A Brief Introduction to Functional Ecology (Outline) (relating the performance of organisms’ phenotypes to their environments)

- Species have a set of optimal conditions and ecological tolerances that may ultimately define their distribution(average, variability, extremes, predictability)

- Adaptation to the physical environment (Chap 4,5,…6) e.g., desert plants

- Adaptation to varying environments the “Hierarchy of animal responses”

The Fundamental versus the Realized Niche- definitions- e.g., Connell’s barnacle study (1961)

Climate or the physical environment does more than just determine the abundanceor distribution of species – it also shapes organisms (morphologically, physiologically,behaviorally, etc.), and similar environments shape organisms in similar ways Convergent Evolution

Cactus, Oaxaca, Mexico Euphorb tree, east Africa

Morphologically,

Deciduous leaves are broadand thin producing a large surfacearea for maximum light absorption,but this also leads to high loss of H2O.

TRADEOFFS

Instead, desert plants have small leaves and many edges to reduce the total amount of incoming heat and to lose heat at leaf edges via convection

In addition, leaves possess thick, waxy cuticles and dense hair to trap a boundary layer of air which reduces evaporative water loss

Physiologically, different pathways of photosynthesis

CB-cycle requires high [CO2]for efficient photosynthesis open stomata

but opened stomata increase water loss

Solution: spatial separationof gas exchange and carbonassimilation

CAM plants separate the two processes in time

Fixing CO2: spatial temporal segregation segregation neither

Stomata open: infrequently

infrequently and at night often

H2O loss: low very low high

Temp. (C) at maxPhoto Syn efficiency: 30-35 40-45 20-30

Examples: corn, millet, desert most woodymost grasses succulents plants

C4 CAM C3

C3 C4 CAM

Developmentally, in response to unpredictable environments desert plants have evolved seed banks and delayed germination

Unpredictability%

see

ds g

erm

inat

ing

per

year

There are additional convergentcharacteristics of desert plants that have evolved more in response to other organisms (biotic forces) rather than to thephysical environment, e.g., the possession of spines or thorns and toxic substances (oxalic acid, alkaloids, tannins) that reduce herbivory.

A Brief Introduction to Functional Ecology (Outline) (relating the performance of organisms’ phenotypes to their environments)

- Species have a set of optimal conditions and ecological tolerances that may ultimately define their distribution(average, variability, extremes, predictability)

- Adaptation to the physical environment (Chap 4,5,…6) e.g., desert plants

- Adaptation to varying environments the “Hierarchy of animal responses”

The Fundamental versus the Realized Niche- definitions- e.g., Connell’s barnacle study (1961)

Hierarchy of responses

What do you do in response to a hot environment?

Environments are also constantly changing (in space and in time) and that organisms also possess adaptations that help them cope with their changing environment

The cactus wren’s response to heat:

Select cool environments – habitat selection

#1: Behavioral response

#2: Physiological response

#2: Physiological response

In response to heat (or at least sunlight): tan - melanin

#2: Physiological response

In response to heat (or at least sunlight): tan - melanin

Acclimate: red-blood cells at high elevations density of fur in the winterTrees harden before the onset of winter

#2: Physiological response

In response to heat (or at least sunlight): tan - melanin

Acclimate: red-blood cells at high elevations density of fur in the winterTrees harden before the onset of winter

Behavioral and physiological responses are quick, they arereversible, and occur within an individual’s lifetime (often many times).

#3: Developmental response – Tadpoles developing under the risk of predation, i.e., in the presence of a predator, produce a larger mouth and larger tail

w/o pred.

with pred.

Daphnia in the presence of the Chaoborus midge develops crests and spines

Unlike behavioral and physiological responses, developmentalresponses are non-reversible within an individual’s lifetime andmost often seen in organisms with several generations/year.

Every 3rd generation of Monarch butterflies are migratory

Water striders raised in large ponds develop minute wings, those raised in ephemeral ponds develop either minute wings (hatch in spring) or large wings (hatch in summer).

#4: Evolutionary response – when subjected to persistent environments, organisms may adapt to local conditions such that when individuals are grown under identical conditions they retain their differences

Ecotypes or subspecies

e.g., Yarrow (Achillae millefolium)

So in conclusion, what can we say about Abiotic factors, especially climate?

(1) Abiotic factors influence species’ distribution and abundance

But it also –

(2) Shapes organisms: morphology, physiology, and behavior

Darwin’s Postulates:

(1) There is heritable variation

(2) There is a struggle for existence

(3) Variation influences the struggle

and Natural Selection follows ...

(1) There is heritable variation

Heritability in selected human traits:

Handedness 30%Diastolic blood pressure 45%Twinning 50%Systolic blood pressure 55%Body weight 65%Stature and tooth size 85%

Fertility 10-20%IQ 60-80%

(2) There is a struggle for existence

Resources are limitingThere is competition for resources, including mates

(3) Variation influences the struggle

dicots

monocots

vs..

Columbian ground squirrel

min energyconstraint

timeconstraint

Digestiveconstraint

Optimal diet

Dicots consumed

Mon

ocot

s co

nsum

ed

Mixture of monocots and dicots- Monocots limited by handling time- Dicots limited by digestion

Mark Ritchie compare the predicted “optimal” diet and theactual diet for 109 individuals squirrels

Dicots consumed

Mon

ocot

s co

nsum

ed

r2 = 0.94

(a) variation in the ability to forage optimally

Mother’s deviation

Off

spri

ng’s

dev

iati

on

(b) optimal foraging is a heritable trait

Mothers raise offspring

Offspring on their own

(c) There is a struggle for existence

Relative to optimal foragers, deviators have lower surplus energy intake and ....

(c) Variation influences the struggle

... as a consequence, deviators havei) lower somatic growth ii) lower survivaliii) smaller litter sizes

Mark Ritchie’s study beautifully illustrates Darwin's Postulates in action:

Heritable VariationStruggle for ExistenceVariation influences the Struggle

but...falls short of documenting Natural Selection

Evolution by Natural Selection – Guppies on the island of Trinidad

Life history traits

Schooling behavior- dilutes individual risk- greater vigilance- group confusion

Predator-inspection behavior- method to ascertain the identity and intentions of the assailant

lowrisk low

risk

(Magurran et al. 1996)

Male coloration and female choice

Predation risk(cichlids)

Predation risk(prawns)

Low risk

Start of exp

w/predators

w/o

Months

mean # spots

mean size

(Endler 1980)

Correlations vs. experimental testsHaskin’s 1957 transplant experiment

black = % females schooling

10mm

(Magurran et al. 1996)

Transplant experiment results:

Summary:

1) “Natural experiment” – Guppy populations that have experienced different regimes of predation risk show different levels of anti-predator behavior

2) Transplanted (1957) high-risk guppies behave like native low-risk guppies (evolution in 34 years or ~100 generation)

3) Changes in color-patterns that function in mate choice were apparent after

13 months!!