Analysis of Distributions 1 Transplant experiments Why doesn t a species occur everywhere That is what is the reason from absence of a species from a given area To answer this set up a transplant experiment o Establish a control group Handle individuals identically to treatment group but place them back into their native site o Establish a treatment group Handle individuals identically to control group but move them to a non native site o Assess results Did the treatment group survive and reproduce as well as the control group If yes the non native site must be perfectly suitable no survival reproduction differences dispersal limitation or limitation by habitat selection If no non native site is not suitable limitation by biotic factors or limitation by physical or chemical factors 2 Physical tolerances Shelford s law of tolerance o Distribution controlled by environmental factor for which the organism has the narrowest range of physiological adaptability Complications o Several factors may interact to set distributional limits o Acclimation can alter ranges of tolerance E g artic charr Lower lethal critical minima Upper lethal critical maxima i Temps vary with acclimation temp 3 Detecting local adaptation Local adaptation result of natural selection favoring traits that are advantageous under particular ecological circumstances o E g toxic mine soils and grasses Plants moved from toxic to non toxic soil and plants moved from nontoxic to toxic soil locations suffered compared to controls adaptation to toxins or lack of adaptation Can be detected using reciprocal transplant experiment o Plants from site A are moved to site B o Reciprocal plants moved from site B to site A o Survival reproduction is compared to control groups 4 Sequential analysis to reasons for species absence Species absent because of Limited dispersal abilities limited time for dispersal dispersal Habitat selection Behavior Limitation by other species Biotic factors Physical or chemical factors Abiotic factors