Ecological Interactions Within Communities PDF

11/5/24 Chapter VII Ecological Interactions within Communities Krizler C. Tanalgo Angelo R. Agduma 1 Intended IntendedLearning Outcomes Learning (ILO) (ILO)...

11/5/24 Chapter VII Ecological Interactions within Communities Krizler C. Tanalgo Angelo R. Agduma 1 Intended IntendedLearning Outcomes Learning (ILO) (ILO) Outcomes 1. Identify Ecological Relationships: Students will learn to identify and categorize ecological relationships like predation, competition, mutualism, and parasitism in ecosystems and offer real-world examples. 2. Analyse Ecosystem Resilience: Students should analyse how ecological interactions impact ecosystem stability and resilience and predict how disturbances like climate change or habitat destruction affect ecological equilibrium. 3. Design Conservation Strategies: Learners will be able to create conservation strategies that address ecological interactions to safeguard biodiversity and ecosystem health. 4. Evaluate Human Impact: Graduates should critically assess human impact on ecological interactions and environmental consequences, understanding ethical and ecological implications. 2 1  11/5/24 Topic Outline Ecological interactions Types of positive and negative interactions Consequences of the interactions 3 What are some ecological interactions? Population – group of individuals of the same species living in the same area, potentially interacting. Community – group of populations of different species living in the same area, potentially interacting. 4 2  11/5/24 Why are ecological interactions important? Interactions can affect distribution and abundance. Interactions can influence evolution. Think about how the following interactions can affect distribution, abundance, and evolution. 5 Types of Ecological Interactions Competition Predation Parasitism Mutualism Commensalism Symbiosis 6 3  11/5/24 7 Competition Two species share a requirement for a limited resource à reduces fitness of one or both species. 8 4  11/5/24 Competition Mutually negative interaction between two species in the same guild or trophic level. Changes in abundance, fitness, or some fitness component (growth, feeding rate, body size, survival). 9 Modes of Competition Intraspecific: Competition with members of own species; includes exploitative competition Interspecific: Competition between individuals of two species - reduces fitness of both. 10 5  11/5/24 Interference competition - when an individual directly alters the resource- attaining behavior of other individuals Ex. male gorilla prohibits other males from accessing a mate by using physical aggression Exploitative competition - when individuals interact indirectly as they compete for common resources, like territory, prey or food. Ex. the use of the resource by one individual will decrease the amount available for other individuals. Apparent competition - when two individuals that do not directly compete for resources affect each other indirectly by being prey for the same predator. Ex. a hawk that preys both on squirrels and mice, the squirrel population increases, then the mouse population may be positively affected since more squirrels will be available as prey for the hawks. However, an increased squirrel population may eventually lead to a higher population of hawks requiring more prey, thus, negatively affecting the mice through increased predation pressure as the squirrel population declines. 11 Intraspecific Competition among Herbaceous Plants Plant growth rates and weights have been found to increase in low density populations. Competition for resources is more intense at higher population densities. Usually leads to mortality among competing plants. Self-Thinning 12 6  11/5/24 Ecological Niches Niche: Summarizes environmental factors that influence growth, survival, and reproduction of a species. Gause: Principle of Competitive Exclusion Two species with identical niches cannot coexist indefinitely. One will be a better competitor and thus have higher fitness and eventually exclude the other. 13 Ecological Niches Hutchinson defined niche as: n-dimensional hyper-volume n equates the number of environmental factors important to survival and reproduction of a species. Fundamental niche - hypervolume Realized niche includes interactions such as competition that may restrict environments where a species may live. 14 7  11/5/24 Feeding Niches of Galapagos Finches Grant found differences in beak size among ground finches translates directly into diet. Size of seeds eaten can be estimated by measuring beak depths. Individuals with deepest beaks fed on hardest seeds. After 1977 drought, the remaining seeds were very hard. Thus, mortality was most heavy in birds with smaller beaks. 15 Feeding Niches of Galapagos Finches 16 8  11/5/24 Competition and Niches Competition can restrict species to their realized niches. But if competitive interactions are strong and pervasive enough, they may produce an evolutionary response in the competitor population. Changes fundamental niche. 17 Fundamental niche - total range of environmental conditions that are suitable for existence without the influence of interspecific competition or predation from other species. The realized niche describes that part of the fundamental niche actually occupied by the species. 18 9  11/5/24 Niche Overlap and Competition Between Barnacles Connell discovered interspecific competition in barnacles. Balanus plays a role in determining lower limit of Chthamalus within intertidal zone. Did not account for all observed patterns. 19 20 10  11/5/24 Ecological Interactions that Drive Selection 2. Predation - one organism kills and consumes another provides energy to prolong the life and promote the reproduction of the organism that does the killing, the predator, to the detriment of the organism being consumed, the prey a. Carnivory a. Animal Carnivory Cannibalism (intraspecific) b. Carnivorous plants b. Herbivory Drives adaptations in both the herbivore and the plant species it eats. For example, to reduce the damage done by herbivores, plants have evolved defenses, including thorns and chemicals 21 Predation – one species feeds on another à enhances fitness of predator but reduces fitness of prey 22 11  11/5/24 Three general categories of hunting tactics 1. Ambush - lie and wait; requires minimal energy; low frequency of success. 2. Stalking - deliberate tracking of prey; quick attack, most time spent encountering prey. 3. Pursuit - Minimal search time; (chasing) pursuit time great 23 Lotka Volterra Effect of interspecific competition on population growth of each species. 24 12  11/5/24 Lotka-Volterra Effect of interspecific competition on population growth of each species: dN1 / dt = rm1N1 ((K1-N1-⍺12N2) / K1) dN2 / dt = rm2N2 ((K2-N2- ⍺21N1) / K2) ⍺12: Effect of individual of species 2 on rate of pop. growth of species 1. ⍺21: Effect of individual of species 1 on rate of pop. growth of species 2. Predicts coexistence of two species when, for both species, interspecific competition is weaker than intraspecific competition. 25 Assumptions of the Lotka-Voltera Oscillatory Dynamics: The equations predict oscillations in both prey and predator populations, meaning they fluctuate over time. When prey is abundant, predators increase; as predators rise, prey declines; with less prey, predator numbers fall, allowing prey to recover, and so on. Closed System: The model assumes no immigration or emigration, meaning the populations are closed and isolated. Constant Rates: Growth and predation rates (α\alphaα, β\betaβ, δ\deltaδ, and γ\gammaγ) are assumed constant, which is rarely the case in natural systems where environmental factors change. 26 13  11/5/24 Prey-Predator Relationship based on LV 27 Causal Loop Diagram of Predator Prey In general, LV predicts coexistence of two species when, for both species, interspecific competition is weaker than intraspecific competition. 28 14  11/5/24 Ecological Interactions that Drive Selection Parasitism – a relationship in which one organism, the parasite, lives off of another organism, the host, harming it and possibly causing death. The parasite lives on (ectoparasite) or in (endoparasite) the body of the host. Taenia, Ascaris Fleas, lice Barnacle (Sacculina carcini) Viruses 29 Holoparasites vs Hemiparasites Holoparasites derive all of its fixed carbon, water nutrients from the host plant. Commonly lacking chlorophyll Rafflesia Hemiparasites may obtain only water and mineral nutrients from the host plant and remain photosynthetic, or many also obtain a part of their organic nutrients from the host. Mistletoe 30 15  11/5/24 Rafflesia arnoldii: A holoparasite on vines of the genus Tetrastigma http://carnivorousockhom.blogspot.com/2020/05/meeting-with-rafflesia-arnoldii-world.html 31 Hemiparasite A. Cuscuta B. Mistletoe 32 16  11/5/24 Avian Brood Parasitism A Reproductive Strategy Brood parasitic birds lay their eggs in the nests of others, sparing themselves the expense of rearing their own young Diminished nestling growth Eviction of all host eggs Killing of host hatchlings Common Cuckoos (Cuculus canorus) parasitizing Common Redstarts (Phoenicurus phoenicurus) Brown-headed Cowbirds (Molothrus ater) at the nestling site of the Eastern Phoebe (Sayornis phoebe) 33 Parasitoid-Parasite An organism that lives in close association with its host at the host's expense, eventually resulting in the death of the host Protective and active strategies Avoid and deactivate the recognition processes, neutralizing the host immune response Diadegma stenosomus 34 17  11/5/24 Ecological Interactions that Drive Selection Pathogens (Disease) Are organisms that cause disease. Bacteria, fungi and viruses Three components necessary for a disease to occur a susceptible host a virulent pathogen a favorable environment 35 Mutualism Two species provide resources or services to each other à enhances fitness of both species. 36 18  11/5/24 Mutualism as defense by other organism Example: fungal endophytes providing grass hosts with chemical defences against herbivores, and ants protecting acacia trees from herbivores in exchange for nesting sites. 37 Figure 14.16 An Ant–Plant Mutualism 38 19  11/5/24 Characteristics of Mutualism A mutualist may withdraw the reward that it usually provides. In high-nutrient environments, plants can easily get nutrients and may reduce the carbohydrate reward to mycorrhizal fungi. The costs of supporting the fungus are greater than the benefits the fungus can provide. 39 Characteristics of Mutualism Cheaters are individuals that increase offspring production by overexploiting their mutualistic partner. If this happens, the interaction probably won’t persist. Several factors contribute to the persistence of mutualisms. “Penalties” may be imposed on cheaters 40 20  11/5/24 Figure 14.14 Yuccas and Yucca Moths 41 Figure 14.15 A Penalty for Cheating 42 21  11/5/24 Positive Interactions Commensalism (+/0 ) Examples: lichens that grow on trees, bacteria on your skin. 43 Commensalism One species receives a benefit from another species à enhances fitness of one species; no effect on fitness of the other species 44 22  11/5/24 Symbiosis* A relationship in which the two species live in close physiological contact with each other, such as corals and algae. Symbioses can include parasitism (+/–), commensalism (+/0), and mutualism (+/+). 45 Positive Interactions Some positive interactions are highly species- specific and obligate (not optional for either species). Example: Fig trees and wasp pollinators 46 23  11/5/24 Figure 14.6 Fig Flowers and the Wasp That Pollinates Them 47 Figure 14.6 Fig Flowers and the Wasp That Pollinates Them 48 24  11/5/24 Organizing Ecological Interactions effect on species 1 + 0 - predation herbivory + mutualism commensalism parasitism effect on species 2 0 commensalism competition predation - herbivory parasitism competition competition 49 50 25  11/5/24 coordinate model of two-species interactions 51 Thank you! 52 26