Spatial Relationships Lab

dispersion

number of individuals of one species in relation to each other and to individuals of other species

random dispersion

one individual bears no relation to the locations of other individuals

even dispersion

distance between neighboring individuals is maximized

clumped dispersion

distance between neighboring individuals is minimized

random

- caused by an abundance of resources

- least common dispersion pattern

even/uniform

- occurs in arid environments

- strong competition in this type of dispersion pattern

clumped

- characterized by an environment w/ patchy resources or underlying social factors

- most common type of dispersion pattern

spatial scale

change that occurs due to space between individuals (i.e., competition)

temporal scale

change that occurs over time (i.e., migration)

Clark-Evans Nearest Neighbor Test

- measure the distance between an individual and its nearest neighbor to be compared to the expected mean distance

Using CENNT, when R>1

dispersion pattern is even/uniform

Using CENNT, when R<1

dispersion pattern is clumped

Variance/Mean Ratio Method

- count the number of individuals in a sample plot and compare the results w/ an expected randomly disperesed sample

Using V/MR when R>1, the dispersion pattern is

clumped

Using V/MR when R<1, the dispersion pattern is

even/uniform

Interspecific Association

- whether 2 species tend to occur in the same place

- note the presence or absence of each species and form X²

if p-value>alpha-value

Fail to Reject null hypothesis

if p-value<alpha-value

Reject null hypothesis