Lecture 6: Inter-specific interactions Flashcards
Herbivory & plant defences: plants have evolved an array of __, ___, ___ & ____ ways to attack, poison, starve or avoid herbivores
biotic, chemical, mechanical and phenological
Herbivory & plant defences: interaction of herbivores and young leaves of tree seedlings is important in regulating
trophic dynamics, as it determines herbivore population sizes and / or seedling persistence
Herbivory & plant defences: ___ are the most important consumers of leaf material tropical forests although vertebrates, fungi and other pathogens have an effect
INSECTS
On Barro Colorado Island, Panama about __ of annual leaf consumption is due to herbivores
3/4
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
average 7% of leaf area and in tropical humid forests this is 11% for shade tolerant plants and 48% for gap specialists.
insect herbivores are very
diverse
herbivory impacts can be __ or __
obvious or hidden
how to plants defend themselves?
- Physical defence
- Chemical defence
physical defence: examples
-spines on the stems of rattans, bamboos and acacias
-stinging plants i.e. seed pods of Mucuna climbers
both protect against vertebrate herbivores
chemical defence examples:
-Ugandan forest some trees have toxic bark to deter elephants (Antiaris toxicaria)
___ are the most important herbivores in tropical forests
invertebrates
majority of herbivore damage in the tropics occurs ______
during the short window when leaves are young and expanding
leaves of shade-tolerant species live for many years, yet 75% of the lifetime damage occurs when?
during the few weeks that leaves are expanding
species vary ___, losing from ___% of their areas during leaf development
six fold
12-74%
plants invest in a range of leaf defences:
- 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
delayed greening of tropical leaves: WHY
-reduces loss of energy & nitrogen by delaying development of chloroplasts (appear white/red-purple)
delayed greening of tropical leaves: red/purple colour due to
the presence of other pigments such as anthocyanin (which are masked by chlorophyll)
delayed greening of tropical leaves: appearance to herbivores
not nutritious and not as attractive to herbivores as young green leaves
the cost of reducing herbivory by delayed greening is forfeited by
photosynthate
delayed greening is prevalent (but not exclusive) to ____
understory plants where photosynthesis is limited by shed
ant plants:
myrmecophytes
myrmecophytes:
leaves of some plants species are protected by ants (ant-plant mutualism)
ant-plant mutualism (how does it benefit both)
- 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
Macaranga bancana:
macaranga bancana has developed an obligatory relationship with the Heart Gaster Ants
-plants are usually colonised as saplings
how do ants colonise a plant?
- 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
what are stipules?
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
myrmecophytes: what do ants protect the plants from?
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.
traits of defence classified into two strategies:
defence & escape
traits of defence classified into two strategies: defence syndrome:
those that have well-defended young leaves
traits of defence classified into two strategies: escape syndrome
those that rely on rapid expansion to minimise the period when leaves are young and most vulnerable to herbivores
are defence and escape syndrome always discrete classes?
NO, can sometimes be a continuum
Ingus species example of escape:
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
Ingus species example of defence:
- 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
both Inga species are closely related but have ___
diverged in terms of defence adaptions
what evolutionary trade off is represented between the to Inga species
Represents and evolutionary trade off in which energy is devoted to either defence or growth and rapid escape from herbivores.
what shows that there is neither a competitive advantage to either defence/espace syndromes?
the fact that the end result of each defence strategy was the same amount of herbivore damage
