Oct28lecture

Oct28lecture - EEMB 120 Introduction to Ecology October 28,...

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Unformatted text preview: EEMB 120 Introduction to Ecology October 28, 2008 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 LV Model predicts effects on Population Size - What do experiments measure ???? Field Experiments - 50 studies involving vertebrates Behavior changes in location, feeding rates, diet Performance changes in growth rate or condition Demography changes in birth or death rates Aspect Studied No. of Studies Duration (mos.) Behavior 5 6.8 Demography 19 8.2 Behavior & Demography 6 4.8 Total 30 7.3 What to measure ???? Field Experiments Ultimately want to measure change in density We assume short term changes in behavior, demography and/or performance lead to long term changes in density (not usually seen) Aspect Studied No. of Studies Duration (mos.) Density 7 31.5 Demography & Density 5 20.6 Behavior & Density 4 23.6 Behavior, Demo. & Density 4 27.3 Total 20 26.3 Lotka-Volterra Model Predicts Density Effects on Competing Species What Do Ecologists Measure? Response Variables Measured in 50 Field Experiments of Vertebrate Competition More than half (30 out of 50) studies did not measure a density response Studies that measured density response took longer (26 months vs. 7 months) Only 4 out of 50 studies looked at full range of short- and long-term responses Little evidence that it is safe to scale up results to predict density costs of competition Competition between polychaetes and oligochaetes in a sandflat (Gallagher, Gardner, and Jumars, 1990) Competitors: Hobsonia florida (polychaete) 3 species of oligochaetes Resource: benthic diatoms Competition between polychaetes and oligochaetes in a sandflat (Gallagher, Gardner, and Jumars, 1990) Both sets of competitors are pioneer species in the seasonal succession Both are abundant in the spring and summer months Both feed heavily on benthic diatoms potential for exploitative competition Competition between polychaetes and oligochaetes in a sandflat (Gallagher, Gardner, and Jumars, 1990) Studied abundances of the two species over time...
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This note was uploaded on 02/26/2009 for the course EEMB 122 taught by Professor Levine during the Spring '09 term at UCSB.

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Oct28lecture - EEMB 120 Introduction to Ecology October 28,...

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