Lecture 14: Climate and other niche axes

Question 1

The 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.

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 (Hutchinson 1957)

Question 3

What are the global gradients?

Answer 3

temperature, rainfall, seasonality

Question 4

Explain temperature as a global gradient

Answer 4

• Temperature mostly a function of latitude
• Higher latitudes colder; seasonality a function of temperature (summer-winter)
• at higher temperature , light strikes the earth’s surface at a lower angle and spread over greater area
• at equator, sun is closer to ti the perpendicular and shines directly on earth’s surface

-Temperature: land changes temperature more readily than water; maritime climates are moderate, continental climates are extreme; oceans provide thermal inertia

Question 5

Explain rainfall as a global gradient

Answer 5

Lower latitudes warmer; seasonality a function of rainfall (dry season-wet season)
* Rainfall mostly depends on atmospheric circulation, offshore ocean currents, rain shadows

Question 6

Explain Hadley cells

Answer 6

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 7

Coriolis effect:

Answer 7

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 8

Explain the general trends of terrestrial vegetation with climatic variables

Answer 8

• 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 9

Orographic precipitation

Answer 9

air forced up mountainsides undergoes cooling, precipitates on upper windward slopes

• Rain shadows created on leeward slopes of mountain ranges

Question 10

Rain shadows

Answer 10

created on leeward slopes of mountain ranges

Question 11

What is ecological niche modelling and what are its uses

Answer 11

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)