Mutualism,Commensalism etc.

Question 1

Mutualism

Answer 1

+/+ interaction

Both parties benefit
Can lead to coevolution
Interspecific interaction that benefits both species

Question 2

Mutualism examples

Answer 2

Ex: heterospecific cleaning – marine ecosystems specialized fish and shrimp clean parasites from gills and fins of fish; cleaners benefit from food, groomed fish benefit from the removal of parasites

Ex: mycorrhizae fungi; extract inorganic nutrients from soil and make them available to plants; plants then supply fungi with carbohydrates

Question 3

Is mutualism altruistic?

Answer 3

• not necessarily; each species ultimately acts in their own self-interest
• Selection seems to favour some level of cooperation

Question 4

Mutualism example: Ant - Aphid

Answer 4

o Ants protect aphids from predators and in return harvest honeydew that aphids excrete
o Did this happen through co-evolution?
- Hard to know for sure, ants are generally aggressive to other insects… so are they actually protecting aphids? Or just a natural response
- Are the ants protecting aphids or the plant structure?

Question 5

Mutualism example: Fruit production and seed dispersal

Answer 5

• animals eat fruit and then disperse seeds

Question 6

Mutualism example: pollination

Answer 6

• animal gets nectar and then cross pollinates

Question 7

Pollination vectors

Answer 7

• Water
• Wind:
  • Conspecifics closely spaced
  • Little intervening vegetation
  • Low frequency of rainfall
  • Animal pollinators not available: early
  • Good cues for synchronization
• Animals:
  • More efficient
  • Fewer pollen grain required
  • More likely to promote cross-breeding
  • Animal pollination arose before angiosperms (seed-producing flowering plants, vascular, most diverse on land) - Not angiosperms: conifers and cycads, mosses and liverwort, ferns

Question 8

Cycads are beetle pollinated (mutualism)

Answer 8

Cycad adaptations:

• Australian cycad has dual specialist pollinators (thrifts and train weevils) – insects utilize male cones for development and then carry pollen from male to other cycads
• Uses push-pull method: male emits odour, attracts adult thrips (or weevils) –> Thrips feeds and becomes covered with pollen –> male heats up cone and increases odour to inhibitory levels; thrips leave (basically come here and then go away)

Question 9

Pollination syndromes - Bees

Answer 9

• Flowers open day/night
• Colour: violet, yellow, UV
• Odour: sweet
• Bilateral symmetry, flat/broad tube
• Honey guides
• Nectar (hexose, sucrose)

Question 10

Pollination syndromes - Moths

Answer 10

• Flowers open at night
• Colour: pale
• Odour: sweet, heavy
• Radial symmetry, tubes or spurs
• Nectar: ample (sucrose)

Question 11

Pollination syndromes - Butterflies

Answer 11

• Flowers: open in day
• Colour: bright, often pink
• Odour: sweet
• Radial symmetry with tubes or spurs
• Nectar: sucrose

Question 12

Pollination syndromes - Birds

Answer 12

• Flowers open in day
• Colour: vivid, red
• Odour: none
• Radial or bilateral symmetry
• Tubes (hummingbirds) or landing platform
• Nectar (sucrose)

Question 13

Pollination syndromes - Bats

Answer 13

• Flowers open at night
• Colour: pale
• Odour: heavy, musky
• Radial symmetry with flat or broad tube, tuft of stamens
• Nectar: ample (hexose)

Question 14

Spatial ecology of pollination

Answer 14

• Tropics: beetles, bats, birds
• Arctic: flies
• Temperate: bees, moths, butterflies

Question 15

Interests of mutualists do not coincide

Answer 15

o Flowers want animals that visit only one species and fly an optimal distance between plants to ensure cross-pollination
o Animals want maximum energy gains for minimal handling or travel time
o Angiosperm radiation (about 100 MYA): competition to attract animals as pollinators and seed dispersers?

Question 16

Nectar robbers

Answer 16

o Consume nectar without transporting pollen, often by piercing hole in flower
o Pollination may still happen accidentally

Question 17

Commensalism

Answer 17

0/+
One individual benefits, the other not harmed OR benefitted

Host - commensal
Ex: Lion is the host, vulture is the commensal

Question 18

Commensalism example: Pitcher plant, midge larvae, mosquito larvae

Answer 18

o Pitchers fill with rain-water
o Terrestrial insects attracted to red fall in
o Hairs on pitcher make it hard to climb out
o Insects down, decompose and plant absorbs nitrogen
**aquatic insects do not drown, so pitcher provides habitat’ midge larvae feed on insect carcasses at early stage decomposition; mosquito larvae feed at later stages of decomposition on broken up parts **

Question 19

Study: Heard (1994) - Artificial pitchers

Answer 19

Artificial pitchers: supplement mosquito food in one
- Results: no effect of mosquito mass on midge mass, positive effect of midge mass on mosquito mass when no supplement, no relationship when supplemented (so midge no effect, but mosquito benefit)

Question 20

Other types of commensalism

Answer 20

o Phoresy: one animal uses another for transport
Ex millipedes on birds, burrs on animals
o Inquilinism: one organism provides shelter or habitat for another without being damaged
Ex moss on tree, many bacteria on us
o Metabiosis: one organisms provides for another after death
Ex maggots on dead animals, hermit crabs on gastropod shells

Question 21

Facilitation

Answer 21

o Different from mutualism and commensalism because no direct intimate relationship between species
o One species benefits and other no difference but also not direct
- common in plants
Ex: altiplano: high altitude tropics
- Thick, spongy trunk; hairy, tightly clustered leaves; maintains it’s dead leaves –> gathers moisture from air and deposits extra into ground
- Provides ground water for other plants and animals without direct

Question 22

Amensalism

Answer 22

o One species hurt, other no benefit

• Ex: wild pigs dig up soil surface as they forage, exposing many soil organisms to desiccation and predation
• Ex: elephants trampling through fields

Question 23

Neutralism

Answer 23

0/0; individuals from two different species interact but don’t affect one another