Principles of Ecology (LSU BIOL 4253, Section 3, Fall 2014) Composite satellite image (“Blue Marble 2012”) from Wikimedia Commons.

Principles of Ecology(LSU BIOL 4253, Section 3, Fall 2014)

Composite satellite image (“Blue Marble 2012”) from Wikimedia Commons

A312 Life Sciences [email protected]

Dr. Kyle E. Harms

http://www.kharms.biology.lsu.edu

K. Harms photo

Complex Causation of Amphibian Deformities & Declines

The Web of Life

Cain, Bowman & Hacker (2014), Fig. 1.13

Ernst HaeckelGerman scientist, philosopher, physician

“oekologie” – combined Greek words for “household” & “knowledge”

What is Ecology?

Photo of Haeckel from Wikimedia Commons

The scientific study of interactions among organisms and their environments

What is Ecology?

K. Harms photo

Ecology is a Component of Environmental Science

Environmental Science – interdisciplinary field that draws concepts, expertise, and tools from natural and social sciences

Map of seasonal Gulf Coast hypoxia – the “dead zone” – from Wikimedia Commons

Environmental Movement – "a political and ethical movement that seeks to improve and protect the quality of the natural environment through changes to

environmentally harmful human activities"

Ecology Can Inform Environmentalism

Quote – Encyclopedia Britannica Online; photos of Carson and her 1962 book – Wikimedia Commons

Rachel Carson

Image from Wikimedia Commons

Levels of Biological Organization

Principal realm of Ecology

Joseph H. Connell

50+ Years of Personal Ecological Research(Rocky inter-tidal, coral reefs, tropical forests, etc.)

Photo of Connell courtesy of Pete Green

Ecological Patterns

Cain, Bowman & Hacker (2014), Fig. 12.9

Observations: Barnacle Inter-tidal Zonation

Semibalanus – Larger barnacle, lower in intertidal

Chthamalus – Smaller barnacle, higher in intertidal

Why?

Barnacle Inter-tidal Zonation

Abiotic influences –

Differential physiological tolerances to desiccation or submersion

Biotic interactions –

Interspecific competition

Predation (e.g., Thais snails preyon Semibalanus)

Alternative Mechanistic HypothesesNatural ecological & evolutionary processes that

could have produced the patterns (i.e., cause-and-effect)

Testable Predictions

Barnacle Inter-tidal Zonation

Abiotic influences –

Move barnacles outside current zones and performance should decline

Biotic interactions –

Remove competition and zones should shift

Remove predators and zones should shift

Selected Experimental Results

Barnacle Inter-tidal Zonation

The absence of competitors & predators produced no change in upper distributions

For Chthamalus, removing Semibalanus increased downslope survivorship & distribution

For Semibalanus, removing Thais increased downslope survivorship & distribution

Barnacle zonation

Mechanistic Explanation / Interpretation

Connell (1961) Ecology, Fig. 5

Observations

Scientific Advancements

Jane Goodall and chimp

Jane Goodall

ObservationsModels (mathematical and computer)

Scientific Advancements

Chaotic population growth

Per capita rate of increase

Pop

ulat

ion

size

(s

cale

d to

max

. si

ze a

tta

inab

le)

ObservationsModels (mathematical and computer)

Controlled Experiments (e.g., laboratory, microcosm, mesocosm)

Scientific Advancements

http://lishaopeng.weebly.com/aquatic-algal-microcosm-experiment.html

ObservationsModels (mathematical and computer)

Controlled Experiments (e.g., laboratory, microcosm, mesocosm)Field Experiments

Scientific Advancements

Replicated fuel-manipulation treatments in Louisiana pine savanna; photo courtesy of Jonathan Myers

Replication (i.e., n>1)

Experiments

Why?

1.0 m

1.5 m

2.0 m

1.0 m

1.5 m

2.0 m

vs.

Avoid spurious influence of uncontrolled variables!

Experiments

Why?

1.0 m

1.5 m

1.0 m

1.5 m

2.0 m2.0 m

Avoid spurious influence of uncontrolled variables!

vs.

Random Assignment of Controls & Treatments

Statistical Analysis

Experiments

Why?

To objectively determine whether results match predictions!

1.0 m

1.5 m

1.0 m

1.5 m

2.0 m2.0 m

vs.

Average male

Average female

E.g., Chi-squared Goodness-of-Fit Test

Statistical Analysis

0

2

4

6

Num

ber

of in

divi

dual

s

p-value – probability of obtaining a test statistic at least as extreme as observed, assuming the null hypothesis is true

6

6

Observed Expected(Null)

6

6

p = 1.0(accept null)

E.g., Chi-squared Goodness-of-Fit Test

Statistical Analysis

p-value – probability of obtaining a test statistic at least as extreme as observed, assuming the null hypothesis is true

0

20

40

60

Num

ber

of in

divi

dual

s

60

40

Observed Expected(Null)

50

50

p < 0.05(reject null;

support alternativehypothesis)

E.g., t-Test

Statistical Analysis

0

40

120

160

Hei

ght (

cm)

180175

172160

p = 0.19(accept null at 5%

level of significance)

165 140155 135148 130130 125

Height (cm)

80

Mean = 158.83 18.50

Mean =143.67 18.40

E.g., Correlation

Statistical Analysis

Correlation coefficient (r) – varies between -1 and 1;0 = no relationship

r = 0.87

120 130 140 150 160 170 180 1900

20

40

60

80

100

120

140

160

180

200

Height (cm)

Leng

th o

f rt

. ha

nd (

mm

)

E.g., Linear Regression

Statistical Analysis

Slope = -0.34; p < 0.05; r2 = 0.78

Examines the relationship between a dependent and an independent variable; p-value tests the slope against null slope = 0; coefficient of determination (r2) expresses how well the data fit the model

120 130 140 150 160 170 180 1900

10

20

30

40

50

60

70

80

90

100

Height (cm)

Num

ber

of r

abbi

ts c

augh

t pe

r m

onth

Photo of Levin from Princeton U.

“It is argued that the problem of pattern and scale is the central problem in ecology, unifying population biology

and ecosystems science, and marrying basic and applied ecology”

S. Levin (1992)

Scale in Ecology

E.g., species-area relationship(s)

Focus

Extent

Hubbell (2001) The Unified Neutral Theory of Biodiversity & Biogeography, Fig. 6.2

Spatial & temporal patterns often change with the scale of measurement

Scale in Ecology

Photos from Wikimedia Commons

E.g., how can we extrapolate from one scale to another (e.g., leaf-level gas exchange and photosynthesis

forest productivity global climate change)?

We seek mechanistic links among patterns and processes across scales

Scale in Ecology