scholarly journals Unravelling anisogamy: egg size and ejaculate size mediate selection on morphology in free-swimming sperm

2016 ◽  
Vol 283 (1834) ◽  
pp. 20160671 ◽  
Author(s):  
Keyne Monro ◽  
Dustin J. Marshall
Keyword(s):  
Egg Size ◽  
Free Swimming ◽  
External Fertilization ◽  
Selection Pressures ◽  
Sperm Density ◽  
Ejaculate Size ◽  
Selection For ◽  
The Stability ◽  
Multicellular Organisms ◽  
Sperm Size

Gamete dimorphism (anisogamy) defines the sexes in most multicellular organisms. Theoretical explanations for its maintenance usually emphasize the size-related selection pressures of sperm competition and zygote survival, assuming that fertilization of all eggs precludes selection for phenotypes that enhance fertility. In external fertilizers, however, fertilization is often incomplete due to sperm limitation, and the risk of polyspermy weakens the advantage of high sperm numbers that is predicted to limit sperm size, allowing alternative selection pressures to target free-swimming sperm. We asked whether egg size and ejaculate size mediate selection on the free-swimming sperm of Galeolaria caespitosa , a marine tubeworm with external fertilization, by comparing relationships between sperm morphology and male fertility across manipulations of egg size and sperm density. Our results suggest that selection pressures exerted by these factors may aid the maintenance of anisogamy in external fertilizers by limiting the adaptive value of larger sperm in the absence of competition. In doing so, our study offers a more complete explanation for the stability of anisogamy across the range of sperm environments typical of this mating system and identifies new potential for the sexes to coevolve via mutual selection pressures exerted by gametes at fertilization.

scholarly journals Fisher vs. The Worms: Extraordinary Sex Ratios in Nematodes and the Mechanisms That Produce Them

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1793
Author(s):  
Justin Van Goor ◽  
Diane C. Shakes ◽  
Eric S. Haag
Keyword(s):  
Sex Ratio ◽  
Sperm Competition ◽  
Sex Chromosomes ◽  
Sex Ratios ◽  
Environmental Sex Determination ◽  
Fitness Advantage ◽  
Selection For ◽  
Facultative Parthenogenesis ◽  
Multicellular Organisms ◽  
Inbred Populations

Parker, Baker, and Smith provided the first robust theory explaining why anisogamy evolves in parallel in multicellular organisms. Anisogamy sets the stage for the emergence of separate sexes, and for another phenomenon with which Parker is associated: sperm competition. In outcrossing taxa with separate sexes, Fisher proposed that the sex ratio will tend towards unity in large, randomly mating populations due to a fitness advantage that accrues in individuals of the rarer sex. This creates a vast excess of sperm over that required to fertilize all available eggs, and intense competition as a result. However, small, inbred populations can experience selection for skewed sex ratios. This is widely appreciated in haplodiploid organisms, in which females can control the sex ratio behaviorally. In this review, we discuss recent research in nematodes that has characterized the mechanisms underlying highly skewed sex ratios in fully diploid systems. These include self-fertile hermaphroditism and the adaptive elimination of sperm competition factors, facultative parthenogenesis, non-Mendelian meiotic oddities involving the sex chromosomes, and environmental sex determination. By connecting sex ratio evolution and sperm biology in surprising ways, these phenomena link two “seminal” contributions of G. A. Parker. 

scholarly journals Cooperation and the evolution of intelligence

2012 ◽  
Vol 279 (1740) ◽  
pp. 3027-3034 ◽  
Author(s):  
Luke McNally ◽  
Sam P. Brown ◽  
Andrew L. Jackson
Keyword(s):  
Decision Making ◽  
Social Interactions ◽  
Cognitive Abilities ◽  
Artificial Neural Network Model ◽  
Social Intelligence ◽  
Arms Race ◽  
Selection Pressures ◽  
Social Intelligence Hypothesis ◽  
The Social ◽  
Selection For

The high levels of intelligence seen in humans, other primates, certain cetaceans and birds remain a major puzzle for evolutionary biologists, anthropologists and psychologists. It has long been held that social interactions provide the selection pressures necessary for the evolution of advanced cognitive abilities (the ‘social intelligence hypothesis’), and in recent years decision-making in the context of cooperative social interactions has been conjectured to be of particular importance. Here we use an artificial neural network model to show that selection for efficient decision-making in cooperative dilemmas can give rise to selection pressures for greater cognitive abilities, and that intelligent strategies can themselves select for greater intelligence, leading to a Machiavellian arms race. Our results provide mechanistic support for the social intelligence hypothesis, highlight the potential importance of cooperative behaviour in the evolution of intelligence and may help us to explain the distribution of cooperation with intelligence across taxa.

Selection for soyabeans with high and environmentally stable lutein concentrations

2014 ◽  
Vol 12 (S1) ◽  
pp. S12-S16 ◽  
Author(s):  
Krishna Hari Dhakal ◽  
Myoung-Gun Choung ◽  
Young-Sun Hwang ◽  
Felix B. Fritschi ◽  
J. Grover Shannon ◽  
...  
Keyword(s):  
Human Health ◽  
High Stability ◽  
Planting Dates ◽  
Early Maturity ◽  
Breeding Objective ◽  
Late Maturity ◽  
Selection For ◽  
High Concentrations ◽  
The Stability ◽  
Nutritional Benefits

Lutein has significant nutritional benefits for human health. Therefore, enhancing soybean lutein concentrations is an important breeding objective. However, selection for soybeans with high and environmentally stable lutein concentrations has been limited. The objectives of this study were to select soybeans with high seed lutein concentrations and to determine the stability of lutein concentrations across environments. A total of 314 genotypes were screened and 18 genotypes with high lutein concentrations and five genotypes with low lutein concentrations were selected for further examination. These 23 genotypes and two check varieties were evaluated under six environments (two planting dates for 2 years at one location and two planting dates for 1 year at another location). Lutein concentrations were influenced by genotype, environment and genotype × environment interactions. Genotypes with late maturity and low lutein concentrations were more stable than those with early maturity and high concentrations. Early (May) planting resulted in greater lutein concentrations than late (June) planting. Among the genotypes evaluated, PI603423B (7.7 μg/g) and PI89772 (5.8 μg/g) had the greatest mean lutein concentrations and exhibited medium and high stability across the six environments, respectively. Thus, these genotypes may be useful for breeding soybeans with high and stable seed lutein concentrations.

Stability indicatrices of nonnegative matrices and some of their applications in problems of biology and epidemiology

2019 ◽  
Vol 34 (5) ◽  
pp. 269-275
Author(s):  
Valery N. Razzhevaikin
Keyword(s):  
Nonnegative Matrix ◽  
Host Population ◽  
Nonnegative Matrices ◽  
Biological Communities ◽  
Evolutionary Selection ◽  
Evolutionary Optimality ◽  
Selection For ◽  
The Stability ◽  
Series Of Functions

Abstract The method of constructing a stability indicatrix of a nonnegative matrix having the form of a polynomial of its coefficients is presented. The algorithm of construction and conditions of its applicability are specified. The applicability of the algorithm is illustrated on examples of constructing the stability indicatrix for a series of functions widely used in simulation of the dynamics of discrete biological communities, for solving evolutionary optimality problems arising in biological problems of evolutionary selection, for identification of the conditions of the pandemic in a distributed host population.

The Copepodid of Peniculisa Shiinoi Izawa, 1965 (Copepoda, Siphonostomatoida, Pennellidae), a Single Free-Swimming Larval Stage of the Species

Crustaceana ◽  
1997 ◽  
Vol 70 (8) ◽  
pp. 911-919 ◽  
Author(s):  
Kunihiko Izawa
Keyword(s):  
Larval Stage ◽  
Egg Size ◽  
Parasitic Copepod ◽  
Free Swimming ◽  
Nauplius Stage ◽  
Puffer Fish ◽  
Copepodid Stage

AbstractThe copepodid stage of the parasitic copepod Peniculisa shiinoi Izawa, 1965 (Siphonostomatoida, Pennellidae), parasitic on the fins of a puffer fish, Canthigaster rivulatus, is described based on specimens reared from eggs. This is the only free-swimming larval stage of P. shiinoi. The copepodid is distinctly smaller than those of the known pennellids. However, the dispensability of the free-swimming nauplius stage is independent of the egg-size. The copepodid antennae of the pennellids are certainly uniramous. The setation of the rami of the copepodid legs varies among pennellids.

scholarly journals Cry-wolf signals emerging from coevolutionary feedbacks in a tritrophic system

2015 ◽  
Vol 282 (1818) ◽  
pp. 20152169 ◽  
Author(s):  
Atsushi Yamauchi ◽  
Minus van Baalen ◽  
Yutaka Kobayashi ◽  
Junji Takabayashi ◽  
Kaori Shiojiri ◽  
...  
Keyword(s):  
Communication Systems ◽  
Feedback Loops ◽  
Tritrophic System ◽  
Evolution Of Communication ◽  
Herbivore Induced Plant Volatiles ◽  
Plant Signals ◽  
Selection For ◽  
The Stability ◽  
Plant Herbivore ◽  
Heavy Damage

For a communication system to be stable, senders should convey honest information. Providing dishonest information, however, can be advantageous to senders, which imposes a constraint on the evolution of communication systems. Beyond single populations and bitrophic systems, one may ask whether stable communication systems can evolve in multitrophic systems. Consider cross-species signalling where herbivore-induced plant volatiles (HIPVs) attract predators to reduce the damage from arthropod herbivores. Such plant signals may be honest and help predators to identify profitable prey/plant types via HIPV composition and to assess prey density via the amount of HIPVs. There could be selection for dishonest signals that attract predators for protection from possible future herbivory. Recently, we described a case in which plants release a fixed, high amount of HIPVs independent of herbivore load, adopting what we labelled a ‘cry-wolf’ strategy. To understand when such signals evolve, we model coevolutionary interactions between plants, herbivores and predators, and show that both ‘honest’ and ‘cry-wolf’ types can emerge, depending on the assumed plant–herbivore encounter rates and herbivore population density. It is suggested that the ‘cry-wolf’ strategy may have evolved to reduce the risk of heavy damage in the future. Our model suggests that eco-evolutionary feedback loops involving a third species may have important consequences for the stability of this outcome.

scholarly journals Sex allocation in haplodiploids is mediated by egg size: evidence in the spider mite Tetranychus urticae Koch

2010 ◽  
Vol 278 (1708) ◽  
pp. 1054-1063 ◽  
Author(s):  
Emilie Macke ◽  
Sara Magalhães ◽  
Hong Do-Thi Khan ◽  
Anthony Luciano ◽  
Adrien Frantz ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Tetranychus Urticae ◽  
Egg Size ◽  
Spider Mite ◽  
Sex Ratios ◽  
Size Difference ◽  
Adult Size ◽  
External Fertilization ◽  
Offspring Sex Ratio ◽  
Egg Provisioning

Haplodiploid species display extraordinary sex ratios. However, a differential investment in male and female offspring might also be achieved by a differential provisioning of eggs, as observed in birds and lizards. We investigated this hypothesis in the haplodiploid spider mite Tetranychus urticae , which displays highly female-biased sex ratios. We show that egg size significantly determines not only larval size, juvenile survival and adult size, but also fertilization probability, as in marine invertebrates with external fertilization, so that female (fertilized) eggs are significantly larger than male (unfertilized) eggs. Moreover, females with on average larger eggs before fertilization produce a more female-biased sex ratio afterwards. Egg size thus mediates sex-specific egg provisioning, sex and offspring sex ratio. Finally, sex-specific egg provisioning has another major consequence: male eggs produced by mated mothers are smaller than male eggs produced by virgins, and this size difference persists in adults. Virgin females might thus have a (male) fitness advantage over mated females.

An Identifier-Selection Method for Expressway Network Based on Toll Collection Accuracy of Multi-Path

2013 ◽  
Vol 321-324 ◽  
pp. 2260-2264
Author(s):  
Dong Bin Xu ◽  
Shu Zhen Shi ◽  
Hao Zhang
Keyword(s):  
Network Model ◽  
Selection Method ◽  
Basic Information ◽  
Selection Probability ◽  
Selection Scheme ◽  
Running Time ◽  
Candidate Strategy ◽  
Selection For ◽  
Toll Collection ◽  
The Stability

A method for identifier-selection in expressway network is proposed based on toll collection accuracy of multi-path. Using basic information of the expressway network, the network model is built. Toll collection accuracy of the model is computed by the following steps: selection for competitive and valid paths, calculation for selection probability, toll calculation and calculation for toll collection accuracy. Through multi-period and multi-candidate strategy, the identifier-selection scheme is adopted to improve the stability and save the running time. The results verify the rationality and practicality of the method.

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