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Symbiotic
Relationships
Marianne E. Geisler
University of Winnipeg
Learning Objectives
1. define symbiosis
2. differentiate and understand the three different types of symbiotic relationships
3. define and describe co-evolution
Symbiosis
4. explore and identify examples of symbiosis
Species Relationships
- THEY'RE EVERYWHERE!
- interactions between species found all over the biosphere
Species Relationships
- intentional symbiotic relationships are surprisingly common in nature
What is Symbiosis?
"sym" = together
"bios" = life
SYMBIOSIS = living together
Symbiosis
- close and prolonged union of two or more organisms of different species
- must be beneficial for at least one of them
Types of Symbiosis
PARASITISM
- interactions between organisms where one species benefits at the expense of the other
ORGANISM 1
ORGANISM 2
COMMENSALISM
- interactions between organisms where one species benefits and the other is unharmed
ORGANISM 1
ORGANISM 2
MUTUALISM
- interactions between organisms which benefit both partners
ORGANISM 1
ORGANISM 2
Parasitism
- parasite(s) benefits while the host organism is harmed
- survival of the parasite dependent on survival of the host
- fitness of the parasite is increased by exploiting the host
Parasitism
HOST
PARASITE
Parasite uses the host for...
FOOD
DISPERSAL
- movement of seeds to a breeding or growing site
SAFE HABITAT
Host Exploitation
fungal corn smut
intestinal worm
cricket parasite
Types of Parasites
Types of Parasites
MICROPARASITES
MACROPARASITES
- Includes viruses, bacteria and fungi
- Small size and develop rapidly
- Includes flatworms, lice, fleas and ticks
- Large size and develop slowly
Types of Parasites
ECTOPARASITES
ENDOPARASITES
- Live on the skin, within the hair or feathers of the host
- Live within the hosts body (heart, brain, spinal cord, digestive system etc.)
Cordyceps fungus
Co-evolution with Parasites
- Hosts develop response mechanisms as defense against parasites
CO-EVOLUTION = evolution (genetic change) of morphology and physiology of interacting groups of species
- Attempts to minimize impacts and reduce risk of infection
Evolution of Defense
Animal grooming
Plant galls
Commensalism
- relationship between two species in which one lives on/in/with the other without damage to either
- one species benefits and the other is unharmed
Commensalism
Barnacles hitching a ride on a whale
HOST
COMMENSALIST
ADVANTAGES?
DISADVANTAGES?
Neutrality is hard to prove...
- symbiosis is not black and white, but instead a spectrum
- ranges from positive (benefit) to negative (cost) for host
- depending on the life stage, may be at different points on the spectrum
The Symbiosis Spectrum
The Spectrum of Symbiosis
Spanish moss
Mutualism
- interactions between individuals of different species that benefit both partners
MUTUALISTS RECEIVE BENEFITS SUCH AS:
Mutualism
MUTUALIST 1
MUTUALIST 2
- acqusition of resources/nutrients
- shelter
- protection
- increased competitive advantage
Types of Mutualisms
Types of Mutualisms
FACULTATIVE
OBLIGATE
- Reproduction and survival of both species are dependent on interaction with the other
- "Obligated" to rely on each other
- Organisms are not dependent on each other for survival, but do better working together
- Populations will persist even in absence of the other species
GUT MICROBIOTA
- human body home to 10-100 trillion types of bacteria
- many are beneficial to both
BENEFITS TO MICROBES
BENEFITS TO HUMAN
- source of nutrients
- warm, moist environment
- protect us from pathogens
- process food via bacterial digestion
FECAL TRANSPLANT
- co-evolution with bacteria has made the relationship obligate
healthy gut bacteria re-introduced in systems where it is no longer present
Co-evolution of Mutualists
Co-evolution of Mutualists
- Mutualists will evolve where the benefits exceed the costs
- Successful mutualists will both give and receive benefits
- Evolution of traits between interacting populations
- Selective advantage of evolution given to those who minimize costs and maximize benefits
Greater honeyguide bird and Hadza tribe (Tanzania)
The Ultimate Co-evolution
Symbiotic association between ALGAE and FUNGI
Lichen
Fungi
Algae
=
+
- Algae provides the food, fungi provides the shelter
- Fusion of mutualists where it is now difficult to tell where one ends and the other begins
- Lichen has its own individual properties
Summary
SYMBIOSIS is very common in nature, and includes interactions of:
MUTUALISM (+,+)
COMMENSALISM (+,0)
PARASITISM (+,-)
Summary
- has an effect on population dynamics of these interacting species, as well as their evolutionary changes
How much do you know?!
Mutualism, Commensalism or Parasitism?
Strawberry Poision Dart Frog and Bromeliad Plant
COMMENSALISM
Mutualism, Commensalism or Parasitism?
Mosquito feeding on Human Host and transmitting Malaria
PARASITISM
Mutualism, Commensalism or Parasitism?
Hummingbird spreading pollen between plants
MUTUALISM
These relationships are crucial!
Without plant/animal interactions...
- No pollinators (bees, birds etc.)
- No coral reefs
IMPORTANT FOR THE BIOSPHERE AND ALL THE SPECIES IT CONTAINS!
For more info, check out...
Biron, DG et al. 2005. Behavioural manipulation in a grasshopper harbouring hairworm. Proc. R. Soc. 272:2117-2126.
Cordyceps video: https://www.youtube.com/watch?v=XuKjBIBBAL8
References
Greater honeyguide video: https://www.youtube.com/watch?v=6ETvF9z8pc0
Molles, MJ. 2015. Ecology: Concepts and Applications (7th Ed.), McGraw Hill.
Seilacher, AD. 2005. Whale barnacles: exaptational access to a forbidden paradise. Paleobiology. 31:27-35.
Starr, CE. et al. 2016. Biology: The Unity and Diversity of Life (14th Ed.), Cengage Learning.