VL 2 Flashcards
4 types of species interactions
Mutualism
Commensalism
Antagonism
Competition
Definiton Mutualism
An association between two species which is beneficial to both
can be:
obligate - necessary association for survival and reproduction
facultative - beneficial but not essential
How do mutualisms develop?
If selective advantages to both species to associate -> rapid development
Usually develop between organisms using different resources, not competitors
Both organisms should gain / lose roughly the same amount
Possible development: parasitic -> commensalism -> mutualism
Dispersal
Insects disperse seeds or pollen or spores
Eliasomes (like fruit)
Edible Flesh attached to seeds encouraging dispersal by eg. ants
Pollination
Fertilization and sexual reproduction in exchange for:
Food / home for larvae - fig wasps
Nectar / pollen - bees, butterflies, moths, ants
Nutritional mutualism
New resources made available:
- Partner ofers new food source or facilitates access to one
- Insect provides transport, care, pollination or a place to live
Examples:
Digestion of wood / cellulose
(partner: fungi/yeast/bacteria)
Termites
Wood wasps
Digestion of plant tissues
(partner: fungi)
Leafcutter ants
Termites
Nectar and Pollen
(partner: plants)
Moths + butterflies
Bees
Ants
Protective mutualism
Insects protect plants / other insects
The protected species offers some kind of reward to the partner
Protection against enemies:
Parasitoids/predators are recruited by plant volatiles
Ants protect plants and feed on extrafloral nectaries
Ants protect aphids in exchange for honeydew
Ants protect lycanenid larvae for sugar secretions
Protection against environment / pathogens:
Bacteria protect aphids
Why do plants need pollinators?
Some plants self pollinate or seeds are carried by wind and water, but 75% of crop plants need insect pollination
-> need an insect to visit, then visit another of the same flower species
Buzz pollination
10% flowering plant species require specialist ‘buzz’ behaviour by bees, including all solanaceous crops
pollen release is restricted by modification of the stamens - poricidal flowers
has evolved independently in plants multiple times
Solitary bee
Solitary bees do not live in colonies, produce honey or have a queen
Examples: mason bees, mining bees, leafcutter bees, wool carder bees
A single red mason bee is as effective at pollinating as 120 worker honeybees
Plant signals
Higher successful pollination rate if encourage fidelity
Plant must therefore be recognisable / distinguishable and rewarding
Floral pigments, UV spectra, volatile organic compounds
Different signals in the day / night
Flowers may signal they have already been pollinated
Plant signals - visual
Diverse bee species have conserved colour visual system and flower colour in angiosperms worldwide is coded by this system
-> if flowers are lookd at under UV light, special patterns can be seen, see page 14
Plant signals - olfaction
Night blooming plants may focus more on having a strong scent than visual cues
Odour plumes maintain specific volatile ratios, allowing detection in ‘bursts’ at many meters away
Manduca sexta hawkmoths detect the volatile blends of flower species and choose the ones they have a matching proboscis length for
Plant signals - electric fields
bees have positive electric potential, flowers negative
when bee lands, pollen is more likely to stick on bee
flower will change its potential -> important for bee to know where there is pollen left
Plant signals - multimodal
more than one signal leads to enhanced foraging efficiency and pollination in bumblebees
Insect signals - bee damage
when bees bite plants, it’s a signal for plant that there are pollinators nearby
Figs and fig wasps
S. 19
Fig is not a fruit, it’s an inversive flower
- A pollen-laden female wasp enters an unripe fig
- the wasp pollinates the flowers and lays her eggs
- Flowers with wasp larvae form galls, and some other flowers produce seeds
- Male wasps leave the galls first and fertilize the females. The males will die before leaving the fig
- Females then leave their galls and collect pollen from mature male flowers within the fig
6a. Females exit the fig through a tunnel and search for another fruit where they will lay a new generation of eggs -> 1
6b. In some cases, though, females exit the fig without first collecting pollen
- Females without pollen will still enter another unripe fig, where they will lay their eggs. But without being pollinated, the fig will not grow seeds and may be aborted by the tree. Any offspring in the dropped fig will die.
Nectar robbing
Insects puncture the back of the flower to ‘rob’ the nectar
non specialist species can tackle flower shapes they otherwise couldn’t
Flowers may then be ignored by pollinators
Deception pollination: orchids
Spider orchids mimic solitary wasp sex pheromones
Hammer orchids use both smell and visual cues - looking like a female wasp
Lords-and-ladies flowers use odours of rotting meat to trap owl midges and force pollination
Plant protection
Ants can provide protection to trees / shrubs they have nests in, as well as surrounding plants, as they will hunt herbivorous insects for food
Ants produce antimicrobials that can reduce pathogens in the host plant
For some species, they can also scare off inefficient pollinators, allowing only larger species through thet result in higher fruit production
Ants and acacia trees
About 10% Acacia species don’t use traditional chemical defenses and instead specialize in ant partnership
The ants live in the swollen thorns and the plant provides sugar from extrafloral nectaries
In return the ants ‘patrol’ the plant attacking herbivores, fungus and competing plants
Ants and acacia tees - manipulation
In order to keep ant species with more effective defenses, the tree will produce more sugar as a reward
When occupied by weak defenders, acacia trees locate extra floral nectaries at the tips of leaves to encourage ants to patrol more
The tree may also manipulate the ants by disabling their ability to digest sugar from other sources, forcing them to stay
Ants may attack the flowers, ‘castrating’ the plant causing more vegetative growth instead
More vegetative growth = more living space, allowing for bigger colonies
In acacias, while it halts reproduction, it may not affect lifetime fitness
