Symbioses - Mutualism

Symbioses Symbioses - species living in close association Parasitism +,- parasite benefits, host harmed Commensalism +,0 or 0,0 can have positive effect for one species or for neither Mutualism +,+ both species benefit

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 (+,+)

General Features of Mutualisms 1. The life cycle of most mutualistic species is very simple (in contrast to parasites) 2. There is no conspicuous dispersal phase for most endosymbionts (endomutualists) 3. Populations of most mutualists are stable in size - no epidemics as seen in parasites 4. The ecological range (niche breadth) of organisms in mutualisms usually appears to be greater than that of either species alone 5. Host specificity is usually flexible 6. Within populations of mutualists, the number of endosymbionts per host is relatively constant

Two types of Mutualism Facultative - each partner gains a benefit but is not dependent on the other - the vast majority of mutualisms are facultative. Obligate - one or both partners is dependent on the other and cannot survive without the other.

Mutualisms Involving Links in Behavior

Greater Honeyguide

Honey Badger

Ants and Acacia Trees

Beltian bodies (yellow) on Acacia leaves

Ant larvae inside Acacia “horn”

Pollination Mutualisms

Pollination syndromes among the phloxes

Honeybee covered with pollen

Honeybee pollinating beebalm – Monarda sp.

With visible lightwith UV light Nectar guides for honeybees

Cyrtid fly pollinating a composite

Caralluma – carrion fly pollinated

Erysimum – butterfly pollinated

Hummingbird pollination

Greater double-collared sunbird

Episcia – moth pollinated

Bat pollination

Hammer Orchid and Wasp

Figs and Fig Wasps

Mutualisms involving Culture of Crops or Livestock

Leaf-cutter Ants – genus Atta

Diagram of Leaf-cutter ant colony nest

Human Agriculture Sustainable DairyIndustrial Wheat

Digestive Mutualisms Involving Gut Inhabitants

Ruminant with multiple stomachs

Ruminant by-products

Termite Mound Western Australia

Termites

Mycorrhizae

Ectomycorrhizae

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 Lynne Margulis

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