Mutualism (DONE) Flashcards
Define parasitism:
One species benefits, while other suffers
e.g. ticks on mammals
(+,-)
Define commensalism:
One species benefits, while the other is unaffected
(Rare in nature)
(+,0)
Define mutualism:
Both species benefit from the interaction
e.g. pollination, nutrient exchange
(+,+) = cooperation
Define symbiosis:
A long-term, co-evolved relationship between species, not necessarily mutualistic
(Long-term, closely-evolved)
(+,-) (+,0) (+,+)
Are mutualistic relationships always mutual?
No
Mutualisms can fluctuate between mutual benefit & parasitism depending on environmental or contextual factors
Give an example of a relationship that was thought to be mutual, but was not after being studied
Relationship between Oxpeckers and Cattle
- Oxpeckers originally thought to pick ticks (mutualistic)
- Studies show they often open wounds, consume blood & inc earwax build up (parasitism)
Is mutualism typically altruistic?
No, mutualism is not normally altruistic
Both species act in their self interest & mutual benefits are a byproduct of maximising their fitness
Do both species always benefit from every interaction in a mutualistic relationship?
No, both parties may not benefit from every interaction
e.g. a pollinator may consume nectar w/o delivering pollen
How can fitness increases in one species affect the other in mutualism?
Fitness inc in one species are often at the expense of the other, reflecting trade-offs in the relationship
Why do conflicts of interest arise in mutualistic relationships?
Conflicts of interest arise bc each species has its own goals, such as plants maximising pollen dispersal while pollinators prioritise nectar collection
How is mutualism related to reciprocal exploitation?
Mutualism can be seen as reciprocal exploitation, where both species “use” each other to maximise their own gain, even if it comes at some cost to the other
How does the Prisoner’s Dilemma relate to mutualism?
The Prisoner’s Dilemma models how cooperation in mutualism can break down if both partners prioritise self-interest, leading to potential collapse of the relationship
Are mutual relationships static?
No, mutualisms are dynamic & can shift along a spectrum from mutualism to parasitism based on environmental conditions, resource availability & evolutionary pressures
What is visitor mutualism?
Temporary interactions where one species benefits during visits
e.g. pollinators visiting flowers, frugivore-plant, pollinator-plant & cleaner fish
What is obligate/symbiotic mutualism?
A long-term, speciealised relationship where species survival depends on the interaction
e..g figs & fig wasps, mycorrhizal associations, lichens & animal endosymbiosis
How dan mutualistic relationships drive coevolution?
They lead to coevolutionary arms races, where species evolve traits to maximise mutual benefits
Provide an example of coevolution in mutualism:
Madagascan Star Orchis & Hawk moths
Orchid nectar spurs have nectar at the bottom –> longer spurs = more pollination as moth’s body must touch flower
Orchids evolved longer spurs & Moths evolved longer tongues to access nectar efficiently
Nectar tubes were shortened experimentally & reduced pollen success –> selection favours long spurs & tongues
What mechanisms help maintain mutualism?
Mechanisms like sanctions or selective pressures prevent cheating or overexploitation
What are 3 examples of interactions where sanctions are used?
- Yucca & Yucca moths
- Figs & fig wasps
- Legume-rhizobia symbiosis
How do yucca plants maintain balance in their mutualism w yucca moths?
Yucca plants abort flowers w excessive moth eggs to reduce exploitation
How do figs and fig wasps maintain mutualism?
Figs abort fruit if pollination fails or if wasps overexploit
Explain the legume-rhizobia symbiosis mechanism:
Plants reduce resources to non-fixing (cheating) bacteria, maintaining mutualistic balance
What are specialist pollination syndromes?
Traits evolved in plants to match specific pollinators, like nectar spurs for long-tongued polliantors
How do mutualisms impact ecosystems?
They can have community-level effects, such as regulating populations
e.g. parasitoid wasps regulating pollinator wasps in fig ecosystems
Provide an example of ant-plant mutualism:
Acacia trees provide food (nectaries) and shelter (hollow spines) to ants, which protect the trees from herbivores
How do acacia trees ensure ant dependency?
They produce nectar with chitinase
The chitinase inhibits ant metabolism of sucrose, making ants reliant on glucose from the tree
What is the relationship between fitness & mutualistic traits?
Fitness correlates positively w the effectiveness of mutualistic traits
Fitness ∝ Trait Effectiveness
How do sanctions prevent overexploitation in mutualisms?
Sanctions, like flower or fruit abortion, increase in strength w the degree of overexploitation
Sanction Strength ∝ Degree of Overexploitation
Summary:
Mutualisms are diverse interactions where both species benefit but often involve mechanisms to prevent exploitation. These relationships can be short-term or obligate, shaped by coevolutionary dynamics. Empirical examples (e.g., yucca moths, fig wasps) highlight how mutualisms maintain balance through adaptations like sanctions, dependency creation, or fitness trade-offs, playing vital roles in ecosystems.
