Ecology, Biology 216

Todd Livdahl

Requirements

• Essays (3) 20%

• Lab exercises 20%

• Quizzes (3) 30%

• Final Exam (comp) 20%

Essays

1. Practical ecological problem

2. Population study

3. Species interaction (2 spp or more)

Lab Exercises

• Interpret ecological data• Clarify relationship between

field observations and central concepts

• Develop skills in computation and analysis

Quizzes and Final

• 3 Quizzes, equal weight

• Full class in length

• Concept-driven

• Qualitative

Substitution

Final = 2 x (quiz)

If Final/2 > (lowest quiz), then Final/2 will be substituted for the lowest quiz score

Example: Quizzes-- 25 27 19 (out of 30)

Final-- 44 (out of 60), 44/2 > 19

lowest quiz score (19) is replaced by (22)

NO MAKEUP QUIZZES

First Essay

Due Jan. 28

Description of problem

Justification as a problem

Solution strategies possible or solution strategies attempted

Problems arising from solutions

3-4 pages should suffice

Borneo

Mosquitoes Malaria

Caterpillars

Roof Thatching

Wasps

The Borneo Cat Crisis

Housefly control

Houseflies

Geckos

Cats

Rats

The Coconut Leaf-mining Beetle Crisis, Fiji

1850-1880 Early development, plantations

1880-1900 Intensive cultivation and shipping

1900-1920 Gradual increase in impact of beetle

1920 Outbreaks threaten Fiji economy

Natural Coconut Community

Coconut

Beetle:Egg Larva Pupa Adult

Ants Mite 1 Ants Lizards Birds

Mite 2

Mite 3

Mite 4

Intensive Cultivation:

Coconut

Beetle:Egg Larva Pupa Adult

Ants Mite 1 Ants Lizards Birds

Mite 2

Mite 3

Mite 4Mite 5

Container-breeding Mosquitoes

Adults

Eggs

Larvae

Pupae

Container habitat

Container HabitatsNatural examples• Treeholes• Bromeliads• Pitcher plants• Bamboo stems• Leaf axils• Crab holes• Snail shells• Snow-melt pools• Water-filled hoof

prints

Domestic examples (short list)

• Bird baths• Cemetery urns• Discarded junk

Bottle caps to Bath tubs

• Downspouts, eave troughs

• Cisterns• Trash barrels• Tires

Meetings of interest (from AMCA Newsletter):

Aedes albopictus and the New Globalism

Distribution: 1983: tropical and temperate Asia, Pacific Islands1984, 1985: Memphis, TennesseeHouston, Texas-- the most abundant mosquito in a pile of used tires

First discovery of Aedes albopictus in Western Hemisphere

Aedes albopictus since 1985

Numerous US localitiesSouth America, esp. BrazilCentral America, MexicoEurope (Italy, Albania)CaribbeanBermuda

Used Tire Importation

19851980197519700

1

2

3

From countries in the range of albopictus From countries outside albopictus range

Year

Use

d T

ires

Im

po

rted

(m

illi

on

s)

Potential Habitats

Potential Habitats

Treehole

Long-range Prospects for Invasion

Depend on:

Adaptations to physical challenges

Success in dealing with native community

• Competition with native species

• Other interactions with native species (predation, hatch inhibition, parasitism)

Origin from temperate Asia

KEY ADAPTATION: Winter Diapause

504030201000

20

40

60

80

100

U.S.

Asian

Latitude

Dif

fere

nce

(%

H,

Lo

ng

- %

H,

Sh

ort

day

s)

Beijing

Korea

Tokyo

Kyoto

Nagasaki

Shanghai

Potential interactions with resident species

North:

Competition with treehole mosquitoes in treeholes and tires

South:

Competition with Aedes aegypti in open tire habitats

Competition with treehole mosquitoes in forested tires and treeholes

Predation

Parasitism

Topics, 2nd & 3rd Lecture

2nd Lecture

Origins of Ecology

Influence of Evolution

Determining Inheritance

3rd Lecture

Reasons to study Evolution

Criteria for Natural Selection

Forms of Selection

Forest type (% recapt)

Polluted Unpolluted

Dark 34.1 6.3

Light 16.0 12.5

Genes, Alleles, and Allele Frequencies

Locus: location on chromosome that influences a particular trait

Alleles: variations of genes that occur at a particular locus

Chromosome pair

Locus

Type a

Type b Chromosome pair with 2 alleles at a single locus: a Heterozygote for that locus

Type a

Chromosome pair with the same allele on both chromosomes at the locus: a Homozygote

Genotype ab

Type a

Genotype aa

Type b

Genotype bb

Type b

Chromosome pair with the same allele on both chromosomes at the locus: a Homozygote

Allele Frequency: the fraction of all genes at a locus that are of a particular type

Genotype Number Number of a allele Number of b alleleaa

abbb

105

35

2050

25

05

70

75Totals:

Frequency of the a allele = p = = 0.252525+75

Frequency of the b allele = q = = 0.75 = 1-p7525+75

Our experimental population:

Basic Life cycle

JuvenilesEggs Adults

Mortality Gamete production

Hatch

Pool of GametesUniting at

random

Life Cycle with Genetic Variation:

E Juv. A

aa

ab

bb

Pool of GametesUniting at

random

E Juv. A

aa

ab

bb

Pool of GametesUniting at

random

Rules for joining gametes:

1. Randomness. Gametes fuse with other gametes without regard to genotype.

2. Many, many gametes.

These rules permit us to calculate the number of eggs for each new generation for each genotype:

Male gametes

Allele a Allele b q

FemaleGametes

Allele a

Allele b

p

p

q

p pq2

pq q2

Fractions of eggs produced = p (aa) 2pq (ab) and q (bb)2 2

E Juv. A

aa

ab

bb

Pool of GametesUniting at

random

Survival: For each

Genotype,

The number of

adults produced

= Number of eggs

XGenotype survival fraction

Reproduction:For each Genotype,

The number of successful

gametes= Number

of adultsX

Genotype fertility rate

Fitness: Fraction Surviving x #Offspring for each genotype

A sample of calculations involved in predicting changes in allele frequencies. The initial frequency of the a allele (p) is 0.4.

Genotype aa ab bb Total

Number of zygotes 30 20 50 100 at time 0

Survival fraction 0.5 0.8 0.9

Number of adults 0.5x30 = 15 16 45 76

Number of successful 10 5 2 gametes per adult

Number of 10x15=150 80 90 320 successful gametes produced

Fitness 0.5x10/2=2.5 2.0 0.9

New allele p=(150+80/2)/320=0.59 q=0.41 frequenciesNext fraction 0.592^2=0.35 2x0.59x0.41=0.48 0.402^2=0.17 1 of zygotes

Number of 0.35*320/2=56.4 77.2 26.4 147.8 zygotes at time 1

Figure 1. Changes in the frequency of allele a through time. Selection in this case is against allele b. For both cases, Waa = 1 and Wbb=0.5. For curve 1, Wab=0.5; for curve 2, Wab=1.

1.0

00

0.5

100Time (generations)

1. b dominant

2. b recessive

Selection against allele bSelection against allele b

Creating ecological islands

Warwickshire,

England

Costa Rica

U.S.

MainlandOrange environmentPopulation is all orangep = 0

IslandBlue environment

Blue individuals (initially rare) survive at higher rate

Inheritance:aa: blueab: orangebb: orangeOR:aa: blueab: bluebb: orange

Dispersal from Mainland to Island:fixed fraction of individuals on island (I) have been born on the mainland

I=0I=0.05

I=0.10

I=0.15

I=0.2

0.5

1.0

0

0 100

Time (generations)

Changes in the frequency of allele a through time for different fractions of immigrants to an island population. Selection in this case is against a dominant allele (b). I denotes the fraction of immigrant individuals arriving into the population with each generation. The initial frequency of the a allele in the island population is 0.2; mainland frequency=0. Fitness values are: Waa=1, Wab=0.5, Wbb=0.5.

I=0

I=0.05

I=0.10

I=0.15

I=0.20

I=0.25

I=0.30

I=0.35

I=0.40

I=0.45

0

1

0.5

0 100

Time (generations)

Changes in the frequency of allele a through time for different fractions of immigrants to an island population. Selection in this case is against a recessive allele (b). I denotes the fraction of immigrant individuals arriving into the population with each generation. The initial frequency of the a allele in the island population is 0.2; mainland frequency=0. Fitness values are: Waa=1, Wab=1, Wbb=0.5.

MainlandPopulation is all wingedp = 0

IslandLow initial fraction wingless (aa)

Some fraction of winged individuals disperse away from the island

Inheritance:aa: winglessab: wingedbb: wingedOR:aa: winglessab: winglessbb: winged

Genotypes have same fitness

Dispersal from Mainland to Island:fixed fraction of individuals on island (I) have been born on the mainland (all winged, all bb)

Low I

High I

Low I

High I

Genetic Drift

N=10

N=20

Drift

N=20

N=100

N=1000

Chance deviations in frequencyresult in loss of genetic variation,especially in small populations

Measuring Genetic Variation

Gel electrophoresis

Alleles:1

23

Genotypes:12 22 23

Heterozygotes

24 12 Etc…

Do this for many individualsDo this for many loci

Pgm

Heterozygosity: fraction heterozygous/locus

0

2

4

6

8

10

12

14

16

18

0 5 10 15 20

Distance Index

Heterozygosity

0

2

4

6

8

10

12

14

16

18

0 5000 10000 15000 20000 25000 30000 35000

Population Size

Heterozygosity

Genetic Variation

FinnishSpittlebugs

Oropendula colony, Ecuador

Giant Cowbird

Oropendula

Oropendula egg

Cowbird eggs

mimeticnon-mimetic

Number of nestling Oropendula in nestsWith Cowbirds Without Cowbirds

With Bot-fly parasites 57 382Without Bot-flies 619 42

Fledgling success of oropendulas in discriminator and nondiscriminator colonies relates to the presence or absence of cowbirds:

Fledgling success (fraction of Oropendula leaving nest)

Oropendula Cowbird Discriminator Nondiscriminator

2 0 0.53 0.193 0 0.55 0.192 1 0.28 0.532 2 0.20 0.43

Discriminators do best without cowbirdsNondiscriminators do best with cowbirds

Attributes of discriminator and nondiscriminator Oropendula colonies

Discriminator Nondiscriminator

Wasp nests Present Absent

Bot flies Slight or absent Heavy

Cowbird effects Disadvantage Advantage

Cowbird eggs Mimetic Non-mimetic

Foreign objects innest

Rejected Accepted

Cowbird behavior Timid Aggressive

Nesting season Late Early

Nonevolutionary Responses to Environmental Change

Organisms can change to perform better in different conditions, without

a change in population genetic makeup

Time scales, mechanisms, flexibility

Regulatory Physiological/behavioral <<1 generation ReversibleAcclimatory Physiological/behavioral <1 generation ReversibleDevelopmental Developmental/behavioral ~1 generation IrreversibleEvolutionary Genetic/ecological >1 generation Reversible

Regulatory Responses

No morphological change required, involves physiology or behavior

Modified activity to maintain favorable body conditions

Examples:

Sweating, panting, shivering, altered kidney filtration, altered heart rate, drinking, basking

Objective: homeostasis-- buffer the internal environment of an individual, or to modify the immediate external environment.

Acclimatory Responses

Change in physiology, behavior, or morphology, in response to environmental changes, especially seasonal changes

Examples:

Fur growthColor changeFoliage lossFloweringMating colorationAntler growthMating ritualsFeeding patterns

Responses to environmental cues (e.g. change in day length)

Developmental Responses (Phenotypic Plasticity)

Differences in body form or behavior depending on environmentalconditions

Induced defenses and cyclomorphosis

Nonevolutionary responsesare not adaptations, but they are

adaptive

Response itself is done without genetic change, butthe ABILITY to make the response has very likely evolvedthrough adaptation (i.e. natural selection)

Success of response

Survival andReproduction

Establishment andMaintenance of population

DistributionsSummarize the locations where a species has been successful

Do not tell us about locations where they could be successful

Do not tell us about places where a species has failed

Understanding distributions relies on knowing what factors prevent species from occupying a particular location or region

Ranges

Geographic-- set of places actually occupied

Ecological-- set of placeswith suitable conditions

Ecological > GeographicReasons why involve most topicsof interest to ecologists

A B C

Explaining an Absence

Species does not occur because:

1) It can’t reach it

2) It doesn’t choose to (habitat selection)

3) Physical or chemical conditions not favorable

4) Other organisms in the area prevent establishment (competition, predation, parasitism) or a key species (food, mutualist) is missing

5) Chance

Transplant experiments

Remove suspected dispersal barrier

Success: transplanted populations growReject: physical/chemical factorsReject: species interactionsSupport: dispersal barrier

Failure: transplanted populations dwindleReject: dispersal barrierConsistent with species interactions or physical/chemical factors

Problem: ethical considerations of transplantation

Solutions:

Compare occupied and unoccupied environmentsWhat major factors differ? --> hypotheses

Duplicate differences in laboratory setting“Transplant” occurs in lab; hypotheses testedlimitation: lab setting

Conduct transplants in field under highly controlled conditions

Catch species in the act of invasion

Lessons from Invasions and Introductions

Starling

Gypsy moth

A albopictus

Rabbits to Australia

Failed introductions:Fish stockingSeeds in wool

Norway mapleHessian FlyDutch Elm Disease

Chestnut Blight