Spatial Ecology & Biogeography

POP AND COM lecture 3

What does biogeography study?

It studies where species live, why regions differ in biodiversity, and how spatial/environmental factors shape diversity.

What is the Wallace Line?

A biogeographic boundary separating Asian and Australian fauna due to deep-water trenches and historical geology.

What is the SAR - species area relationship formula and what does it mean?

S = cA^z, showing species richness increases with area. On log-log scale: logS = logc + zlogA.

What determines the number of species on an island?

A dynamic balance between colonization (arrival) and extinction (loss).

What influences colonization and extinction rates?

Island size and distance from the mainland.

What is a metapopulation?

A group of spatially separated populations connected by dispersal.

What is the metapopulation equation?

df/dt = cf(1-f) - ef

f: Proportion of occupied patches

• c: Colonization rate

• e: Extinction rate

What is the equilibrium proportion of occupied patches?

f* = 1 - e/c

What are occupancy models used for?

Modeling species presence/absence across many patches with identical colonization/extinction rates.

occupancy model assumptions

1. Many patches (local habitats).
   

2. Identical colonization/extinction rates.
   

3. Independence of patch dynamics
   

Only presence/absence is considered.

occupancy model equation

rate of change of occupied patches

dN/dt=cN(1-N/T)-eN

Where:

• N: Occupied patches
  
  

• T: Total patches
  
  

• c: Colonization rate
  
  

e: Extinction rate

What is the equilibrium occupancy equation?

N* = T(1 - e/c)

What effects does dispersal have on populations?

It aids persistence, synchronizes nearby populations, and enables rescue effects.

What is metacommunity theory

It extends metapopulation ideas to communities, including patch dynamics, species sorting, mass effects, and neutral theory.

What does SAR describe?

More area leads to more species; S = cA^z.

What is the island biogeography equilibrium formula?

S = (cSp)/(c + e)

What is the metapopulation dynamic equation?

df/dt = cf(1-f) - ef

difference the between occupancy and meta population equation

number vs proportion

Dispersal affects:

• Persistence

Persistence of populations

Dispersal affects

• Synchrony

populations in nearby patches may fluctuate together.

Rescue effects

empty patches recolonized from nearby ones.

 Metacommunity Theory

Expands metapopulation ideas to entire ecological communities:

 Metacommunity Theory

Patch dynamics

species trade off between competition and colonization

 Metacommunity Theory

Species sorting

1.  environmental filtering dominates.
   
   

 Metacommunity Theory

Mass effects

dispersal alters local dynamics.

 Metacommunity Theory

Neutral theory

species are functionally equivalent.