Community Ecology I Competition Iawhat Is a Community?

Community Ecology I Competition I.A.What is a community? I. Intro to Community Ecology A. What is a community? Definition: Any assemblage of populations in B. Types of interactions an area or habitat, i.e., all the different Reading: Chap. 13 C. Regulation of population dynamics species interacting in a given location II. Competition A. Terms and Concepts B. Competitive exclusion principle Encompasses many populations of different C. Factors that allow for coexistence species. D. Predicting Outcomes of Comp. Questions B. Types of interactions - How do biotic interactions affect the distribution of particular species? Neutral: 0 0 Mutualism: + + - What biotic interactions structure communities? Commensalism: + 0 Predation: + - - What factors cause changes in species richness Parasitism + - across community types? Competition: - - Understanding interactions Understanding interactions helps restoration Cows are good?! Bay checkerspot D. Hooper ©1992 Serpentine grassland Plantago erecta Invasive grasses L. Gonzalez photos 2005 D. Hooper photos 2005 1 C. Control of populations II. Competition (-/-) Density independent vs. Density dependent Multiple organisms or species trying to maximize their own use of a limited pool of resources. A. Terms II. Competition Intraspecific - among individuals of one A. Terms species Exploitative - implicit in the logistic population growth curve Interference (density dependence) Interspecific - among individuals of different species - may restrict the range of one or the other species Intraspecific competition and niches A. Terms And NUH is the letter I use to spell Nutches Niche Who live in small caves, known as Niches, for hutches. n-dimensional hypervolume These Nutches have troubles, the biggest of which is The fact that there are many more Nutches than Niches. Fundamental vs. Realized Each Nutch in a Nich knows that some other Nutch Would like to move into his Nich very much. So each Nutch in a Nich has to watch that small Nich or Nutches who haven't got Niches will snitch. “On beyond zebra”, Dr. Suess (Geisel, 1955) 2 Many invasive species have similar fundamental Niches: fundamental and realized niches to the areas they invade. fundamental niche The fundamental niche is defined by an organism’s adaptations to persist in a given realized niche abiotic environment Realized niche The realized niche of an organism could be larger than is often smaller than the fundamental due to mutualisms fundamental niche due to competition, predation, parasitism, and recruitment limitations Competitive exclusion and the niche B. Competitive exclusion principle Gause: Competitive exclusion principle. Ricklefs Fig. 19.6 Niche overlap – regulation of population size C. What allows coexistence? 1. Non-overlapping niches 2. Variable environmental conditions 3. Other species interactions 3 1. Non-overlapping niches Resource partitioning among animals = resource partitioning (Norberg et al. 1999) (Krebs 2001) Resource partitioning in plants Rooting depth Light interception E L (Vandermeer 1990) (Gulmon et al. 1983) 2. Variation in environmental conditions 4 Competitive dominant depends on temperature and humidity Climatic variability and coexistence San Jose, California 30 25 20 15 Goldfields 10 5 Annual precip. (inches) precip. Annual 0 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year Plantago D. Hooper photos 2005 Diatom competition depends on variation in nutrient availability 3. Effects of other species interactions (see Ecobeaker barnacles) Predation can lead to coexistence if… • Selective predation 2. for the competitive dominant. Understanding interactions Cows are good?! D. Predicting Outcomes of Competition Lotka-Volterra models • Models Bay checkerspot • Outcomes • Assumptions Plantago erecta Invasive grasses L. Gonzalez photos 2005 D. Hooper photos 2005 5 Where will each population grow? Where will each population grow in competition? Put both species’ isoclines together Zero growth isoclines: solve for dN/dt = 0 http://www.tiem.utk.edu/bioed/bealsmodules/competition.html http://www.tiem.utk.edu/bioed/bealsmodules/competition.html L-V Predictions Assumptions of L-V models Competitive dominant depends on relative magnitudes of K’s and α’s 1. Environment is homogenous and stable, without fluctuations (K’s and α’s constant); 2. Coexistence requires a stable equilibrium point; 3. Migration is unimportant; 4. The effect of competition is instantaneous; 5. Competition is the only important biological interaction. Spp 1 wins Spp 2 wins Unstable: either Stable could win coexistence End Diatom Competition – multiple resources 6.

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