Historical Context of Symbiosis

• Darwin ?• de Bary (1879)• Symbiosis and mutualism

Unifying Concepts of Symbiosis

1. Symbiotic interactions have been, and are, an important feature of the biotic environment

2. Context of symbiotic interactions is complex• Plasmodium/mosquitoes/bacteria/humans• figs and their pollinators• aphid/ant interactions

3. Most of world’s biodiversity is composed of specialists.

Distribution of specialists• 50 % of all species are parasitic (Price, 1980)• in at least 4 fungi families, all species are mycorrhizal• 80% of all British fungi are mycorrhizal• 21% of all fungi form lichen associations• 13/30 animal phyla have taxa with chronic endosymbionts • e.g. 162 specialist beetles on one tropical plant (Erwin,

1982)• 50% of 3142 species of caterpillars and moths feed on

one plant species (Janzen, 1988)• fungi, nematodes and mites ?• 98% of tropical flowering plants rely on animals for

pollination or dispersal of seeds• 100% of trees in some tropical lowlands have fleshy fruits

4. Symbiotic interactions fit somewhere on an antagonistic/cooperation continuum.

5. The outcomes of symbiotic interactions are context-dependent.

• Trypanosomes in ground squirrels• Amphibian declines and pathogens• Immunity vs. malnutrition vs. infection

6. Symbionts face three basic ‘problems’ that must be solved for R > 0.

• Finding a host• Staying in a host• Reproduction/dispersal

7. Most major questions in the study of symbiosis have anthropogenic applications.

8. Co-evolution is a major process by which symbioses are formed, are maintained, and change over time.