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Competition . Coastal sage scrub – note bare spots near shrubs. Rabbit grazing – source of apparent competition . Species Coexistence. Serengeti National Park . Species Coexistence.
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Species Coexistence Serengeti National Park
Species Coexistence Competition is a common feature of species interactions, yet often we find very similar species coexisting in nature, species that seem to need the same resources. How do they coexist? • Refuge from competition • Predation keeps populations of each species low enough that they do not compete • Resources may be variable in space and time, so that the species coexist because both do not find resource at same time
Dung – a valuable, variable resource Dung Beetles Dung Fly
Predation Great White Shark and Fur Seal
Specialists and Generalist Predators Advantages to being a specialist 1. Avoid interspecific competition 2. Allows evolution to overcome chemical defense 3. Allows evolution of cryptic coloration that matches prey - mostly for insects on plants 4. Increases chance of mate encounter Advantages of being a generalist 1. Flexibility in face of environmental uncertainty 2. Broad diet needed to get all necessary nutrients and vitamins 3. Avoid overdosing on any one toxin - mostly for animals grazing on chemically defended plants
Mink Muskrat
Red grouse in heather
Bank vole Tawny Owl
Lynx Ruffed Grouse Snowshoe hare
Kelp Forest
Comparison of kelp and urchin biomass with and without sea otters