Climate and other niche axes

Question 1

Ecological Niche

Answer 1

The combination of physiological tolerances
and resource requirements of a species
* More casually, a species’ place in the world –
what climate it prefers, what it eats, etc.
* A concept with a long history in ecology …

Question 2

The Hutchinsonian niche

Answer 2

The niche is “an n-dimensional
hypervolume” in which each
axis is an “ecological factor”
important to the species being
considered

Question 3

Temperature, Rainfall, Seasonality

Answer 3

Temperature mostly a function of latitude
* Higher latitudes colder; seasonality a function
of temperature (summer-winter)
* Lower latitudes warmer; seasonality a
function of rainfall (dry season-wet season)
* Rainfall mostly depends on atmospheric
circulation, offshore ocean currents, rain
shadows
* These factors determine biomes

Question 4

Hadley cells make equatorial regions rainy

Answer 4

Heated air rises.
Air cools as it rises,
5-10 °C/km
As air cools, water
vapour condenses
and falls as rain near
the equator
Air warms again as it
falls
Dry, high-pressure
areas at +/- 30
degrees latitude

Question 5

Coriolis Effect

Answer 5

Objects
(including
hurricanes)
appear to be
deflected
eastwards as they
move away from
the equator and
deflected
westwards as
they move
towards the
equator

Question 6

Coupled cells + Coriolis effect =
prevailing wind patterns

Answer 6

Polar easterlies
Westerlies
Horse Latitudes
Northeast Trade Winds
Doldrums
Southeast Trade Winds
Horse Latitudes
Westerlies (South 30-60, Roaring Forties)
Polar easterlies

Question 7

General trends of terrestrial
vegetation with climatic variables

Answer 7

Vegetation growth (primary productivity)
increases with moisture and temperature
* Vegetation stature also increases…
* …so regions with certain combinations of
moisture and temperature develop predictable,
characteristic types of vegetation = biomes
* Seasonality is secondarily important

Question 8

Biomes

Answer 8

Whittaker’s
Diagram
Latitude mostly determines terrestrial biomes

Question 9

climate patchiness
overlaid on basic latitudinal belts

Answer 9

Temperature: land changes temperature more readily
than water; maritime climates are moderate,
continental climates are extreme; oceans provide
thermal inertia
* Evaporation high from warm bodies of water, low from cold
* Prevailing winds
- cold water = dry air

Question 10

Orographic precipitation

Answer 10

air forced up mountainsides
undergoes cooling, precipitates on upper windward slopes
* Rain shadows created on leeward slopes of mountain ranges
* Seasonality of moisture also important

Question 11

Niche limits versus
geographic range limits

Answer 11

Animals’ geographical ranges often correspond
to biomes, i.e., limited by climate or vegetation
…
* … but sometimes not. Possibilities include:
* Transcend biomes (ecological versatility,
super generalists)
* Not at limits because of recent history (e.g.,
limited dispersal)
* Limited by other organisms (enemies, friends)

Question 12

Ecological niche modelling

Answer 12

Also called species distribution modelling
* Uses data from a species’ present distribution
to predict where a species can live
* Useful for modelling:
* Biological invasions
* How species’ ranges may shift as climate changes
* Spread of vector-borne diseases
* Etc.
* Usually relies on climate data (more rarely on
other niche axes, such as resources)

Question 13

Observed range shifts

Answer 13

In 2003, a study of 1046 species estimated
that species are moving polewards at a rate of
6.1 km per decade (Parmesan & Yohe, Nature)
* In 2011, a study of 1367 species estimated
that species are moving polewards even
faster, at a rate of 16.9 km per decade (Chen
et al., Science)
* Although many factors influence a species’
range, there is considerable evidence that
numerous species are moving polewards to
track recent changes in climate