ET2 - Spatial Patterns in the distribution of species

Question 1

Why might a species be rare in given habitat? (2)

Answer 1

1) Actual rarity: Species are rare in all habitats.
2) Apparent rarity: Species are common in a few habitats but rare elsewhere.

A species may be rare due to a combination of (1) and (2).

For example, Novotny and Basset (2000) showed that species rare on one species of plant tended to be more common on other plants sampled (Apparent rarity) but that singletons still made up ~45% of individuals indicating overall rareness (actual rarity).

Question 2

What affects species distributions

Answer 2

1) Abiotic factors
2) Symbioses, hosts and food sources
3) Interspecific competition
4) Intraspecific competition
5) Chance

Changing climates can change species distributions by altering these factors.

Question 3

Examples of changing interaction

Answer 3

Brown argus adopts new food plant (geranium)

Increase in warm loving butterflies and birds in Europe (Devictor et al 2000).

Question 4

Global patterns of species diversity

Answer 4

Biodiversity increases towards the equator. Peak diversity is generally just north of the equator.

Question 5

Ultimate reasons for higher tropical diversity

Answer 5

1) Species evolve faster
2) Fewer extinctions
3) Species migrate to tropics from elsewhere

Question 6

Proximate reasons for higher tropical diversity

Answer 6

1) Higher productive energy –> More individuals and species can be supported.
2) Higher mutation and speciation rates due to ambient energy.
3) Less climatic variation –> less dispersal and more speciation. Longer species lives (less extinction).
4) Species beget species.

Question 7

Biodiversity hotspots

Answer 7

Myers et al 2000, 25 hotspots contain 44% of plant species, 35% of vertebrate species and make up 1.4% of Earth’s surface.