Competition

Coastal sage scrub – note bare spots near shrubs

Rabbit grazing – source of apparent competition

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

Lions hunting – True Predator

Moose Browsing – Partial Predator

Parasitoid Wasp

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

Pied Wagtail

Caribou eating lichens

Edible mussel – Mytilus edulis

Black oystercatcher

Bluegill sunfish

Mink Muskrat

Red grouse in heather

Tawny Owl Bank vole

Cinnabar Moth and Caterpillar on Ragwort Tansy

Snowshoe hare and Lynx

Lynx Ruffed GrouseSnowshoe hare

Sea Otter

Sea Urchin

Kelp Forest

Sea Otter eating Sea Urchin in Kelp Forest

Comparison of kelp and urchin biomass with and without sea otters

Kelp forest ecsystems with and without sea otters