AE2001 Fundamentals of ecology / 13 Mutualism

Mutualism

Symbiotic relationship where both species benefit, crucial for biodiversity and ecosystem stability.

Obligate mutualism

Relationship where both species depend entirely on each other for survival.

Example: yucca and yucca moths.

Facultative mutualism

Relationship that is beneficial but not necessary for survival. Example: nitrogen-fixing bacteria in legumes.

Pollination syndrome

Specific traits in plants adapted to attract certain pollinators: scent, colour & flower shape.

Example: Hummingbirds & flowers, plants evolve deep corollas, birds evolve longer beaks to minimize nectar loss.

Specialist vs. generalist pollinators

Specialists target specific plants for precise pollen transfer. (Agaonid fig wasps eggs inside fig flowers; larvae develop by consuming some seeds)

Generalists use multiple plant species, more resources but reduced pollination (honey bees)

Bee orchid mimicry

Ophrys apifera by mimicking female bees’ scent and appearance but pattracts male bees rovides no nectar reward.

Seed dispersal mutualisms

~30% of mutualisms involve animals dispersing seeds in exchange for food rewards. (Corvids cache seeds = plant dispersal when they forget where the seed was)

Bird- vs. bat-dispersed fruits

Bird-dispersed fruits = Small, brightly colored, no strong scent.

Bat-dispersed fruits = Larger, pale, strong smell, nocturnal attraction.

Leaf-cutting ants & fungus

Cultivation: Harvest leaves to grow mutualistic fungus Leucoagaricus gongylophorus, produces gongylidia as food.

Defense: Ants have Pseudonocardia bacteria in exoskeleton = antibiotics against parasitic Escovopsis fungus.

Ant-aphid mutualism

Ants protect aphids from predators in exchange for honeydew.

Ant-acacia mutualism

Acacia trees provide food (Beltian bodies) & shelter, ants protect against herbivores & competing plants.

Mycorrhizae

Fungal-root mutualism where fungi enhance plant nutrient uptake in exchange for carbohydrates.

Lichens

Mutualism between fungi & algae. Algae provides food & fungi provides habitat.

Ruminants & gut bacteria

Bacteria in herbivore guts break down cellulose = digestion of plant material.

Sloth-algae-moth mutualism

Sloths fur = habitat for algae & moths.

Moths fertilise algae, increases growth.

Sloths consume algae for nutrients.

Sloth defecation cycle

Sloths descend to transport moths to oviposition sites = cycle of sloth fur algae growth.

Lowest metabolic rate of any non-hibernating mammal; digestion takes 157 hours to 50 days.

Asymmetric mutualisms

Mutualisms can favour one species more = mutual benefit to parasitism.

Nectar robbery

Bumblebees & other insects steal nectar by piercing flowers without pollinating them.

Example: Comfrey