Why is animal involvement crucial for seed dispersal?
Written by
Julia Anderson
Reviewed by
Prof. Martin Thorne, Ph.D.Involvement of animals changes the action of the seed distribution into machines of targeted delivery. Birds digest fruits and pass valuable seeds in their droppings, serving as natural fertilizers. Mammals carry on fur hooked seeds to new centers of distribution. Ants relocate seeds to underground nests that are rich in fertilizers. The collaborating agencies ensure that seeds reach the most favorable microhabitat in which to germinate.
Endozoochory (Digestive Transport)
- Animals eat fruits and excrete seeds intact elsewhere
- Digestive acids scarify seed coats boosting germination 300%
- Birds disperse berry seeds 5-20km from parent plants
- Feces provide fertilizer enhancing seedling growth rates
Epizoochory (External Attachment)
- Seeds attach to fur via hooks barbs or sticky coatings
- Burdock burs travel 10km on deer and livestock
- Hooks withstand 0.5N force ensuring transport duration
- Specialized designs inspired human inventions like Velcro
Myrmecochory (Ant Relocation)
- Ants carry seeds with fatty elaiosome attachments to nests
- Seeds gain pathogen-free underground germination chambers
- Elaiosomes provide 0.5kcal energy rewarding ant behavior
- 30% of forest understory plants use this strategy
Seed Caching
- Squirrels bury acorns 50m from trees creating hidden stores
- 25% of cached seeds germinate when forgotten by animals
- Jays dispersed oaks across continents after ice ages
- Cache densities reach 10,000 seeds per hectare
Coevolution gives rise to specialized relationships between plants and animals. Bright fruits signal ripeness to birds. Elaiosomes are products of specific chemical substances that attract native species of ants, e.g., the elaiosome of Croton and Dorstenia; hook-angle adaptations correspond with the texture of the pelage of native animals. Many orchids have evolved scent signals that are literally adapting themselves to the needs of their respective pollinator partners.
Animal vectors exhibit remarkable precision of dispersal, with targeted delivery of seeds to nutrient-rich foci such as ant nests or suitable dung heaps, with the aid of spatial memory of scatter-hoarders to distribute seeds evenly and migratory patterns to distribute seeds through continents, which is with greater precision than if random wind or water dispersed the seeds.
Conservation entails safeguarding these fragile relationships. Some endangered plants, such as figs, depend on specific wasps. Damage to habitat hampers these vital dispersal networks. I've focused on supporting wildlife corridors that provide jay-oak interactions. Conserving animal connectivity can aid ecosystem resilience.
Read the full article: 6 Key Seed Dispersal Methods Explained
