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Abstract The factors contributing to evolution of androdioecy, the coexistence of hermaphrodites and males such as in Caenorhabditis elegans, remains poorly known. However, nematodes exhibit androdioecy in at last 13 genera with the predatory genus Pristionchus having seven independent transitions towards androdioecy. Nonetheless, associated genomic architecture and sex determination mechanisms are largely known from Caenorhabditis. Here, studying 47 Pristionchus species, we observed repeated chromosome evolution which abolished the ancestral XX/XO sex chromosome system. Two phylogenetically unrelated androdioecious Pristionchus species have no genomic differences between sexes and mating hermaphrodites with males resulted in hermaphroditic offspring only. We demonstrate that stochastic sex determination is influenced by temperature in P. mayeri and P. entomophagus, and CRISPR engineering indicated a conserved role of the transcription factor TRA-1 in P. mayeri. Chromosome-level genome assemblies and subsequent genomic analysis of related Pristionchus species revealed stochastic sex determination to be derived from XY sex chromosome systems through sex chromosome-autosome fusions. Thus, rapid karyotype evolution, sex chromosome evolution and evolvable sex determination mechanisms are general features of this genus, and represent a dynamic background against which androdioecy has evolved recurrently. Future studies might indicate that stochastic sex determination is more common than currently appreciated.

To start with an infinitely repeated game of supply chains of public goods, a stout reciprocity mechanism is introduced into income games to build a matric dynamic equation. The conventional evolutionary game method is employed to propose a model called the evolutionary game for the cooperative strategy of both the manufacturer and the seller groups in the supply chain of public goods. Also, white Gaussian noise (WGN) is added to reflect random interference in the evolution process. Then, a stochastic dynamic system is established, and Ito’s differential equation is used to analyze both sides’ strategy evolution in a game, interpret changes in system stability when random disturbance is added, and finally test the influence of different situations on the system stability by running a numerical simulation. The research shows that the stronger the reciprocity coefficient is, and the system is subjected to random interference, the greater the strategy choice change in players’ decision-making procedures when the repeated game of public goods is conducted.

Abstract Background The first metazoan genome sequenced, that of Caenorhabditis elegans, has motivated animal genome evolution studies. To date > 50 species from the genus Caenorhabditis have been sequenced, allowing research on genome variation. Results In the present study, we describe a new gonochoristic species, Caenorhabditis niphades n. sp., previously referred as C. sp. 36, isolated from adult weevils (Niphades variegatus), with whom they appear to be tightly associated during its life cycle. Along with a species description, we sequenced the genome of C. niphades n. sp. and produced a chromosome-level assembly. A genome comparison highlighted that C. niphades n. sp. has the smallest genome (59 Mbp) so far sequenced in the Elegans supergroup, despite being closely related to a species with an exceptionally large genome, C. japonica. Conclusions The compact genome of C. niphades n. sp. can serve as a key resource for comparative evolutionary studies of genome and gene number expansions in Caenorhabditis species.

In most species, sex is determined by genetic or environmental factors. Here, the authors present evidence that sex determination in Bursaphelenchus nematodes is instead likely to be regulated by a random, epigenetic mechanism.

We developed a repeated quantum game of public goods by using quantum entanglement and strong reciprocity mechanisms. Utilizing the framework of quantum game analysis, a comparative investigation incorporating both entangled and non-entangled states reveals that the player will choose a fully cooperative strategy when the expected cooperation strategy of the competitor exceeds a certain threshold. When the entanglement of states is not considered, the prisoner’s dilemma still exists, and the cooperating party must bear the cost of defactoring the quantum strategy themselves; when considering the entanglement of states, the benefits of both parties in the game are closely related, forming a community of benefits. By signing a strong reciprocity contract, the degree of cooperation between the game parties can be considered using the strong reciprocity entanglement contract mechanism. The party striving to cooperate does not have to bear the risk of the other party’s defector, and to some extent, it can solve the prisoner’s dilemma problem. Finally, taking the public goods green planting industry project as an example, by jointly entrusting a third party to determine and sign a strong reciprocity entanglement contract, both parties can ensure a complete quantum strategy to maximize cooperation and achieve Pareto optimality, ultimately enabling the long-term and stable development of the public goods industry project.

Kikuchi et al. sequence the genome of the fatal tapeworm Sparganum proliferum and a closely related non–life-threatening tapeworm Spirometra erinaceieuropaei, and describe its genomic features suggesting the natural history and molecular mechanisms underlying pathogenicity. Their findings indicate that nonordinal extracellular matrix coordination is important for its asexual reproduction, and suggest that loss of sexual maturity contributes to the fatal pathogenicity of S. proliferum to humans.

Abstract Caenorhabditis auriculariae, which was morphologically described in 1999, was re-isolated from a Platydema mushroom-associated beetle. Based on the re-isolated materials, some morphological characteristics were re-examined and ascribed to the species. In addition, to clarify phylogenetic relationships with other Caenorhabditis species and biological features of the nematode, the whole genome was sequenced and assembled into 109.5 Mb with 16,279 predicted protein-coding genes. Molecular phylogenetic analyses based on ribosomal RNA and 269 single-copy genes revealed the species is closely related to C. sonorae and C. monodelphis placing them at the most basal clade of the genus. C. auriculariae has morphological characteristics clearly differed from those two species and harbours a number of species-specific gene families, indicating its usefulness as a new outgroup species for Caenorhabditis evolutionary studies. A comparison of carbohydrate-active enzyme (CAZy) repertoires in genomes, which we found useful to speculate about the lifestyle of Caenorhabditis nematodes, suggested that C. auriculariae likely has a life-cycle with tight-association with insects.

Based on a tripartite game model among suppliers of public goods, consumers, and the government, a tripartite repeated game model is constructed to analyze the evolution mechanism of which suppliers supply at low prices, consumers purchase, and the government provides incentives, and to establish the dynamics system of a repeated game. The equilibrium points of the evolutionary game are solved, and among them, the equilibrium points are found to satisfy the parameter conditions of ESS. The numerical simulation is employed to verify the impact of penalty coefficients and discount factors on the stability of strategies, which are adopted by the three players in a tripartite repeated game on public goods, and scenario analyses are conducted. The research results of this paper could provide a reference for the government, suppliers, and consumers to make rapid decisions, who are in the supply chain of public goods, especially quasi-public goods, such as coal, water, electricity, and gas, and help them to obtain stable incomes and then ensure the stable operation of the market.