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 ...
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!!