Keystone Species Lecture

Definition

• Keystone species: A plant or animal species that plays a crucial role in the structure and maintenance of an ecological community.
• Affects other species in the community and the overall functioning of the community.

Types of Keystone Species

Predatory Keystone Species

• Occur when predators keep the population of other predators or consumers down the food chain in check.
• Helps reduce predation on many species below the main predator, maintaining community balance.
• Example: Sea otters preying on sea urchins.
  • Sea urchins consume sea kelp, which provides habitat for diverse species.
  • Predation by otters keeps the urchin population in check, maintaining the kelp forest and associated species.
  • Removal of sea otters leads to an increase in sea urchin population, over-consumption of kelp, and disruption of the community.

Mutualistic Keystone Species

• Involve species with mutualistic relationships that are crucial for the survival and propagation of community members.
• Example: Cassowary birds and fruiting plants.
  • Cassowary birds aid in seed germination and dispersal for many plants.
  • If cassowaries are removed, plants dependent on them for germination would decline, altering species composition in the community.

Non-Keystone Species

• Generalist species that do not have a specific mutualistic relationship with other species.
• Removal of one species would not significantly affect the community structure due to the presence of other generalist species.
• Example: Various frugivorous birds and generalist trees.
  • If one bird species is removed, other birds can still fulfill the role of seed germination and dispersal.

Conclusion

• Keystone species have a disproportionately large impact on their communities compared to non-keystone species.
• Understanding and protecting keystone species is crucial for maintaining ecological balance.

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