Lecture 6: Inter-specific interactions

Question 1

Herbivory & plant defences: plants have evolved an array of __, ___, ___ & ____ ways to attack, poison, starve or avoid herbivores

Answer 1

biotic, chemical, mechanical and phenological

Question 2

Herbivory & plant defences: interaction of herbivores and young leaves of tree seedlings is important in regulating

Answer 2

trophic dynamics, as it determines herbivore population sizes and / or seedling persistence

Question 3

Herbivory & plant defences: ___ are the most important consumers of leaf material tropical forests although vertebrates, fungi and other pathogens have an effect

Answer 3

INSECTS

Question 4

On Barro Colorado Island, Panama about __ of annual leaf consumption is due to herbivores

Answer 4

3/4

Question 5

annual herbivory rates in temperate forests have been estimated to average __% of leaf area and in tropical humid forests this is __% for shade tolerant plants and __% for gap specialists

Answer 5

average 7% of leaf area and in tropical humid forests this is 11% for shade tolerant plants and 48% for gap specialists.

Question 6

insect herbivores are very

Answer 6

diverse

Question 7

herbivory impacts can be __ or __

Answer 7

obvious or hidden

Question 8

how to plants defend themselves?

Answer 8

• Physical defence

- Chemical defence

Question 9

physical defence: examples

Answer 9

-spines on the stems of rattans, bamboos and acacias
-stinging plants i.e. seed pods of Mucuna climbers
both protect against vertebrate herbivores

Question 10

chemical defence examples:

Answer 10

-Ugandan forest some trees have toxic bark to deter elephants (Antiaris toxicaria)

Question 11

___ are the most important herbivores in tropical forests

Answer 11

invertebrates

Question 12

majority of herbivore damage in the tropics occurs ______

Answer 12

during the short window when leaves are young and expanding

Question 13

leaves of shade-tolerant species live for many years, yet 75% of the lifetime damage occurs when?

Answer 13

during the few weeks that leaves are expanding

Question 14

species vary ___, losing from ___% of their areas during leaf development

Answer 14

six fold

12-74%

Question 15

plants invest in a range of leaf defences:

Answer 15

• leaf toughness, high fibre content and other physical defences are effect in mature leave but are not compatible with young expanding leaves
• chemical defences including, alkaloids, tannins and phenols
• rapid leaf expansion
• synchronous leaf production to satiate herbivores
• delayed greening of young leaves
• extra-floral nectaries and ant defense

Question 16

delayed greening of tropical leaves: WHY

Answer 16

-reduces loss of energy & nitrogen by delaying development of chloroplasts (appear white/red-purple)

Question 17

delayed greening of tropical leaves: red/purple colour due to

Answer 17

the presence of other pigments such as anthocyanin (which are masked by chlorophyll)

Question 18

delayed greening of tropical leaves: appearance to herbivores

Answer 18

not nutritious and not as attractive to herbivores as young green leaves

Question 19

the cost of reducing herbivory by delayed greening is forfeited by

Answer 19

photosynthate

Question 20

delayed greening is prevalent (but not exclusive) to ____

Answer 20

understory plants where photosynthesis is limited by shed

Question 21

ant plants:

Answer 21

myrmecophytes

Question 22

myrmecophytes:

Answer 22

leaves of some plants species are protected by ants (ant-plant mutualism)

Question 23

ant-plant mutualism (how does it benefit both)

Answer 23

• in exchange for a home and food ants will aggressively attack both invertebrate and vertebrate herbivores
• plants provide ants with extra floral nectaries, food bodies and nesting sites called DOMATIA

Question 24

Macaranga bancana:

Answer 24

macaranga bancana has developed an obligatory relationship with the Heart Gaster Ants
-plants are usually colonised as saplings

Question 25

how do ants colonise a plant?

Answer 25

• queen ant enters the young plant by chewing her way through a shoot
• seals herself inside and lays eggs
• care for larvae until they turn into worker ants
• these workers then look after subsequent batches that they queen lays

Question 26

what are stipules?

Answer 26

brownish red structures found along the stem on both sides of the leg stalk
- The plant provides food for the ants in the form of the many small, white, starchy bodies found on the undersurface of the stipules

Question 27

myrmecophytes: what do ants protect the plants from?

Answer 27

pathogenic fungi, insects and herbivores

• whenever insects or other large organisms land on the plant, the resulting vibrations will alert the ants
• It has been reported that the ants will then raise their rear portion, the gaster, in agitation and squirt formic acid on to the intruders.

Question 28

traits of defence classified into two strategies:

Answer 28

defence & escape

Question 29

traits of defence classified into two strategies: defence syndrome:

Answer 29

those that have well-defended young leaves

Question 30

traits of defence classified into two strategies: escape syndrome

Answer 30

those that rely on rapid expansion to minimise the period when leaves are young and most vulnerable to herbivores

Question 31

are defence and escape syndrome always discrete classes?

Answer 31

NO, can sometimes be a continuum

Question 32

Ingus species example of escape:

Answer 32

I. umbellifera:

• leaves were produced in fewer but more synchronous flushes and expanded more quickly than I. goldmanii
• leaves exhibited delayed greening
• leaves had different (less effective) suites of chemical defence compounds compared to I. goldmanii and no ant defence

Question 33

Ingus species example of defence:

Answer 33

• young leave had normal chloroplast development, with little synchronous leaf production ad slow expansion of leaves
• leaf defence chemicals differed from those of I. umbellifera and were more bioactive against herbivores
• plant was protected by ants

Question 34

both Inga species are closely related but have ___

Answer 34

diverged in terms of defence adaptions

Question 35

what evolutionary trade off is represented between the to Inga species

Answer 35

Represents and evolutionary trade off in which energy is devoted to either defence or growth and rapid escape from herbivores.

Question 36

what shows that there is neither a competitive advantage to either defence/espace syndromes?

Answer 36

the fact that the end result of each defence strategy was the same amount of herbivore damage