Research Projects

• Grant-in-Aid for Scientific Research (C), Apr. 2022 - Mar. 2025, 22K06401, Principal investigator, Theoretical studies on spatial ecology in terms of point patterns, TAKASU Fugo, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Nara Women's University, 3120000, 2400000, 720000, kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (C), 01 Apr. 2014 - 31 Mar. 2017, 26440239, Spatial modeling in ecology as point pattern dynamics, TAKASU Fugo, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Nara Women's University, 4940000, 3800000, 1140000, I have revisited classical spatial population models described such as patch model, lattice model, reaction diffusion model in terms of "point pattern dynamics". These models have been implemented as stochastic point pattern dynamics. I have derived a set of deterministic dynamics of the 1st order (density of points) and the 2nd order (distribution of distances in pair made by two points) which are expected to describe simulations. Triplet density made by thee points appears in the dynamics. With a simple moment closure, the derived deterministic dynamics quite well describes stochastic simulation results, especially when birth and death of points are ignored. I have established the way how classical population dynamics (competition, prey-predator, epidemic models, etc.) can be translated to stochastic point pattern dynamics., kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (A), 01 Apr. 2011 - 31 Mar. 2015, 23255004, Evolutionary arms race between tropical cuckoos and their hosts:Exodus from old dogma of western countries., UEDA Keisuke; EGUCHI Kazuhiro; NISHIUMI Isao; TAKASU Fugo; TAKAGI Masaoki; MIKAMI Osamu, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Rikkyo University, 44200000, 34000000, 10200000, We succeeded to reveal the cuckoo-host arms-tace in New Caredonia. We published 3 main papers on the international journal and 12 oral and/or poster papers were presented at several academical societies. Those are often cited by many cuckoo researchers. We also symposium for citizens twice. Many people attended and we have good assessment from them., kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (C), 2011 - 2013, 23570026, Evolutionary games revisited in terms of individual interactions, TAKASU Fugo, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Nara Women's University, 5330000, 4100000, 1230000, I revisited classical evolutionary games such as Hawk-dove games, Prisoner's dilemma game, evolution of cooperation in terms of individual interactions. Mechanistic interactions among individuals located on a continuous space, not lattice, are algorithmically described and an efficient way to simulate these algorithm of birth, death, and movement, of individuals is implemented by using parallel computing. Population dynamics of each strategy (hawk, dove, defect, cooperate, tit-for-tat, etc.) was analyzed by the singlet density (number of individuals) and the pair density (number of pairs made by two individuals displaced by a certain distance)., kaken

  対象リソースIRI
• 2010, 空間個体群動態ならびに空間進化動態, 科学研究費補助金, 0, 0, 0, Competitive research funding
• 2010, Spatial population and evolutionary dynamics, Grant-in-Aid for Scientific Research, 0, 0, 0, Competitive research funding
• Grant-in-Aid for Scientific Research (B), 2006 - 2009, 18405009, Evolutionary arms race between Australian cuckoos and their hosts., UEDA Keisuke; EGUCHI Kazuhiro; BISHIUMI Isao; TAKAGI Masaoki; TAKASU Fugo; HAMAO Shoji, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Rikkyo University, 13190000, 11000000, 2190000, A new anti-parasitism behaviour was observed in the Large-billed Gerygone Gerygone magnirostris and the Mangrove Gerygone G. laevigaster which are hosts of the Little Bronze-cuckoo Chalcites (formally Chrysococcyx) minutillus. This behaviour, termed parasite nestling ejection, involves the physical removal of live parasite nestlings from active nests and represents a type of chick discrimination. The discovery of parasite nestling ejection by Gerygones represented a significant finding for anti-parasitic behaviour research at the nestling stage. Although the Little Bronze-cuckoo seemed to start parasitism to Large-billed Gerygone historically, then they seemed to explore the Mangrove Gerygone as a new host., kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (B), 2002 - 2005, 14340243, Does the host specific races of the common cuckoo evolve with the gene by the side of female lineages?, NAKAMURA Hiroshi; HAYASHIDA Nobuaki; TAGUCHI Goro; TAKASU Fugo, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Shinshu University, 13300000, 13300000, The common cuckoo is divided into host-specific races (gentes). Females of each race lay a distinctive egg type that tends to match the host's eggs. It was provided genetic evidence that gentes restricted to female lineages from the fact that there is differentiation between gentes in maternally inherited mitochondrial DNA, but not in microsatellite loci of nuclear DNA. This supports recent behavioural evidence that female, but not male, common cuckoos specialize on a particular host, and is consistent with the possibility that genes affecting cuckoo egg type are located on the female-specific W sex chromosome. Our results in Japan also supported these ideas, but the host races are not so clear in Japan, due to colonization by separated ancestral lineages., kaken

  対象リソースIRI
• 若手研究(B), 2002 - 2004, 14740421, 群集動態に関する新しい理論アプローチの展開, 高須 夫悟, 日本学術振興会, 科学研究費助成事業, 奈良女子大学, 3400000, 3400000, 平成16年度は主に以下の2点に注目した研究を行った。
  1)寄生系におけるパラサイトのハンドリングタイムの進化モデル解析
  ホスト・パラサイトの個体群動態において、パラサイトが寄生を実行するに要する時間(ハンドリングタイム)が小さくなると安定平衡点が不安定化し周期解・カオスが出現する事は既に古典モデルの解析に明らかになっている。本研究ではパラサイト集団中にハンドリングタイムに関する集団内変異が存在すると仮定した場合、ハンドリングタイムの進化が個体群動態の安定性に及ぼす影響について解析した。前年度に行った、パラサイトの探索効率の進化モデルと同様、ハンドリングタイムは小さくなる方向へ進化するが、パラサイトのハンドリングタイムに関する集団内変異の存在は、個体群動態をより長期にわたって安定することを見いだした。また、探索効率やハンドリングタイムといった個体群動態に関係するパラメータの進化と個体群動態の安定性に関する一般的な研究を行った。
  2)解析的モデルと個体ベースシミュレーションモデルの比較
  群集動態や個体群動態の理論研究で用いられる数理モデルの多くは解析的な取り扱いが易い決定論的解析的モデル(差分式、微分方程式等)を用いて記述される。しかし、現実の系では確率論的な効果が無視できず決定論的モデルで起こりうる微小密度下での振る舞いは、必ずしも現実の系を反映していないと思われる。本研究では、決定論的解析モデルで設定される様々な仮定を確率論的ルールに置き換えた確率論的個体ベースモデルを構築し、両者の振る舞いを比べる事で、決定論的解析モデルでは捉えられない現象がある事を見いだした。具体的には、適応度の谷間をすり抜けて形質の進化が起こりうる等である。同様の解析を寄生系の個体群動態モデル及び群集動態モデルに対して行い、確率的な効果の重要性を再認識した。現在はこれを発展させたモデル解析を進めている。, kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (C), 2001 - 2003, 13640627, Modeling spatio-temporal pattern of biological invasions that involve short-and long-distance dispersals, SHIGESADA Nanako; TAKASU Fugo; KAWASAKI Kohkichi, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Nara Women's University, 2900000, 2900000, The range expansion of an invading species shows a variety of spatio-temporal patterns depending on how the dispersal and reproduction of the organisms take place. To grasp the spatial pattern of invasion and its rate of spread quantitatively, we have constructed two different mathematical models that deal with short-and long-distance dispersals as well as the Allee effect and/or demographic stochasticity : 1)the stratified diffusion model and 2)the integral-kernel-based models. By solving these models either analytically or numerically, we derived formulae for the rate of spread and used them to explore how long-distance dispersal and reproduction interplay to accelerate the speed, or how the Allee effect or demographic stochasticity decelerates it.
  Integrating the ideas of the above two models together with a cell-automaton model, we carried out simulations for the spread of pine wilt disease in Inbaragi Prefecture, Japan. Pine wilt disease is caused by the pinewood nematode that is vectored by the pine sawyer beetle. The dispersal of the beetle often involves two modes, short-range dispersal and long-range dispersal. We estimated the proportion of long-range dispersers in the population of the disease vector (the pine sawyer beetle) on the basis of field data. Thus we concluded that the dispersal distance of beetles critically affects the expansion speed of the disease, which is sharply amplified, as the fraction of beetles undergoing long distance dispersal increases from zero., kaken

  対象リソースIRI
• 奨励研究(A), 2000 - 2001, 12740422, 量的形質に関する共進化の数理的解析, 高須 夫悟, 日本学術振興会, 科学研究費助成事業, 奈良女子大学, 2100000, 2100000, 平成13年度は、昨年度に実施した量的形質に関する共進化モデルの解析をさらに推し進めた。理論解析を進めると同時に、野外での寄生者宿主の関係(カッコウとその宿主)に関するデータを収集し、モデル解析結果と実際の系との比較検討を現在進めている。以下に今年度の研究成果の要点をまとめる。
  1)積分差分方程式で記述される本研究のモデルは、遺伝変異が集団内に十分存在すると仮定した場合、従来の量的遺伝モデルとの接点を持つ。しかし、数学的な関連性は未だ不明な点が多く、今後の理論的研究が必要である。また、本研究では卵模様のように量的形質が親から子へそのまま受け継がれる場合を解析したが、有性生殖に一般的な交配による量的形質の変化の効果をモデルに組み込むアイデアをモデル解析の過程で得ることが出来た。現在、その数理的取り扱いについて研究中である。
  2)進化一般を議論する新しい理論的枠組みとして、理想自由進化モデルを提唱した。従来の多くのESSモデルの様に集団を一様な「点」として取り扱うのではなく、変異を持った「分布」として取り扱うことで、より柔軟な理論解析が可能になる。
  3)托卵鳥系における寄生者と宿主の卵模様(量的形質)の変化を実証することを目指して、2001年6月に琵琶湖にてカッコウの宿主であるオオヨシキリの卵の写真を撮影し、卵模様の画像データを入手した。現在画像データの定量的解析を進めており、共進化の実証を試みている。
  4)2年間の研究の取りまとめとして、2001年7月に開催された、数理生物国際会議にて研究発表を行い、内外の研究者と議論を交わした。本研究成果は論文として国際誌に投稿し、査読中である(2001年11月Evolution誌に投稿済み)。
  5)寄生系以外の系でも、量的形質を巡る共進化が積分方程式を用いた基本的に同じ枠組みで理論的に取り扱い可能であることを明らかにした。
  平成12・13年の2年間で量的形質の共進化に関する理論的研究を大きく推進することが出来た。同時に、今後取り組むべき新たな課題も浮かび上がってきた。この2年間の研究補助をきっかけに、更なる理論的解析を推進していきたい。, kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (C), 1998 - 2000, 10640616, Mathematical Analyses of Spatial Spread of Pine Wilt Disease, SHIGESADA Nanako; FUGO Takasu; KAWASAKI Kohkichi, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Nara Women's University, 2400000, 2400000, Pine wilt disease is caused by the pinewood nematode, Bursaphelenchus xylophilus, that is vectored by the pine sawyer beetle, Monochamus alternatus. Native Japanese pines, black pine (Pinus thunbergii) and red pine (P.densiflora), are extremely sensitive to the nematode infection and the disease has been expanding nationwide in the last several decades despite intensive control efforts. The dispersal of the beetle often involves two modes, short-range dispersal and long-range dispersal. Short-range dispersal generally occurs through their own active flying, while long-range dispersal is mediated by passive transport on wind or artificial transportation facilities. To evaluate the speed of disease's expansion, we present a model that combines the local dynamics of the pine wilt disease with the dispersal of beetles. Our model predicts several results.
  (1) The distribution of the dispersal distance of beetles critically affects the expansion speed of the disease. The expansion speed is sharply amplified, as the fraction of beetles undergoing long distance dispersal increases from zero.
  (2) However, if long range dispersers become too frequent, the disease ceases to expand due to the Allee effect. Thus suggests the importance of correct assessment of the beetle's mobility in predicting the expansion speed of the disease.
  (3) As the eradication rate is increased, the expansion speed decreases gradually at first and suddenly drops to zero at a certain value of the eradication rate., kaken

  対象リソースIRI
• Grant-in-Aid for Scientific Research (C), 1996 - 1997, 08640804, Mathematical Study of Spatial Spread of Biological Invasion, SHIGESADA Nanako; FUGO Takasu; KAWASAKI Kohkichi, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Nara Women's University, 2500000, 2500000, 1. An epidemic of pine wilt disease has been spreading in wide areas of Japan for several decades. The disease is caused by the pinewood nematode, Bursaphelenchus xylophilus, which the pine sawyer, Monochamus alternatus, as vector. We present a mathematical model to describe the host-parasite interaction between pines and pine sawyers carrying nematodes based on detailed data on the population dynamics of pine sawyers and the incidence of pine wilt disease at a study site located on the northwest coast of Japan. By analyzing the model we simulate the temporal change in the incidence of the disease and predict how the epidemic could be controlled by eradication of the pine sawyer. The main results are : 1) There is a minimum threshold of the initial pine density for successful invasion of the disease. However, even if the pine density exceeds the minimum threshold, the disease fails in invasion due to the Allee effect of the pine sawyer when its density is very low. 2) The minimum threshold density increases disproportionately with increase in the eradication rate. 3) The probability for a healthy tree to escape from infection until the epidemic dies out decreases sharply with increase in the initial pine density, when the eradication rate is low.
  2. We analyzed the range expansion of an invading species and derived the conditions for persistence of a species two kinds of fragmented environments :
  (1) an environment segmented into belts, with favorable and unfavorable patches arranged alterately.
  (2) an environment segmented in both horizontal and vertical axs, with square-shaped favorable patches regularly distributed within the unfavorable environment., kaken

  対象リソースIRI
• 奨励研究(A), 1996 - 1996, 08740600, Generalist托卵鳥系における宿主の行動進化の理論的研究, 高須 夫悟, 日本学術振興会, 科学研究費助成事業, 奈良女子大学, 1000000, 1000000, 托卵鳥とその宿主の関係における進化生態学的な問題について数理モデルを用いた研究を行った。托卵されたあるホスト集団は、托卵鳥(パラサイト)の卵を認識して排除する托卵対抗手段をとることが野外研究によって明らかなっているが、托卵対抗手段の確立度はホスト集団ごとに異なっており、この事実に対する明確な説明はなされていなかった。本研究は、托卵鳥が同時に複数の種類のホスト集団に托卵する系(Generalist系)について、托卵対抗手段がそれぞれのホスト集団中でどのように確立されるのかについての数理モデルを組み立て、モデル解析を通じて現実に対する新たな視点を見出すことを目的とした。本研究により明らかになった点は以下の通りである。
  1.托卵鳥コウウチョウに托卵されるホストは、托卵対抗手段を殆ど行わないAccepter speciesと、ほぼ完璧な托卵対抗手段をみせるRejecter speciesに分類されることが野外研究から明らかにされているが、このような極端な2分化は、コウウチョウの繁殖戦略-Generalistによって引き起こされている可能性が高い。
  2.托卵されながらも托卵対抗手段を行わないAccepter speciesは、対抗手段が突然変異として出現すればRejecter speciesになるという説(Evolutionary Lag説)がある。これに対し、モデル解析から、Accepter speciesの存在は進化的に安定であり、2局化した托卵対抗手段の確立度分布は安定である可能性(Evolutionary Equilibrium説)が示された。この場合、Accepter speciesとRejecter speicesの間には、集団サイズの大きさなどの測定可能な量に違いがあり、これを測定することによって2つの説のどちらがより適切であるかが検討可能である。, kaken

  対象リソースIRI
• 進化動態に関する数理的研究, 0, 0, 0, Competitive research funding
• 動物の分散に関する理論的研究, 0, 0, 0, Competitive research funding
• 鳥類の育児寄生における共進化の理論的研究, 0, 0, 0, Competitive research funding
• Evolurionary dynamics, 0, 0, 0, Competitive research funding
• Theoretical Study on animal dispersal, 0, 0, 0, Competitive research funding
• Theoretical study on avian brood parasitism, 0, 0, 0, Competitive research funding
• 基盤研究C, 2022 - 2024, 22K06401, Principal investigator, 点パターンの視点に基づく空間生態学理論の新たな展開
• 基盤研究 (C), 01 Apr. 2022 - 31 Mar. 2025, 22K06401, Principal investigator, 点パターンの視点に基づく空間生態学理論の新たな展開