Mechanisms

"Detailed knowledge of the genetic,

developmental, and physiological

mechanisms that affect life history mechanisms that affect life history

traits is of major importance for

understanding, from first principles,

how life history traits are expressed,

why they vary, and how they evolve."

Fruit flies (and fish)

Parameter r R0

Fecundity coefficient Earlier maturation No effect

Allometric exponent

size on Fecundity

Later maturation Later maturation

Growth coefficient Earlier maturation No effect

Growth speed – size

allometry

Earlier maturation Earlier maturation

Immature mortality Earlier maturation Earlier maturation

Adult mortality Later maturation No effect

Roff 1981

Stage structure is essential to understand these results

Fruit flies only grow as larvae

Demographic parameters evolve

Reaction Norms for Age and Size at Maturity

D. melanogaster

Expected response to variation in crowding

Many simple (without explicit density

expected correlation between adult size and development time

-Many simple (without explicit density dependence) models

Mueller (1988): explicit non-linear population dynamics

larvae change (evolve) threshold for metamorphosis

adjust efficiency of food processing

-

-

+

Reaction Norms for Age and Size at Maturity

variation in crowding - competition for food

Instead response with specific adaptations to crowding and ammonia:

higher pupae against trampling in the medium-> larger size

polymorphism (Borash et al. 1998, 2000):polymorphism (Borash et al. 1998, 2000):

lower feeding rate – late - ammonia toleranthigh feeding rate – early - ammonia sensitive

Use better models for the "environment"

Classical models with simple demography not allowing

individual variation must give biased results

More mechanisms - mappings

Love for Meccano?

Stearns chapter:

"The glass is at least half empty"

"For them life history theory provided a

general motivational structure"

Budgets and Trade-offs

Life history evolution

• Size at Birth

• Growth Pattern

• Age and Size at Maturity

• Number, Size, Sex Ratio of Offspring

Life history Traits

A Heterogeneous Bunch

Morphology Behaviour Demography

+

+

+ +

++• Number, Size, Sex Ratio of Offspring

• Schedules of Reproductive Investment

• Mortality Schedules

• Life Span

• Foraging Efficiency

• (Dispersal)

+

+

+

+

+

+

++

Genetic Variation and Evolution

Trait twoEvolutionarily

Convergence Stable

Traits

Trait one

Genetic Variation

Initial Population

Selection

Response

Selective

advantage

Selective

disadvantage

Evolution of Life History Traits

In each ecological situation,

Simply reproducing more or surviving longer is

always better

LHE is only interesting because of trade-offs and

constraints:

When faced with several options, which ones do

you invest in, and how much do you allocate to each

option?

Onto the boundary of a feasibility set

LH Trait two Fitness often increases

in this direction:

The more of survival

and reproduction, the

better

LH Trait one

Feasibility Set

Rueffler et al. 2004

Options - Fitness contours

Begon et al. 2005

Classification of Environments

Sensitive to growthInSensitive to growth

Begon et al. 2005

Begon et al. 2005

Reproductive value effort

Begon et al. 2005

Trade-offs

Begon et al. 2005

Testing for Trade - Offs (Reznick 1992)

Experimental

Manipulation

Phenotypic

Observation

Manipulation

Artificial Selection

LH Trait one

LH Trait two

Feasibility Set

Testing for trade-offs

Usually seemingly absent when phenotypes are compared within populations

(Reznick 1992)

1) Natural selection works on genetic variation. Trade-offs must have a genetic

component in order to influence evolution.

2) Not every pair of demographic traits is directly coupled by a trade-off. Indirect 2) Not every pair of demographic traits is directly coupled by a trade-off. Indirect

coupling is harder to detect.

3) Favourable conditions can mask trade-offs.

4) A lot of variation in acquisition relative to allocation can mask trade-offs.

Total budget = Reproduction + Survival

T = R + S

T = aT + (1-a)T with R = aT and S = (1-a)T

Allocation and Acquisition

Van Noordwijk and de Jong (1986)

Total Acquisition =

Allocation to Reproduction + Allocation to Survival

T = aT + (1-a)T

SurvivalSurvival

T Increases

a Increases

T Increases

a Increases

Van Noordwijk and de Jong (1986)

Reproduction Reproduction

Little variation in allocation, a lot in

acquisition

A lot of variation in allocation

relative to acquisition

Trade – off hidden Trade – off visible

Evolution of Life History Traits

When ecological conditions change, the pattern of selective

(dis-) advantage can change.

Environmental variation and the effects on genetics and

selection are too little studied in LHE.

One of the reasons is the difficulty of collecting appropriate data

and doing a good analysis of complicated data.

Plasticity

Begon et al. 2005

Van Kleunen 2005

Correlations between Life history Traits

Life History Trait 1

Life History Trait 2

Environmental variable

Traits 1 and 2 depend on the same or

related environmental variables

Traits 1 and 2 are coupled by a trade-off

Selection on one trait always changes the other

Selection changes traits which are environment-dependent,

which has an impact on the environment.

This changes selection

current paradigm

Evolution of plasticity

Related to evolution of robustnessRelated to evolution of robustness

Phylogenetic patterns Novelties

Palmer 2005

Summary

• Feasibility set – trade off curve

• Different constraints appear into view when explicit mechanisms are considered

• Allocation vs. acquisition

• Plasticity is on the rise / robustness

• Cost of plasticity unclear

• Genetic assimilation

Specialization

2011: The panda genome

Phylogenetic patterns Novelties

M. E. Rumpho, J. M. Worful, J. Lee, K. Kannan, M. S. Tyler, D. Bhattacharya,

A. Moustafa, J. R. Manhart (2008). From the Cover: Horizontal gene transfer

of the algal nuclear gene psbO to the photosynthetic sea slug Elysia chlorotica

Proceedings of the National Academy of Sciences, 105 (46), 17867-17871

DOI: 10.1073/pnas.0804968105

Phylogenetic patterns

Are genes leaders or followers

Conversion of mechanisms

Which type of Ecological Polymorphism is this?

Heliconia

bihaiPurple-throated Carib (Eulampis jugularis)Heliconia

caribaea

2000. Science 289:441-443

bihai

Species?

Sexes?

Within-sexes?

Dominance-Recessivity?

Purple-throated Carib (Eulampis jugularis) caribaea

Sexes or Species?

Similar but different selection pressures

Slatkin (1984)

Character displacement can make species or

sexes diverge, and the models look almost the

same

Doebeli and Dieckmann (1999)

The evolution of character displacement can lead

to speciation

Evolutionary Branching → Emergence of Large Effects

1

time

Gene Product x

10

1

Phenotype f

habitat 1 Habitat 2

Van Dooren 1999

Classification of candidate ESS’s

trait value

Directional

Selection

Directional

Selection

CSS, convergence stable, non-invadable

Stabilizing Selection

trait value

Directional

Selection

Disruptive Selection

Directional

Selection

Evolutionary Branching Point

Classification of candidate ESS’s

trait value

Directional

Selection

Directional

Selection

Evolutionary Branching Point

Disruptive Selection

This can eventually lead to

-sympatric species

- reduced migration

- dominance-recessivity

The Evolution of Sexual Dimorphism

trait value

Directional Selection

Stabilizing Selection

Directional Selection

CSS, convergence stable, non-invadable

Clonal

trait value

females

trait value

males

Two Sex

The Evolution of Sexual Dimorphism

trait value

Directional Selection

Disruptive Selection

Directional Selection

Evolutionary Branching Points

Clonal

trait value

females

trait value

males

Two Sex

Dimorphic Sexes or Sympatric Species

trait value

malesSympatric

Clonal Branching Point -> Saddle Point

trait value

females

Sympatric Speciation will usually occur after passing

here

FROM BLOWS, BROOKS & KRAFT.

EVOLUTION 57: 622-630 (2003).

Constraints can arise from

specialization

Phylogenetic patterns

Development + genomic architecture is a machinery trying

to make best use of genetic and environmental variation

When there is lack of information: some gambling can be

requiredrequired

Constraints:

gambling “adaptive coin flipping” is probably not easy

Bifurcating Reaction Norms

et

2.5

1.5

I

Van Dooren, TJM (2001) Proc. R. Soc. Lond B 268:279-287.

time0.5

1800

observationprediction,observation

360

II

life history IIlife history I

540

3/2 cycle1/2 cycle 1 cycle

Bifurcating Reaction Norms

1 3Probability of Bet-Hedgingat Intermediate eobs

0 10

ele

ctio

n

31 Pre

dic

tio

n e

pre

d

Lag between Observation and Selection

2 4

Observation eobs

Pre

dic

tio

n e

pre

d

Str

en

gth

of

Se

2 4

Observation eobs

Summary

• Novelties can allow radiations

• Polymorphisms can appear and disappear while trait architecture

evolves

• Genome + development are an architecture adapting to use

information

• Selection in polymorphisms has more effects on architecture

• Specialization can lead to constraints

• Information is often incomplete

• Randomness (= antirobustness) is difficult – maybe unnecessary

ReferencesBegon et al. 2005 Ecology: From Individuals to Ecosystems, 4th Edition Borash, D.J., A.G. Gibbs, A. Joshi and L.D. Mueller 1998. A genetic polymorphism maintained by natural selection in a temporally varying environment. The American Naturalist 151: 148-156 Borash, D. J., Teotónio, H., M. R. Rose, and L. D. Mueller. 2000. Density-dependent natural selection in Drosophila: correlations between feeding rate, development time, and viability. Journal of Evolutionary Biology 13:181-187 Dieckmann U, Doebeli M On the origin of species by sympatric speciation NATURE 400 (6742): 354-357 JUL 22 1999 Mechanisms of Life History Evolution. The Genetics and Physiology of Life History Traits and Trade-Offs. Edited by Thomas Flatt and Andreas Heyland. Mueller, L.D., 1988. Density-dependent population growth and natural selection in food limited environments: the Drosophila model. The American Naturalist 132: 786-809 Reznick D 1992 Measuring costs of reproduction. Trends Ecol. Evol. 7, 42–45. Reznick D 1992 Measuring costs of reproduction. Trends Ecol. Evol. 7, 42–45. doi:10.1016/0169-5347(92)90150-A.Roff, D.A. 1981. On being the right size. Am. Nat. 118: 405-422.Rueffler C., Van Dooren T.J.M., and Metz J.A.J. (2004). Adaptive walks on changing landscapes: Levins' approach extended. Theoretical Population Biology 65: 165-178.Schwander, T. and Leimar, O. 2011. Genes as leaders and followers in evolution. Trends Ecol. Evol. 26: 143-151, doi:10.1016/j.tree.2010.12.010Slatkin, M. 1984. Ecological causes of sexual dimorphism. Evolution, 38, 622–630. van Kleunen M & Fischer M (2005) Constraints on the evolution of phenotypic plasticity in plants. New Phytologist 166:49-60.van Noordwijk, A.J. & G. de Jong, 1986. Acquisition and allocation of resources: their influence on variation in life history tactics. Am. Nat. 128 : 137 - 142.The molecular origins of evolutionary innovations. Wagner A. Trends Genet. 2011 Oct;27(10):397-410.