lecture 15 Flashcards
how do we think about populations in a fragmented habitat/landscape?
- disconnected
- what might have been one large population can be split up in many smaller isolated populations
what are the 4 conditions that define metapopulations?
- suitable habitat is in discrete patches that are occupied by breeding populations
- even the largest patch has a risk of extinction
- habitat patches aren’t too isolated to prevent recolonization
- population dynamics are not synchronized
what are the 2 different spatial scales?
- local scale
- regional scale
what is the local scale?
within a patch
what is the regional scale?
between patches (metapopulation)
how does colonization and extinction play a part in metapopulations?
metapopulations is a balance between the extinction of local populations and recolonization of empty habitat
what is colonization?
the movement of individuals from occupied sites to unoccupied sites to form a new local population
what are the factors affecting colonization?
- ability to move
- reasons to move
what is the ability to move?
- distance between patches
- mobility of individuation
what are the reasons to move?
- resource abundance in current patch
- biotic interactions (competition, predation)
- disturbance
what are the factors affecting extinction?
- disease
- resource availability
- predation
- disturbance
- population size
what does the colonization rate depend on?
- the proportion of empty patches available to be colonized
- the propoertion of occupied patches that are providing colonists with some probability of colonization
what are assumptions of the model?
- all patches are equal in quantity
- rates of extinction and colonization for each patch are the same
- each occupied patch contributes equally to dispersial
- colonization and extinction in each patch occur independently of other patches
- the colonization rate is proportional to the fraction of occupied patches
what is a source-sink population?
dispersial from a source population in high quality habitat may permit sink populations to persist in inferior habitat
when does the population sink?
when r is less than 0
when does the population source?
when r is bigger than 0
what is the rescue effect?
high immigration rates protect a poulation from extinction due to frequent recolonization
what is the mainland - island metapopulation structure?
a single patch (mainland) is the dominant source of individuals migrating to other habitat patches
how do metapopulations change the way we think?
- spatial structure is important in population persistance
- local populations can’t be considered in isolation
- metapopulation structure may be as important as traditional population regulation factors in accounting for species persistence on the landscape
- useful for park design, developing plans for protecting sing-species populations
- focus our attention on population dynamics in small-scale, fragmented landscapes and on the importance of corridors and barriers
