Mutualism: So What Is It Anyway?

1. Mutualism:So What Is It Anyway? Eric Ribbens Western Illinois University

2. In The Garden Joel and Lisa were exploring a garden. They sniffed appreciatively at blooming lavender, pulled petals from a white daisy (“he loves me, he loves me not …”)and whistled back at a killdeer running away, wing drooping. Joel stooped over to peer at an odd plant.

4. Ants and Aphids “What are those ants DOING?” Joel asked. Lisa stared too. “It looks like they are aphid farmers.” “Aphid farmers? Huh?”

5. Ants and Aphids Lisa pointed. “Look here! This ant is collecting honeydew from the aphid. It’s basically plant sap, rich in sugar. The ant eats it after the aphid sucks it from the plant.” Joel shuddered. “No way I’m sucking honey from someone’s butt!”

6. Ants and Aphids Lisa laughed. “Nope, but that’s what ant farmers do. They take care of the aphids, carry them around, and protect them. In turn, they get food from the aphids.” Joel nodded eagerly. “So that would be an example of … whatdid my odd biology professor call it … a mutualism?”

7. Mutualism Lisa smirked. “You mean you actually remember something from that class? What else do you know about mutualisms?” Joel frowned. “Hey, I got a C! Well, a C-.” “Yeah, so you’re not God’s gift to biology. You’re stalling …”

8. Mutualism Joel scowled. “Hmm. Two species interacting in a way that benefits one of the species …” Shaking her head, Lisa corrected “No! That’s commensalism. Mutualism benefits both species.” “And isn’t there something about cymbals or something like that?” “You mean symbiosis. An interesting word.”

9. Symbiosis “Sym means with. Think symphony … sounds with other sounds. Biosis means life. So symbiosis means living with another species.” Joel nodded vigorously. “Like these ants and the aphids. But don’t the aphids also live with the plant? That’s not a mutualism, is it?”

10. Symbiosis ? Mutualism “Good point,” agreed Lisa. “And interestingly, a rather common confusion. Come on, let’s go to the library. I want to show you something.”

11. At the Library Lisa started pulling textbooks from the shelves. Joel turned the computer on. “What are you doing?” Lisa asked. “Getting ready to search the internet, of course!” Joel replied. “I love Wikipedia!” “Huh? Real knowledge only comes in books!” snorted Lisa.

12. The Textbooks Lisa flipped through a biology textbook. She read: “Mutualism: an interaction between two species in which both benefit from the association.” “Symbiosis: in a broad sense, the living together of two or more organisms of different species; in a narrow sense, synonymous with ‘mutualism’.”

13. The Internet Joel frowned. “That’s not what you just said! But read here: This webpage has it wrong too!” Symbiosis is defined as: "the intimate living together of two dissimilar organisms in a mutually beneficial relationship.” http://www.flickr.com/people/symbiosis/

14. Lisa agreed. “What does Wikipedia say?” Joel typed. The screen showed: “The term symbiosis (from the Greek: σύν syn "with"; and βίωσις biosis "living") commonly describes close and often long-term interactions between different biological species. The term was first used in 1879 by the GermanmycologistHeinrich Anton de Bary, who defined it as "the living together of unlike organisms."[1][2]

15. Symbiosis : Mutualism? Lisa said, “So this nicely shows the controversy. Is symbiosis another name for mutualism, or is it a completely different concept?” Joel said absently, “Why would you want two terms that mean the same thing? It makes more sense for mutualism to mean both benefit, and symbiosis to mean living together. But can symbiosis not be mutualisms?”

16. Lisa said “The plural of symbiosis is symbioses, dummy. Good question. Can you think of an example of a symbiosis that is not a mutualism?” “What about malaria? The malaria, um, protistans, live in your blood, but they sure don’t give you a benefit!”

17. Is it Science? Joel sighed. “How can I be expected to learn something when the experts can’t even agree?” Lisa punched him. “You know that scientists are people! They make mistakes too. But science is so powerful because it ends up selecting the ideas that are supported by evidence. This is just science in process!”

18. How Did They Evolve? “I remember something else,” Joel murmured. My bio prof kept insisting that evolution is one of the great ideas of science. But how could these different kinds of interactions evolve?” Lisa nodded vigorously. “A great question! Remember that evolutionary theory says that every species will tend to develop traits that increase the ability of that species to survive.”

19. Evolutionary Predictions “Yeah, but that’s my point. How could some of these interactions develop, and wouldn’t you expect them to change over time?”

20. Two-Species Interactions • Research time! What are the categories of possible interactions between two species, and how are the different categories defined?

21. Next Question • Should symbiosis refer only to mutualisms? Should mutualism and symbiosis mean the same thing?

22. Credits Slide 2 Description: Bee on daisy Author: Tony Wills Link: http://commons.wikimedia.org/wiki/File:Fly_on_daisy_02.jpg Clearance: Creative Commons Attribution-Share Alike 3.0 Unported license. Slide 3 Description: Ant Lasius flavus and aphids Fordinae Author: Nbharakey Link: http://commons.wikimedia.org/wiki/File:Ant_Lasius_flavus_and_aphids_Fordinae.jpg Clearance: Public domain. Slide 4 Description: Ant cultivating aphids Author: Fir0002 Link: http://commons.wikimedia.org/wiki/File:Ant_cultivating_aphids.jpg Clearance: Creative Commons Attribution-Share Alike 3.0 Unported license. Slide 5 Description: Aphids visited by black garden ants (Lasius niger) and brimming over with honeydew. Author: Jens Buurgaard Nielsen Link: http://commons.wikimedia.org/wiki/File:Aphids_with_honeydew_and_ants.JPG Clearance: Creative Commons Attribution-Share Alike 3.0 Unported license.

23. Credits cont. Slide 6 Description: Ant guards its aphids. Author: ViaMoi Link: http://commons.wikimedia.org/wiki/File:Ant_guards_its_Aphids.jpg Clearance: Creative Commons Attribution 2.0 Generic license. Slide 10 Description: Woman retrieving book at San Diego City College Author: Joe Crawford from Moorpark, California, USA Link: http://commons.wikimedia.org/wiki/File:SanDiegoCityCollegeLearingRecourceCity-bookshelf.jpg Clearance: Creative Commons Attribution 2.0 Generic license. Slide 16 Description: Young girl suffering of cerebral malaria. Coming from a remote village; she was referred to the main hospital in Cotonou, Benin. Author: WHO/Benoist Carpentier Link: http://www.who.int/malaria/world_malaria_report_2009/photos/en/index.html Clearance: Used in accordance with terms of use as stated on the image source page, link above.