Symbiosis, the living together of unlike organisms, encompasses a spectrum of interactions ranging from mutually beneficial to reciprocally detrimental.  We will focus on a selection of ecologically important symbioses, including interactions of bacteria and fungi with plants, invertebrates, and vertebrates.  We will consider the evolutionary origins, and explore conditions required for the establishment and maintenance of these associations. 

Our studies of symbiosis will be based on a series of research and review papers.  Links to pdf copies of all papers are available on Blackboard (http://blackboard.cornell.edu/).  Chapters from ‘The Biology of Mutualism’ edited by D.H. Boucher (Oxford University Press, New York, 1985) are on reserve at the Mann Library.

There are two types of readings:  assigned and supplemental.  You are required to read the assigned papers before each class.  Points to consider while reading the assigned papers are posted on Blackboard.  Please be prepared to discuss each assigned paper in class.  To contribute to the in-class discussions, you are expected to formulate at least one question or comment about each paper.  Supplemental papers were selected to complement the lectures and in-class discussions, and you are responsible for their relevant sections.
Evaluation:
In-class ‘open book’ examination I (FEB. 26) 15% of final score,
In-class ‘open book’ examination II (APRIL 10)            15% of final score,
Cumulative ‘open book’ final exam (MAY 14, 2:00 - 4:30 pm) 20% of final score,
In-class presentation            15% of final score,
Referee’s reports on two draft mini-review papers 10% of final score,
Revised version of the mini-review paper 20% of final score,
Participation in discussions (questions & comments) 5% of final score.

Grading on a percentage basis: A = 90-100%, B = 75-90%, C = 60-75%, D = 50-60%, F < 50% of final score.

The in-class presentation will be a 10-minute talk with slides (or overheads) about your favorite symbiotic interaction that is not included in the syllabus.  Please be prepared to declare your topic on FEBRUARY 26.  You will also describe your favorite symbiosis in a mini-review paper.  The mini-review is expected to be between 2500 and 3000 word-long (excluding references).  A draft version of the mini-review is due MARCH 27.  This version will not be graded but will be distributed to two anonymous peer-referees (two randomly selected fellow students in the class) for comments and suggestions.  Each referee will complete an evaluation form, and write a page-long report with suggestions to the author on how to improve the draft.  Each referee will be asked to comment on two drafts.  The referee’s reports are due on APRIL 15.  The revised version of the mini-review paper is due MAY 1 in class.
Lecture Date Topic Assigned reading Supplemental
reading
1 Jan 22 Organization.
Definitions of symbiotic interactions.
Intro to molecular phylogeny reconstruction.		 [1, 2]
2 Jan 24 Origin of the eukaryotic cell:
- the birth of the nucleus,
- multiple guises of mitochondria.
 [3-5] [6]
3 Jan 29 Origin of the eukaryotic cell II: Amazing evolutionary turns of algal plastids.
 [7] [8]
4 Jan 31 Evolution of parasite virulence: nematode parasites of fig wasps.
 [9] [10]
5 Feb 5 Fungal endophytes of grasses: a switch from horizontal to vertical transmission and a transition from parasitism to mutualism.
 [11] [12]
6 Feb 7 Game theory as a tool to explain evolution of interspecific mutualisms. Significance of cheaters in evolution of mutualisms.
How to investigate your favorite symbiotic interaction, construct an oral presentation, and write a mini-review paper.
 [13-15]
7 Feb 12 Market models to explain persistence of mutualisms: partner choice and sanctions in Rhizobium/legumes interaction.
 [16] [17]
8 Feb 14 More about partner choice and sanctions: Vibrio/squid.
Compare and contrast mechanisms of partner recognition and sanctions in Rhizobium/legumes & Vibrio/squid symbioses.
 [18] [19, 20]
9 Feb 19 Evolution of symbiotic lifestyle by acquisition of genomic symbiosis islands: Mesorhizobium loti/Lotus.
 [21] [22]
10 Feb 21 Epulopiscium: a giant bacterium symbiotic with surgeonfish. Guest lecture by Dr. Esther Angert (Dept. of Microbiology, Cornell).
 [23] [24]
11 Feb 26 Prelim I
Declare the topic of your oral presentation and a mini-review paper.
12 Feb 28 Molecular evolution patterns after transition to the endosymbiotic lifestyle: accelerated rate of molecular evolution, accumulation of deleterious mutations, and genome reduction: mutualistic bacterial endosymbionts of insects.
 [25] [26]
13 March 4 Not all maternally transmitted endosymbionts are benign: Wolbachia.
[27] [28]
14 March 6 Student oral presentations.
15 March 11 Student oral presentations.
16 March 13 Human agriculture as a symbiotic system.
 [29] [30-32]
17 March 25 Rates of evolution in the antagonistic environment: the Red Queen effect.
 [33] [34, 35]
18 March 27 Rates of evolution in the mutualistic environment: the Red King effect.
Draft of the mini-review paper due.
 [36] [37]
19 April 1 Arbuscular mycorrhiza: the most widespread terrestrial symbiosis. Demo of a procedure to extract spores of arbuscular mycorrhizal fungi from soil.
Mini-review drafts out for comments to student referees.
20 April 3 Complex symbiotic interactions: bacterial endosymbionts of fungal pathogens and mutualists of plants.
 [38, 39]
21 April 8 Fungal parasites and predators of nematodes, insects and other fungi.
 [40] [41]
22 April 10 Prelim II.
23 April 15 Symbioses and biological invasions: mycorrhizae.
Referee's report due.
[42] [43]
24 April 17 Eusocial insects and their agricultural systems: fungus-growing ants. Guest lecture by Dr. Kathie Hodge (Dept. of Plant Pathology & Plant-Microbe Interactions).
Referees' reports back to the authors.
 [44] [45-47]
25 April 22 Eusocial insects and their agricultural systems: fungus-growing termites.
 [48] [49]
26 April 24 Symbioses and global change: mycorrhizae.
 [50]
27 April 29 Symbioses and global change: corals/zooxanthellae. Guest lecture.
28 May 1 Symbioses at hydrothermal vents and cold seeps.
Summary and conclusions.
Revised version of the mini-review due.
 [51]


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