Population Density: seven types of rarity (refer to slide 35 on 0828)oRarity – the quality of being infrequently encountered.oCriteria for rarity:Geographic range size is smallHabitat tolerance is narrowLocal abundance is lowSpatial distribution The pattersof Spatial distribution:
oProcesses:oSpatial Distribution – CLUMPEDi.e. Butterfly fish, Yellow popularlarge quantities of seed but they do not disperse very well so they are clumped together (High density around adult plants), Woodland cariboudefensive against wolf predators more eyes that are able to see danger, Schools of fish Schooling resulting in random movements (always safest in the middle)Attraction between individuals or local depletion of resourcesSafety in numbers oSpatial Distribution – UNIFORMi.e. Emperor penguinsThey are all evenly spaced apart to where they can flap their wings and not slap each other, Golden eagles(Look at purple dots) areas where eagles have nested and have produced a chick. Among nesting grounds they are very evenly spaced out. It is a territorial thing – guarding their nests. As with Eagles nests that are evenly spaced also.Interacting in a negative way Antagonistic interactions between individuals or local depletion of resourcesThese individuals are competing for resourcesoSpatial Distribution – RANDOMi.e. Juvenile oysters-the currents distribute the oyster offspring. Over time oysters compete overspace and eventually become UNIFORMLY distributed but as juveniles they are RANDOM. Dandelions-seeds are disbursed by the winds and get a random distribution. Passively dispersed by the wind. Tropical tree species-super high population in the forests but they are randomly distributed.Harder to quantifyIn the tropics the plants seeds are ofen dropped by animals in random places which produce random distribution of these plants.Neutral interactions between individuals, and between individuals and environmentNeither attracted to each other or repelled to each other.oSpatial Distribution of Creosote Bushillustrating (all three distributions) competitive for water
Small shrubs establish in high densities and produce a clumped distribution (young, small shrubs,small juvenile) – CLUMPED (Like yellow popper)Mortality as the shrubs grow reduces clumping and produces a random distribution among medium shrubs (medium shrubs) – RANDOMCompetition enforces a regular distribution among large shrubs (large adult shrubs) –REGULAR/UNIFORMThey just keep dying from lack of water creating a uniform distributionDistribution of tropical bee coloniesPredicted that if bees are aggressive they should be evenly distributedBees are a modular organism (focused on the colony being the individual)Aggressive colonies: hypothesized that they would form uniform distributionsNon-aggressive colonies: hypothesized that they would form a random or clumped distributionsAs predicted, four species with regular distributions were highly aggressive. The fifh was non-
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