lecture_11November_2_without_questions

lecture_11November_2_without_questions - E EM B 120 I ntr...

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EEMB 120 – Introduction to Ecology November 2, 2010 Vote Today!
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Establish patterns of species composition, resource use or community structure that could result from actions of interspecific competition Determine existence and/ or strength of competition using field experiments Study cases of competitive exclusion Establish patterns of co-evolution of competitors – character displacement Approaches used in studying Interspecific Competition
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Resource Gradient (e.g. seed size) Abundance of resource Large Seeds Small Seeds Regular Spacing of Species Along Resource Gradients Species will be arranged along resource gradients in a pattern that minimizes overlap in resource use Assume a normal distribution for some limiting resource If only 1 species present, will utilize full range of resource (reduces Intrasp. Competition) Species 1 Frequency of use Species 2 Species 2 uses some of the same resources Complete overlap w/ Species 1
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Regular Spacing of Species Along Resource Gradients Predict over time, two species will evolve or change resource use to minimize overlap reduces Intersp. Competition Resource Gradient (e.g. seed size) Large Seeds Small Seeds Frequency of use Species 2 Species 1 Expect to see competing species in a community exhibit regular spacing along resource gradient Prevents competitive exclusion Resource Gradient (e.g. seed size) Large Seeds Small Seeds Frequency of use Species 5 Species 4 Species 3 Species 2 Species 1
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Regular Spacing of Species Along Resource Gradients If species not competing, expect to see random overlap along the resource gradient Resource Gradient (e.g. seed size) Large Seeds Small Seeds Frequency of use Species 5 Species 4 Species 3 Species 2 Species 1 Compare observed overlaps in resource use with “neutral” model – Resource Gradient (e.g. seed size) Large Seeds Small Seeds Frequency of use Species 5 Species 4 Species 3 Species 2 Species 1 Neutral model – without interspecific competition Observed overlap – with interspecific competition Ex. N. American lizards (Lawlor) 10 different communities Overlap less than predicted Regular spacing along resource Are differences in resource use larger than predicted by neutral model ?
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Establish patterns of species composition, resource use or community structure that could result from actions of interspecific competition Determine existence and/ or strength of competition using field experiments Study cases of competitive exclusion Establish patterns of co-evolution of competitors – character displacement Approaches used in studying Interspecific Competition
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Competitive Exclusion of a Native Snail by an Introduced Snail (Text page 305-306) Competition between mud snails Native snail: Cerithidea californica Batillaria attramentaria introduced into northern California bays in early 1900’s Species very similar in resource use, but: Batillaria makes more efficient use of resources
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