Lecture 15 Flashcards
(19 cards)
What two factors determine the colonization rate (C) in a simple model?
- The proportion of empty patches available for colonization (1 - P)
- The proportion of occupied patches (P) that provide colonists with colonization probability (m)
C=mP(1−P)
What is the equation for change in proportion of occupied patches (P) over time?
dP/dt =mP(1−P)−eP
Where:
- mP(1 - P) = Colonization rate
- eP = Extinction rate
What does the intersection of colonization (C) and extinction (E) curves represent?
The equilibrium proportion of occupied patches where colonization and extinction rates are equal (C = E)
Why is the colonization rate (C) curved, while the extinction rate (E) is linear?
- C is curved because colonization depends on both occupied patches (P) and empty patches (1 - P).
- E is linear because extinction is directly proportional to the number of occupied patches.
What happens if organisms disperse more?
Colonization rate increases, leading to a higher equilibrium P (more occupied patches)
What happens if patch distance increases?
Dispersal decreases, leading to lower colonization and potentially more empty patches
What are the key assumptions of the simple metapopulation model?
- All patches are equal in quality.
- Colonization and extinction rates are the same across patches.
- Each occupied patch contributes equally to dispersal.
- Colonization and extinction occur independently in each patch.
- Colonization rate is proportional to the fraction of occupied patches.
What is a source-sink population?
- Source (r > 0): High-quality habitat where the population grows and produces emigrants.
- Sink (r < 0): Low-quality habitat where the population cannot sustain itself without immigration.
What is the Rescue Effect?
High immigration rates prevent a population from going extinct by ensuring frequent recolonization
What is a Mainland-Island Metapopulation Structure?
A single mainland patch serves as the dominant source of individuals migrating to smaller habitat patches
How do metapopulations change our understanding of population dynamics?
- Spatial structure is key for population persistence.
- Local populations cannot be considered in isolation.
- Metapopulation structure can be as important as traditional factors (e.g., birth/death rates).
How are metapopulation models useful for conservation?
- Help design parks and species protection plans.
- Emphasize corridors & barriers in fragmented landscapes.
- Raise questions about whether corridors can counteract habitat loss.
What key question must be asked when studying metapopulations?
- Is the population a single unit, or part of a larger connected metapopulation?
- How does scale impact our assessment of landscape structure?
4 conditions that define metapopulation
- Suitable habitat is in discrete patches that are
occupied by breeding populations - Even the largest patch has a risk of extinction
- Habitat patches are not too isolated to prevent
recolonization - Population dynamics are not synchronized
Spatial scales?
- Local scale: within a patch
- Regional scale: between patcher (metapopulation)
Colonization
the movement of individuals from
occupied sites to unoccupied sites to form a new local population
Does scale matter when assessing metapopulations and landscape structure?
a
Yes, it is important to pick the right scale when we draw a map of a metapopulation and its landscape
b
Yes, the landscape used (patch size, distance between patches) needs to match the biology of the species studied
c
No, landscape structure stays the same and follow the same theoretical model without being influenced by scale
d
No, the methodology followed stays the same across scales
b
Yes, the landscape used (patch size, distance between patches) needs to match the biology of the species studied
What is P while modelling a metapopulation?
The fraction of patches occupied in a metapopulation (ranges from 0-1)
