Dispersal

Changes in geographcic distribution:

- Dispersal

- Colonisation

- Invasion

Propagule:

- Stage in lifecycle

○ T.d. Seed

- Part of organism

○ Self-propagating

- Group of organisms

○ A breeding pair

○ Humans

Dispersal:

- Intra-range (ecological)

- Extra-range (biogeographical)

○ Beyond it's normal area

○ Colonisation

Stragtegies:

- Passive dispersal (plants)

○ Outside force required

§ Biological

□ Water or wind

® Seeds that have wings

- Active dispersal (animals)

○ Seeking a partner

○ Looking for what one needs

Passive dispersal:

- Different mechinisms

○ Anemochores:

§ Wind:

□ Can travel far

□ Winged

® Dandileons and tumbleweed

○ Hydrochorose:

§ Water:

□ Buoyant

□ Salt resistant

□ Submergence

® Coocunt seeds

○ Anemo- and hydrochores:

§ Both

§ Flood plains and island species

○ Zoochores:

§ Animals:

□ Hooked

□ Attached themselves to animals

® Sticky

□ Some can only germinate after passing through an animal

® Birds are important

○ Anthropocores:

§ Humans:

□ Accidently or deliberately

® Agriculture

® Horticulture

◊ On clothing, footwear, fur

} Barly

– Depends on humans

The bigger the seed, the more chances it will surviive

Clonal colonies:

- Pando

○ The biggest living organism in the world today

Seasonal migration:

- Obligate:

○ Feeds up at the stop

○ Very predictable:

§ May follow the wind, magnetic poles or daylight

- Irruptive migration (facultative):

○ Masses arrive because of a shortage in food supply in the homelands

○ Unpredictable

Colonisation:

- Ocupying an area beyond the normal range

- Invision:

○ Deliberate or accidental through human agency

○ Emotive reaction:

§ They see a change in the landscape (t.d. Lúpína)

□ Not for every invasion... introduced plants

- Supertramps:

○ Widley dispersed propagules

○ Rapid population growth rates

○ Generalist niche

○ Facour?? "disturbance"

§ T.d. Dandelion

Slow diffusion:

- With each generation, the range of the species increases

Rapid diffusion:

??

Jump dispersal:

- Dictated to proximity to other islands and the mainland

- How quickly species can get there

- Competition

○ New species established

○ Fundamental to the colonistation of islands

Constrants to clolonisations:

- Barriers,:

○ T.d. Oceans, mountain ranges and deserts

- Corridors:

○ T.d. Rivers, isthmus? And woodlands

- Filters:

○ T.d. Geography, temperature, competation and behaviour

- Stepping stones:

○ T.d. Archipelagos, pathcwork and habitat mosaics

- Waifs:

○ Long distance dispersal (atolls?, islands)

§ The longer it is from the source, the harder it is to disperse

- Sweepstake:

○ Transatlantic colonisation:

§ Pure chance