Power4_AutecologyNiches - Big ecology questions 1 What...

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1 Big ecology questions: 1. What factors determine distribution and abundance of organisms ? 2. What regulates populations ? 3. How will organisms, ecosystems or the planet respond to changes in environment (climate, land use, extinctions, invasions of new species) ? 2 Distributions and performances of species along environmental gradients or across thresholds How do environmental conditions change across landscapes (seascapes)? Physical factors Energy sources Where in the landscape (or seascape) do boundaries occur that limit species? How might these boundaries change with environmental change? 3 Macan’s filter (similar to Fig. 50.5, p. 1056 Campbell): If a species is absent from a habitat, is it because of: 1. Dispersal Yes: hasn’t arrived yet (barriers, insufficient time) No: propagules* have arrived, but don’t persist *propagule: a dispersing unit capable of establishing a new population (e.g., one asexual spore, Adam and Eve, a pregnant female fish, or a fragment of a plant that can reproduce vegetatively) 2. Behavior Yes: colonists avoid habitat No: colonists select habitat, but don’t persist 4 Macan’s filter, continued 3. Abiotic factors? Yes: temperature, salinity, pH, moisture conditions* etc. are outside the range that the species can tolerate No: abiotic conditions are tolerable. 4. Biotic interactions? Yes: species is excluded by predators, pathogens, competitors, or the lack of prey resources** or mutualists No: ? you’ve missed the organism in your sampling observations… complex interactions of several factors above… 5 Fig. 50.5, p. 1056 Campbell How do traits of organisms affect their response to environmental factors? 6 Example: Africanized bees may have been selected in tropics to withstand or avoid predation by army ants --aggressive defensive stinging --bees disperse at small colony size European bees shiver to warm hives during winter. Will second trait limit the northward spread of Africanized bees? (Don’t build up large enough colonies to warm hive by collective shivering.)
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7 Resources, conditions, and the fundamental niche What determines the distribution and abundance of species? – In part, their tolerance of conditions, and their need for certain resources * condition : abiotic environmental factor that varies in space and time and affects the performance of organism ** resource : all things consumed (used up) by organisms (space, nutrients, water, prey, holes for refuge, etc) 8 Performance is generally nonlinear across a range of intensities of an
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  • Fall '07
  • Carlson,Mischel,Power
  • Ecology, Plants, Evolution, Sufficient resource Tolerable, resources Intolerable conditions, resource Tolerable conditions, Tolerable conditions Insufficient

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