Transcript Competition
Competition The struggle for existence Competitive exclusion in action? •Florida's native anole, the Green Anole (Anolis carolinensis, far left) is a direct competitor with the introduced Brown Anole (Anolis sagrei, near left). • Intraspecific competition: between individuals of the same species species • Interspecific competition: between closely related species. It isn’t only animals that compete An invasive red marine red algae, Bangia, was in the western basin of Lake Erie, it was able to compete well for space with the native green algae Cladophora, Scramble competition • scramble form = no direct interaction; each party tries to obtain resource as rapidly or efficiently as possible • All individuals have an equal chance for success • All individuals suffer equally as resources become depleted • Interspecific contest competition • Includes an active attempt to reduce competitor's access to resources, • If the “free-for-all” limits the ability of one competitor to quickly eliminate the competition • There are winners and losers Wolfgang Bayer © Discovery Education Interspecific competition • Different species compete for a single resource. – There are winners and losers • The Bull Thistle spread to North America from Eurasia in contaminated seed. Each plant produces 5,000 to 50,000 seeds • When they move into an area – they out compete native plants for water, nutrients, and space. Paul Fuqua © Discovery Education Thistles are regarded as outlaw weeds in most of the United States. Intraspecific contest competition 1. active attempt to reduce competitor's access to resources (aggression, territoriality, 2. It isn’t always good for a species to have so even a distribution of resources that all starve • Pikas are hearty little mammals who live in rock piles high in the mountains of western North America. They have relatives in Asia too. They are related to rabbits and are about the size of large hamsters Rain Forests • No one plant can monopolize all of the resources – but some try • Trees grow buttress roots in the poor soil of rainforests. • Competition for light results in plants with long branches, wide leaves, and/or climbing vines Paul Fuqua© Discovery Education Scramble or contest? Competition affects fitness & Evolution Wild type and white eyed flies have equal fitness when grown in isolation When grown together – white larva (which eat faster) out compete the wild type. This “scramble” competition results in reduced fitness of the wild type fly Interspecific competition • Different species compete for a single resource. – There are winners and losers • When exotic animals they into an area – they out compete native plants for water, nutrients, and space. Paul Fuqua © Discovery Education Fox bringing down a wallaby competitive exclusion principle . • The classic experiments were by Gause using two species of Paramecium • When two species occupy the same – they can not coexist for long • Species that are closely related compete more f than do distant relatives Competition between species • May lead to the extinction of one species • When two species coexist – it is due to differential use of resources • This is called niche formation What are plant resources? • Growth of plants in monoculture compared to growth of plants in a mixed culture • Plants compete for a limited variety of resources: nutrients, water and light • What factors contribute to “fitness”? When plants compete • Limited resources may lead to stable coexistence, due to Source utilization and production • Plants suffer a constant loss of biomass to herbivores – Growth rate must = loss rate • If the requirements for two species are not exactly the same – greater intraspecific competition levels permit coexistentce • (the growth of species 1 affects species 1 more that species 2) Below the ground, plants compete for resources we can not see If the red plant is the good competitor If the red plant is a poor competitor Lotka-Volterra model • A mathematical summery of the interactions of competing species • Inter-specific competition vs intraspecific competition • If Inter-specific competition > intraspecific competition, one species will be driven to extinction Lotka-Volterra model This is a modification for logistic growth (density dependency) – now the effect of different species are factored in Can a habitat accept an invader? 1. All may coexist 2. The invader displaces one of the original species 3. The invader dies out. • Species 1 eliminates (blue) Species 2 (red) – Species 1 is a good competitor & uses more resources • Species 1 and 2 can coexist at the intersection (the equilibrium point) Outcomes of Competition 1. Reduction in population sizes (coexistence) 2. Change in space use or activity (coexistence) 3. Competitive exclusion (local extinction) 4. Character displacement => behavioral or morphological changes in characteristics that diminish the intensity of competition Coral reefs • This is about as complex an environment as you will find: • There are in infinite number of association that go on. Ecological Niche • Fundamental niche: composite of the characteristic food, temperature • Third aspect could be altitude, or another abiotic factor