Symbioses - Mutualism

Mutualism

• Definition - the individuals in a population of each mutualist species grow and/or survive and/or reproduce at a higher rate when in the presence of individuals of the other. Each benefits (+,+)

Mutualisms involving Culture of Crops or Livestock

Leaf-cutter Ants – genus Atta

Diagram of Leaf-cutter ant colony nest

Human Agriculture

Sustainable Dairy Industrial Wheat

Digestive Mutualisms Involving Gut Inhabitants

Ruminant with multiple stomachs

Ruminant by-products

Termite Mound Western Australia

Termites

Mycorrhizae

Ectomycorrhizae

Ectomycorrhizae

Mycorrhizae – world’s largest organisms?

• The mycelium of some forest fungi can extend enormous distances. In 1992 a single individual of Armillaria bulbosa was discovered that permeates more than 30 acres of forest soil in northern Michigan and was thought to be one of the world's largest living organisms. It may have been spawned by a single spore thousands of years ago. In 1998 another species Armillaria solidipes in the Blue Mountains of Oregon was found to consist of a subterranean mycelial network extending across 2400 acres. It must weigh thousands of metric tons. Its age could be from 2500 to 8400 years old.

Armillaria solidipes

VAM – Vesicular Arbuscular Mycorrhizae

Nitrogen Fixing Mutualisms

Red Clover – A Classic Legume

Normal Nitrogen Fixation

Legume Root Nodules

Rhizobium root nodules on a bean plant

Animal-Algae Mutualisms

Healthy Coral Reef - Indonesia

Coral polyp with zooxanthellae- a dinoflagellate, Symbiodinium

Coral polyp – coral animal is green,Zooxanthellae is red

Endosymbiotic Origin of Eukaryotes

Lynn Margulis

Endosymbiotic Origin of Eukaryotes

Endosymbiotic Origin of Eukaryotes• The earliest eukaryotes acquired mitochondria by engulfing alpha

proteobacteria.• The early origin of mitochondria is supported by the fact that all

eukaryotes studied so far either have mitochondria or had them in the past. Mitochondria have their own DNA and replicate themselves during cell division.

• Later in eukaryotic history, some lineages of heterotrophic eukaryotes acquired an additional endosymbiont—a photosynthetic cyanobacterium—that evolved into plastids.

• This hypothesis is supported by the observation that the DNA of plastids in red and green algae closely resembles the DNA of cyanobacteria.

• Plastids in these algae are surrounded by two membranes, presumably derived from the cell membranes of host and endosymbiont.

Stromatolites on coast of Western Australia

The Nature of Communities and Ecosystems

Sourdough bread – ingredients and final product

Redwood Forest

Scale of Ecosystem – Lake Superior

Scale of Ecosystem – Isle Royale

Scale of Ecosystem – Isle Royale – Forest and Pond

Scale of Ecosystem – Isle Royale Wetland

Scale of Ecosystem – Isle Royale Pitcher Plants

Ecotone – region where two communities/ecosystems grade into each

other

Forest-Marsh Ecotone

Stability

A stable community or ecosystem is one that has the ability to replace

itself – exist in place for more than one generation

Douglas-Fir

Pea Aphids

Life cycle of the Pea Aphid

Components of Stability

2 major components:

1) resistance - the ability of a community or ecosystem to avoid disturbance

2) resilience - the speed with which a community or ecosystem returns to its former state following a disturbance that has displaced it from its initial condition

Ecosystems and Stability

Grassland – South Africa Rainforest – Puerto Rico

Additional Components of Stability

• Local stability describes the tendency of a community to return to its original state following a small disturbance

• Global stability describes the tendency of a community to return to its original state following a large disturbance

Adaptive Capacity of an Ecosystem

Adaptive Capacity of an Ecosystem

Adaptive Capacity of an Ecosystem- Chesapeake Bay

Adaptive Capacity in 3D

Current Adaptive Capacity

From Local vs. Global Stability

• dynamically fragile - a community which is stable only within a narrow range of environmental conditions

• dynamically robust - a community which is stable within a wide range of environmental conditions