slides lecture 03(for students) - the ant life · parasitizing egg rejection egg ... drone (male)...

27/Jan/2014

1

ANT DIVERSITY

LECTURE 03

Spring 2014: Mondays 10:15am – 12:05pm (Fox Hall, Room 204)

Instructor: D. Magdalena SorgerWebsite: theantlife.com/teaching/bio295-islands-evolution

27/Jan/2014

2

Today:

Follow‐up on minute papers

Sources of variation

Phenotypic plasticity

Guest speaker: Dr. Terry Campbell

Summary

FOLLOW-UP MINUTE PAPERS

27/Jan/2014

3

Follow‐up on minute papers

• Scientific writing process (how long? Work distributed among group? Authorship? Order of writing?)

• Marcupials vs. placentals

• Neutral theory of evolution

• Epigenetics – royal jelly in honey bees?

• “optimal fitness level” – no need to evolve further?

Evolution does not optimize. It only improves. Just needs to be good ENOUGH.

Environments change. What is good (enough) today might not be good (enough) tomorrow. predator/prey, host/parasite, climate change

27/Jan/2014

4

Red Queen = evolutionary arms race

Through the Looking Glass (Lewis Carroll 1871, illustration by John Tenniel )

must constantly adapt, evolve, and proliferate to survive

around ever‐evolving organisms in an ever‐changing environment

‘(…) it takes all the running you can do to keep in the same place.’

How to test for Red queen dynamics?

27/Jan/2014

5

…seems to involve time travel…

COMPARE success of past and future generations of predators

AGAINSTcurrent prey populations

CASE STUDY

DAPHNIA

27/Jan/2014

6

Water flea (Daphnia magna)

DAPHNIA

Life history

Daphnia:

planktonic crustaceans

Crustacea, Branchiopoda (class), Cladocera(order)

1‐5 mm in length

lifespan 5‐6 months in typical conditions

DAPHNIA

27/Jan/2014

7

Parasite: Pasteuria ramosa

DAPHNIA

Life history

P. ramosa:

spore‐forming bacterium

infects water fleas

makes them bloated

darkens their body

castrates them in the process

DAPHNIA

27/Jan/2014

8

Infected water flea

DAPHNIA

Life history

Host & parasite produce resting stages

Accumulate in lake sediment

DAPHNIA

27/Jan/2014

9

DAPHNIA

METHODS

Dormant eggs reactivated (over 39‐year period)

Daphnia exposed to parasites from different time periods:

‐ Contemporary

‐ Past

‐ Future

DAPHNIA

De Caestaecker et al. 2007

27/Jan/2014

10

METHODS

DAPHNIA

39 years

39 years ago TODAY20 years ago


METHODSDAPHNIA

39 years



INFECTIVITY LOWERDaphnia evolved to beat past parasite genotypes

27/Jan/2014

11

METHODS

DAPHNIA

39 years



INFECTIVITY LOWERParasite adaptations specific to current host populations

METHODSDAPHNIA

39 years



CONTEMPORARY paras i tes

NO OVERALL CHANGE IN INFECTIVITY (no significant difference between infectivity rates)Relative success of host and parasite remains

the same over the generations

27/Jan/2014

12

How cool is that?

Researchers managed to reactivate 700‐year‐old Daphnia!!!

DAPHNIA

CASE STUDY

CUCKO

O

27/Jan/2014

13

Life history

Brood parasites

Lay eggs in nests of other species (hosts)

Get young raised for free

Brood parasite gains benefit, host suffers

Not all cuckoo species cheat (60 % are parental)

Cheating habit evolved 3 times independently

CUCKO

OLife history: how they cheat

Female cuckoo finds host nest

Watches hosts build

Waits until hosts have begun clutch

Parasitizes during nest hosts’ laying period Removes one host egg (swallows it)

Very quick Cuckoo chick hatches first Ejects other eggs and chicks

CUCKO

O

27/Jan/2014

14

Host defenses

REJECT IF:

• single egg in nest

• poorly matched egg

• egg laid too early (before hosts begin to lay)

• hosts see cuckoo on their nests

CUCKO

OEvolutionary arms race

Defenses evolve in response to parasitism

Species untainted by cuckoos show no rejection of odd eggs

Egg patterns evolve

Species exploited by cuckoos have less variation in appearance of eggs within a clutch and more variation between clutches of different females

CUCKO

O

27/Jan/2014

15

Not parasitizing

No rejection

Parasitizing

Egg rejection

Egg mimicry

More distinctive egg signatures

Better egg mimicry

Evolutionary arms race

CUCKO

O

HOST SPECIES

CUCKOO

EGG MIMICRYCUCKO

O

27/Jan/2014

16

CHICK MIMICRY

CUCKO

O

CUCKOO HOST

Πάντα ῥεῖ (panta rhei)

Everything flows.

Characterizing Heraclitus’ thought (by Simplicius, & Plato)

27/Jan/2014

17

VARIATION

ANT

FISH

MONKEY

BIRD

SHRIMP

27/Jan/2014

18

Artforms of Nature (Ernst Haeckel, 1904)

Thalamphora= ForaminiferaAmoeboid protists

27/Jan/2014

19


DiscomedusaeJellyfish


ArachnidaArachnids

27/Jan/2014

20


ChiropteraBats

SOURCES OF VARIATION

27/Jan/2014

21

GENOTYPE inherited instructions carried within genetic code

PHENOTYPEobservable characteristics or traits of an organism (morphology, development, biochemical or physiological properties, phenology, behavior)

GENOTYPE+ environment = PHENOTYPE

27/Jan/2014

22

EPIGENETICS

Heritable changes in gene activity that are NOT caused by changes in the DNA sequence

For instance:

• DNA methylation & histone modification …alters gene expression without altering DNA sequence

• Maternal effects

Maternal effects

Effects of mother on her offspring due to non‐genetic influences

Amount and composition of yolk in eggs

Amount and kind of maternal care provided

Mother’s physical condition while she carries eggs/embryo

Consumption of alcohol/tobacco/drugs by pregnant women increases risk of non‐genetic birth defects in babies

27/Jan/2014

23

How to determine whether characteristics are genetic, environmental or both?

How to determine whether characteristics are genetic, environmental or both?

Backcrossing (Test cross)

Correlation

Common garden experiments

27/Jan/2014

24

BACKCROSSING

Mendelian ratios serve as evidence of simple genetic control

BACKCROSSINGA A

A a

a a

Mendelian Genetics

homozygous dominant

heterozygous

homozygous recessive

27/Jan/2014

25

Mendelian Genetics

3:1

F1 generation

F2 generation

2:2 4:0

Parent generation

Parent ParentParent

BACKCROSSING

CORRELATION

between average phenotype of offspring and that of parents or resemblance among siblings (greater than among unrelated individuals)

27/Jan/2014

26

CORRELATION

CORRELATION

Williams RW (2000) Mapping genes that modulate brain development: a quantitative genetic approach. In: Mouse brain development (Goffinet AF, Rakic P, eds). Springer Verlag, New York, pp 21–49.

Figure 2. The correlation between brain weights of parents and their offspring estimates heritability. Animals are from a multigenerational cross between C57BL/6J and DBA/2J inbred strains (G. Zhou and R. W. Williams, in progress). Parental values are the average unfixed weights of mothers and fathers without correction for variation in age or body weight. Offspring data are average brain weight per litter. Brains weights are also presented without correction for variation in body weight, sex, or age. Offspring weights tend to be slightly less than those of the parents because of offspring are on average about 50 days younger. The correlation between pairs of values is 0.38 and is a direct estimate of the narrow‐sense heritability of brain weight in this cross and environment. Correlations between mothers and offspring and fathers and offspring do not differ significantly. Thus, this estimate of heritability is not inflated by maternal effect.

27/Jan/2014

27

COMMON GARDEN EXP.

Rear offspring from phenotypically different parents in uniform environment and see if phenotypic differences in offspring persist

At least 2 generations are advisable to distinguish from maternal effects

COMMON GARDEN

EXP.

RESEARCH QUESTIONAre observed morphological differences among wild populations of Anolis carolinensis a result of genetic changes among populations or phenotypic plasticity

during development and growth?

Yoel Stuart

27/Jan/2014

28

COMMON GARDEN

EXP.

METHODS• Catch individuals from wild

populations

• Collect eggs, incubate and hatch

Do offspring maintain differentiation observed in wild under common growth conditions?

If yes: Evidence that observed differences have an evolved, genetic component

Yoel Stuart

PHENOTYPIC PLASTICITY

27/Jan/2014

29

PHENOTYPIC PLASTICITY

ability of an individual to express different features under different environmental conditions

NORM OF REACTIONof a genotype is the set of phenotypes it expresses in different environments

27/Jan/2014

30

Snow geese Chen caerulescens: white and blue form

Cepea nemoralis variation

27/Jan/2014

31

Bivalve Donax variabilis variation

Peppered moth Biston betularia: 2 forms

27/Jan/2014

32

Biston petularia larvae: 2 morphs

Wet season form Dry season form

Peacock Pansy Junonia almana:

27/Jan/2014

33

Reversible vs. irreversible plasticity

Behavioral: Tadpoles change foraging patterns in response to presence of

predators

Physiological: Increase in mitochondrial density in terrestrial vertebrates in

response to experiencing lower oxygen levels Changes in specific fatty acids incorporated into animal cell

membrane in response to changing thermal conditions

Morphological: Gills of aquatic salamander increase/decrease in response to

oxygen levels they receive Muscles in vertebrates get bigger when used

Reversible plasticity

27/Jan/2014

34

appears when environmental conditions change, often within an individual’s lifetime



27/Jan/2014

35

Organism adjusts timing of life history event: Annual plant flowering in response to lighting conditions

Features that cannot be altered once expressed: Water fleas (Daphnia) develop spines and thicker carapace in response to presence of predatory fly larva in pond (can’t be altered even if predator disappears)

Species of African acacia develops long spines on its stems in response to being browsed by giraffes and elephants (spines remain even if browsing stops)

Irreversible plasticity


Typical and predator‐induced morphs of Daphnia cucullata

Agrawal et al. 1999

27/Jan/2014

36

appears when environmental conditions are less volatile and less likely to change drastically

within lifetime of individual


Being phenotypically plastic can be an adaptation.

27/Jan/2014

37

Adaptive plasticity should evolve when…

individuals with capacity to adjust their development to conditions outperform individuals who express same trait constitutively

Adap

tive plasticity

Shade avoidance in plants (Impatiens capensis)

Individual can perceive presence of other plants

(= competition)

2 phenotypes:

Elongated, shade‐adapted

Short, sun‐adapted

Dudley & Schmitt 1996

27/Jan/2014

38

Adap

tive plasticity

ARE PHENOTYPES ADAPTIVE?

Test by doing transplant experiment:

put both phenotypes in both environments, see which ones do better


Adap

tive plasticity

If the two environments are experienced frequently enough under natural conditions then more plastic genotypes do better on average than less plastic ones


27/Jan/2014

39

Isn’t being plastic ALWAYS better then?

…consider costs!

Costs of plasticity

Maintenance – energetic cost of sensory and regulatory mechanisms

Production – excess cost of producing structure plastically

Information acquisition – energy/time cost of sampling

environment, could be used otherwise

Developmental instability – reduced canalization, developmental

imprecision

Genetic costs – deleterious effects of plasticity genes through linkage

with other genes (pleiotropy, epistasis)

27/Jan/2014

40

CASE STUDY

HONEYBEES

Life historyHONEYBEES

27/Jan/2014

41

Ant life cycle

HONEYBEES

Bee life cycleHONEYBEES

27/Jan/2014

42

Bee life cycle

HONEYBEES

worker (female)

Fertilized egg Unfertilized egg

queen(female)

drone(male)

Dr. David TarpyAssociate Professor

Dr. Ming Hua Huangformer Postdoctoral Fellow (Tarpy Lab)

HONEYBEES

27/Jan/2014

43

Queen morphs

HONEYBEES

Life historyHONEYBEES

27/Jan/2014

44

HONEYBEES

Larval stage: on average 5 days

Day 0 Day 1 Day2 Day 3 Day 4 Day 5

METHODS

Transfer to queen chamber

worker larva

DAY(start feeding royal jelly)

RESULTSHONEYBEES

Reproductive quality

low

high

27/Jan/2014

45

HONEYBEES

Reproductive quality

low

high

critical age

DAY(start feeding royal jelly)

RESULTS

Royal jelly (royalactin) & fruit flies

27/Jan/2014

46

GUEST SPEAKER

Dr. Terry Campbell

27/Jan/2014

47

SUMMARY

SUMMARY

1. What was the most important thing you learned during this class?

2. What important question regarding what you learned remains unanswered for you? (What would you like to know about next?)

NAME & DATE 1/27/2014

27/Jan/2014

48

For next week:

The Beak of the Finch: Read Chapter 4

Read paper (will be posted)

Homework 1 due Tuesday, February 4th 5pm (submit electronically)

slides lecture 03(for students) - the ant life · parasitizing egg rejection egg ... drone (male)...

Documents