Spatial patterning Flashcards
More organisms are dispersal limited. What does this mean?
They can only disperse by a certain amount.
Give an example of a factor that limits dispersal.
Size: large organisms do not disperse as uniformly as small ones. Small is classed as <1mm, as these organisms are hugely affected by the environment, e.g. blown in the wind.
Nearly all ecological interactions are local ones. Give 3 examples.
- Predator-prey (+,-)
- Competition (-,-)
- Mutualism (+,+)
There are 2 types of spatial heterogeneity. What are they?
- Externally generated: created by the abiotic environment.
2. Internally generated: created by biotic interactions
What generates spatial pattern?
Local dispersal
What does spatial patterning determine?
Local neighbourhood.
There is a link between spatial patterning and mortality rate. True or false?
True: if organisms are aggregated into high densities they will suffer.
Ecological neighbourhoods are defined where the focal individual sits in a circle. The circle represents a boundary. What does this boundary signify?
The distance at which neighbours no longer have an effect on the growth/mortality/fecundity rate etc. of the focal individual.
There are 3 main spatial patterns. What are they?
- Aggregated
- Segregated
- Random
Explain aggregated patterning.
Small groups of individuals clustered together.
What kind of a) dispersal and b) interaction is involved in aggregated spacing?
a) short range - organisms stay close to parent/family group
b) short range - organisms thrive on close interaction, sociality
What are other names for segregated spacing?
Over-dispersed or even-spaced.
Describe segregated spacing.
Individuals are evenly spaced - there are exclusion zones around each organism as competition is intense.
What kind of a) dispersal and b) interaction is involved in aggregated spacing?
a) long range - organisms travel far from their original location
c) short range - close competition between neighbours
Describe random spacing.
The distribution of each individual is independent of its closest neighbours.
In random spacing, organisms neither inhibit each other, as in segregated spacing, or promote each other as in aggregated spacing. True or false?
True.
What kind of a) dispersal and b) interaction is involved in aggregated spacing?
a) long range
b) long range - organisms rarely interact
What 2 things do we assume about a population if it is randomly spaced?
- There is a high birth rate
2. There are high levels of post-birth movement
Aggregated spacing is the most common pattern and serves as the null hypothesis in dispersal experiments. True or false?
False - aggregated is the most common pattern, but random distribution serves as the null hypothesis as it assumes there is no interaction between individuals.
Individuals in densely aggregated populations do not often survive. Why?
Due to competition, there are not enough resources to sustain that many organisms in one space.
What is ballistic dispersal mode?
Seeds in a pod are thrown out.
What are the 3 main dispersal mechanisms for seeds?
- Ballistic
- Wind
- Animal
Which type of seed dispersal results in the least clumped spacing?
Wind
What does the Logistic equation of dN/dt = rN(1-N/K) where N pop size, r births-deaths, K carrying capacity assume about spatial patterning?
It is random and the population is well mixed.