Overview of Species Interactions

		Species 1
Species 2	0	+	-
0	0,0 Neutralism	+,0 Commensalism (Herbivory?)	0,- Amensalism
+	0,+	+,+ Mutualism (Herbivory?)	-,+ Predation Parasitism Herbivory
-	0,-	+,-	-,- Competition

Mutualism

• Both species benefit from interaction
• More common than generally appreciated
• Most examples of mutualism come from natural history observations
• Studies of mutualism are gradually becoming more experimental

Types of Mutualisms

1. Direct - interactions between two species

• obligate - partner is required
• facultative - partner is not required
• direct mutualisms are often cited as evidence of coevolution - reciprocal evolutionary responses between species

2. Diffuse - interactions among many species

Examples of Mutualisms

Direct

• lichens, termite gut protozoans
• plant protection from herbivory by ants or endophytes
• few mycorrhizae, pollinators and seed dispersers

Diffuse

• most mycorrhizae, pollinators and seed dispersers