ENVS-438,538 Lecture 7 - Native Plants Sustainability ENVS...

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Native Plants & Sustainability – ENVS 247 Course offered in upcoming Spring quarter MWF 11:00 – 11:50am Plants are an integral part of our daily lives in nearly every way,directly or indirectly. Increasingly, our landscapes are becoming dominated with species that are introduced from other parts of the world (intentionally or by accident), displacing many of the species that were once key components of our ecosystems. The impacts of the loss of native plants are profound. This course will give students an overview of the many reasons why native plants are critically important to us, and the problems that arise when non-­‐native plants replace them. There will be discussions about topics ranging from evolutionary theory, conservation, agriculture, public health, nutrition, and more.
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Assignment #2
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Assignment #2
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Discussion on Tuesday March 1 (Week 9)! Assignment #2
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Species Richness Patterns (Continued)
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Species Richness Patterns (continued) Many general patterns in species richness have been noted. A major current aim of ecology is to find general underlying causes. We discussed some of these over the past two lectures
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Species Richness Patterns and Area Effects There have been many hypotheses put forward about the relationship between area and predicted species diversity. We’ll go over just a small sample of these and attempt to simplify the discussion. Some major contributions include those of Arrhenius (1920), MacArthur and Wilson (1967), Hubbell (2001).
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Species Richness Patterns and Area Effects The species area relationship may be the oldest ecological pattern to be recognized. It was first noted by Johann Reinhold Forster (1772-75, Capt. Cook’s second voyage). “Islands only produce a greater or less number of species as their circumference is more or less extensive.” This seems intuitive (even obvious) now. But that doesn’t make it much of a model to just say that an increase in area leads to an increase in species richness.
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S = cA Z S = Number of spp. A = Area C and Z are constants that are determined by the survey data itself Z is less than one (typically in the range of 0.2 to 0.3). It yields a decelerating exponential curve: approach to asymptote The Arrhenius Relationship of Species Richness to Area
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S = cA Z S = Number of spp. A = Area C and Z are constants that are determined by the survey data itself Z is less than one (typically in the range of 0.2 to 0.3). It yields a decelerating exponential curve: approach to asymptote From Darlington’s 1957 study on island size and # of amphibians and reptiles in the Antilles The Arrhenius Relationship of Species Richness to Area
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The Arrhenius Relationship of Species Richness to Area Species-area relationships are asymptotic when using arithmetic axes. The same data can be graphed using log axes to display a linear relationship.
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The Arrhenius Relationship of Species Richness to Area Some basic consequences of this principal: A 10x increase in area leads to a 2x increase in spp. richness
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The number of species established on an island represents a dynamic equilibrium between the immigration of new colonizing species and the extinction of previously established ones.
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  • Winter '15
  • Daniel Duran
  • Ecology, Extinction event

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