Dimorphism in cryptophytes—The case of Teleaulax amphioxeia/Plagioselmis prolonga and its ecological implications

Growing evidence suggests that sexual reproduction might be common in unicellular organisms, but observations are sparse. Limited knowledge of sexual reproduction constrains understanding of protist ecology. Although Teleaulax amphioxeia and Plagioselmis prolonga are common marine cryptophytes worldwide, and are also important plastid donors for some kleptoplastic ciliates and dinoflagellates, the ecology and development of these protists are poorly known. We demonstrate that P. prolonga is the haploid form of the diploid T. amphioxeia and describe the seasonal dynamics of these two life stages. The diploid T. amphioxeia dominates during periods of high dissolved inorganic nitrogen (DIN) and low irradiance, temperature, and grazing (winter and early spring), whereas the haploid P. prolonga becomes more abundant during the summer, when DIN is low and irradiance, temperature, and grazing are high. Dimorphic sexual life cycles might explain the success of this species by fostering high genetic diversity and enabling endurance in adverse conditions.

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Effects of Surface Soil Removal on Dynamics of Dissolved Inorganic Nitrogen in a Snow-Dominated Forest

The Scientific World JOURNAL ◽

10.1100/tsw.2001.311 ◽

2001 ◽

Vol 1 ◽

pp. 527-533 ◽

Cited By ~ 15

Author(s):

M. Ozawa ◽

H. Shibata ◽

F. Satoh ◽

K. Sasa

Keyword(s):

Soil Solution ◽

Soil Removal ◽

Surface Soil ◽

Water Movement ◽

Inorganic Nitrogen ◽

Seasonal Fluctuation ◽

Early Spring ◽

Dissolved Inorganic Nitrogen ◽

And Control ◽

Treated Site

To clarify the effect of vegetation and surface soil removal on dissolved inorganic nitrogen (N) dynamics in a snow-dominated forest soil in northern Japan, the seasonal fluctuation of N concentrations in soil solution and the annual flux of N in soil were investigated at a treated site (in which surface soil, including understory vegetation and organic and A horizons, was removed) and control sites from July 1998 to June 2000. Nitrate (NO3–) concentration in soil solution at the treated site was significantly higher than that of the control in the no-snow period, and it was decreased by dilution from melting snow. The annual net outputs of NO3–from soil at the treated site and control sites were 257 and –12 mmol m–2year–1, and about 57% of the net output at the treated site occurred during the snowmelt period. NO3–was transported from the upper level to the lower level of soil via water movement during late autumn and winter, and it was retained in soil and leached by melt water in early spring. Removing vegetation and surface soil resulted in an increase in NO3–concentration of soil solution, and snowmelt strongly affected the NO3–leaching from treated soil and the NO3–restoration process in a snow-dominated region.

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Sexual conflict and the evolution of asexuality at low population densities

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.1280 ◽

2016 ◽

Vol 283 (1841) ◽

pp. 20161280 ◽

Cited By ~ 12

Author(s):

Nina Gerber ◽

Hanna Kokko

Keyword(s):

Sexual Harassment ◽

Sexual Reproduction ◽

Sexual Conflict ◽

Life Cycles ◽

Sexual Life ◽

Relative Advantage ◽

Male Mating ◽

Population Densities ◽

Asexual Populations ◽

Sexual Life Cycle

Theories for the evolution of sex rarely include facultatively sexual reproduction. Sexual harassment by males is an underappreciated factor: it should at first sight increase the relative advantage of asexual reproduction by increasing the cost of sex. However, if the same females can perform either sexual or asexual life cycles, then females trying to reproduce asexually may not escape harassment. If resisting male harassment is costly, it might be beneficial for a female to accept a mating and undertake a sexual life cycle rather than ‘insist’ on an asexual one. We investigate the effects of sexual harassment on the maintenance of sex under different population densities. Our model shows that resisting matings pays off at low population densities, which leads to the complete extinction of males, and thus to the evolution of completely asexual populations. Facultative sex persists in a narrow range of slightly higher densities. At high densities, selection favours giving up resisting male mating attempts and thus sexual reproduction takes over. These interactions between the outcomes of sexual conflict and population density suggest an explanation for the rarity of facultative sex and also patterns of geographical parthenogenesis, where marginal environments with potentially low densities are associated with asexuality.

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Evolutionary mysteries in meiosis

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2016.0001 ◽

2016 ◽

Vol 371 (1706) ◽

pp. 20160001 ◽

Cited By ~ 50

Author(s):

Thomas Lenormand ◽

Jan Engelstädter ◽

Susan E. Johnston ◽

Erik Wijnker ◽

Christoph R. Haag

Keyword(s):

Sexual Reproduction ◽

Life Cycles ◽

Sexual Life ◽

Model Organisms ◽

Evolutionary Significance ◽

Crossover Interference ◽

Selective Pressures

Meiosis is a key event of sexual life cycles in eukaryotes. Its mechanistic details have been uncovered in several model organisms, and most of its essential features have received various and often contradictory evolutionary interpretations. In this perspective, we present an overview of these often ‘weird’ features. We discuss the origin of meiosis (origin of ploidy reduction and recombination, two-step meiosis), its secondary modifications (in polyploids or asexuals, inverted meiosis), its importance in punctuating life cycles (meiotic arrests, epigenetic resetting, meiotic asymmetry, meiotic fairness) and features associated with recombination (disjunction constraints, heterochiasmy, crossover interference and hotspots). We present the various evolutionary scenarios and selective pressures that have been proposed to account for these features, and we highlight that their evolutionary significance often remains largely mysterious. Resolving these mysteries will likely provide decisive steps towards understanding why sex and recombination are found in the majority of eukaryotes. This article is part of the themed issue ‘Weird sex: the underappreciated diversity of sexual reproduction’.

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Unholy marriages and eternal triangles: how competition in the mushroom life cycle can lead to genomic conflict

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2015.0533 ◽

2016 ◽

Vol 371 (1706) ◽

pp. 20150533 ◽

Cited By ~ 9

Author(s):

Sabine Vreeburg ◽

Kristiina Nygren ◽

Duur K. Aanen

Keyword(s):

Life Cycle ◽

Sexual Reproduction ◽

Male Gamete ◽

Life Cycles ◽

Spore Formation ◽

Sexual Life ◽

Gamete Fusion ◽

Extramarital Affairs ◽

Living Apart Together ◽

Genomic Conflict

In the vast majority of sexual life cycles, fusion between single-celled gametes is directly followed by nuclear fusion, leading to a diploid zygote and a lifelong commitment between two haploid genomes. Mushroom-forming basidiomycetes differ in two key respects. First, the multicellular haploid mating partners are fertilized in their entirety, each cell being a gamete that simultaneously can behave as a female, i.e. contributing the cytoplasm to a zygote by accepting nuclei, and a male gamete, i.e. only donating nuclei to the zygote. Second, after gamete union, the two haploid genomes remain separate so that the main vegetative stage, the dikaryon, has two haploid nuclei per cell. Only when the dikaryon produces mushrooms, do the nuclei fuse to enter a short diploid stage, immediately followed by meiosis and haploid spore formation. So in basidiomycetes, gamete fusion and genome mixing (sex) are separated in time. The ‘living apart together’ of nuclei in the dikaryon maintains some autonomy for nuclei to engage in a relationship with a different nucleus. We show that competition among the two nuclei of the dikaryon for such ‘extramarital affairs’ may lead to genomic conflict by favouring genes beneficial at the level of the nucleus, but deleterious at that of the dikaryon. This article is part of the themed issue ‘Weird sex: the underappreciated diversity of sexual reproduction’.

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Definitions and concepts of reproductive biology of diatoms (terminological glossary)

Novosti sistematiki nizshikh rastenii ◽

10.31111/nsnr/2017.51.71 ◽

2017 ◽

Vol 51 ◽

pp. 71-105 ◽

Cited By ~ 3

Author(s):

N. A. Davidovich

Keyword(s):

Mating System ◽

Sexual Reproduction ◽

Reproductive Biology ◽

World Literature ◽

Russian Literature ◽

Life Cycles ◽

Transfer Of Knowledge ◽

Research Experience ◽

Key Terms

The absence of a conceptual terminology, sufficiently developed and widely accepted in the Russian literature, significantly hinders progress in the field of reproductive biology of diatoms, restricts communication and debate, prevents training and transfer of knowledge. The present work is an attempt, based on world literature and our own research experience, to summarize, systematize, add, and clarify the existing terms, concepts and definitions related to research which are focused on sex and sexual reproduction in diatoms. A glossary of key terms (more than 200, including synonyms) is provided. Terms refer to diatom reproductive biology, life cycles, fertilization, mating system, gender (including inheritance and determination of sex, as well as inheritance associated with sex). Contradictions between possible interpretations of certain terms are briefly discussed.

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Characteristics of Non-Point Source N Export via Surface Runoff from Sloping Croplands in Northeast China

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.347-353.2302 ◽

2011 ◽

Vol 347-353 ◽

pp. 2302-2307 ◽

Cited By ~ 1

Author(s):

Hong Xiang Wang ◽

Yi Shi ◽

Jian Ma ◽

Cai Yan Lu ◽

Xin Chen

Keyword(s):

Point Source ◽

Surface Runoff ◽

Rainfall Intensity ◽

Inorganic Nitrogen ◽

Rainfall Amount ◽

Organic N ◽

Dissolved Inorganic Nitrogen ◽

Slope Gradient ◽

N Loss ◽

Total N

A field experiment was conducted to study the characteristics of non-point source nitrogen (N) in the surface runoff from sloping croplands and the influences of rainfall and cropland slope gradient. The results showed that dissolved total N (DTN) was the major form of N in the runoff, and the proportion occupied by dissolved inorganic nitrogen (DIN) ranged from 45% to 85%. The level of NH4+-N was generally higher than the level of NO3--N, and averaged at 2.50 mg·L-1and 1.07 mg·L-1respectively. DIN was positively correlated with DTN (R2=0.962). Dissolved organic N (DON) presented a moderate seasonal change and averaged at 1.40 mg·L-1. Rainfall amount and rainfall intensity significantly affected the components of DTN in the runoff. With the increase of rainfall amount and rainfall intensity, the concentrations of DTN, NH4+-N and NO3--N presented a decreased trend, while the concentration of DON showed an increased trend. N loss went up with an increase in the gradient of sloping cropland, and was less when the duration was longer from the time of N fertilization.fertilization.

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SIMULATION AND EXPERIMENT OF EXTINCTION OR ADAPTATION OF BIOLOGICAL SPECIES AFTER TEMPERATURE CHANGES

International Journal of Modern Physics C ◽

10.1142/s0129183105007194 ◽

2005 ◽

Vol 16 (03) ◽

pp. 389-392 ◽

Cited By ~ 4

Author(s):

D. STAUFFER ◽

H. ARNDT

Keyword(s):

Sexual Reproduction ◽

Temperature Change ◽

Biological Species ◽

Biological Aging ◽

Heterotrophic Flagellates ◽

Temperature Changes ◽

Penna Model ◽

Simulation And Experiment ◽

Unicellular Organisms

Can unicellular organisms survive a drastic temperature change, and adapt to it after many generations? In simulations of the Penna model of biological aging, both extinction and adaptation were found for asexual and sexual reproduction as well as for parasex. These model investigations are the basis for the design of evolution experiments with heterotrophic flagellates.

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