Presentation on theme: "Mutualisms - Chap. 15 I. Terms and concepts A. Symbiosis vs. Mutualism B. Degree of dependence: Obligate vs. facultative C. Degree of specialization: Specialists."— Presentation transcript:
Mutualisms - Chap. 15 I. Terms and concepts A. Symbiosis vs. Mutualism B. Degree of dependence: Obligate vs. facultative C. Degree of specialization: Specialists vs. generalists D. What types of "currency“? E. Coevolution F. Effects on realized niche II. Examples A. Mycorrhizae - fungi and plants Ectomycorrhizae Endomycorrhizae (Arbuscular) B. Nitrogen fixation C. Corals- zooxanthellae, anthozoans
Questions to focus on 1.What is the difference between symbiosis and mutualism? 2. What do the terms “obligate” and “facultative” mean with respect to mutualisms? How do the mutualisms discussed in the book and powerpoint differ in their degree of dependence? 3. What are specialists and generalists? If one species in a mutualism is a specialist, does that mean the other must be as well? 4. What are the different types of “currency” exchanged in mutualisms? Which ones are important for the different examples in the book and powerpoint? 5. What is co-evolution and how does it differ from convergent evolution? How might mutualisms affect the realized niche of the species involved? 6. For the different examples of mutualisms in the book and powerpoint, know what the different currencies are, the relative degrees of dependence and specificity, and how those mutualisms are important in community and/or ecosystem processes.
A.Symbiosis vs. Mutualism Symbiosis: “sym” = together, “biosis”= living; close physical association (e.g., host and internal symbiont). Could be beneficial or parasitic. Mutualism: +/+ interaction, both species benefit. Could be symbiotic or free- living
B. Degree of dependence Obligate: at least on species could not grow and reproduce without the other Facultative: both organisms do better with their mutualist, but can survive and reproduce without it.
Facultative or Obligate? 15.815.9
Leafcutter ants: a complex mutualism Currie et al. 2006 Science http://www.wildernessclassroom.com http://bio.kuleuven.be/ento/photo_gallery.htm Leaf cutter ants
C. Degree of specialization Specialists: reliant on only one other species Generalists: multiple species can perform the function
Degree of specialization? Pollination Hawk moth pollinated Hummingbird pollinated
D. The “currency” Nutrition – energy and nutrients Protection – biotic and abiotic Fertilization/gamete dispersal (e.g., pollination) Seed dispersal
E. Co-evolution Co-evolution occurs when two species interact so strongly with one another that they are dominant evolutionary forces on one another. Examples: - Obligate, specialist mutualisms - Specialist predator/prey interactions (the term was first coined in describing the “evolutionary arms race” between plant chemical defenses and insect herbivores that evolve resistance to those defenses).
F. Effects on realized niche fundamental niche realized niche Competition, exploitationoften reduce the realized niche of an organism compared to it’s fundamental niche. Competition, exploitation often reduce the realized niche of an organism compared to it’s fundamental niche. Mutalisms can increase the size of the realized niche compared to the fundamental niche.
II. Examples of important mutualisms
A. Mycorrhizae “mycor” = fungi, “rhizae” = roots - In almost all families of vascular plants