Biology 2483A Lecture 14: Bio 2483 Lecture 14
14 Jan 2019
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Document Summary
Positive interactions have influenced key events in the history of life and continue to shape communities and influence ecosystem functions. Trophic mutualism: symbiosis: 2 species live in close physical contact with each other. Symbioses can include parasitism (+/-), commensalism (+/0), and mutualism (+/+: herbivores (e. g. , cattle, sheep) depend on bacteria and protists that live in their guts to help metabolize cellulose. From benefactor to competitor: each partner in a mutualistic interaction acts in ways that serve its own ecological and evolutionary interests. Some ants protect treehoppers from predators, and the treehoppers secrete honeydew (sugar solution), which the ants feed on. Treehoppers always secrete honeydew, so ants always have this resource: but if predators are few, the treehoppers may get no benefit. The interaction shifts from +/+ (mutualism) to +/0 (commensalism) or +/ (parasitism), if consumption of honeydew by ants reduces treehopper growth or reproduction. Cheaters are individuals that increase offspring production by overexploiting their mutualistic partner.
