferentially outcrossing species, with studies showing costs of self-fertilisation (Ramm et al 2012, Giannakara andRamm 2020) and delayed selfing in isolation, at least in some populations (Ramm et al 2012)-was found to be more plastic than M. pusillum.…”

Section: Discussionmentioning

confidence: 97%

Self-fertilization, but not mating strategy, predicts the evolution of sex allocation plasticity in a hermaphroditic flatworm genus

Singh

Schärer

2020

Preprint

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Local sperm competition (LSC), which occurs when related sperm compete for access to a given set of eggs, can influence sex allocation (SA) in simultaneous hermaphrodites. Different factors that have been predicted to affect LSC—and hence, optimal SA—include the mating strategy (such as reciprocal mating vs. hypodermic insemination) and the ability to self-fertilize. Moreover, the level of LSC experienced could vary temporally and/or spatially, favouring the evolution of SA plasticity. However, it is unknown how the mating strategy and ability to self-fertilize can influence SA and SA plasticity. Here, we explored this by collecting estimates of SA and SA plasticity for seven species of the flatworm genus, Macrostomum, and performing analyses while controlling for phylogeny. While we found substantial interspecific variation in SA, neither the mating strategy nor the ability to self-fertilize had a significant effect on SA. Next, we estimated standardized effect sizes for SA plasticity in response to i) the presence of mating partners and ii) the strength of LSC for each species, and tested if the mating strategy or ability to self-fertilize predicted these effect sizes. We found considerable interspecific variation in SA plasticity, with some species being highly plastic and others showing no significant plasticity. Moreover, self-fertilization predicted SA plasticity with respect to the presence of mating partners, with SA plasticity being lower for self-fertilizing species. Finally, we showed that interspecific variation in SA is nearly three times higher than intraspecific variation, suggesting that SA estimates in field-collected specimens can, at least to some degree, be interpreted as representing interspecific rather than intraspecific variation. Our study suggests that both SA and SA plasticity can evolve rapidly, with self-fertilization being an important predictor for the latter in Macrostomum.

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Section: Discussionmentioning

confidence: 97%

Self-fertilization, but not mating strategy, predicts the evolution of sex allocation plasticity in a hermaphroditic flatworm genus

Singh

Schärer

2020

Preprint

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“…In fact, flatworms collected at different sites show substantial differences in waiting time. While some seem to delay selfing (Ramm et al 2012), flatworms from other locations do not (Giannakara and Ramm 2020).…”

Section: Discussionmentioning

confidence: 99%

Waiting for love but not forever: modelling the evolution of waiting time to selfing in hermaphrodites

Blüml

Ramm

Benthem

et al. 2020

Preprint

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Although mixed mating systems involving both selfing and outcrossing are fairly common in hermaphrodites, it is unclear how they are maintained. In some species, individuals delay self-fertilization while they have not found a mating partner. The ′waiting time′ is subject to two opposing selection pressures: waiting helps to avoid inbreeding depression in offspring by increasing the density-dependent probability to encounter a mate, but also increases the risk of dying before reproduction. In some species waiting time can vary between individuals and be heritable. We therefore used an individual-based model to explore how delayed selfing evolves in response to density and density fluctuations. We find that at high density, when individuals meet often, drift drives waiting time; at intermediate densities, strong inbreeding depression causes waiting time to increase; and at low densities, inbreeding depression is purged, and waiting time approaches zero. Positive feedback loops drive the system to either complete selfing or complete outcrossing. Fluctuating density can slow down convergence to these alternative stable states. However, mixed mating, in the sense of either a stable polymorphism in waiting times, or stable intermediate times, was never observed. Thus, additional factors need to be explored to explain the persistence of delayed selfing.

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“…For example, in 51% of 105 surveyed plant species, populations did not fall into a single matingsystem category (Whitehead et al 2018). Our knowledge on animal populations is sparser, but where selfing rates or the delay in the onset of reproduction when selfing (termed "waiting time", Tsitrone et al 2003) have been estimated across populations, inter-population variation was the norm (Viard et al 1997;Trouvé et al 2003;Bousset et al 2004;Charbonnel et al 2005;Mackiewicz et al 2006;Puurtinen et al 2007;Escobar et al 2009;Kupfernagel et al 2010;Giannakara and Ramm 2020), with few exceptions (Tian-Bi et al 2019). These studies Felmy et al -Variation in selfing propensity 4 demonstrate the importance of characterising species by more than one population estimate, lest crucial differences between populations are overlooked.…”

Section: Introductionmentioning

confidence: 99%

“…The propensity thus consists of a fundamental, individual-level component and a contextual component. This definition emphasises the environmental dependence of realised selfing rates, thereby allowing a separate exploration of Felmy et al -Variation in selfing propensity 6 the individual (supposedly genetic) versus ecological determinants of variation in selfing rates, the need for which recent studies have abundantly shown (Escobar et al 2011;Whitehead et al 2018;Giannakara and Ramm 2020;Latron et al 2020).…”

Section: Introductionmentioning

confidence: 99%

“…For example, in 51% of 105 surveyed plant species, populations fell into several mating-system categories (11). Our knowledge on animal populations is sparser, but where selfing rates or the delay in the onset of reproduction when selfing (termed "waiting time", 12) have been estimated across populations, inter-population variation was the norm (13)(14)(15)(16)(17)(18)(19)(20). It thus is important to characterise species by more than one population estimate, lest crucial differences between populations are overlooked.…”

Section: Introductionmentioning

confidence: 99%

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Selfing-outcrossing as a gradient, not a dichotomy: propensity for selfing varies within a population of hermaphroditic animals

Felmy

Streiff

Jokela

2021

Preprint

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For mating-system evolution, individual-level variation is essential. In self-compatible hermaphrodites, individuals may vary in their lifetime propensity for selfing, which consists of an individual and environmental component. According to the reproductive assurance hypothesis explaining partial selfing, a key environmental factor is mate availability, which fluctuates with population density.We quantified individual variation in selfing propensity in a hermaphroditic snail by manipulating mate availability, recording mating behaviour, estimating selfing rates from progeny arrays, and measuring female lifetime fitness. We found four classes of individuals: pure outcrossers, pure selfers, and two types of plastic individuals. These classes only became apparent in the laboratory; the field population is outcrossing. All classes were present both under low and increased mate availability. This large variation in selfing propensities rendered effects of differential mate availability on selfing rates non-significant despite large effect sizes and sufficient statistical power.We suspect that selfing propensities have a genetic component and when selected on cause mean selfing rates to evolve. We propose that heritable variation in selfing propensities offers a reconciliation between the reproductive assurance hypothesis and its weak empirical support: distributions of selfing propensities vary temporally and spatially, thus obscuring the relationship between population density and realised selfing rates.

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Evidence for inter-population variation in waiting times in a self-fertilizing flatworm

Cited by 9 publications

References 54 publications

Self-fertilization, but not mating strategy, predicts the evolution of sex allocation plasticity in a hermaphroditic flatworm genus

Self-fertilization, but not mating strategy, predicts the evolution of sex allocation plasticity in a hermaphroditic flatworm genus

Waiting for love but not forever: modelling the evolution of waiting time to selfing in hermaphrodites

Selfing-outcrossing as a gradient, not a dichotomy: propensity for selfing varies within a population of hermaphroditic animals

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