Dispersal

Question 1

Whats dispersal?

Answer 1

Process by which species enter a local community from the surrounding area

Question 2

What is alpha, beta and gamma diversity?

Answer 2

Alpha (α) diversity: number of species in a local community; avg. # of species in
local communities

Beta (β) diversity: species turnover among local communities (various formulas); effective # of
 distinct units

Gamma (γ) diversity: number of species across a broad region; regional sp. pool

Question 3

Local vs regional species richness?

Answer 3

Greater regional influence
(dispersal)
Greater local influence
(selection,drift)
-Local species richness increases with regional dispersal rate

Question 4

Explain neutral model with dispersal.

Answer 4

-Fixed # of individuals in local communities
-Lottery model with local drift
100 species in regional pool
-Varying dispersal rates (m)
into 4 local communities

Question 5

Island biogeography

Answer 5

Turn over and species richness intersect

Question 6

Whats turn over rate?

Answer 6

• Number of species reaches equilibrium, but species composition is continually turning over
• Equilibrium rate of immigration of extinction

Question 7

Effect of dispersal- island mainland vs far islands

Answer 7

• Islands close to mainland have higher immigration than far islands
• Leads to higher species richness and turnover

Question 8

How do large islands effect extinction?

Answer 8

• Large islands have lower extinction than small islands

- Leads to higher species richness and lower turnover

Question 9

Species-area relationship

Answer 9

-Area effect produces well known relationship between size of an area (A) and the number of species (S) there

Question 10

Rescue effect and target effect

Answer 10

• Rescue effect: closer islands have lower extinction 
(same idea as for metapopulations)
• Target effect: larger islands have higher immigration