BIO 373 1st Edition Lecture 22 Outline of Last Lecture I. Communities contda. Changes in communities contdi. Chapin experimentii. Mechanism of successioniii. Alternative stable states1. Fouling communities2. Stability, change, hysteresisII. Species Diversitya. Spatial scalesi. Global, regional, landscape, localb. Filters i. Importance in invasive speciesc. Models of coexistencei. Resource portioningii. Intermediate disturbance hypothesisiii. Lottery modelIII. Energy in ecosystemsOutline of Current Lecture These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.I. Species Diversity contda. Hutchinson’s modeli. Paradox of the planktonb. Processes that promote coexistencei. Paineii. Intermediate disturbance hypothesisiii. Hacker and Gainesc. Lottery modeld. Consequences of Diversityi. Diversity-stability theorye. Species richness and community functionCurrent LectureSpecies Diversity Contd- Hutchinson’s Modelo Paradox of the plankton 30-40 species, 4-5 different resources so how can they coexist?- Explained that there were so many species because frequent minimal disturbances prevented a species from dominatingo Time required for one species to exclude another (tc)o Time it takes for environmental variation to act on population growth of the two species (te)o If Tc<<Te, coexistence can not occur because species can reach carrying capacity without disturbance happeningo In a fluctuating environment to which competitors are adapted to, Tc>>Te and competitive exclusion can occur Effect of disturbance is not high because species is adaptedo Coexistence can only occur when Tc=Te- Processes that promote coexistenceo Paine Tested Hutchinson’s idea that competitive exclusion is rare in nature by using predation as an environmental factor precluding competitive exclusiono Intermediate disturbance hypothesis (Connel—stimulated by Paine’s research) Coexistence defined by disturbance level- At low disturbance, competitive exclusion decreases diversity- At intermediate disturbance, there is a balance between disruption of competition and mortality, which increases diversity- At high disturbance, diversity decreases and mortality increases Predation is considered an agent of change, not a disturbance, but has that effecto Hacker and Gaines—positive interaction in intermediate disturbance hypothesis Importance of facilitation in communities- At low disturbance competition decreases diversity- Lottery Modelo Above theories assume underlying competitive hierarchyo In lottery model, all species must have equal chances of obtaining resources made available by stress and disturbanceo Must have similar interaction strength and growth rates and be able to respond quickly to events- Consequences of diversityo Species diversity can control community function, like plant productivity, soil fertility, water quality, resistance to disturbanceo Diversity-Stability Theory Species richness is positively related to community stability- Community stability= tendency of a community to remain the same structurally and functionally Low diversity, low resistance to change, high change in biomass and vice versao Species richness and community function With similar function, species richness has a limit Without similar functions, species richness has no limit With a dominate species, greater impact, more difficult to predict the function of a communityEnergy in Ecosystems- Energyo Ecosystem energy views species within communities as entities linked to each other via the transformation of energy and nutrients achieved when they engage in consumer- resource