TOPIC 9: SPATIAL POPULATION STRUCTURE Flashcards
Population
A group of individuals of the same species living together
Population Ecology
How the processes of birth, death, migration influence the abundance & distribution patterns
of groups of organisms
How is pop. structure characterized?
- Spatial Structure
- Age/Size Structure
- Genetic Structure
Spatial Structure
how individuals organize themselves in space
* geographic distribution/range
* patterns of dispersal
* patterns of dispersion
* population size (# of indiv. that make up pop within that range)
Age/Size Structure –
– number of individuals in each age/size class
* demographic rates (b, d, migration) of individuals change throughout their
lifetime
Genetic Structure
genetic composition of all individuals combined within the population
- more diff alleles more structure genetic structure will be
- Geographical distribution/range
= geographical area in which a species occurs
* where they can be found on earth
what is Geographical distribution determined by?
determined by presence of suitable environmental conditions & resources
- Habitat patch
area of homogeneous environmental conditions
* contains suitable conditions and resources needed to sustain a population
*indiv can group themselves within habitat patches moving between patches= dispersal
(subpopulation)
- Habitat patches can be heterogeneously distributed over the range, separated by
unsuitable habitat
results in many local populations of a species within a range
(subpopulation) - when talking abt pop. we talk abt subpop
- when looking at genetic structure we need to consider all subpop. together b/c they could be interbreeding
- Devil’s Hole Pupfish
- Exists in a single desert pool in Death Valley, Nevada
- 7 x 3 m and 15 m deep
- only exist within this pool so range is very small
Describe the distribution of Coyotes, Norway Rats, E. Coli and Whales
- Coyotes over most of North America
- Rats and E. Coli spread with human movements; range is enormous
- Whales are very large migratory species with a lot of “ground” to cover
What is range based on?
- Based on historical and recent human observation; DOESNt mean species doesn’t exist if we’ve never seen it (could exist out of its range) or if we saw it there once doesn’t mean it will still exist there due to changes in envri. conditions like habitat destruction
- Range limitations are a malleable construct as environmental conditions shift
- Just because ideal conditions exist does not mean you will find a species there
- Must account for the colonization abilities of ancestral species; need to consider whether or not ancestral pop. were able to migrate to those areas
- Why are there no polar bears in Antarctica?
What causes most population to be divided into subpopulations ?
environmental heterogeneity; conditions are diff in diff areas across diff scales
Each subpopulation exists in a suitable habitat and is separated from other
subpopulations by unsuitable habitat
- Metapopulations
are the collective of all subpopulations
* Ecology typically occurs at the level of the subpopulation rather than the entire
population over its entire geographic range
dispersal
Movement of individuals in space
= movement of individuals away from place of birth or areas of high population
density
indiv will be born in a habitat patch and then move to a diff patch
At some stage in their life or life cycle most organisms are mobile
Movements of individuals directly influences…
their local density
* affects evolution within subpop.
Movement of individuals among the subpopulations is key to the dynamics of
metapopulations
How do animals disperse?
With animals dispersal is active but many use passive means like wind and water
- Wind carries the young of spiders and moths
- Larval forms of many invertebrates are carried downstream by currents
How do plants disperse?
Plants tend to move at the level of seed
* Dispersal of seeds involves gravity, wind, water and animals
- Plants that have adaptations designed for increased dispersal
- Release of fluid pressure allows some plants to physically eject seeds a
considerable distance - Buoyancy allows fruits/seeds to be carried away by water
- Other plants use sugar rewards to attract herbivores
- Incentive to consume the fruit and transport seeds to another location
- Seeds pass unharmed though the digestive tract
- Fruits and seeds armed with hooks and spines to catch on the fur on animal; use animal dispersal for own dispersal
Emigration
movement of individuals out of a population
Emigration
movement of individuals out of a population
Immigration –
– movement of individuals into a population
How are emigration and immigration linked?
every emigration= immigration
- when they move out of a pop they also move into a new pop
