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.• mbush@fit.edu

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

• 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 number Jaguar Puma

(kg) in hunting diet % diet %

area

Peccary 25 200 60% 10%

Agouti 5 100 30% 70%

Deer 20 40 10% 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.

• What factor might be causing this change in diversity?

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

• 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

• 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?