Species Interactions:
The Good, the Bad, and the Ugly
Types of species interactions
• Positive
• Negative
• Neutral
Positive species interactions
• Mutualism
– Both species benefit by interacting with each
other
Ant-Acacia mutualism
Mutualism
http://www.australiangeographic.com.au/news/
Mutualism
http://coglab.hbcse.tifr.res.in/teacher-resources/
Mutualism
http://mathotter.wordpress.com
Mutualism
Negative species interactions
• One species benefits while the other species is
harmed
http://www-rohan.sdsu.edu
Negative interactions (herbivory)
http://en.wikipedia.org/wiki/Herbivore
Negative interactions (competition)
Negative interactions
Strangler Fig
Nectar Robbing
Neutral species interactions
• Commensalism
– One species benefits while the other is unaffected
Plant-bacteria-herbivore experiment
• Do herbivores prefer plants with rhizobia or
plants without rhizobia?
Materials
• 10 legume plants (such as beans, peas,
clover), in 10 separate pots
• Rhizobia (bacteria) inoculant (purchase online)
• 20 slugs or other insect herbivores (aphids,
beetles, caterpillars)
• Old fish tank or large plastic bin, screen or
netting to put over top
Instructions
1. Plant legumes 3 weeks prior to conducting
experiment. Inoculate half of the 10 plants
with rhizobia bacteria.
+ rhizobia
- rhizobia
Instructions
2. Once plants are mature, put them all into an
old fish tank or clear plastic bin and put 2
herbivores on the soil surface in each pot.
Make sure pots are close enough to touch.
3. After 1-2 days, estimate the percent of
damage to each leaf
4. Record data and analyze results (graphing
activity)