Spatial Relations

BSC 2011L

Distribute yourselves!

• Plant in the desert – need to have your roots

reach water.

• Poison arrow tree

• Algae in deep ocean

• Mushrooms on a rotting log

• Mayfly mating frenzy

Spatial relations• Distribution of individuals within a population

– how individuals are arranged in space

Random

Not random

---Even/Uniform

---Clumped 1. Clumped

2. Even/Uniform

3. RandomWhich is most common?

Non-random – Clumped

“Patchy” Physical, chemical, and

environmental conditions

Hiding places (prey or predators)

Limited dispersal of juveniles,

seeds, larvae, baby birds

Social Factors

Selfish herd

Family groups

Non-random -- Uniform• Distances between individuals

are maximized

• strong competition for a resource

– Ex. Allelopathy

– Other examples?

nest distribution of blue

tilapia in sewage treatment

ponds

creosote bushes in southwest

Random

• The location of one individual bears no relationship to the locations of other individuals

• Usually found:

– in homogeneous environments

– individuals neither attract nor repel one another

• Distributions may change:

– seasons as resources change

– spatial scale is very important

Collect data for 3 tests.

2 tests of species distribution (clumped,

even, or random)

-- Clark-Evans nearest neighbor

method

-- Variance/Mean ratio

1 test of Interspecific Association

Clark-Evans nearest neighbor

method – Ant Lions

Measure to 4 nearest neighbors

Estimate area in cm2

Clark-Evans nearest neighbor

method – ant lions

• Measure distance to „nearest neighbor‟

• Calculate RATIO of measured / expected

R = 1 RANDOM

R > 1 EVEN

R < 1 CLUMPED

Do t test to test if the R value is „significantly different

that 1 (at alpha level of 0.05)

Variance/mean ratio method

50 hoop tosses

(for our class)

COUNT

NUMBER OF

PLANTS

Colocasia esculenta

(Araceae)

Variance/mean ratio method

• If v/m near 1 random

• If v/m <1 even distribution

• If v/m >1 clumped

• TEST for significance using t test

Interspecific association

At same time as above, record presence or absence of species B in quadrant.

For each hoop

toss, record

presence or

absence of each

species

Justicia americana(Acanthaceae) 50 hoop tosses

(for our class)

Interspecific Association

Record number of hoop tosses in each category (W,X, Y, Z)

N = number of total hoop tosses

If W x Z > X x Y, positive association

If W x Z < X x Y, negative association

Do Chi-squared test

You will be doing this

worksheet at home.

*Remember this sheet is

worth 15 points

• Pgs. 147-148 in the lab manual

• Do not do computer version on

bioviewer!

Due Wednesday

• 1. Spatial Relations datasheet (pgs 147-148

using data collected in lab Saturday) (15

pts).

• 2. Quiz 4 -- Do quiz bank questions OR

improve one of the WIKI articles (turn in

paragraph explaining briefly what you did)

OR take quiz at end of lab on Spatial

Relations. (5 pts)

• 3. Population Ecology PRE-LAB (pgs 129-

130) (5 pts)