Plant-Animal Interactions

Question 1

What are the different types of animal interactions?

Answer 1

• Plant-animal interactions (PAI) can be:
  » Commensal (positive effect on one species, no effect on the other): +/0
  » Antagonistic (positive effect on one, negative effect on the other): +/-
  » Mutualistic (positive effect on both species): +/+

Question 2

What is the effect on animals and plants for Commensal interactions?

Answer 2

• Commensal (+/0)
  » + for animals: eg, bird nesting, shelter
  » + for plants: eg, seeds hitch-hiking on animals (particularly furry ones)

Question 3

What is the effect on animals and plants for Antagonistic (+/-) interactions?

Answer 3

» + for animals: direct consumption of the plant (herbivores) for food
» + for plants: sometimes the plant is the deceiver!
• Eg, carnivorous plants
• Eg, bee orchid: bee orchids trick bees by visual and chemical mimicry (female pheromone) into “mating” with the flower

Question 4

What is the effect on animals and plants for Mutualistic (+/+) interactions?

Answer 4

» Eg, ants and Acacia (ants serve as bodyguards, clear out nearby plants)
» Eg, edible seeds eaten (and defecated) by animals
» Eg, pollination (plants get pollinated, animals get nectar reward)

Question 5

What is the role of animals in angiosperm reproduction

Answer 5

• Pollination is the process by which pollen (the male gamete) is transferred to the female reproductive organ of a plant, enabling fertilisation
• Gymnosperm pollination relies on abiotic (non-living) dispersal mechanisms (eg, wind), highly affected by chance (→ high % loss)
• Most angiosperms rely on animals to transfer pollen from the anther of one flower to the stigma of the flower on another plant

Question 6

What percentage of plants require insects for pollination?

Answer 6

• About 65% of all flowering plants require insects for pollination
• Animal pollinator is usually rewarded for doing so:
  » Most get nectar, a specialized sugary “thank you” treat

Question 7

What insects and animals are usually used for pollination?

Answer 7

» Bees
» Flies
» Moths and butterflies
- But other animals also involved
» Birds
» Mammals

Question 8

What is Nectar?

Answer 8

Nectar is a specialized sugar rich liquid produced in special glands (“nectarines”) to reward animal mutualists

Question 9

How is nectar produced?

Answer 9

Nectar can be produced:
» Floral nectarines: in flowers to reward pollinators
» Extrafloral nectarines: elsewhere (eg, base of leaves) to reward
“bodyguards” (eg, ants, wasps)

Question 10

How does pollination by bees work?

Answer 10

• Bees are attracted to bright colors
  » Primarily yellow and blue
  » But can also see ultraviolet radiation, so many flowers of plants pollinated by bees also have ultraviolet markings (“nectar guides”)
  » Up to 80% of commercial crops are pollinated by bees

Question 11

What are the first 3 steps in making honey?

Answer 11

1) Foraging bee sucks up nectar into special storage stomach
» Enzyme that breaks sucrose into fructose and glucose
2) Returns to hives, and passes it (mouth to mouth) to “indoor bee”
3) Stored it into specialized storage cells (honeycomb)

Question 12

what are the last three steps in the process of honey?

Answer 12

4) Moisture content is decreased from 70% to 18% (either by natural evaporation, or aided by wing fanning)
5) Once thickened, honey is capped with beeswax
6) Pollen is mixed with honey to make “bee bread” (mix of sugars and proteins), fed to larvae

Question 13

What is Colony Collapse Disorder? (CCD)

Answer 13

• Since mid-2000s, worldwide collapse of bee colonies (first detected in the US)
• Exact cause still uncertain but is expected to be a chemical
• Some restrictions on use, but still only limited action

Question 14

What is the Chemical used that is expected to be cause CCD and what are its effects”

Answer 14

» Neonicotinoid insecticides commonly used for seed treatment … residues routinely detected in bees
» Cause chemical stress, reduce reproduction and life span
» Parasites (mites) more likely to infect stressed individuals
» Colonies with inexperienced younger males less likely to thrive

Question 15

How does pollination by flies work?

Answer 15

• Flowers usually reddish and fleshy, with an odour like rotten meat
• Flies mistake the flower for rotten meat, and visit it to lay eggs (which die after they hatch, as there is no food for them)
  » Limited benefit for flies some research suggest that flies may harvest chemical scents, which are used as in production of male pheromone

Question 16

How does pollination by moths and butterflies work?

Answer 16

• Moths and butterfly detect odours
• Flowers often sweetly fragrant
• Can be colourful (butterflies perceive colours) or white/yellow (stand out at night, when moths are most active)

Question 17

How does pollination by birds work

Answer 17

• Birds generally do not have a highly developed sense of smell
• Flowers usually large and bright-red or yellow, but have little odour
• However, flowers produce highly sugary nectar to meet high energy requirements of pollinating birds

Question 18

How does pollination by mammals work?

Answer 18

• Bats and non-flying mammals

- Light-coloured and aromatic, to attract nocturnal pollinators

Question 19

What is Co-evolution?

Answer 19

• Co-evolution: the large diversity in insects is linked to the large diversity in floral morphology and physiology of angiosperms
  » Eg, Madagascar orchid and the hawk moth (Xanthopan morganii praedicta)

Question 20

How does Co-evolution work?

Answer 20

• Attracting pollinators that are loyal to a given plant species is in the interest of the plant, so that pollen is transferred to another flower of the same species
• Natural selection thus favours deviations in floral structure that make it more likely to be pollinated by a dedicated pollinator