Transcript Ecology of a Changing Planet

Welcome to Community Ecology
Dr. Mark B. Bush
Spring 2006
Course Requirements
• Lectures and labs are required. Period.
• You are required to be professional in your
behavior, that means no eating or drinking in
class, and be punctual.
• No make-up quizzes or exams without physicians
note.
• This is a 4000 level class…it is much harder than
any class you have taken so far….much more is
expected of you.
Readings
• All readings must be
read BEFORE class.
Keys to success.
• 100% attendance.
• Good project work.
• Doing ALL discussion readings BEFORE
the class.
• Doing the required readings before quizzes
• Don’t sit at the back of the class
Grading
• 2 midterms (15% each), and 1 cumulative final
(30%) will test your detailed knowledge and
understanding of the material from lecture and
textbook.
• Lab will be worth 30%
• Sigma Xi grant proposal 10%
• Two missed lectures or discussions or 1 missed lab
= grade lowered by a half point (e.g. from low b to
high c).
I can help
• I don’t bite, talk to me.
• Office or lab: Room 218/220.
• If you can, set up an appointment in the Bio
office to see me during office hours.
• As a last resort email me to set up another
time.
• [email protected]
Office hours
• Tuesday 9 - 11 am
• Wednesday 10 - noon
• Thursday 1 - 2pm
Goal of class
• Provide an introduction to theoretical and
applied community ecology.
• Introduce concepts that are the mainstays of
conservation biology.
• Develop skills in experimental design and
reporting.
And now the good news!
• These notes and additional readings are
available on-line via Blackboard (course
documents)
• I will continue to put them up so long as
YOU attend class.
What is community ecology?
• The study of the interactions of species and their
relationship to the environment.
• General Ecology (Bio 3410) introduced population
biology…we will build on that basis to consider
interactions of suites of species.
• Can be approached through mathematical models,
experiments, and descriptive investigations.
Topics we’ll cover
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Niche and guild structure
Succession
Influence of climate
Patterns and measures of diversity
Influence of environmental change
Why study community ecology?
• Species do not operate in isolation…..to
understand any individual species it must be
seen in the context of its ecosystem.
• Ecosystems do not operate in isolation. Cannot
understand coral bleaching without
understanding global climate change.
• Cannot understand global climate change
without understanding carbon flux and
transpiration of forest systems.
Application of community
ecology
• How will ecosystems change in the future?
• How can conservation designs incorporate
global climate change and habitat loss?
• To get to these issues we have to understand
the process of ecological responses to
stimuli…..that is community ecology.
Ecology must be based on sound
science
• Scientific process:
• Observation -> hypothesis generation ->
experimental observation -> inference ->
hypothesis accepted or rejected.
• Sounds simple but takes a lot of practice to
be good at this.
Observation to hypothesis
• Science is founded on accurate, unbiased,
repeatable observations.
• From these observations we construct a
hypothesis.
• A good hypothesis is consistent with all the
data and is testable.
What is the hypothesis being
tested here?
• 30 snakes were starved for a month. Group 1 (n
=10) snakes had their eyes covered with an opaque
film, Group 2(n = 10) had the nerve receptors
from their pits severed, Group 3 (n = 10) had both
treatments. Live mice were introduced to their
cages. Group 3 fed the most successfully, Group 2
the least successfully.
What is wrong with this experiment?
What hypotheses can you
generate from these data?
prey
mass
(kg)
Peccary
Agouti
Deer
25
5
20
number
in hunting
area
200
100
40
Jaguar
diet %
60%
30%
10%
Puma
diet %
10%
70%
20%
Testing a hypothesis
• A hypothesis must be testable
– It should lead to a deeper
understanding of the issue, i.e. be
non-trivial
• Can you prove a hypothesis?
NO!
You cannot prove a hypothesis!
A Theory
• There are NO facts in biological science.
• There are hypotheses that have been tested
and have not been refuted.
• A complimentary group of hypotheses form
a THEORY.
• A theory is science’s most powerful idea,
i.e. Theory of Gravity, Theory of Electricity,
Theory of Evolution.
Experimental design
Gaining data to test a hypothesis
Simple interactions
• So far you have considered one-on-one interactions.
 Models, e.g. Lotka-Volterra competition or predation
models.
 Can also look at environmental variables, e.g. the
effect of fire on population size.
 Statistical testing: choose the appropriate test from
those taught in Biometry.
• These relationships form the basis for understanding all
ecology.
Complex interactions
• However, we often have multiple
interacting species and other variables (e.g.
soil, climate, area), and so it is more
complex to evaluate interactions.
– Models must include more factors.
– Statistical treatment may not be able to test a
single variable, but rather help to refine
hypotheses.
Correlation not causation
• Community ecology often deals with correlation
not causation.
• When studying communities we are often asked:
– How similar is this community to that one?
– Does factor A correlate with a change in
community?
– Can we predict what will happen to the
community if we change factor A?
Why
experiment?
• This image plots
altitude against plant
diversity in the
Himalayas. What
explains the change in
plant diversity?
• Altitude and diversity
are correlated. You do
not know if they are
causally connected.
D
i
v
e
r
s
i
t
y
• What factor might be
causing this change in
diversity?
Altitude
Sigma Xi design
• Here are some key pointers to consider as
you design any experiment.
• When you do your Sigma Xi design be sure
to think through all these elements.
Identify problem
• Your research topic should be based on a rationale.
• Research a topic to see what has been done before.
Remember a lot of excellent science was done
before 1985 and so computer-based search engines
may not reveal older work.
• Apply the minnow test:- substitute your target
organism with a minnow, is this still interesting
science? If not, think again.
• Take a bite-sized piece of the problem.
Essence of good experimental
design
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Simplicity
Tractability
Controls
Replicates
Designing an experiment
• Decide if you are going to test for correlation
or causality.
• Formulate a TESTABLE hypothesis.
• Decide what data you need to test the
hypothesis.
• What data would refute the hypothesis?
• Now design an experiment to gather those data.
Check your design
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Is it realistic to do all you intend?
Is your survey method appropriate?
Have you identified controls?
Have you replicates and are they sufficient
for the stats you want to run?