Ecological Issues for Plants

1. Ecological Issues for Plants

2. Problems of being a sessile organism. dispersal finding a good living space mating protection deal with harsh conditions. Clue ; look for variety of solutions, and alternative strategies or bet hedging strategies, – in the same plant Remember about biological “rules” They apply except when they don’t = many variables, alternative strategies.

3. Dispersal • Why bother? If you are living in a good place, why not stay there?? Conditions change = disease, fire, flood Spread to new areas Get offspring best chance of survival = find a good habitat away from parent.

4. Use of seeds for Dispersal • Options: • choice between large and small - which is available to an annual vs a perennial plant? • Choice of how many seeds – annual vs perennial • In all cases, have seed designed to germinate only when conditions are good. What are the problems of waiting?? Large seeds vs small?

5. dispersal Use of wind no choice about where seed goes must be small seed – light weight not much nutrient So need to make lots of seeds – guarantee that some find a good area. Who uses this strategy?? Annuals, ferns (use spores, not seeds) In what environments should it work best?? (where are randomly placed seeds most likely to survive?? Where is their no choice???

6. Ways to use fewer seeds. Get them further away or to a good place. Animal transport: cocklebur – stick in fur of passing animal Bigger seed; still no control over where it goes – need a lot, but can store more energy in seed.

7. Coconut – large seed – floats, water dispersal from beach Fewer seeds, lots of energy storage Will land on a beach

8. Seychelles Island Palm nut

9. Fruits: get someone to eat the seed – carry it elsewhere, and deposit in dung (fertilizer) Get dispersal, get fertilizer. Still no guarantee of where it will go And must make fruit – fewer seeds and more energy per seed

10. Seed disperser For large tropical seeds What happens when disperser Dies out??

11. Finding a good place to live How to guarantee seeds get to a good spot. 1. long lasting seeds – can wait to germinate until conditions are good 2. Lots of seeds – heavy loss. 3. Pass through a gut as seed – get deposited with dung (manure) 4. Growth variation – stem vs leaves in case of shade.

12. Bet hedging strategies in reproduction • Can always reproduce by a clone - aspen groves

13. Aspen; each grove changes color simultaneously, why? All same clone, same genes. Problems: if a fire?? Won’t work in tropics. Why?

14. Mating in plants • primitive – motile sperm, advanced, pollen • dependent on wind or luck to find female; need lots of them • Advanced - use a flower • bet hedging = clone or self pollinate • can still, in some cases use wind • but can use insects, birds, etc. to carry pollen to another flower. • Allows for production of less pollen – more efficient transfer.

15. Pollination: how to play the game alternatives.

16. Some flowering plants have reverted to use of wind. Flowers very minimal

17. Ultraviolet patterns (right) that insects can see.

18. Red trumpet shaped flowers designed for hummingbirds.

19. Tropical Heliconia – flower designed to match hermit (hummingbird) bill shape.

20. CP51: Perhaps the most striking of all orchid flower mimics are the Ophrys family members that grow in Europe. This specimen from Turkey has flowers whose lips look like the abdomen of a female bee. The male bee's energetic efforts to mate with it scatters the pollen everywhere. The orchid gets pollinated and the frustrated bee gets nothing.

21. Natural selection has molded the flowers of these orchids (many in the genus Ophyrys) into mimics of the insects that pollinate them. Horny male insects, thinking that the petals are a female, land on them and engage in fruitless attempts to copulate (“pseudocopulation”). During the barren act, the insects’ heads or bodies contact the orchids’ pollen sacs, which break off and attach to the insect. The frustrated insect flies off, but soon tries to copulate with another orchid, which puts the hitchhiking pollen in contact with the new orchid’s stigma. In such a way the bees/wasps serve as “flying penises,” helping the orchids have sex. Here are some specimens: Ophyrys insectifera (fly orchid), which deceives male digger wasps.

22. Meat smelling flower – attracts flies as if to carrion – a specialty pollinator.

23. When is the best time to flower?? in desert?? In tropics?? What determines flowering time in the desert??, in temperate region?

24. The economics of flowering Desert: must be synchronous of all annuals – after rain or after winter. = lots of competition for insect pollinators = buyers market big reward to attract a few insects. Plant choices: big showy flowers, lots of nectar So how come some desert plants have tiny flowers?? or don’t play the game – use wind pollination or self pollination

25. When should you flower in the tropics?? When can you flower? Flowering times of 41 tropical trees; If you want to cross pollinate – and there are few trees, and no change in day length (seasonality) how do you synchronize flowering time within a species? Answer – use time of sunset, sun rise.

26. Top of page Abstract In tropical rainforests, 30−65% of tree species grow at densities of less than one individual per hectare1. At these low population densities, successful cross-pollination relies on synchronous flowering. In rainforests with low climatic seasonality, photoperiodic control is the only reliable mechanism for inducing synchronous flowering2, 3. This poses a problem because there is no variation in day length at the Equator. Here we propose a new mechanism of photoperiodic timekeeping based on the perception of variation in sunrise or sunset time, which explains and predicts the annually repeated, staggered, synchronous and bimodal flowering of many tree species in Amazonian rainforests near the Equator.

27. In tropics – conditions always good, so can flower at any time No synchrony ; sellers market – one seller, lots of buyers so small reward = low nectar, etc. to attract insects.

28. Flowering of annual vs perennial Which has the biggest flowers – all things being equal? Wind vs insect pollination; which has the biggest flowers? Why are there exceptions?? Tiny flowers of grass (use wind) And some trees (use wind)

29. Protection How does a plant protect itself from being eaten?? Fence off the enemy – plant galls. Develop poisons in tissue; most efficient way – only in response to injury Out grow whoever is eating you. – new leaves Mechanical devices; thorns, etc. Find bodyguards – ants and acacia

30. Oak galls – wasp egg in oak walled off by gall.

32. ocotillo

33. Madagascar thorn forest

34. Madagascar thorn forest when wet

35. Madagascar elephant bird; extinct soon after humans arrived about 1000 ad

39. Acacia tree with ants and hollow spine homes for them.

40. Harsh conditions Mostly a perennial problem Dry – store water, loose surface area when dry – cactus, etc. chlorophyl in stem – palo verde Need to protect self (and water supply) = cactus thorns, poisons, etc.

43. Local coastal sage Size of leaves compared to well watered area Waxiness of leaves Deciduous leaves. All reasons for fire danger.

44. Many mosses can grow in desert conditions because they can dry up and then, when water returns, expand their cells again.

45. Other harsh conditions Cold: avoid it (annuals) : low surface area, no freezing : oils to avoid freezing Salt: adapt

46. Pickleweed – salt tolerant

47. Human caused problems for plants • Fire ( frequency) • Water supply • lowering of water table in Arizona • Diseases • dutch elm disease • new insects. • New Competators

48. Fire: if an area regularly burns, all plants living there have a way of surviving. - annuals as seeds - perennials – resistant bark - underground storage roots.

49. Number of fires has gone down

50. But severity of fires has gone up. Reason: wood is a resource to be protected = prevent fires Get fuel build up – now fires more severe that before.