Community Ecology

BDC321 Pt2

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

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 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. Please note that

some official classes will be rescheduled.

IT IS EXPECTED THAT YOU WILL ATTEND ALL CLASSES

ON TIME

Day Week Date Period Official Type Duration Topic Assignment dateTues 1 23-Mar-10 pm P 3 Introduction, Aims, Definitions ETCThurs 1 25-Mar-10 2 L 1 MSExcel & Population Dynamics: AssessThurs 1 25-Mar-10 3-4 P 2 Community Properties; Area problems

Fri 1 26-Mar-10 1 L 1 Community Properties; diversity indicesMon 2 29-Mar-10 1 L 1 How to ID Communities: Conceptual overviewTues 2 30-Mar-10 pm P 3 How to ID Communities: similarity matrices by handThurs 2 01-Apr-10 2 L 1 How to ID Communities: drawing dendrograms by handThurs 2 01-Apr-10 3-4 P 2

Fri 2 02-Apr-10 1 L 1Mon 3 05-Apr-10 1 L 1Tues 3 06-Apr-10 pm P 3 How to ID Communities: drawing dendrograms by hand ETCWed 3 07-Apr-10 pm P 3 How to ID Communities - PRIMER & CorrelationThurs 3 08-Apr-10 2 L 1 Competition - MechanismsThurs 3 08-Apr-10 3-4 P 2 Competition - Simple 2 spp Models

Fri 3 09-Apr-10 1 L 1 Competition - Summary: Niche widthMon 4 12-Apr-10 1 L 1 Predation - Types & Effects Prelim REPORT DeadlineTues 4 13-Apr-10 pm P 3 Predation Models: Simple 2 spp models - exponentialThurs 4 15-Apr-10 2 L 1 Predation Models: Simple 2 spp models - logisticThurs 4 15-Apr-10 3-4 P 2 TEST 1

Fri 4 16-Apr-10 1 L 1 Predation Models: Simple 2 spp models - exponential with refugesMon 5 19-Apr-10 1 L 1Tues 5 20-Apr-10 pm P 3Thurs 5 22-Apr-10 2 L 1Thurs 5 22-Apr-10 3-4 P 2

Fri 5 23-Apr-10 1 L 1 POSTER Deadline 1Mon 6 26-Apr-10 1 L 1 Succession - Markov ChainMon 6 26-Apr-10 4 L 1 Succession - biological mechanisms I: Markov ChainsTues 6 27-Apr-10 pm P 3Wed 6 28-Apr-10 pm P 3 Go through test, report back on posterThurs 6 29-Apr-10 2 L 1 Succession - biological mechanisms II, Climax conceptThurs 6 29-Apr-10 3-4 P 2 Analyse data on succession from literature

Fri 6 30-Apr-10 1 L 1 Disturbance POSTER Deadline 2Mon 7 03-May-10 1 L 1 Disturbance in Markov Chain ModelsMon 7 03-May-10 4 L 1 Disturbance in Markov Chain ModelsTues 7 04-May-10 pm P 3 Analysis of Field DataWed 7 05-May-10 pm P 3 Competition and Communities - IThurs 7 06-May-10 2 L 1 Null ModelsThurs 7 06-May-10 3-4 P 2 Null Models

Fri 7 07-May-10 1 L 1 Predation and Communities - I Final REPORT DeadlineMon 8 10-May-10 2-pm ALL 7 REVISIONTues 8 11-May-10 2-pm ALL 7 REVISION

Public HolidaysMJG AwayExtra Lessons

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 Thursday 15 April 2010 during

periods 2-4: Z29. Students will be tested on ALL material

covered up to and including that of Tuesday 13 April 2010.

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

the first test), this will be held on Saturday 8 May 2010 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 7 May 2010.

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

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

Practical Work

In this course, the practical component will comprise two

evaluations. These are listed below:

PLEASE BE ADVISED THAT FACULTY RULES REGARDING

PLAGIARISM AND THE SUBMISSION OF LATE

ASSIGNMENTS WILL BE UPHELD

You will be expected to use Turnitin

Poster – 40% towards Practical Mark

Preliminary Deadline – Friday 23 April 2010

Final Deadline – Friday 30 April 2010

Report - 60% towards Practical Mark

Preliminary Deadline – Monday 12 April 2010

Final Deadline – Friday 7 May 2010

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

of the following topics:

POSTER

1. Mutualism2. Commensalism3. Amensalism4. Parasitism

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 OR that CLEARLY shows how the

concept can influence biological community structure

The poster MUST be professional in appearance

The poster will be assessed using a rubric and ALL TEXT must be submitted to Turnitin and the

report attached

TITLE

CONCEPT NOTE & DEFINITION

Article Details

METHODS

RESULTS & DISCUSSION

Legend

*Legend

Legend

LegendAcknowledgements

REPORT

Rocky shore communities along the NW

coast of False Bay, South Africa

Prepare a 2 000 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. Tide data

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.

YOU MUST SUBMIT YOUR REPORTS TO TURNITIN

BEFORE FINAL SUBMISSION (report from Turnitin must

be attached) – AND YOU ARE ADVISED TO USE THE

WRITING CENTRE IN ADVANCE!

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.

REPORT POSTER TEST EXAM Attendance N Mark % Pass Pass Mark

REPORT 9 45.4 33.3 58.6

POSTER 0.54 9 58.1 77.8 61.8

TEST -0.20 0.09 9 49.5 44.4 58.4

EXAM 0.57 0.09 0.08 9 55.0 88.9 58.5

Attendance 0.60 0.21 0.05 0.93

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 1.41 (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.

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

REFRESHER……

10 minutes…..

R 1.41

K 643215t N R

2007 12 1.4099892008 16.91987 1.4099852009 23.85676 1.4099792010 33.63752 1.409972011 47.42789 1.409957

2012 66.8713 1.40994

2013 94.28451 1.4099152014 132.9332 1.4098812015 187.4199 1.4098322016 264.2305 1.4097632017 372.5022 1.4096652018 525.1035 1.4095282019 740.1482 1.4093352020 1043.117 1.4090632021 1469.817 1.408682022 2070.503 1.4081422023 2915.561 1.4073842024 4103.315 1.4063222025 5770.581 1.4048332026 8106.7 1.4027512027 11371.69 1.3998532028 15918.69 1.3958372029 22219.89 1.3903082030 30892.5 1.3827712031 42717.25 1.3726252032 58634.76 1.35922033 79696.35 1.3418342034 106939.3 1.32002

2035 141162 1.2936022036 182607.5 1.262992037 230631.4 1.2292832038 283511.4 1.194192039 338566.4 1.1597212040 392642.5 1.1277482041 442801.8 1.0996282042 486917.2 1.076032043 523937.6 1.0569952044 553799.6 1.0421252045 577128.5 1.0307962046 594901.7 1.0223292047 608185.2 1.0160912048 617971.4 1.0115442049 625105.1 1.0082552050 630265 1.0058892051 633976.6 1.0041942052 636635.4 1.0029832053 638534.7 1.002122054 639888.6 1.0015062055 640852.3 1.0010692056 641537.5 1.0007592057 642024.4 1.0005392058 642370.2 1.0003822059 642615.6 1.0002712060 642789.8 1.0001922061 642913.4 1.0001362062 643001 1.0000972063 643063.2 1.0000692064 643107.4 1.0000492065 643138.7 1.0000352066 643160.9 1.0000242067 643176.6 1.0000172068 643187.8 1.0000122069 643195.7 1.0000092070 643201.3 1.000006

0

100000

200000

300000

400000

500000

600000

700000

2007

2011

2015

2019

2023

2027

2031

2035

2039

2043

2047

2051

2055

2059

2063

2067

2071

Year

Nu

mb

ers

Assuming that you can ALL project

populations growing under the

influence of intra-specific

competition into the future……..

Length (mm) Frequency Table 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……..

X F20.6 020.8 121 1

21.2 321.4 521.6 1721.8 2122 26

22.2 3722.4 4422.6 5622.8 5823 45

23.2 3223.4 1923.6 1223.8 1324 3

24.2 124.4 324.6 0

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

X F X.F X-MEAN (X-MEAN)2 F(X-MEAN)2

20.6 0 0 -2.04 4.16 020.8 1 20.8 -1.84 3.39 3.3921 1 21 -1.64 2.69 2.69

21.2 3 63.6 -1.44 2.08 6.2321.4 5 107 -1.24 1.54 7.7021.6 17 367.2 -1.04 1.08 18.4221.8 21 457.8 -0.84 0.71 14.8522 26 572 -0.64 0.41 10.68

22.2 37 821.4 -0.44 0.19 7.1922.4 44 985.6 -0.24 0.06 2.5522.6 56 1265.6 -0.04 0.00 0.0922.8 58 1322.4 0.16 0.03 1.4723 45 1035 0.36 0.13 5.81

23.2 32 742.4 0.56 0.31 10.0123.4 19 444.6 0.76 0.58 10.9523.6 12 283.2 0.96 0.92 11.0423.8 13 309.4 1.16 1.34 17.4724 3 72 1.36 1.85 5.54

24.2 1 24.2 1.56 2.43 2.4324.4 3 73.2 1.76 3.09 9.2824.6 0 0 1.96 3.84 0

SUMS 397 8988.40 147.78Mean 22.64Variance 0.37STDev 0.61St Error 0.03t 1.96t. St Error 0.06Upper 22.70Lower 22.58

Basic Model Building……

1) – How many tennis balls could fill this room?

You have 60 seconds to come up with an answer

How did you arrive at your answer?

Real world vs model worldResolutionAssumptions and trade-offs

2) – in groups of two, and using your PC, tell me how many tennis balls could fill this room?

You have 5 minutes to come up with an answer

How did you arrive at your answer?

A gas storage tank has a Vol of 3000 cubic m. It currently contains methane. The tank must be emptied & then cleaned before being modified for use as a milk storage vessel.

Safety regulations require that it should contain no more than 1 part in 100 of methane before it can be cleaned.

Nitrogen is available and can be pumped into an opening near one end of the tank. Another opening near the other end will let gases escape.

How much nitrogen will you need to dilute the methane effectively?

Working in groups of two, think about the problem for about 30 mins and prepare a plan, before explaning it to the rest of the class.

DO NOT solve the problem at this stage.

Solve the problem

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