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opencc-zeroMar 2024View details →

Data from: Do pheromones contribute to the persistence of asexual populations in a facultatively parthenogenetic stick insect?

Facultative parthenogenesis is a form of reproduction in which females can either lay unfertilised eggs that typically develop into female offspring only, or mate and lay fertilised eggs that develop into male and female offspring. Facultative parthenogens often occur in mixed-sex populations where reproduction is mostly sexual, and all-female populations where reproduction is asexual. How all-female populations avoid invasion by males remains unknown. Here, we investigated the role of volatile and non-volatile (cuticular hydrocarbons, CHCs) pheromones in the persistence of all-female populations in the facultatively parthenogenetic stick insect, Megacrania batesii. We found that M. batesii exhibits slight sexual dimorphism in antenna morphology, and behavioural assays provided little evidence that males could locate females solely by volatile pheromones. However, CHC profiles differed substantially between different types of females. Analysis of CHC structure and abundance indicated a clear genetic difference between females from all-female versus mixed-sex populations, as well as a maternal effect of female parthenogenesis versus sexual development. Together, our results suggest that males might rely more on close-range chemical cues to differentiate females, and chemical communication could play a role in the persistence of all-female populations.

opencc-zeroMay 2022View details →

Asymmetric density-dependent competition does not contribute to the maintenance of sex in a mixed population of sexual and asexual Potamopyrgus antipodarum

Asexual reproduction is expected to have a two-fold reproductive advantage over sexual reproduction, owing to the cost of producing males in sexual subpopulations. The persistence of sexual females thus requires an advantage to sexual reproduction, at least periodically. Here we tested the hypothesis that asexual females are more sensitive to limited resources. Under this idea, fluctuations in the availability of resources (per capita) could periodically favor sexual females when resources become limited. We combined sexual and asexual freshwater snails (Potamopyrgus antipodarum) together in nylon mesh enclosures at three different densities in an outdoor mesocosm. After one month, we counted the brood size of fertile female snails. We found that fecundity declined significantly with increasing density. However, sexual females did not produce more offspring than asexual females at any of the experimental densities. Our results thus suggest that the cost of sexual reproduction in P. antipodarum is not ameliorated by periods of intense resource competition.

opencc-zeroAug 2021View details →

Greater reproductive assurance of asexual plant compared to sexual relative in a low density sympatric population – experimental evidence for pollen limitation

This dataset contains data from a common garden experiment described in the paper: "Mráz P, Mrázová V. 2021. Greater reproductive assurance of asexual plant compared to sexual relative in a low density sympatric population – experimental evidence for pollen limitation. Journal of Evolutionary Ecology ". We compared the level and stability of reproductive assurance between sexual self-incompatible and asexual autonomously apomictic plants of Hieracium alpinum (Asteraceae) cultivated in a sympatric low-density population with two levels of spatial clumping of sexual plants. Overall, we found that the realized seed set (i.e. proportion of well developed seeds per capitulum) of asexuals was ca. 3-times greater than that of sexuals (83% versus 27%), while the variance of this trait expressed as coefficient of variation was ca. 4-times smaller in asexuals compared to sexuals (19% versus 83%). Solitary sexual plants had more than 2-times lower realized seed set when compared to clumps composed of two spatially close (20-30 cm) sexual plants (13% versus 34%). Our study provides experimental evidence for benefit of uniparental reproduction of asexuals in a sympatric situation when the availability of mates is limited. This, together with unpredictability of pollinator environment could provide autonomous apomicts with an ultimate demographic superiority during colonization reflected in geographical parthenogenesis observed in this species.

publicMay 2022View details →

Asymmetric density-dependent competition does not contribute to the maintenance of sex in a mixed population of sexual and asexual Potamopyrgus antipodarum

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publicAug 2021View details →

Greater reproductive assurance of asexual plant compared to sexual relative in a low density sympatric population – experimental evidence for pollen limitation

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opencc-zeroMar 2020View details →

After a catastrophe, a little bit of sex is better than nothing: genetic consequences of a major earthquake on asexual and sexual populations

Catastrophic events can have profound effects on the demography of a population and consequently, on genetic diversity. The dynamics of post-catastrophic recovery as well as the role of sexual versus asexual reproduction in buffering the effects of massive perturbations remain poorly understood, in part because the opportunity to document genetic diversity before and after such events is rare. Six natural (purely sexual) and seven cultivated (mainly clonal due to farming practices) populations of the red alga Agarophyton chilense were surveyed along the Chilean coast before, in the days after and two years after the 8.8 magnitude earthquake in 2010. The genetic diversity of sexual populations appeared sensitive to this massive perturbation, notably through the loss of rare alleles immediately after the earthquake. By 2012, the levels of diversity returned to those observed before the catastrophe, probably due to migration. In contrast, enhanced rates of clonality in cultivated populations conferred a surprising ability to buffer the instantaneous loss of diversity. After the earthquake, farmers increased the already high rate of clonality to maintain the few surviving beds, but most of them collapsed rapidly. Contrasting fates between sexual and clonal populations suggest that betting on strict clonality to sustain production is risky, probably because this extreme strategy hampered adaptation to the brutal environmental perturbation induced by the catastrophe.

opencc-zeroMar 2024View details →

Data from: To lose is to win: long-term co-occurrence of two asexual populations realized by a dormant strategy of the inferior competitor

Asexual organisms are ubiquitous. While they are the same single species with the same ecological requirements, multiple asexual genotypes within a species are often found in a single habitat. Niche partitioning in time and space among genotypes has been proposed to explain this phenomenon. However, it is not clear whether these different genotypes co-occur in the long term. Therefore, we examined the population dynamics of two asexual Daphnia cf. pulex genotypes (JPN1 and JPN2) over nine years in a small mountain lake. These two genotypes consistently occurred in the same seasons and layers, suggesting that niche partitioning cannot explain their long-term co-occurrence. The abundance of JPN1 was typically higher in most years. However, the abundance of dormant eggs in lake sediments was at the same level between the genotypes. The laboratory experiment showed that JPN1 excluded JPN2. However, many JPN2 individuals produced the dormant eggs before JPN1 competitively excluded them from the experiment. Furthermore, the competitively inferior JPN2 produced the dormant eggs abundantly in the medium containing a crowding cue from JPN1. However, no such trend was observed for JPN1. These results showed that the competitively inferior asexual genotype could maintain the population with the competitively superior genotype for a long period of time because it had the ability to detect the increase in competitors and produce the dormant eggs each year before being competitively eliminated. Based on these results, we suggest that the variation in the genotype-specific response in dormant egg production to environmental change plays a key role in the long-term co-occurrence of different asexual genotypes in single habitats.

publicMar 2020View details →

After a catastrophe, a little bit of sex is better than nothing: genetic consequences of a major earthquake on asexual and sexual populations

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publicMar 2024View details →

Data from: To lose is to win: long-term co-occurrence of two asexual populations realized by a dormant strategy of the inferior competitor

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publicFeb 2021View details →

Genomic population structure of sympatric sexual and asexual populations in a parasitic wasp, Meteorus pulchricornis (Hymenoptera: Braconidae), inferred from six hundred single-nucleotide polymorphism loci

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opencc-zeroDec 2012View details →

Data from: Long-term dynamics of adaptation in asexual populations

Experimental studies of evolution have increased greatly in recent years, stimulated by the growing power of genomic tools. However, organismal fitness remains the ultimate metric for interpreting these experiments, and the dynamics of fitness remain poorly understood over long timescales. Here, we examine fitness trajectories for 12 Escherichia coli populations during 50,000 generations. Mean fitness appears to increase without bound, consistent with a power law. We also derive this power-law relation theoretically by incorporating clonal interference and diminishing-returns epistasis into a dynamical model of changes in mean fitness over time.

opencc-zeroDec 2012View details →

Data from: Infection dynamics in coexisting sexual and asexual host populations: support for the Red Queen hypothesis

The persistence of sexual reproduction is a classic problem in evolutionary biology. The problem stems from the fact that, all else equal, asexual lineages should rapidly replace coexisting sexual individuals due to the cost of producing males in sexual populations. One possible countervailing advantage to sexual reproduction is that, on average, outcrossed offspring are more resistant than common clones to coevolving parasites, as predicted under the Red Queen hypothesis. In the present study, we evaluated the prevalence of infection by a sterilizing trematode (Microphallus sp.) in a natural population of freshwater snails that was composed of both sexual and asexual individuals (Potamopyrgus antipodarum). More specifically, we compared the frequency of infection in sexual and asexual individuals over a five-year period at four sites at a natural glacial lake (Lake Alexandrina, South Island, New Zealand). We found that at most sites and over most years, the sexual population was less infected than the coexisting asexual population. Moreover, the frequency of uninfected sexual females was periodically greater than two times the frequency of uninfected asexual females. These results give clear support for a fluctuating parasite-mediated advantage to sexual reproduction in a natural population.

Figure 4 in Genetic variation within and among asexual populations of Porphyra umbilicalis Kützing (Bangiales, Rhodophyta) in the Gulf of Maine, USA

Figure 4: Four possible scenarios that explain colonization of the NW Atlantic from the NE Atlantic that attempt to reconcile data from this study and others that find no sexual reproduction in the NW Atlantic.

Figure 1 in Genetic variation within and among asexual populations of Porphyra umbilicalis Kützing (Bangiales, Rhodophyta) in the Gulf of Maine, USA

Figure 1: Collection localities of Porphyra umbilicalis populations in New Hampshire and Maine, USA. Pie charts show frequencies of genotypes in each population collection. The sum of genotype frequencies among all populations is also given.

Figure 2 in Genetic variation within and among asexual populations of Porphyra umbilicalis Kützing (Bangiales, Rhodophyta) in the Gulf of Maine, USA

Figure 2: Principal Components Analysis based on Nei's genetic distances among Porphyra umbilicalis genotypes. The genotypes as well as the individuals assayed with the genotype are given (DP =Dover Point, FS=Fort Stark, NL= Nubble Light, QH =Quoddy Head, RSP=Reid State Park, and W =Wiscasset).

Figure 3 in Genetic variation within and among asexual populations of Porphyra umbilicalis Kützing (Bangiales, Rhodophyta) in the Gulf of Maine, USA

Figure 3: Principal components analysis based on Nei's unbiased genetic distances among populations of Porphyra umbilicalis in the Gulf of Maine, USA.

opencc-zeroNov 2021View details →

Data files for: Hazardous loss of genetic diversity through selective sweeps in asexual populations

With the two-fold cost of sex, derived asexual organisms have an immediate reproductive advantage over their sexual sisters. Yet the "twiggy'' phylogenetic distribution of asexual lineages implies that they go extinct relatively quickly over evolutionary time. Meanwhile, bacteria and archaea have persisted for billions of years without requiring sexual reproduction. A simple explanation for this difference is that prokaryotes have very large population sizes that are not subject to the accumulation of deleterious mutations, but this implies that drift and mutational meltdown dominate derived asexual populations. We explored a different hazard, quantifying the degree to which genetic variation is lost in asexual populations experiencing selective sweeps. Even though large populations generate diversity by mutation during sweeps, we find that populations that are safe from mutational meltdown may still be reduced to dangerous effective population sizes by sweeps. Thus, ironically, adaptation itself reduces further adaptive potential and may predispose asexual populations to extinction. Our data give results for the probability of mutational meltdown across various population sizes, the critical population size required to avoid meltdown, and the effect of selective sweeps on heterozygosity. Analytical predictions are confirmed by simulation. We also derive a simple approximation for the effective population size after a hard sweep, and quantify the impact of recent sweeps on evolutionary rescue. These factors may help to explain the phylogenetic twigginess of asexuals, the maintenance of sex and recombination, and the evolutionary persistence of prokaryotes.

publicNov 2014View details →

Data from: Long-term dynamics of adaptation in asexual populations

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publicSep 2017View details →

Data from: Infection dynamics in coexisting sexual and asexual host populations: support for the Red Queen hypothesis

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