Lecture 11: mutualism Flashcards
brood site pollination mutualism
species one pollinates species two, species 2 provides home for species one
mutualism is an arrangement where both parties
benefit
get interspecific and intraspecific
mutualisms can be __ or ___
facultative or obligate
obligate they can’t survive or reproduce without other species
obligate mutualism insect example
have micro-organisms in their gut (termites and gut protozoa)
microorganisms get food source
insects get help w digestion
BUT usually conflict between species
Orius and Macaranga
have mutualism. Orius lays egg in Macaranga but often conflict as one species exploits the other
Pollination mutualisms =
- pollen of many angiosperms moved by insects / birds (animals)
- if plant M&F benefits from movement of its pollen, but new pollen brought to it
- pollinator benefits, usually getting an incentive (nectar) to visit
insects cheating plants: bees
some bees visit plant without pollinating them
-they work the flower from the side or chew through the corolla tube and insert their tongue
plants cheating insects: Kiwi Fruit
(Actinidia) has female and male plants
- both have pollen as a reward for bees
- but pollen from female plants is just the indigestible outer coating, no nutritional value
plants cheating insects: Orchids
mimic female bees and wasps, males who try to copulate with them spread pollen via attempted matings
- W. Australian orchid by thynnine wasp
- wasp at loss
fig/fig wasp mutualism has more / less conflict between yucca plants and yucca moths
less conflict
fig & fig wasps
- OBLIGATE
- stranlger fig
- fig climbs tree which it eventually kills
- flowers located inside the body of fig
- female fig wasp enters via ostiole and lays egg
- releases pollen from the fig where it developed
- F & M wasps emerge and they mate (only F has wings)
- mated pollen carrying F leave through holes which males cut w mandibles for them
- F disperse to other fig plants for pollination
mutualistic and parasitic fig wasps
Torymidae fig wasps parasitise both fig and mutualistic fig wasp
- use ovipositor to lay eggs (don’t enter fig themselves)
- need fig for developing larvae
- need fig wasps to pollinate the fig
- cost to plant is quite small –> as most of ovules exploited produce females that transmit pollen
- optimal sex ratio for plant is 50:50 (females & seeds)
- obv some are males only help by cutting exit holes
- in many fig wasps there is LMC, so most offspring are females anyway
- fig benefits from having some but not all of its ovules parasitised
- plants control was entry by evolving tight ostioles, short ostiole opening, rapid fig development (HERRE 1996)
- 55% of seed per fig r lost to wasps
Defence against non-polinaing wasps
- wasps have long ovipositor, fig could evolve a thicker skin, but likely to cause an arms race. who would win?
- wasp likely, less costly to increase length of ovipositor than whole skin and fig can afford to lose the odd egg to wasps but parasite can’t afford to fail to reproduce
Gynodiecious figs (some plants have females, some have male and female [hermaphrodites])
Hermaphrodite plant:
- female wasp enters, pollinate, lays egg, hatch,mate,pick up pollen and leave to fertilise another fig
- – ok for plant, good for wasps—
female only
f wasps enters, pollinates but cannot lay eggs (as they have long styles ovipositors can’t reach ovule) so no young wasps emerge, figs produce seed from all flowers
– good for plant, bad for wasps —
why do females still enter female only figs? they can’t tell till inside
fig wasps and figs: species specificity
thought must be one species per fig, but some wasps switch hosts, some figs support more than one pollinator wasp and all associates have coevolved separately
