Yoh Iwasa

Verified email at kyudai.jp

Department of Biology
Kyushu University



                                         

https://researchid.co/yohiwasa

Yoh Iwasa is a professor emeritus at Kyushu University, Japan. He received PhD from Kyoto University (Theoretical Biophysics) in 1980. After postdoctoral studies at Stanford and Cornell, he joined the faculty of Department of Biology, Kyushu University in 1985. Dr Yoh Iwasa started his carrier in the theoretical study of ecology, evolution, and animal behavior, including the evolution of mate preference, the dynamics of tropical forests, and social-ecological coupled dynamics for ecosystem management. More recently he has also been working on biological rhythm, cancer, development, and immune system, as well as cultural/social studies. He has repeatedly found that the same mathematical and computational methods are applicable to diverse branches of biology, and similar concepts are able to give insights in different subfields of life sciences. Director, Institute of Advanced Study Kyushu University (since 2010). FHM of American Academy of Arts and Sciences (since 2006).

EDUCATION

1975 B Sc Kyoto University, Japan
1980 Ph.D Kyoto University, Japan

RESEARCH INTERESTS

mathematical biology

361

Scopus Publications

24875

Scholar Citations

78

Scholar h-index

269

Scholar i10-index

Scopus Publications

  • On the role of eviction in group living sex changers
    Yoh Iwasa and Sachi Yamaguchi

    Behavioral Ecology and Sociobiology, ISSN: 03405443, eISSN: 14320762, Published: April 2022 Springer Science and Business Media LLC
    Abstract In most sex-changing fishes in coral reefs, a dominant male and multiple females form a mating group (harem). In a few species, the subordinates are simultaneous hermaphrodites that may act as sneakers. In this paper, we ask whether the subordinates in most sex changers choose to be female or whether they are forced to give up their male function to avoid eviction by the harem holder. We consider a game model in which (1) the dominant male evicts some hermaphroditic subordinates if the risk of sperm competition in regard to fertilizing eggs is high, and (2) each subordinate individual chooses its own sex allocation considering the risk of being evicted. In the evolutionarily stable state, the dominant male evicts subordinates only when the subordinates vary greatly in their reproductive resources. All the subordinate individuals are female if the summed male function of the subordinates is smaller than that of the dominant male. Otherwise, all the subordinates are hermaphrodites, and the large individuals have the same male investment but a greatly different female investment, while small individuals have a reduced male investment to avoid eviction risk. We conclude that situations in which the sex allocation of subordinates is affected by the possibility of eviction by the harem holder are rather limited Significance statement We studied the role of eviction in social evolution. In most sex-changing fishes in coral reefs, a dominant male and multiple females form a mating group. In a few species, subordinates are simultaneous hermaphrodites. We asked whether the subordinates are forced to give up their male function to avoid eviction by the harem holder. We examined a game model in which the dominant male evicts hermaphroditic subordinates with a high risk of sperm competition, and each subordinate chooses its own sex allocation considering the eviction risk. We derived mathematical conditions for when subordinates are females or hermaphrodites in the ESS. The model demonstrated that the control by the dominant over subordinate reproductive decisions is rather limited.

  • Escaping stochastic extinction of mutant virus: Temporal pattern of emergence of drug resistance within a host
    Rena Hayashi, Shingo Iwami, and Yoh Iwasa

    Journal of Theoretical Biology, ISSN: 00225193, eISSN: 10958541, Volume: 537, Published: 21 March 2022 Elsevier BV

  • Optimal composition of chloride cells for osmoregulation in a randomly fluctuating environment
    Yuka Uchiyama, Yoh Iwasa, and Sachi Yamaguchi

    Journal of Theoretical Biology, ISSN: 00225193, eISSN: 10958541, Volume: 537, Published: 21 March 2022 Elsevier BV

  • Evolutionary game of life-cycle types in marine benthic invertebrates: Feeding larvae versus nonfeeding larvae versus direct development
    Yoh Iwasa, Yoichi Yusa, and Sachi Yamaguchi

    Journal of Theoretical Biology, ISSN: 00225193, eISSN: 10958541, Volume: 537, Published: 21 March 2022 Elsevier BV

  • Evolution of male nuptial gift and female remating: A quantitative genetic model
    Yoh Iwasa and Sachi Yamaguchi

    Journal of Theoretical Biology, ISSN: 00225193, eISSN: 10958541, Volume: 533, Published: 21 January 2022 Elsevier BV

  • Virulence of a virus: How it depends on growth rate, effectors, memory cells, and immune escape
    Yoh Iwasa, Akane Hara, and Shihomi Ozone

    Journal of Theoretical Biology, ISSN: 00225193, eISSN: 10958541, Volume: 530, Published: 7 December 2021 Elsevier BV

  • The Great Oxygenation Event as a consequence of ecological dynamics modulated by planetary change
    Jason Olejarz, Yoh Iwasa, Andrew H. Knoll, and Martin A. Nowak

    Nature Communications, eISSN: 20411723, Published: December 2021 Springer Science and Business Media LLC
    AbstractThe Great Oxygenation Event (GOE), ca. 2.4 billion years ago, transformed life and environments on Earth. Its causes, however, are debated. We mathematically analyze the GOE in terms of ecological dynamics coupled with a changing Earth. Anoxygenic photosynthetic bacteria initially dominate over cyanobacteria, but their success depends on the availability of suitable electron donors that are vulnerable to oxidation. The GOE is triggered when the difference between the influxes of relevant reductants and phosphate falls below a critical value that is an increasing function of the reproductive rate of cyanobacteria. The transition can be either gradual and reversible or sudden and irreversible, depending on sources and sinks of oxygen. Increasing sources and decreasing sinks of oxygen can also trigger the GOE, but this possibility depends strongly on migration of cyanobacteria from privileged sites. Our model links ecological dynamics to planetary change, with geophysical evolution determining the relevant time scales.

  • Evolution of life cycle dimorphism: An example of sacoglossan sea slugs
    Sachi Yamaguchi, Yoichi Yusa, and Yoh Iwasa

    Journal of Theoretical Biology, ISSN: 00225193, eISSN: 10958541, Volume: 525, Published: 21 September 2021 Elsevier BV
    Many sea slugs of Sacoglossa (Mollusca: Heterobranchia) are sometimes called "solar-powered sea slugs" because they keep chloroplasts obtained from their food algae and receive photosynthetic products (termed kleptoplasty). Some species show life cycle dimorphism, in which a single species has some individuals with a complex life cycle (the mother produces planktotrophic larvae, which later settle in the adult habitat) and others with a simple life cycle (mothers produce benthic offspring by direct development or short-term nonfeeding larvae in which feeding planktonic stages are skipped). Life cycle dimorphism is not common among marine species. In this paper, we ask whether some aspects of the ecology of solar-powered sea slugs have promoted the evolution of life cycle dimorphism in them. We study the population dynamics of the two life-cycle types that differ in summer (one with planktonic life and the other with benthic life), but both have benthic life in other seasons. We obtain the conditions in which two types with different life cycles coexist stably or a single type generating offspring with different life cycles evolves. We conclude that the stable coexistence of two life cycles can evolve if benthic individuals in summer experience strongly density-dependent processes or if the between-year fluctuation of biomass growth in summer is very large. We discuss whether these results match the life cycles of solar-powered sea slugs with life cycle dimorphism.

  • Spatial distribution of gut microbes along the intestinal duct
    Shintaro Hishida and Yoh Iwasa

    Journal of Theoretical Biology, ISSN: 00225193, eISSN: 10958541, Volume: 523, Published: 21 August 2021 Elsevier BV
    We studied the spatial pattern of two microbial strains along the intestinal duct. Probiotic bacteria acidify the environment and suppress their competitors, non-probiotic bacteria. Food resources are supplied from the proximal end, and there exists a flow from the proximal end to the distal end. In the steady state, we observed three major patterns. In the "standard" pattern (ST), the abundance of probiotic bacteria was high in the proximal end, and it decreased toward the distal end; in contrast, the abundance of non-probiotic bacteria was low in the proximal end, and it increased toward the distal end. In the "proximal reversion" pattern (PR), non-probiotic bacteria were dominant and probiotic bacteria were suppressed in the proximal portion of the duct. Subsequently, the abundance values of the two competitors switched, followed by a spatial pattern similar to ST. In the "distal suppression" pattern (DS), the pattern was similar to ST in the proximal portion; however, toward the distal end, the abundance of probiotic bacteria remained at an intermediate level and suppressed the abundance of non-probiotic bacteria, resulting in a peak abundance of non-probiotic bacteria in the middle portion of the duct. We additionally discuss the nonmonotonic increase in the abundance of non-probiotic bacteria in ST and the transition of the spatial pattern from one type to another due to changes in the resource abundance in the influx.

  • Processes affecting size of fish schools in agent-based model
    Kazuto Kiriyama and Yoh Iwasa

    Population Ecology, ISSN: 14383896, Pages: 219-229, Published: July 2021 Wiley

  • Eco-evolutionary dynamics may show an irreversible regime shift, illustrated by salmonids facing climate change
    Junnosuke Horita, Yoh Iwasa, and Yuuya Tachiki

    Theoretical Ecology, ISSN: 18741738, eISSN: 18741746, Pages: 345-357, Published: June 2021 Springer Science and Business Media LLC
    AbstractThe enhanced or reduced growth of juvenile masu salmon (Oncorhynchus masou masou) may result from climate changes to their environment and thus impact on the eco-evolutionary dynamics of their life-history choices. Male juveniles with status, i.e., if their body size is larger than a threshold, stay in the stream and become resident males reproducing for multiple years, while those with smaller status, i.e., their body size is below the threshold, migrate to the ocean and return to the stream one year later to reproduce only once. Since juvenile growth is suppressed by the density of resident males, the fraction of resident males may stay in equilibrium or fluctuate wildly over a 2-year period. When the threshold value evolves, the convergence stable strategy may generate either an equilibrium or large fluctuations of male residents. If environmental changes occur faster than the rate of evolutionary adaptation, the eco-evolutionary dynamics exhibit a qualitative shift in the population dynamics. We also investigated the relative assessment models, in which individual life-history choices are made based on the individual’s relative status within the juvenile population. The eco-evolutionary dynamics are very different from the absolute assessment model, demonstrating the importance of understanding the mechanisms of life history choices when predicting the impacts of climate change.

  • Recurrent speciation rates on islands decline with species number
    Ryo Yamaguchi, Yoh Iwasa, and Yuuya Tachiki

    Proceedings of the Royal Society B: Biological Sciences, ISSN: 09628452, eISSN: 14712954, Volume: 288, Issue: 1949, Published: 28 April 2021 The Royal Society
    In an archipelagic system, species diversity is maintained and determined by the balance among speciation, extinction and migration. As the number of species increases, the average population size of each species decreases, and the extinction likelihood of any given species grows. By contrast, the role of reduced population size in geographic speciation has received comparatively less research attention. Here, to study the rate of recurrent speciation, we adopted a simple multi-species two-island model and considered symmetric interspecific competition on each island. As the number of species increases on an island, the competition intensifies, and the size of the resident population decreases. By contrast, the number of migrants is likely to exhibit a weaker than proportional relationship with the size of the source population due to rare oceanic dispersal. If this is the case, as the number of species on the recipient island increases, the impact of migration strengthens and decelerates the occurrence of further speciation events. According to our analyses, the number of species can be stabilized at a finite level, even in the absence of extinction.

  • Evolutionary game in an androdioecious population: Coupling of outcrossing and male production
    Sachi Yamaguchi and Yoh Iwasa

    Journal of Theoretical Biology, ISSN: 00225193, eISSN: 10958541, Volume: 513, Published: 21 March 2021 Elsevier BV
    Androdioecy, the coexistence of hermaphrodites and males, is very rare in vertebrates but occurs in mangrove killifish living in ephemeral or unstable habitats. Hermaphrodites reproduce both by outcrossing with males and by selfing. Outbreeding is advantageous because of inbreeding depression, but it requires encounters with males. The advantages of a propensity for outcrossing among hermaphrodites and the production of males affect each other very strongly. To study the evolutionary coupling of these two aspects, we here analyze a simple evolutionary game for a population composed of three phenotypes: outcrossing-oriented hermaphrodites, selfing-oriented hermaphrodites, and males. Outcrossing-oriented hermaphrodites first attempt to search for males and perform outcrossing if they encounter males. If they fail to encounter males, they reproduce via selfing. Selfing-oriented hermaphrodites simply reproduce by selfing. The replicator dynamics may show bistability, in which both the androdioecious population (with outcrossing-oriented hermaphrodites and males) and the pure hermaphroditic population are locally stable. The model shows the fraction of males is either zero or relatively high (more than 25%), which is not consistent with the observed low fraction of males (less than 5%). To explain this discrepancy, we studied several models including immigration and enforced copulation. We concluded that the observed pattern can be most likely explained by a population dominated by selfing-oriented hermaphrodites receiving immigration of males.

  • Optimal control of root nodulation – Prediction of life history theory of a mutualistic system
    Ryota Kobayashi, Sachi Yamaguchi, and Yoh Iwasa

    Journal of Theoretical Biology, ISSN: 00225193, eISSN: 10958541, Volume: 510, Published: 7 February 2021 Elsevier BV
    Legumes produce root nodules containing symbiotic rhizobial bacteria that convert atmospheric molecular nitrogen into ammonia or related nitrogenous compounds. The host plant supplies photosynthetic products to root nodules forming a mutualistic system. Legumes have physiological mechanisms for regulating nodule production with chemical signals produced in leaves, called the autoregulation of nodulation. In this paper, we discuss the optimal number of root nodules that maximizes the performance of the host plant. Here, we study two models. In the stationary plant model, the acquired photosynthetic products minus cost and loss are used for reproduction. In the growing plant model, the excess material is invested to produce leaves, roots, and root nodules, resulting in the exponential growth of the whole plant. The analysis shows that having root nodules is beneficial to the plant for a high leaf nitrogen content, faster plant growth rate, a short leaf longevity, a low root/shoot ratio, and low soil nutrient concentration. We discuss the long-distance control of nodulation-autoregulation and dependence on the environmental conditions of terrestrial plants considering these results.

  • Why did sauropod dinosaurs grow so big? – A possible answer from the life history theory
    Yuki Kanayama and Yoh Iwasa

    Journal of Theoretical Biology, ISSN: 00225193, eISSN: 10958541, Volume: 508, Published: 7 January 2021 Elsevier BV
    Dinosaurs are known for their large body size. Sauropod dinosaurs (Sauropodomorpha) had an especially large body size; some species reached 30 m long and 50 tons. Many hypotheses have been proposed to explain this phenomenon. In this study we examined this question using the life history theory. We constructed a simple model of life history with the following assumptions: the body size of immature individuals increases following a logistic equation. A higher quality and availability of food plants make the initial growth rate faster and the final saturating size larger. The increase in body size stops once reproduction starts. Fertility increases with adult body size and food-plant quality. Mortality due to predation is mitigated by a larger body size. We calculated the optimal body size at maturity that would maximize the lifetime reproductive success or fitness. The analysis showed that adult body size increased with food-plant quality and availability but decreased with higher mortality due to predators and other factors. This conclusion is consistent with geological studies that suggest a high quality and availability of food plants in the Mesozoic era, efficient air-sac breathing, and the lightweight bones of sauropod dinosaurs, allowing rapid growth of small individuals.

  • Enhanced risk of cancer in companion animals as a response to the longevity
    Moeko Tanaka, Sachi Yamaguchi, and Yoh Iwasa

    Scientific Reports, eISSN: 20452322, Published: December 2020 Springer Science and Business Media LLC
    Abstract Cancer is caused by the lifetime accumulation of multiple somatic deformations of the genome and epigenome. At a very low rate, mistakes occur during genomic replication (e.g., mutations or modified epigenetic marks). Long-lived species, such as elephants, are suggested to have evolved mechanisms to slow down the cancer progression. Recently, the life span of companion dogs has increased considerably than before, owing to the improvement of their environment, which has led to an increase in the fraction of companion dogs developing cancer. These findings suggest that short-term responses of cancer risk to longevity differ from long-term responses. In this study, to clarify the situation, we used a simple multi-step model for cancer. The rates of events leading to malignant cancer are assumed to be proportional to those of genomic replication error. Perfect removal of replication error requires a large cost, resulting in the evolution of a positive rate of genomic replication error. The analysis of the model revealed: that, when the environment suddenly becomes benign, the relative importance of cancer enhances, although the age-dependent cancer risk remains unchanged. However, in the long run, the genomic error rate evolves to become smaller and mitigates the cancer risk.

  • Positive feedback between behavioral and hormonal dynamics leads to differentiation of life-history tactics
    Junnosuke Horita, Yoh Iwasa, and Yuuya Tachiki

    American Naturalist, ISSN: 00030147, eISSN: 15375323, Volume: 196, Pages: 679-689, Published: December 2020 University of Chicago Press
    Competitive interaction among individuals of a single population may result in the differentiation of two or more distinct life-history tactics. For example, although they exhibit unimodal size distribution, male juveniles of salmonids differentiate into those going down to the ocean to grow and returning to the natal stream after several years to reproduce (migratory tactic) and those staying in the stream and reproducing for multiple years (resident tactic). In this study, we developed a simple mathematical model for the positive feedback between hormonal and behavioral dynamics, with the expectation of establishing multiple discrete clusters of hormone levels leading to differentiation of life-history tactics. The assumptions were that probability of winning in fighting depends both on the body size and hormone level of the two contestants. An individual with a higher hormone level would be more likely to win the competition, which further enhanced hormone production, forming a positive feedback loop between hormone level and fighting ability. If the positive feedback was strong but not excessive, discrete clusters of hormone levels emerged from a continuous distribution. In contrast, no clear clustering structure appeared in the distribution of hormone levels if the probability of winning in fighting was controlled by the body size.

  • Task allocation in a cooperative society: specialized castes or age-dependent switching among ant workers
    Yoh Iwasa and Sachi Yamaguchi

    Scientific Reports, eISSN: 20452322, Published: 1 December 2020 Springer Science and Business Media LLC
    AbstractSome ant species have multiple worker castes that differ in body size; workers in one caste remain in the colony and those in the other forage outside the colony (caste polyethism). In other species, all workers engage in both tasks, but the younger workers remain in the colony and the older workers forage (age polyethism). Here, we ask which of these two is the most efficient for colony level performance when foragers suffer a higher daily mortality than workers in the colony and when the optimal worker size differs between two tasks. We studied two models: in the stationary colony model, the colony size and composition remain constant, and the amount of excess resources that can be used for producing reproductive individuals is maximized; in the growing colony model, all of the resources obtained are used for producing new workers, and the rate of the colony growth is maximized. In both models, we observed similar results: caste polyethism is more advantageous than age polyethism if the difference in mortality between the two tasks is small and the difference in the optimal size is large. In the opposite situation, the age polyethism is more advantageous.

  • How Thermodynamics Illuminates Population Interactions in Microbial Communities
    Mayumi Seto and Yoh Iwasa

    Frontiers in Ecology and Evolution, eISSN: 2296701X, Published: 30 November 2020 Frontiers Media SA
    In traditional population models of microbial ecology, there are two central players: producers and consumers (including decomposers that depend on organic carbon). Producers support surface ecosystems by generating adenosine triphosphate (ATP) from sunlight, part of which is used to build new biomass from carbon dioxide. In contrast, the productivity of subsurface ecosystems with a limited supply of sunlight must rely on bacteria and archaea that are able generate ATP solely from chemical or electric energy to fix inorganic carbon. These “light-independent producers” are frequently not included in traditional food webs, even though they are ubiquitous in nature and interact with one another through the utilization of the by-products of others. In this review, we introduce theoretical approaches based on population dynamics that incorporate thermodynamics to highlight characteristic interactions in the microbial community of subsurface ecosystems, which may link community structures and ecosystem expansion under conditions of a limited supply of sunlight. In comparison with light-dependent producers, which compete with one another for light, the use of Gibbs free energy (chemical energy) can lead cooperative interactions among light-independent producers through the effects of the relative quantities of products and reactants on the available chemical energy, which is termed abundant resource premium. The development of a population theory that incorporates thermodynamics offers fundamental ecological insights into subsurface microbial ecosystems, which may be applied to fields of study such as environmental science/engineering, astrobiology, or the microbial ecosystems of the early earth.

  • Seasonality in the production of male larvae: A game model for parasitic barnacles (Cirripedia: Rhizocephala)
    Sachi Yamaguchi and Yoh Iwasa

    Journal of Crustacean Biology, ISSN: 02780372, eISSN: 1937240X, Pages: 833-838, Published: 1 November 2020 Oxford University Press (OUP)
    Abstract The male larvae of many parasitic barnacles are planktonic and are seasonally released. To achieve reproductive success, a male must be accepted by a receptive female that has successfully infected a host. To understand the seasonality of the breeding biology of parasitic barnacles, we developed an evolutionary game theoretical model for the seasonal pattern in the production of male larvae. Assumptions are that female parasitic barnacles become receptive following a given seasonal pattern. The parental females (mothers) choose the timing of producing their own male larvae to achieve maximum reproductive success. In the evolutionarily stable seasonal pattern, the production of male larvae often shows a sharp peak on a single day, indicating strongly synchronized production of male larvae, even when the supply of receptive females is distributed over the breeding season. When the total number of male larvae is large, the evolutionarily stable male production pattern may include multiple peaks, but it never shows a continuous distribution. This is very different from the game model previously developed for the emergence pattern of butterflies, where evolutionarily stable male emergence is always continuously distributed over a fraction of the mating season. As planktonic larvae, male parasitic barnacles have a naturally limited ability to find receptive females, and females may stay receptive for many days, whereas in butterflies, newly emerged females are mated within a day of their emergence.

  • Ecotourism development and the heterogeneity of tourists
    Joung Hun Lee and Yoh Iwasa

    Theoretical Ecology, ISSN: 18741738, eISSN: 18741746, Pages: 371-383, Published: 1 September 2020 Springer Science and Business Media LLC
    AbstractEcotourism is potentially capable of making biodiversity conservation and ecosystem management economically feasible. Here, we propose a simple model for ecotourism development considering the heterogeneity of tourists, motivated by the case of Jeju Island, South Korea. We analyze the optimal investment in accommodation capacity (i.e., hotels, restaurants, and transportation) and in improving the quality of the environment (i.e., biodiversity, landscape, and cultural activities). “General tourists” are abundant but will not return to the focal site, and their future number is unpredictable, while “loyal tourists” may return to the site if they are attracted by its environmental and/or cultural assets. The analysis shows that the economically profitable policy is either the one with a large investment in accommodation capacity targeting general tourists or the one with a large investment to environmental quality targeting loyal tourists, but an intermediate mixture of these extremes cannot be the optimal. We also discuss “zoning,” in which a site is separated to two areas, and many visitors stay in the first area and visit the second area to enjoy the high-quality environment.

  • Bovine mastitis and optimal disease management: Dynamic programming analysis
    Tokuharu Sekiya, Sachi Yamaguchi, and Yoh Iwasa

    Journal of Theoretical Biology, ISSN: 00225193, eISSN: 10958541, Volume: 498, Published: 7 August 2020 Elsevier BV
    Wise decision-making for coping with infectious diseases is a key to the success of farming, agriculture, as well as public health. Mastitis of dairy cows causes large economic burden to dairy farmers. Here, we study the optimal operation for a dairy farmer to manage cows infected by mastitis. In the simple model, we considered cows with different number of breasts (quarters) infected by mastitis. In the detailed model, we considered additional complexities: a cow produces milk only after the first birth of a calf, old cows are culled, milking is not practiced for 10 weeks prior to expected calf-birth, and a newborn calf provides an economic benefit. By fitting the parameters to the Japanese dairy farming situation, the dynamic programming analysis reveals whether an infected cow should receive medical treatment depends on the number of breasts infected, age, and season. Cows should be culled if many breasts are infected, they are old, and it is not close to the next calf-birth. The optimal management policy depends critically on milk price, maintenance cost, and recovery rate from mastitis infection, but not on infection rate.

  • Autoimmune diseases initiated by pathogen infection: Mathematical modeling
    Akane Hara and Yoh Iwasa

    Journal of Theoretical Biology, ISSN: 00225193, eISSN: 10958541, Volume: 498, Published: 7 August 2020 Elsevier BV
    Many incurable diseases in humans are related to autoimmunity and are initially induced by a viral infection. Presumably, the virus has antigens with epitopes similar to those found in components of the host's body, thus allowing it to evade immune surveillance. Viral infection activates the immune system, which results in viral clearance. After infection, the enhanced immune system may begin to attack the host's cells, tissues, and organs. In this study, we developed a simple mathematical model in which we identify the conditions needed to trigger an autoimmune response. This model considers the dynamics of T helper (Th) cells, viruses, self-antigens, and memory T cells. Viral infection results in a temporal increase in viral abundance, which is suppressed by an increase in the number of Th cells. For the virus to be eliminated from the body, the level of Th cells must be maintained above a certain threshold to prevent viral replication, even in the absence of virus in the body. This role is realized by memory T cells produced during temporal viral infections. Thus, we investigated the conditions needed for the immune response to be enhanced after viral infection and concluded that cross-immunity must be weak for negative selection and T-cell activation but strong for antigen-suppressing reactions. We also discuss alternative models of cross-immunity and possible extensions of the model.

  • Microbial material cycling, energetic constraints and ecosystem expansion in subsurface ecosystems: Microbial material cycling and energy
    Proceedings of the Royal Society B: Biological Sciences, ISSN: 09628452, eISSN: 14712954, Volume: 287, Issue: 1931, Published: 29 July 2020

  • Coordinated changes in cell membrane and cytoplasm during maturation of apoptotic bleb
    Kana Aoki, Shinsuke Satoi, Shota Harada, Seiichi Uchida, Yoh Iwasa, and Junichi Ikenouchi

    Molecular Biology of the Cell, ISSN: 10591524, eISSN: 19394586, Pages: 833-844, Published: March 2020 American Society for Cell Biology (ASCB)
    In the course of apoptosis, blebs eventually mature into apoptotic bodies that have immune-modulating activities. We clarified changes that occur in the cell membrane during apoptosis, and that those changes are essential for the formation of apoptotic bodies.

RECENT SCHOLAR PUBLICATIONS

  • On the role of eviction in group living sex changers
    Y Iwasa, S Yamaguchi
    Behavioral Ecology and Sociobiology 76 (4), 1-10 2022

  • Escaping stochastic extinction of mutant virus: Temporal pattern of emergence of drug resistance within a host
    R Hayashi, S Iwami, Y Iwasa
    Journal of Theoretical Biology 537, 111029 2022

  • Evolutionary game of life-cycle types in marine benthic invertebrates: Feeding larvae versus nonfeeding larvae versus direct development
    Y Iwasa, Y Yusa, S Yamaguchi
    Journal of Theoretical Biology 537, 111019 2022

  • Optimal composition of chloride cells for osmoregulation in a randomly fluctuating environment
    Y Uchiyama, Y Iwasa, S Yamaguchi
    Journal of Theoretical Biology 537, 111016 2022

  • Evolution of male nuptial gift and female remating: A quantitative genetic model
    Y Iwasa, S Yamaguchi
    Journal of Theoretical Biology 533, 110939 2022

  • The genetic structure within a single tree is determined by the behavior of the stem cells in the meristem
    Y Iwasa, S Tomimoto, A Satake
    bioRxiv 2022

  • Virulence of a virus: How it depends on growth rate, effectors, memory cells, and immune escape
    Y Iwasa, A Hara, S Ozone
    Journal of Theoretical Biology 530, 110875 2021

  • Evolution of life cycle dimorphism: An example of sacoglossan sea slugs
    S Yamaguchi, Y Yusa, Y Iwasa
    Journal of Theoretical Biology 525, 110760 2021

  • Spatial distribution of gut microbes along the intestinal duct
    S Hishida, Y Iwasa
    Journal of Theoretical Biology 523, 110725 2021

  • Processes affecting size of fish schools in agent‐based model
    K Kiriyama, Y Iwasa
    Population Ecology 63 (3), 219-229 2021

  • The Great Oxygenation Event as a consequence of ecological dynamics modulated by planetary change
    J Olejarz, Y Iwasa, AH Knoll, MA Nowak
    Nature Communications 12 (1), 1-9 2021

  • Eco-evolutionary dynamics may show an irreversible regime shift, illustrated by salmonids facing climate change
    J Horita, Y Iwasa, Y Tachiki
    Theoretical Ecology 14 (2), 345-357 2021

  • Cumulative viral load, an indicator of virulence, is controlled by the host's immune response.
    Y Iwasa, A Hara, S Ozone
    2021

  • Recurrent speciation rates on islands decline with species number
    R Yamaguchi, Y Iwasa, Y Tachiki
    Proceedings of the Royal Society B 288 (1949), 20210255 2021

  • Evolutionary game in an androdioecious population: Coupling of outcrossing and male production
    S Yamaguchi, Y Iwasa
    Journal of Theoretical Biology 513, 110594 2021

  • Optimal control of root nodulation–Prediction of life history theory of a mutualistic system
    R Kobayashi, S Yamaguchi, Y Iwasa
    Journal of Theoretical Biology 510, 110544 2021

  • Why did sauropod dinosaurs grow so big?–A possible answer from the life history theory
    Y Kanayama, Y Iwasa
    Journal of Theoretical Biology 508, 110485 2021

  • Positive Feedback between Behavioral and Hormonal Dynamics Leads to Differentiation of Life-History Tactics
    J Horita, Y Iwasa, Y Tachiki
    The American Naturalist 196 (6), 679-689 2020

  • How Thermodynamics Illuminates Population Interactions in Microbial Communities
    M Seto, Y Iwasa
    Frontiers in Ecology and Evolution 8, 602809 2020

  • Enhanced risk of cancer in companion animals as a response to the longevity
    M Tanaka, S Yamaguchi, Y Iwasa
    Scientific reports 10 (1), 1-10 2020

MOST CITED SCHOLAR PUBLICATIONS

  • Dynamics of chronic myeloid leukaemia
    F Michor, TP Hughes, Y Iwasa, S Branford, NP Shah, CL Sawyers, ...
    Nature 435 (7046), 1267-1270 2005
    Citations: 934

  • Influence of nonlinear incidence rates upon the behavior of SIRS epidemiological models
    W Liu, SA Levin, Y Iwasa
    Journal of mathematical biology 23 (2), 187-204 1986
    Citations: 911

  • The evolution of costly mate preferences II. The “handicap” principle
    Y Iwasa, A Pomiankowski, S Nee
    Evolution 45 (6), 1431-1442 1991
    Citations: 885

  • Sexual selection
    M Andersson, Y Iwasa
    Trends in ecology & evolution 11 (2), 53-58 1996
    Citations: 790

  • Demographic theory for an open marine population with space‐limited recruitment
    J Roughgarden, YOH Iwasa, C Baxter
    Ecology 66 (1), 54-67 1985
    Citations: 679

  • Prey distribution as a factor determining the choice of optimal foraging strategy
    Y Iwasa, M Higashi, N Yamamura
    The American Naturalist 117 (5), 710-723 1981
    Citations: 655

  • Dynamics of cancer progression
    F Michor, Y Iwasa, MA Nowak
    Nature reviews cancer 4 (3), 197-205 2004
    Citations: 569

  • The evolution of costly mate preferences I. Fisher and biased mutation
    A Pomiankowski, Y Iwasa, S Nee
    Evolution 45 (6), 1422-1430 1991
    Citations: 461

  • How should we define goodness?—reputation dynamics in indirect reciprocity
    H Ohtsuki, Y Iwasa
    Journal of theoretical biology 231 (1), 107-120 2004
    Citations: 441

  • The leading eight: social norms that can maintain cooperation by indirect reciprocity
    H Ohtsuki, Y Iwasa
    Journal of theoretical biology 239 (4), 435-444 2006
    Citations: 418

  • The evolution of cooperation in a lattice-structured population
    M Nakamaru, H Matsuda, Y Iwasa
    Journal of theoretical Biology 184 (1), 65-81 1997
    Citations: 359

  • Theory of oviposition strategy of parasitoids. I. Effect of mortality and limited egg number
    Y Iwasa, Y Suzuki, H Matsuda
    Theoretical Population Biology 26 (2), 205-227 1984
    Citations: 349

  • Indirect reciprocity provides only a narrow margin of efficiency for costly punishment
    H Ohtsuki, Y Iwasa, MA Nowak
    Nature 457 (7225), 79-82 2009
    Citations: 345

  • The evolution of mate preferences for multiple sexual ornaments
    Y Iwasa, A Pomiankowski
    Evolution 48 (3), 853-867 1994
    Citations: 327

  • Shoot/root balance of plants: optimal growth of a system with many vegetative organs
    Y Iwasa, J Roughgarden
    Theoretical population biology 25 (1), 78-105 1984
    Citations: 297

  • Aggregation in model ecosystems. I. Perfect aggregation
    Y Iwasa, V Andreasen, S Levin
    Ecological Modelling 37 (3-4), 287-302 1987
    Citations: 288

  • Stochastic tunnels in evolutionary dynamics
    Y Iwasa, F Michor, MA Nowak
    Genetics 166 (3), 1571-1579 2004
    Citations: 270

  • Optimal size of storage for recovery after unpredictable disturbances
    YOH Iwasa, T Kubo
    Evolutionary ecology 11 (1), 41-65 1997
    Citations: 264

  • Evolution of resistance during clonal expansion
    Y Iwasa, MA Nowak, F Michor
    Genetics 172 (4), 2557-2566 2006
    Citations: 250

  • Continual change in mate preferences
    Y Iwasa, A Pomiankowski
    Nature 377 (6548), 420-422 1995
    Citations: 240