Transcript Document

Ecology, Biology 216
Todd Livdahl
Requirements
•
•
•
•
Essays (3)
Lab exercises
Quizzes (3)
Final Exam (comp)
20%
20%
30%
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
Wasps
Caterpillars
Roof Thatching
The Borneo Cat Crisis
Housefly control
Cats
Geckos
Houseflies
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
Mite 4
Mite 3
Mite 2
Ants
Beetle:
Mite 1
Egg
Ants
Larva
Lizards
Pupa
Coconut
Adult
Birds
Intensive Cultivation:
Mite 5
Mite 4
Mite 3
Mite 2
Ants
Beetle:
Mite 1
Egg
Ants
Larva
Lizards
Pupa
Coconut
Adult
Birds
Container-breeding Mosquitoes
Adults
Pupae
Eggs
Larvae
Container habitat
Container Habitats
Natural 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
Islands
1984, 1985: Memphis, Tennessee
Houston, 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 localities
South America, esp. Brazil
Central America, Mexico
Europe (Italy, Albania)
Caribbean
Bermuda
Used Tires Imported (millions)
3
From countries in the range of albopictus
From countries outside albopictus range
2
1
0
1970
1975
1980
Year
Used Tire Importation
1985
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)
Difference (%H, Long - %H, Short days)
100
U.S.
Beijing
Asian
80
Korea
Tokyo
Kyoto
60
Nagasaki
Shanghai
40
20
0
0
10
20
30
40
50
Latitude
Origin from temperate Asia
KEY ADAPTATION: Winter Diapause
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
F orest typ e (% reca pt )
P ollut ed
U n pol lut ed
Dar k
3 4. 1
6 .3
L ig ht
1 6. 0
1 2. 5
Genes, Alleles, and Allele Frequencies
Chromosome pair
Locus: location on chromosome
that influences a particular trait
Locus
Alleles: variations of genes that occur at a particular locus
Type a
Genotype ab
Type b
Chromosome pair with 2 alleles at a single locus:
a Heterozygote for that locus
Type a
Genotype aa
Type a
Chromosome pair with the same allele on both
chromosomes at the locus: a Homozygote
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
allele
aa
ab
bb
Number
Number of a allele Number of b
10
5
35
Totals:
20
5
0
0
5
70
25
75
Frequency of the a allele = p =
25 = 0.25
25+75
Frequency of the b allele = q =
75 = 0.75 = 1-p
25+75
Our experimental population:
Basic Life cycle
Eggs
Juveniles
H atch
Mortality
Poo l of Gametes
U niting at
ran dom
Life Cycle with Genetic Variation:
aa
E
A
Juv.
ab
bb
Poo l of Gametes
U niting at
ran dom
Adults
Gamete
prod uctio n
aa
E
A
Juv.
ab
bb
Pool of Gametes
Uniting 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
p
Allele a
Allele b q
Allele a
p
2
p
pq
Allele b
q
pq
2
q
Female
Gametes
Fractions of eggs produced = p (aa)
2
2pq (ab)
and
q (bb)
2
aa
E
A
Juv.
ab
bb
Pool of Gametes
Uniting at
random
Survival:
For each
Genotype,
The
number of
adults
produced
Reproduction:
For each Genotype,
=
Number
of eggs
Genotype
X survival
fraction
The number
of successful
gametes
Fitness: Fraction Surviving x #Offspring for each
genotype
= Number
of adults
Genotype
X fertility
rate
A sample of calculations involved in predicting changes in allele frequencies. The initial frequency of the
Genotype
aa
ab
bb
Total
Number of zygotes
at time 0
30
20
50
100
Survival fraction
0.5
0.8
0.9
Number of adults
0.5x30 = 15 16
45
Number of successful
gametes per adult
10
5
2
Number of
successful gametes
produced
10x15=150
80
90
2.0
0.9
Fitness
0.5x10/2=2.5
76
320
New allele p=(150+80/2)/320=0.59
q=0.41
frequencies
Next fraction
0.592^2=0.35 2x0.59x0.41=0.48 0.402^2=0.17
of zygotes
Number of
0.35*320/2=56.4
zygotes at time 1
77.2
26.4
1
147.8
a allele (p) is 0.4.
Selection against allele b
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.
Creating ecological islands
Warwickshire,
England
Costa Rica
U.S.
Mainland
Orange environment
Population is all orange
p=0
Inheritance:
aa: blue
ab: orange
bb: orange
OR:
aa: blue
ab: blue
bb: orange
Dispersal from Mainland to Island:
fixed fraction of individuals on island (I) have been
born on the mainland
Island
Blue environment
Blue individuals (initially rare) survive at higher rate
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.
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.
Mainland
Population is all winged
p=0
Inheritance:
aa: wingless
ab: winged
bb: winged
OR:
aa: wingless
ab: wingless
bb: 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)
Island
Low initial fraction wingless (aa)
Some fraction of winged individuals disperse away from
the island
Low I
High I
Low I
High I
Genetic Drift
N=10
N=20
N=20
N=100
Drift
Chance deviations in frequency
result in loss of genetic variation,
especially in small populations
N=1000
Measuring Genetic Variation
Gel electrophoresis
Alleles:
1
2
Pgm
3
Genotypes:
Etc…
Do this for many individuals
Heterozygotes
Do this for many loci
Heterozygosity: fraction heterozygous/locus
12 22
23 24
12
Genetic Variation
18
16
H e te r o zy g o s ity
14
Finnish
Spittlebugs
12
10
8
6
4
2
0
0
5
10
15
20
Distance Index
18
16
H e t e r o zy g o s it y
14
12
10
8
6
4
2
0
0
5000
10000
15000
20000
Population Size
25000
30000
35000
Oropendula colony, Ecuador
Oropendula
Giant Cowbird
Oropendula egg
mimetic
non-mimetic
Cowbird eggs
Number of nestling Oropendula in nests
With Cowbirds
Without Cowbirds
With Bot-fly parasites
57
382
Without Bot-flies
619
42
Fledgling success of oropendulas in discriminator and nondiscriminator
colonies relates to the presence or absence of cowbirds:
Fl ed gli n g s uc ces s ( fr acti o n o f O ro pen du la leav in g n est )
Or op en du la C ow bi rd
2
3
2
2
0
0
1
2
D is cr imi na to r
N on discrim in ato r
0 .5 3
0 .5 5
0 .2 8
0 .2 0
0 .1 9
0 .1 9
0 .5 3
0 .4 3
D is cr imi na to rs d o b est w it h ou t c ow bi rd s
N on discrim in ato rs do be st w ith c owb irds
Attributes of discriminator and nondiscriminator
Oropendula colonies
D isc ri m in ato r
N o n di sc ri m in ato r
W a sp n es ts
P re sent
A b se nt
B ot fli es
Sl ight o r a b se n t
H e av y
C o w b ir d e ffe cts
D isa d v anta ge
A d vant ag e
C o w b ir d e g gs
Mi me ti c
N o n -mi me tic
F or eign obj ec ts in
n es t
C o w b ir d b eh avi or
Re je cted
Ac c ept ed
T im id
A g gr e ss ive
Ne st ing s ea son
L at e
E a rly
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
Acclimatory
Developmental
Evolutionary
Physiological/behavioral
Physiological/behavioral
Developmental/behavioral
Genetic/ecological
<<1 generation
<1 generation
~1 generation
>1 generation
Reversible
Reversible
Irreversible
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 growth
Color change
Foliage loss
Flowering
Mating coloration
Antler growth
Mating rituals
Feeding patterns
Responses to environmental cues (e.g. change in day length)
Developmental Responses (Phenotypic Plasticity)
Differences in body form or behavior depending on environmental
conditions
Induced defenses and
cyclomorphosis
Nonevolutionary responses
are not adaptations, but they are
adaptive
Response itself is done without genetic change, but
the ABILITY to make the response has very likely evolved
through adaptation (i.e. natural selection)
Success of
response
Survival and
Reproduction
Establishment and
Maintenance of
population
Distributions
Summarize 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
A
B
Ecological-- set of places
with suitable conditions
C
Ecological > Geographic
Reasons why involve most topics
of interest to ecologists
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 grow
Reject: physical/chemical factors
Reject: species interactions
Support: dispersal barrier
Failure: transplanted populations dwindle
Reject: dispersal barrier
Consistent with species interactions or physical/
chemical factors
Problem: ethical considerations of transplantation
Solutions:
Compare occupied and unoccupied environments
What major factors differ? --> hypotheses
Duplicate differences in laboratory setting
“Transplant” occurs in lab; hypotheses tested
limitation: 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 stocking
Seeds in wool
Chestnut Blight
Dutch Elm Disease
Hessian Fly
Norway maple