The Dynamics of Food Web Model with Defensive Switching Property

In this paper, a food web model consisting of two-predator one-prey with the defensive switching of predation avoidance is proposed and analyzed. It is assumed that the prey growth logistically in the absence of predators and defends itself from relatively abundant predator species by switching to another habitat with relatively rare predator species. Sufficient conditions for the stability of the non-trivial equilibrium point are obtained. The Lyapunov function is constructed to establish the global asymptotic stability of the non-trivial equilibrium point when the intensity of defensive switching equal one. Numerical simulations for different sets of parameter values and for different sets of initial conditions are carried out. It has been shown that the system has a globally asymptotically stable non-trivial point when the two predators have the same mortality rates

Why Punish: Social Reciprocity and the Enforcement of Prosocial Norms

Recently economists have become interested in why people who face social dilemmas in the experimental lab use the seemingly incredible threat of punishment to deter free riding. Three theories with evolvutionary microfoundations have been developed to explain punishment. We survey these theories and use behavioral data from surveys and experiments to show that the theory called social reciprocity in which people punish norm violators indiscriminately explains punishment best.social dilemma, punishment, norm, evolutionary game theory, experiment

Defended fortresses or moving targets? Another model of inducible defenses inspired by military metaphors

Journal ArticleWe use a common framework to compare three models of plant strategies to confront herbivory: constitutive defense, optimal inducible defense, and the "moving target." Plants with constitutive defenses retain a fixed defensive phenotype. Plants with optimal inducible defenses respond to attack by increasing defenses. Plants following the moving target strategy respond to attack by altering phenotype

Foraging for foundations in decision neuroscience: insights from ethology

Modern decision neuroscience offers a powerful and broad account of human behaviour using computational techniques that link psychological and neuroscientific approaches to the ways that individuals can generate near-optimal choices in complex controlled environments. However, until recently, relatively little attention has been paid to the extent to which the structure of experimental environments relates to natural scenarios, and the survival problems that individuals have evolved to solve. This situation not only risks leaving decision-theoretic accounts ungrounded but also makes various aspects of the solutions, such as hard-wired or Pavlovian policies, difficult to interpret in the natural world. Here, we suggest importing concepts, paradigms and approaches from the fields of ethology and behavioural ecology, which concentrate on the contextual and functional correlates of decisions made about foraging and escape and address these lacunae

곤충의 섭식 및 반포식 행동에서 나타나는 유연전략과 고정전략

학위논문(박사)--서울대학교 대학원 :자연과학대학 생명과학부,2020. 2. 피오트르 야브원스키.This dissertation presents my theoretical and empirical studies of flexibility focused on two topics of insect ethology. The first topic is the collective foraging strategy of the ants. Army ants were chosen as an example of extremely low behavioral flexibility in foraging; and on the other hand, carpenter ants were used to study mechanisms of extraordinarily high flexibility. My second interest is the behavioral control of aposematism, the phenomenon in which a defended prey animal gives a warning signal to predators who may recognize its advertised unprofitability. In my first study, I investigated theoretical benefits potentially associated with the evolution of specialized foraging behavior performed by army ants. It is known that a typical colony of Neotropical army ants (subfamily Ecitoninae) regularly raids a large area around their bivouac by forming a narrow directional column that can reach up to one hundred meters in length. Then the raid is finished and then relaunched 12–17 times, each time toward different orientations before the colony relocates to a new area. A hypothetical alternative to this foraging mode is raiding radially and symmetrically by expanding the search front in every direction like a circular bubble. Using an existing agent-based modeling software that simulates army ants behavior, I compared the two possible modes of foraging in different food distributions. Regardless of the food patch abundance, the radial raiding was superior to the directional raiding when food patches had low quality, and the directional raiding was favored when the patches were rich. In terms of energy efficiency, the radial raiding was the better strategy in a wide range of conditions. In contrast, the directional raiding tended to yield more food per coverage area. Based on this model, I suggest that the directional raiding by army ants is an adaptation to the habitats with the abundance of high-quality food patches. This is the first theoretical argument for the adaptive value of the army ant behavioral syndrome which agrees with cumulated body of existing empirical measurements and descriptive models. This conclusion fits well with the known ecological conditions of army ants and their habitat. In the second study, I conducted field experiments using wild colonies of carpenter ants (Camponotus japonicus). Unlike the army ants which obligatorily maintain their tight marching column, C. japonicus shows considerable variation in the coherence when foraging in a group. My investigation on this variability was centered on three sub-questions. First, I observed if higher group dispersion resulted in the lower chances of reaching the food source. As a dispersed group would cover a wider search area collectively, I believed that there would be some balancing disadvantage that can explain the coexistence of coherent and dispersed foraging behaviors. Second, I explored if there is any correlation between the group coherence and the behavior of the scout, the key individual that first discovers the food source and subsequently summons multiple nestmates to the site. As the scouts of related species were known to have central control over their groups of recruits in various ways, I hypothesized that C. japonicus scouts would be also involved in the determination of group behavior. Third, I tested what would happen if I remove the scout from a group. I believed that the lack of scout pheromone would signal dispersion, as the scout seemed to be the source of coherence signals. After my analysis, I reached the following conclusions. First, higher group dispersion leads to lower success rates in correctly finding the food source. Second, the mobility of the scout in the pre-recruitment stage, her characteristic stroking behavior during recruitment, and the dispersion of the recruited group were correlated to each other. Third, the simple lack of scout signal was not adequate to explain the observed variable reactions of the abandoned followers, and their response was linked to the pre-recruitment behaviors of the scout. I believe that C. japonicus possesses one of the most complicated recruitment strategy among the entire Formicidae, and the above findings rendered this species one of the best-understood ants in terms of mechanisms through which the flexible group foraging is controlled. From the above two studies, I revealed each one of the ultimate and proximate mechanisms that maintain different levels of flexibility in ants foraging strategy. My final topic, the behaviorally controlled aposematism, is a variant of aposematism in which the defended prey animal can choose to give different levels of anti-predatory warning signals depending on the circumstances. This switching may occur in reaction to predators approach (pre-attack signals) or attack (post-attack signals). The switchable aposematism has been relatively poorly studied, but it could possess a variety of benefits. First, the switching could startle the predators (deimatism). Second, it could facilitate the aversive learning. Third, it could minimize the exposure or energetic expense, as the signal can be switched off. These potential benefits might offset the cost of developing, maintaining and utilizing the switchable traits. Here I focused on the third benefit of switchability, the cost-saving aspect, and developed an individual-based computer simulation of predators and prey. In 88 128 model runs, I observed the evolution of permanent, pre-attack, or post-attack aposematic signals of varying strength. I found that, in general, the pre-attack switchable aposematism may require moderate predator learning speed, high basal detectability, and moderate to high signal cost. On the other hand, the post-attack signals may arise under slow predator learning, low basal detectability, and high signal cost. When predator population turnover is fast, it may lead to the evolution of post-attack aposematic signals that are not conforming to the above tendency. I also suggest that the high switching cost may exert different pressure on the pre-attack and post-attack switchable strategies. To my knowledge, these are the first theoretical attempts to systematically explore the evolution of the switchable aposematism relative to permanent aposematism in defended prey. These findings in common provided novel view into the proximate and ultimate mechanisms of behavioral flexibility found in insects. In addition, they exposed limitations of our understanding that called for future studies. First, I expect agonistic interactions with competitors or prey animals would considerably affect the collective foraging, aposematism, and food aversion, but I could not successfully provide universal background for such effects within the currently available datasets and literature in spite of many efforts. Second, the qualitative difference of food items such as carbohydrate- or protein-richness is known to be pivotal in insect trophic ecology, but the scarcity of information and logistical limitations left me being unable to incorporate relevant enquiries into this dissertation. I predict that further discussions and experiments regarding these questions will reveal valuable information about the balance between the needs of resource exploitation and defense, which might greatly influence the behavioral flexibility of insects observed in the ecosystem.이 논문은 곤충 행동학상의 두 가지 주제를 중심으로 하여 유연성에 대한 이론적 및 실험적 연구들을 제시한다. 첫 번째 주제는 개미의 집단적 섭식 전략이다. 이 논문에서는 먹이찾기 행동에서 매우 낮은 행동적 유연성을 보이는 예시로 군대개미를 선택하였고, 매우 높은 유연성의 기전을 연구할 대상으로는 왕개미를 택하였다. 두 번째 주제는 방어능력을 갖춘 피식동물이 포식자에게 정보를 주어 그 부적합성을 알게 하는 현상, 즉 경고신호 (aposematism) 의 행동적 통제이다. 첫 번째 연구에서는 군대개미의 특화된 섭식 행동이 진화할 수 있게 한 이론적인 이점들을 조사하였다. 신열대구 군대개미 (Ecitoninae아과) 의 집락은 일반적으로 100여 미터에 이르는 가느다란 행렬을 특정 방향으로 지향하여 영소 (bivouac) 주변의 광활한 지역을 강습하는 것으로 알려져 있다. 이러한 강습 행동이 매번 다른 방향으로 12-17번 반복된 후 집락은 새로운 지역으로 이주한다. 이와 같은 먹이찾기 방법에 대해 하나의 가설적인 대안은 방사적, 대칭적인 형태로 강습하여 수색대의 최전선이 점차 확장되는 원형을 형성하도록 전진하는 것이다. 이와 같은 두 가지 먹이찾기 방법을 다양한 먹이자원 분포 하에서 비교해보기 위해, 군대개미의 행동을 시뮬레이션하는 기존의 개체 기반 모델링 소프트웨어를 활용하였다. 먹이패치의 질이 낮은 경우, 먹이패치의 풍부도와 무관하게 방사형 강습 행동은 지향성 강습보다 우월한 결과를 보였으며, 반면 먹이패치의 질이 높은 경우 지향성 강습이 유리하였다. 에너지 효율의 측면에서는 광범위한 조건에 걸쳐 방사형 강습이 더 나은 전략인 것으로 밝혀졌다. 그에 반해, 지향성 강습은 탐색 면적 당 더 많은 먹이를 구할 수 있는 경향이 있었다. 이 연구에서는 이 모델을 기반으로 하여, 군대개미의 지향성 강습 행동이 양질의 먹이패치가 풍부한 서식지 환경에 적응한 결과임을 주장하였다. 이는 지금까지 누적된 실험적 측정값 및 기술적 모델들과 일치하면서 군대개미 행동군 (behavioral syndrome) 의 적응적 가치를 보여주는 최초의 이론적 논증이다. 이러한 결론은 군대개미와 그 서식지에 대해 기존에 알려진 생태학적 지식과 잘 일치하는 것이다. 두 번째 연구에서는 왕개미 (Camponotus japonicus)의 야생 집락을 대상으로 야외 실험을 진행하였다. 응집된 행진 대열만을 절대적으로 고수하는 군대개미와 달리, C. japonicus는 집단적으로 먹이를 찾을 때 응집도의 변산이 상당히 크다. 이 연구에서는 다음의 세 가지 하위 질문을 중심으로 이 현상에 대한 조사를 진행하였다. 첫째, 집단의 분산도가 높으면 먹이원에 이르는 성공률이 낮아지게 되는가를 관찰하였다. 분산된 집단은 전체적으로 보았을 때 더 넓은 면적을 탐색하게 된다는 점을 감안할 때, 그에 대응되는 단점이 존재하여야 응집형 및 분산형 집단이 공존하는 현상을 설명할 수 있으리라 판단하였다. 둘째, 처음으로 먹이원을 발견하고 이후에 다수의 동료들을 불러모으는 중심 개체인 정찰병의 행동이 집단적 응집도와 어떠한 연관성을 지니는지 탐색하였다. 근연종의 정찰병들이 소집된 집단에 대해 다양한 방식으로 통제력을 행사하는 것이 알려져 있었으므로, C. japonicus 정찰병 역시 집단 행동의 결정에 관여할 것이라는 가설을 수립하였다. 셋째, 집단으로부터 정찰병을 제거하는 경우 어떤 반응이 나타나는지 시험하였다. 정찰병이 응집 신호의 근원인 것으로 생각되었으므로, 정찰병 페로몬의 부재는 곧 분산 신호로 해석될 것이라 판단하였다. 분석 결과, 이 연구는 다음과 같은 결론들에 도달하였다. 첫째, 집단의 분산도가 높으면 먹이원을 올바르게 찾아내는 성공률이 낮아진다. 둘째, 소집 전단계에서 정찰병의 이동성, 소집 중 정찰병의 획긋기 행동, 소집된 집단의 분산도는 모두 서로 연관되어 있다. 셋째, 정찰병 신호의 단순 부재만으로는 남겨진 추종자들의 다양한 반응을 모두 설명할 수 없으며, 이들의 반응은 소집 전단계에서 정찰병이 보였던 행동과 연결되어 있다. C. japonicus는 개미과를 통틀어 가장 복잡한 소집전략을 지닌 종 중 하나로 생각되는데, 위와 같은 발견들을 통해 집단적 섭식행동의 유연성 및 그 제어방법이라는 영역에서 이 종에 대한 이해도는 개미 중 최고 수준에 이르게 되었다. 위의 두 연구에서는 개미의 섭식 전략에서 다양한 수준의 유연성이 유지되게 하는 궁극적 및 직접적 기전 한 가지씩을 규명하였다. 이 논문의 마지막 주제는 행동적으로 통제 가능한 경고신호, 즉 방어능력을 갖춘 피식동물이 상황에 따라 다른 수준의 반포식 경고신호를 택할 수 있는 현상에 대한 것이다. 이와 같은 신호의 전환 은 포식자의 접근에 대응하여 발생할 수도 있고 (공격전 신호) 또는 공격에 대응하는 것일 수도 있다 (공격후 신호). 전환가능한 경고신호는 비교적 연구가 잘 되어 있지 않으나, 다양한 이점을 지닐 것으로 보인다. 첫째, 전환 행동 자체가 포식자를 놀라게 할 수 있다. 둘째, 회피 학습을 촉진할 수 있다. 셋째, 신호를 꺼 놓음으로써 불필요한 노출이나 에너지 소모를 최소화할 수 있다. 이와 같은 잠재적인 이점들은 전환형 형질을 발달시키고 유지하는 데 필요한 비용을 상쇄할 가능성이 있다. 이 연구에서는 전환가능성의 세 번쨰 이점, 즉 비용 절감 측면에 초점을 맞추어 포식자와 피식자에 대한 개체 기반 컴퓨터 시뮬레이션을 개발하였다. 88,128회의 모델 구동을 통하여 다양한 강도의 영구적, 공격전 및 공격후 경고신호가 진화하는 과정을 관찰하였다. 일반적으로, 공격전 경고신호는 중등도의 포식자 학습속도, 높은 기저 발견률, 중등도에서 고도의 신호비용을 요구하리라는 점을 발견하였다. 그에 반해 공격후 진호는 낮은 포식자 학습속도, 낮은 기저 발견률, 높은 신호비용 하에서 나타날 가능성이 높았다. 포식자 개체군의 회전이 빠른 경우, 위의 경향성을 벗어난 공격후 신호의 진화가 가능하였다. 또한 이 연구는 높은 전환비용이 공격전 및 공격후 신호 전략에 대해 서로 다른 압력을 가하리라는 예측을 제시하였다. 이와 같은 발견들은 방어능력이 있는 피식동물에서 영구적 경고신호에 대해 전환가능한 경고신호가 진화하는 과정을 체계적으로 탐색하고자 한 최초의 이론적 시도이다. 이와 같은 발견들은 공통적으로 곤충에서 나타나는 행동적 유연성의 직접적 및 궁극적 기전에 대해 새로운 시각을 제공하였다. 또한 이 연구들은 후속 연구를 필요로 하는 이해의 한계를 노출하기도 하였다. 첫째, 경쟁자나 피식자와의 적대적 상호작용이 집단섭식, 경고신호 및 회피학습에 상당히 큰 영향을 끼칠 것으로 예상되나, 많은 노력에도 불구하고 현재 가용한 데이터와 문헌으로는 이같은 효과에 대해 범용적인 배경지식을 생산할 수 없었다. 둘째, 탄수화물 또는 단백질 함량과 같은 먹이자원의 질적 차이가 곤충의 영양생태에 중대한 영향을 준다는 것이 알려져 있으나, 정보의 희박함과 자원의 한계로 인하여 이와 관련된 조사를 본 논문에 포함시키지 못하였다. 이러한 질문들에 대한 추가적인 논의와 실험이 이루어진다면, 생태계에서 관찰되는 곤충의 행동적 유연성에 큰 영향을 주고 있을 자원 획득과 방어의 균형에 관한 가치 있는 정보들이 밝혀지리라 예상한다.CHAPTER 1: INTRODUCTION 1 1. 1 Opening remarks 1 1. 2 Behavioral flexibility in ant foraging 3 1. 3 Behavioral flexibility in aposematism 5 CHAPTER 2. WHY DO ARMY ANTS, AND ONLY ARMY ANTS, FORAGE IN COLUMNS? 7 2. 1 Introduction 8 2. 2 Methods 9 2. 3 Results 11 2. 4 Discussion 12 CHAPTER 3. COLUMNAR FORAGING WITH VARYING COHESIVENESS: BEHAVIOR OF Camponotus japonicus 20 3. 1 Introduction 20 3. 2 Methods 24 3. 3 Results 33 3. 4 Discussion 35 CHAPTER 4. SWITCHABLE APOSEMATISM: A BEHAVIORALLY CONTROLLED WARNING SIGNAL 65 4. 1 Introduction 66 4. 2 Methods 71 4. 3 Results 90 4. 4 Discussion 93 4. 5 Appendix 122 CHAPTER 5. GENERAL CONCLUSION 140 REFERENCES 145 국 문 초 록 159 ACKNOWLEDGMENT 164Docto

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Modern decision neuroscience offers a powerful and broad account of human behaviour using computational techniques that link psychological and neuroscientific approaches to the ways that individuals can generate near-optimal choices in complex controlled environments. However, until recently, relatively little attention has been paid to the extent to which the structure of experimental environments relates to natural scenarios, and the survival problems that individuals have evolved to solve. This situation not only risks leaving decision-theoretic accounts ungrounded but also makes various aspects of the solutions, such as hard-wired or Pavlovian policies, difficult to interpret in the natural world. Here, we suggest importing concepts, paradigms and approaches from the fields of ethology and behavioural ecology, which concentrate on the contextual and functional correlates of decisions made about foraging and escape and address these lacunae

Influence of Vectors' Risk-Spreading Strategies and Environmental Stochasticity on the Epidemiology and Evolution of Vector-Borne Diseases: The Example of Chagas' Disease

Insects are known to display strategies that spread the risk of encountering unfavorable conditions, thereby decreasing the extinction probability of genetic lineages in unpredictable environments. To what extent these strategies influence the epidemiology and evolution of vector-borne diseases in stochastic environments is largely unknown. In triatomines, the vectors of the parasite Trypanosoma cruzi, the etiological agent of Chagas' disease, juvenile development time varies between individuals and such variation most likely decreases the extinction risk of vector populations in stochastic environments. We developed a simplified multi-stage vector-borne SI epidemiological model to investigate how vector risk-spreading strategies and environmental stochasticity influence the prevalence and evolution of a parasite. This model is based on available knowledge on triatomine biodemography, but its conceptual outcomes apply, to a certain extent, to other vector-borne diseases. Model comparisons between deterministic and stochastic settings led to the conclusion that environmental stochasticity, vector risk-spreading strategies (in particular an increase in the length and variability of development time) and their interaction have drastic consequences on vector population dynamics, disease prevalence, and the relative short-term evolution of parasite virulence. Our work shows that stochastic environments and associated risk-spreading strategies can increase the prevalence of vector-borne diseases and favor the invasion of more virulent parasite strains on relatively short evolutionary timescales. This study raises new questions and challenges in a context of increasingly unpredictable environmental variations as a result of global climate change and human interventions such as habitat destruction or vector control.Centro de Estudios Parasitológicos y de Vectore

Influence of Vectors' Risk-Spreading Strategies and Environmental Stochasticity on the Epidemiology and Evolution of Vector-Borne Diseases: The Example of Chagas' Disease

Insects are known to display strategies that spread the risk of encountering unfavorable conditions, thereby decreasing the extinction probability of genetic lineages in unpredictable environments. To what extent these strategies influence the epidemiology and evolution of vector-borne diseases in stochastic environments is largely unknown. In triatomines, the vectors of the parasite Trypanosoma cruzi, the etiological agent of Chagas' disease, juvenile development time varies between individuals and such variation most likely decreases the extinction risk of vector populations in stochastic environments. We developed a simplified multi-stage vector-borne SI epidemiological model to investigate how vector risk-spreading strategies and environmental stochasticity influence the prevalence and evolution of a parasite. This model is based on available knowledge on triatomine biodemography, but its conceptual outcomes apply, to a certain extent, to other vector-borne diseases. Model comparisons between deterministic and stochastic settings led to the conclusion that environmental stochasticity, vector risk-spreading strategies (in particular an increase in the length and variability of development time) and their interaction have drastic consequences on vector population dynamics, disease prevalence, and the relative short-term evolution of parasite virulence. Our work shows that stochastic environments and associated risk-spreading strategies can increase the prevalence of vector-borne diseases and favor the invasion of more virulent parasite strains on relatively short evolutionary timescales. This study raises new questions and challenges in a context of increasingly unpredictable environmental variations as a result of global climate change and human interventions such as habitat destruction or vector control.Centro de Estudios Parasitológicos y de Vectore