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Ecology Notes F12.docx

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BIOL 2060
Elizabeth Boulding

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Ecology Notes F’12 Ecology: scientific study of interactions between organisms and their environments (abiotic & biotic) Equilibrium theory of insular zoogeography:  Immigration rate decreases as # of species on newly formed island accumulate because most species that arrive from main land species pool will already be present  Extinction rate increases as # of species on new island accumulate because: o Larger island pool of potential extinctions o Increased crowding decreases population size per species o Potential for competitive interactions increases as multiple species w/ similar requirements arrive Hypothesis: cause & effect explanation; A occurs because of B Prediction: C; If A occurs because of B, then you would expect C to be true Essentials of manipulative field experiment design (RRC)  Replication  Randomization  Control -species richness=(island_area) -isolated islands have fewer of mainland species -Theory: species richness on island dynamic equilibrium between immigration rates (distance) & extinction rate (island size) -experimental results mostly support theory but it needs revision Factors affecting distribution and abundance of a species (abiotic)  Transplant through experiments  Physiological ecology o Liebig’s law of the minimum o Shelford’s law of tolerance  Geographical range and climate o Temperature o moisture  Climate change o Range existence o Phonological changes in beginning of reproduction Liebig’s Law of the Minimum (Below Left) Rate of a biological process is limited by the factor in which least amount relative to organism’s requirements Growth is limited by factor farthest from optimum Shelford’s Law of Tolerance (Above Right) Distribution of a species is controlled by the environment factor for which organism has narrowest range of tolerance Can we see the consequences of global climate change yet?  Shifts in breeding times of birds  Changes in intertidal and shallow water communities on the California coast  Appearances of malaria, dengue fever and other mosquito born diseases in highlands of Asia, central Africa and Latin America Factors affecting distribution and abundance of a species (biotic)  Dispersal o Diffusion o Jump dispersal o Secular dispersal  Habitat selection  Interactions w/ other species o Competition o Predation Diffusion: gradual spread of limits of geographic range of a species over ecological time Jump Dispersal: long distance movement of particular individuals, often w/ the aid of wind or another species, followed by successful establishment of a new population Secular Dispersal: diffusion & local adaptation of a species over geological time (very slow diffusion) Invasion Theory  What determines which introduced species becomes established? o Propagule size  Allele effect (must find mate, predator avoidance)  High genetic diversity required o Ability to tolerate climate o Lack of biotic resistance  Few close competitors  Few predators o High fecundity, short generation time: highmax o Good dispersal ability Species may be absent because it:  Is a poor disperser  Avoids selecting that habitat  Is excluded by predators or competitors  Can’t tolerate the abiotic conditions  Can’t compete under abiotic conditions Resource (=exploitation or scramble) competition:  Organisms utilize common resources in short supply  Reduction in availability of resources available  May never meet Interference (=contest) competition:  Organisms seeking a resource harm one another in the process, even if resource is not in short supply  Interference w/ resource acquisition Interspecific competition:  2 species use the same limited resources or harm one another while seeking a resource Intraspecific competition:  Individuals of the same species use the same limited resource or harm one another while seeking resource Ecological methods for estimating population parameters N: population size λ: geometric (finite) rate of increase r:intrinsic capacity for increase (potential per capita rate of population growth) instantaneous rate R : net reproductive rate per generation o G: mean length of a generation Total Counts  Needed when assumptions of quadrats or mark recapture methods fail  Must catch nearly all animals  Permanently mark/photo ID each  Stop when you only catch previously marked animals  Works well for large vertebrates in a well-defined study area Quadrat Sampling  Slow animals/plants  Place quadrat at random in area where the size of population is to be estimated  Count # of individuals completely inside each quadrat  Compute mean and standard deviation for counts  Shape and size of quadrats affects variance if clumped distribution of organisms Assumptions of Lincoln-Peterson Capture/recapture  Single period of marking then single period of recapture  Marked and unmarked animals recaptured in proportion to their abundance  Marks not lost or overlooked  No change in population size over period (closed population)  *Marble
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