Community Ecology

BCB331

Mark J Gibbons, Room Z108, BCB Department, UWC

Tel: 021 959 2475. Email: mgibbons@uwc.ac.za

Image acknowledgements – http://www.google.com

Some Definitions

Environmental Condition

Physical environmental variable or factor, that varies in space and time, and to which organisms respond

Examples include:

Temperature, salinity, moisture, elevation, depth, nitrogen concentration of water, beach grain size etc etc etc

Environmental Gradient e.g. Temperature

Per

form

ance

or

Ab

un

dan

ce

Species ASpecies BSpecies CSpecies DSpecies ESpecies FSpecies GSpecies HSpecies ISpecies J

Resource

Something that is required or used by an organism, the

quantities of which can be reduced by the organism

Examples include:

Dissolved oxygen, sunlight, water, carbon dioxide, mineral

nutrients, organisms as food

Population

A group of individuals of the same species that coexist in space and/or time

Population size / density

Rat

eBirth

Death

K

Born

Population size / densityN

um

ber

s

Dying

Difference = NET Recruitment

0

200

400

600

800

1000

1200

1400

1600

1800

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

Time

N

S-Shaped Growth Curves

Characteristic of intra-specific competition

0

5

10

15

20

25

0 200 400 600 800 1000

Population Size

Net

Rec

ruit

men

t

N - Shaped

K

Community?

A group of interacting populations of different species that coexist in time/space

Outcomes of interactions between two species

Inter-specific Interactions

-+Predation

--Competition

0+Commensalism

0-Amensalism

Species BSpecies A

++Mutualism

A community as viewed from a predator-prey perspective

A group of interacting populations of different species that coexist in time/space

A number of other trophic based units also used

Community subsets

Guild

Communities can have very many interacting populations

of different species and to study all of them requires a

suite of expert taxonomists at the very least.

Community ecologists tend to get around this issue by

studying subsets of the community

Taxocene

Morpho-species

Ecosystem vs Community

How big is a community? ANY SCALE

Broad patterns in terrestrial vegetation can be recognized at the global scale - BIOMES

At this scale, climate is the overwhelming factor that limits vegetation

How small is a community?

Regional Species Pool

Evolutionary Processes

Physiological Constraints

Historic Events

Habitat Selection – Habitat Species Pool

Dispersal Ability – Geographic Species Pool

Local Community

Inter-specific Interactions

Rules – a species will only be present if:

a) It can disperse there

b) Conditions and resources allow it to survive

c) Predators and competitors etc don’t preclude it

Determinants of Community Composition and Structure

Course Aims and Structure

Objectives:

•To train students in the basic theories of community ecology

•To provide students with the necessary field skills to enable them to undertake surveys and identify biological communities

•To provide students with the necessary skills to enable them to determine those environmental factors contributing to community structure

Required Background:

Any course on community ecology requires a certain level of background theory and skills - if it is to be successful. For this course, they include a working knowledge of:

Measures of central tendency and dispersionMSExcel

It is also assumed that students are able to build simple single-species models of population growth and that they have a knowledge of intra-specific competition.

As many of you may lack this background, it will be necessary to spend a short period of time completing this work.

Approach:

The course is a balance between theory, laboratory and

field: any person that goes on to work (e.g.) in nature

conservation needs to know why data on communities need to

be collected, they need to know how to collect the data and then

how to analyse the data. They may also need to make informed

decisions (often of a management nature) based on the data. As

a consequence, any course on community needs to include

elements of theory, fieldwork and laboratory simulation, and

here the theory and laboratory simulation go very much hand in

hand.

NB: It is not possible to cover everything in the theory AND

develop your field, analytical and report-writing skills. As a

consequence, some areas of theory are ignored entirely or are

glossed over very superficially.

ALL LECTURES AND SUPPLEMENTARY MATERIAL WILL BE PROVIDED ON THE INTERNET AFTER THEY HAVE

BEEN PRESENTED

Defining a community

Summarizing characteristics

Examining links

Introduction: Definitions

Inte

r-sp

ecif

ic In

tera

ctio

ns

I:C

om

pet

itio

n

Inte

r-sp

ecif

ic In

tera

ctio

ns

II:P

red

atio

n

Community changesin space and time:

SuccessionDisturbance

Effect of Competition in structuring communities

Effect of Predation in structuring communities

Contents

Field & Analytical

Theory & Modeling

Theory, Modeling and Field

Timetable

There will be three lectures per week and two practical

classes. ALL classes will take place in Z29: it may be

necessary to schedule additional classes on Saturday

mornings: such classes to start at 08h00.

IT IS EXPECTED THAT YOU WILL ATTEND ALL CLASSES

ON TIME

Day Week Date Official Type Duration Topic Assignment dateMon 1 14-Jul-08 L 1 Introduction, Aims, DefinitionsMon 1 14-Jul-08 P 3 MSExcel & Population Dynamics: AssessTues 1 15-Jul-08 L 1 Finish entering Shore DataWed 1 16-Jul-08 L 1 Community Properties; Area problemsThurs 1 17-Jul-08 P 3 Community Properties; diversity indicesMon 2 21-Jul-08 L 1 How to ID Communities: Conceptual overviewMon 2 21-Jul-08 P 3 How to ID Communities: similarity matrices by handTues 2 22-Jul-08 L 1 How to ID Communities: drawing dendrograms by handWed 2 23-Jul-08 L 1 How to ID Communities: drawing dendrograms by handThurs 2 24-Jul-08 P 3 How to ID Communities - PRIMER & CorrelationMon 3 28-Jul-08 L 1 Competition - MechanismsMon 3 28-Jul-08 P 3 Competition - Simple 2 spp ModelsTues 3 29-Jul-08 L 1 Competition - Simple 2 spp ModelsWed 3 30-Jul-08 L 1 Competition - Simple 2 spp ModelsThurs 3 31-Jul-08 P 3 Competition - Summary: Niche width Prelim REPORT DeadlineMon 4 04-Aug-08 L 1 Predation - Types & EffectsMon 4 04-Aug-08 P 3 Predation Models: Simple 2 spp models - exponentialTues 4 05-Aug-08 L 1 Predation Models: Simple 2 spp models - logisticWed 4 06-Aug-08 L 1 Predation Models: Simple 2 spp models - exponential with refugesThurs 4 07-Aug-08 P 3 Predation summary: models revision POSTER Deadline 1Mon 5 11-Aug-08 L 1 Revision periodMon 5 11-Aug-08 P 3 TEST 1Tues 5 12-Aug-08 L 1 Succession - Markov ChainWed 5 13-Aug-08 L 1 Succession - biological mechanisms I: Markov ChainsThurs 5 14-Aug-08 P 3 Go through test, report back on posterMon 6 18-Aug-08 L 1 Succession - biological mechanisms II, Climax conceptMon 6 18-Aug-08 P 3 Analyse data on succession from literatureTues 6 19-Aug-08 L 1 DisturbanceWed 6 20-Aug-08 L 1 Disturbance in Markov Chain Models POSTER Deadline 2Thurs 6 21-Aug-08 P 3 Analysis of Field DataMon 7 25-Aug-08 L 1 Competition and Communities - I ESSAY DeadlineMon 7 25-Aug-08 P 3 Null ModelsTues 7 26-Aug-08 L 1 Predation and Communities - IWed 7 27-Aug-08 L 1 Talks: GWM, MJG, EMThurs 7 28-Aug-08 P 3 CAPE FLATS NATURE RESERVE Final REPORT Deadline

Assessments and Deadlines

Evaluation will take the form of continuous assessment. This continuous assessment is broken up as follows:

Class test (33%) + Practical work (67%) = Course Mark

Class Tests

The Class test will be held on Monday 11 August 2008 at

14h00: Z29. Students will be tested on ALL material covered up

to and including that of Friday 8 August 2008.

If a re-test is necessary (i.e. more than 35% of the class failed

the first test), this will be held on Saturday 16 August 2008 at

08h00 in Z29. ONLY those students that failed the first test will

be eligible to sit the re-test, and the better of the two marks will

be taken into consideration. Students will be tested on ALL

material covered up to and including that of Friday 15 August

2008.

Course Mark (60%) + Exam (40%) = Final Mark

Prac Exam (30%) + Theory Exam (70%) = Exam Mark

Practical Work

This includes essays, group-work, worksheets, tests and

tutorials. In this course, the practical component will comprise

three evaluations. These are listed below as well as their

contributions towards the Final mark.

PLEASE BE ADVISED THAT FACULTY RULES REGARDING

PLAGIARISM AND THE SUBMISSION OF LATE

ASSIGNMENTS WILL BE UPHELD

Poster – 35% towards Practical Mark, 14.07% to Final MarkPreliminary Deadline – Thursday 7 August 2008Final Deadline – Wednesday 20 August 2008

Essay – 20% towards Practical Mark, 10.05% to Final Mark

Submission Deadline – Monday 25 August 2008

Report - 45% towards Practical Mark, 18.09% to Final Mark

Preliminary Deadline – Thursday 31 July 2008

Final Deadline – Monday 8 September 2008

Create a poster (size A0) in MS PowerPoint to illustrate one

of the following topics:

In groups of TWO POSTER

1. Competitive Release2. Character Displacement3. Competitive Exclusion4. Resource Partitioning5. The effect of resource pre-emption on competition6. The effect of gaps on competition7. Apparent Competition8. Mutualism9. Commensalism10. Amensalism11. Defensive responses of plants to grazing12. Herbivory, defoliation and plant growth13. Herbivory and plant fecundity14. Optimal foraging and diet width15. Optimal foraging and patch use16. Pseudo-interference17. Effect of refuges on predator-prey dynamics18. Type I, II and III functional responses19. Primary succession on sand dunes20. Primary succession on lava flows21. Secondary succession in abandoned or ploughed fields22. Secondary succession in forest gaps23. Succession and Markov-Chain Models24. Concept of successional climax25. Competition-colonisation tradeoffs in succession26. Facilitation in succession27. Interactions with enemies in succession28. Resource-ratio hypothesis in succession29. Vital attributes in succession30. The role of animals in succession31. Intermediate disturbance hypothesis in terrestrial communities32. Intermediate disturbance hypothesis in marine communities33. The effect of fire on plant communities34. Parasitism35. Founder-controlled communities36. The niche37. The effect of keystone predators in marine ecosystems38. The effect of keystone predators in terrestrial ecosystems39. Community changes linked to seasonality40. Community changes linked to decomposition

TITLE

CONCEPT NOTE & DEFINITION

Article Details

METHODS

RESULTS & DISCUSSION

Legend

*Legend

Legend

LegendAcknowledgements

The audience is undergraduate students – Teaching Tool

The poster should be based on a published, peer-reviewed

scientific paper that CLEARLY illustrates the concept

behind the topic

The poster MUST be professional in appearance

Rubric based on:

Number of wordsLegends to figures or tables

Picture creditsFont size

Line spacingScientific notation

SpellingGrammar

Overall layoutColour and background

Cluttered or notStructure & flow of text

Tense

ESSAY

1) The role of fire in structuring fynbos communities

2) The role of mega-herbivores in structuring savannah communities

Essays MUST be no longer than 1 500 words, and MUST be no shorter than 1 200 words: the number of words excludes all references and should be indicated at the end of the report.

Essays MUST be typed: font size 12; Times New Roman; sentences with 1.5 line spacing.

Essays MUST make reference to at least three journal articles, and CAN refer to a maximum of three text book articles and a maximum of one internet article.

Copies of ALL the cited journal articles, appropriate sections of text books and internet sources should be attached to the submitted essay, and the relevant sections (i.e. those pieces of information referred to in the report) MUST be highlighted. Failure to attach supporting documentation will result in the essay being returned to the student, with concomitant penalties for late submission being then enforced.

All citations must follow approved procedures – failure to so comply will result in the essay being returned to the student, with concomitant penalties for late submission being then enforced.

A rubric will be provided against which essays will be assessed

REPORT

Rocky shore communities along the NW

coast of False Bay, South Africa

Prepare a 2 500 word paper on the above topic for

submission to the African Journal of Marine Science. The

instructions for authors and an exemplar manuscript have

been provided to assist you prepare your paper. READ

them thoroughly!

Reports MUST make reference to at least three journal

articles, and CAN refer to a maximum of three text book

articles and a maximum of one internet article. Copies of

ALL the cited journal articles, appropriate sections of text

books and internet sources should be attached to the

submitted essay, and the relevant sections (i.e. those

pieces of information referred to in the report) MUST be

highlighted. Failure to attach supporting documentation

will result in the report being returned to the student, with

concomitant penalties for late submission being then

enforced.

The data set that you will use for this exercise was

collected from the shore at Dalebrook. ALL the data, in a

raw state, can be accessed from the www site.

You must prepare the data for analysis yourselves but in

so doing, beware of possible species misidentifications.

ONE other issues are worth mentioning. How will you deal

with replicates from each station samples along the

shore?

Your report should include (at the very least), a

description of changes in animal and plant abundance or

cover and diversity across the shore as well as a

description of changes in communities across the shore.

Credit will be given to those students, whose reports

investigate some of the links between community

members in a quantitative way.

Suitable references could include:

Branch, GM and Branch, M (1983) The living shores of

southern Africa. Struik

Lewis, JR (1964) The ecology of rocky shores. English

Universities Press

Little, C and Kitching, JA (1998) The biology of rocky

shores. Oxford

McQuaid, CD and Branch, GM (1984). Influence of sea

temperature, substratum and wave exposure on rocky

intertidal communities: an analysis of faunal and floral

biomass. Marine Ecology Progress Series, 19: 145-151

McQuaid, CD and Branch, GM (1985). Trophic structure of

rocky intertidal communities: response to wave action and

implications for energy flow. Marine Ecology Progress

Series, 22: 153-161

Stephenson, TA and Stephenson, A (1972) Life between

tidemarks on rocky shores. Freeman.

Pass or Fail?

A student is deemed to have passed the course if her/his Final mark (i.e. Coursework + Exam) is ≥50% AND the Exam mark is ≥40% AND the Practical mark is ≥50%

Should a student obtain a Final mark of ≥50% AND have a Practical mark of ≥50% BUT have an Exam mark <40%, then that student will get an opportunity to write a Supplementary Exam*

Should a student obtain a Final mark of 45-49%, AND the Practical mark is ≥50%, then that student will have an opportunity to write a Supplementary Exam*

Should a student obtain a Coursework mark (i.e. Class tests + Practical) of ≥50% AND have a Practical mark of ≥50% AND have an Exam mark of ≥30% then that student will get an opportunity to write a Supplementary Exam*

A student who does not meet the above grades fails and is not eligible to sit the Supplementary Exam.

A student who fails to get a mark of 50% in the Practical work automatically fails, regardless of the Coursework or Exam mark – such a student not being eligible to sit the final exam.

Similarly, a student that fails to obtain a course-work mark of less than 40% is not eligible to sit the final exam.

* - Supplementary exams will be held at the end of the examination period. This exam will test the student on ALL the work undertaken in the module.

Readings

Although there are no prescribed books for this course, the following texts are recommended (especially those in bold-typeface): all are currently placed on short-loan at the UWC library.

•Begon, M., Harper, J.L. and Townsend, C.R. (1990). Ecology: Individuals, Populations and Communities. Blackwell Scientific Publications, 945pp.

•Begon, M. and Mortimer, M. (1986). Population Ecology: A Unified Study of Animals and Plants. Blackwell Scientific Publications, 220pp.

•Krebs, C.J. (1999). Ecological Methodology. Benjamin Cummings, 620pp.

•Morin. P.J. (1999). Community Ecology. Blackwell Science, 424pp

•Zar, J.H. (1984) Biostatistical Analysis. Prentice-Hall

Nt+1 / Nt = R = R / {1 + [Nt.(R-1)/K]}

For a population of organisms showing discrete breeding

and a fundamental reproductive rate (R) of 1.145 (per year),

determine when the population will reach its carrying

capacity of 643 215 individuals if the initial population size

in 2007 is 12 individuals.

Working in groups of two

Nt+1 = Nt R / {1 + [Nt.(R-1)/K]}

Assuming that you can ALL project populations

growing under the influence of intra-specific

competition into the future……..

Length (mm) of cephalothorax of Euphausia superba collected

during February 2008 from the Weddell Sea, Antarctica.

Calculate the mean cephalothorax length of E.

superba in the Weddell Sea during February

2008 and determine the standard deviation,

variance, standard error and 95% Confidence

limits around your estimate.

ALL CALCULATIONS TO BE CONDUCTED

“LONG-HAND”

20 MINUTES AND COUNTING!

X26.927.632.835.634.332.134.128.037.528.130.523.629.229.741.626.226.734.323.535.034.725.642.329.329.430.727.635.733.540.036.344.428.732.534.939.724.936.5

Variance (δ2 or s2) = Σ (x – x)2

N-1

Mean (μ or x ) = Σx

N

Standard Deviation (δ or s) = √δ2 OR √s2

95% CI = ???

Standard Error (sx) = s

√N

WHY?

What is the difference?

X (x-mean)2

26.9 28.227.6 21.332.8 0.335.6 11.534.3 4.432.1 0.034.1 3.628.0 17.737.5 28.028.1 16.930.5 2.923.6 74.129.2 9.129.7 6.341.6 88.226.2 36.126.7 30.434.3 4.423.5 75.935.0 7.834.7 6.225.6 43.742.3 101.829.3 8.529.4 7.930.7 2.327.6 21.335.7 12.233.5 1.740.0 60.736.3 16.744.4 148.628.7 12.332.5 0.134.9 7.239.7 56.124.9 53.436.5 18.4

Sum 1224.0 1046.0N 38Mean 32.21053Variance 28.26908STDev 5.316867SError 0.86251t - 30 2.042t - 40 2.021t - 37 2.0252t.SError 1.746755Upper 95% 33.95728Lower 95% 30.46377

Critical values of the t distribution

Conf. Level 50% 80% 90% 95% 98% 99%One Tail 0.25 0.1 0.05 0.025 0.01 0.005Two Tail 0.5 0.2 0.1 0.05 0.02 0.01

df . . . . . .1 1 3.078 6.314 12.706 31.821 63.6572 0.816 1.886 2.92 4.303 6.965 9.9253 0.765 1.638 2.353 3.182 4.541 5.8414 0.741 1.533 2.132 2.776 3.747 4.6045 0.727 1.476 2.015 2.571 3.365 4.0326 0.718 1.44 1.943 2.447 3.143 3.7077 0.711 1.415 1.895 2.365 2.998 3.4998 0.706 1.397 1.86 2.306 2.896 3.3559 0.703 1.383 1.833 2.262 2.821 3.2510 0.7 1.372 1.812 2.228 2.764 3.16911 0.697 1.363 1.796 2.201 2.718 3.10612 0.695 1.356 1.782 2.179 2.681 3.05513 0.694 1.35 1.771 2.16 2.65 3.01214 0.692 1.345 1.761 2.145 2.624 2.97715 0.691 1.341 1.753 2.131 2.602 2.94716 0.69 1.337 1.746 2.12 2.583 2.92117 0.689 1.333 1.74 2.11 2.567 2.89818 0.688 1.33 1.734 2.101 2.552 2.87819 0.688 1.328 1.729 2.093 2.539 2.86120 0.687 1.325 1.725 2.086 2.528 2.84521 0.686 1.323 1.721 2.08 2.518 2.83122 0.686 1.321 1.717 2.074 2.508 2.81923 0.685 1.319 1.714 2.069 2.5 2.80724 0.685 1.318 1.711 2.064 2.492 2.79725 0.684 1.316 1.708 2.06 2.485 2.78726 0.684 1.315 1.706 2.056 2.479 2.77927 0.684 1.314 1.703 2.052 2.473 2.77128 0.683 1.313 1.701 2.048 2.467 2.76329 0.683 1.311 1.699 2.045 2.462 2.75630 0.683 1.31 1.697 2.042 2.457 2.7540 0.681 1.303 1.684 2.021 2.423 2.70450 0.679 1.299 1.676 2.009 2.403 2.67860 0.679 1.296 1.671 2 2.39 2.6670 0.678 1.294 1.667 1.994 2.381 2.64880 0.678 1.292 1.664 1.99 2.374 2.63990 0.677 1.291 1.662 1.987 2.368 2.632100 0.677 1.29 1.66 1.984 2.364 2.626z 0.674 1.282 1.645 1.96 2.326 2.576

Identifying or Delineating Communities

1 – physically defined communities

Assemblages of species found in a particular place or habitat

ARTIFICIAL?

2 – taxonomically defined communities

Identified by presence of one or more conspicuous

species that dominate biomass and/or numbers, or which

contribute importantly to the physical attributes of the

community

Topographic distributions of the characteristic dominant tree species of the Great Smokey Mountains, Tennessee, on an idealized west-facing mountain and valley

BG, beech gap; CF, cove forest; F, Fraser fir forest; GB, grassy bald; H, hemlock forest; HB, heath bald; OCF, chestnut oak-chestnut forest; OCH, chestnut oak-chestnut heath; OH, oak-hickory; P, pine forest & heath; ROC, red-oak-chestnut forest; S, spruce forest; SF, spruce-fir forest; WOC, white oak-chestnut forest.

Great Smoky Mountains Tennessee

SUBJECTIVE?

3 – statistically defined communities

Sets of species whose abundances are significantly correlated, positively or negatively, over space and/or time.

Look at numerical and specific composition of samples

Determine similarities between samples

Look for a pattern in the similarities between samples

And so identify communities OBJECTIVELY

4 – interactively defined communities

Subsets of species in a particular place or habitat, whose

interactions influence their abundance.

Only some, and perhaps none, of the species in a physically

defined community may constitute an interactively defined

community.

Hairston (1981: Ecology, 62: 65-72) noted that of the seven

species of plethodontid salamander in his study (North

Carolina, USA), only the two most common influenced each

others abundances: the balance, while ecologically similar,

remained unaffected by each others abundance.

THE END

Image acknowledgements – http://www.google.com