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Flashcards in Dispersal Deck (10):

Whats dispersal?

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


What is alpha, beta and gamma diversity?

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


Local vs regional species richness?

Greater regional influence
Greater local influence
-Local species richness increases with regional dispersal rate


Explain neutral model with dispersal.

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


Island biogeography

Turn over and species richness intersect


Whats turn over rate?

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


Effect of dispersal- island mainland vs far islands

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


How do large islands effect extinction?

-Large islands have lower extinction than small islands
-Leads to higher species richness and lower turnover


Species-area relationship

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


Rescue effect and target effect

-Rescue effect: closer islands have lower extinction 
(same idea as for metapopulations)

-Target effect: larger islands have higher immigration