Dispersal And Habitat Selection Flashcards
What is dispersal by diffusion?
Gradual recolonisation of suitable habitat after population crash due to hunting
Give an example of dispersal by diffusion
The sea otter Enhydra lutris
What is jump dispersal?
When individuals move across large distances, often crossing unsuitable habitat, and establish as a population in a new area.
What is a human example of an accidental transplant experiment
Human activities resulting in the dispersal and introduction of exotic species to new areas.
What are the four stages of pest species commencing?
Imported
Introduced
Established
Pest
How can dispersal be a limiting factor? (S)
Invasive species- they are a consequence of removing barriers to dispersal
Give an example of an invasive species as a result of dispersal as a limiting factor.
Salvinia molesta
- floating pond weed native to South America and introduced via human activity to Africa, India, australia
What was the problem with the invasive species Salvina molesta? (Dispersal as a limiting factor)
-It reproduces vegetatively and grows rapidly, doubling its biomass in 3-4 days.
-Blocks waterways making them unusable for transport or drinking water
- wiped out fish populations
What is the natural predator of Salvina molesta?
Cyrtobagous salvinae, feeds on the buds as adults and roots as larvae
What problems occur from aquatic weeds?
- block access to and disrupts drinking water
-interferes with drainage and irrigation , floods
-changes ecology of natural aquatic systems
What insect species were used to try to control the Salvinia molesta outbreak in Sri Lanka, India, Africa and Fiji?
A weevil, a moth and a grasshopper.
What finally controlled the Salvina molesta outbreak?
A weevil ( C. Salvinae) brought the weed under control in one year.
What was the benefit to cost ratio of the Salvinia molesta outbreak in Sri Lanka?
53:1 monetary terms
1673:1 labour terms
What are the factors that influence species distribution?
-dispersal
-behaviour
-other species
-physical and chemical factora
How can dispersal factors influence species distribution?
-area is inaccessible
- insufficient time for dispersal
How can behaviour influence species distribution?
- habitat selection
How can other species influence species distribution?
- predation
- competition
- parasitism
- disease
What physical factors influence species distribution?
- temperature
-light
-soil structure
-fire
-moisture
What chemical factors influence species distribution?
-water
-oxygen
-salinity
-pH nutrients
What are the two main abiotic factors limiting species distribution?
- temperature
-moisture
What physical factors limit the distribution of coral reefs due to the narrow requirements of zooxanthellae?
- need temps of 18-30 degrees
- need solid substrate to grow on
- need access to light
- narrow range of salinity tolerance
When identifying factors that limit distribution, what do transplant experiments provide?
Transplant experiments provide empirical evidence of species’ ability to survive outside of its current range.
Give an example of the role of dispersal in limiting distribution.
The bull kelp in Kachemak Bay, Alaska
What was the observation in the Bull kelp transplant experiment?
Surveys based on aerial photographs showed that Bull kelp forests only occurred in the outer basin and were absent from the turbid low salinity inner basin.
Where was the Bull kelp present in the transplant experiment!
In the outer basin
Where was the Bull kelp absent in the transplant experiment?
In the turbid low salinity inner basin
What is the hypothesis of the bull kelp transplant experiment?
Decreased salinity and light intensity limits the distribution of Bull kelp in this system.
What was the prediction in the Bull Kelp transplant experiment?
Bull kelp juveniles transplanted from the outer to the inner basin will not survive.
What are the biotic factors that determine distribution of species?
Species interactions
What are the abiotic factors that determine the distribution of species?
Environmental factors
What are species distributions shaped by?
Adaptation and natural selection
Environmental and biotic change
What are reasons a species are absent from a habitat that it could survive within?
-it can’t get there (dispersal)
- it does not recognise it as a suitable habitat (habitat selection)
What factors prevent a species from being able to complete its life cycle outside its current range?
- interactions with other organisms eg: predation, disease, competition
- impacts of physical and chemical factors eg: temperature, light, moisture
What is an Ideal Free Distribution?
When all individuals are free to move into any habitat without constraint
What is an Ideal Despotic Distribution?
When all individuals are not free to move between habitats and the highest quality habitats are protected by territorial behaviour.
