Population Distribution and Abundance Flashcards
Niche
set of all possible environmental conditions that lets the population sustain itself; population profile
Fundamental niche
potential / full range of environment conditions which a population can exist in
Realized niches
the environmental conditions a species occupies as a result of overlapping/pressure from superior competitors
Exclusion Principle
No two species can occupy the same niche indefinitely
How does climate influence species distribution? [4]
- Food production
- Water supply
- Habitat
- Incidence of parasites pathogens and competitors
Distribution of individuals on small scales [3]
- Random - equal chance of being anywhere; uniform distribution of resources
- Regular - uniformly spaced; individuals avoid one another, resource competition is heavvy
- Clustered/Aggregated - resources are clumped/patchy
Allelopathy
secretion of chemicals to ward off other plants / organisms
Distribution of Barncles along an interidal exposure gradient
- CHTAMALUS STELLATUS
- BALANUS BALANOIDES
Balanus is more vulnerable to dessication, excluding it from the upper intertidal zone, Chthamalus adults appear to be excluded from lower areas by competition
Balanus > Chthamalus in size of fundamental niche
Distribution of Tropical Bee Colonies
Hubbell and Johnson proved that aggressive bee colonies would show regular distribution while non-aggressive species would show random or clumped distributions
Distribution of Desert Shrubs
Desert shrubs are NOT regularly spaced BECAUSE of competition.
Phillips and MacMahon: distribution changes from clumped to regular patterns
Clump: germinate at safe sites; not dispersed from parent areas; asexual reproduction
Clump –> Regular: competition between juveniles
Plant Distributions along moisture gradients:
Dry upper slope - ?
Midslope - ?
Moist valley bottom - ?
Dry upper slope - TABLE MOUNTAIN PINES
Midslope - RED MAPLES
Moist valley bottom - HEMLOCKS
Large Scale Distribution Patterns
- Gradients - noticeable trend in increasing/decreasing population along a direction
- Dispersal - movement of individuals either by jump dispersal or range expansion
Jump dispersal
Dispersal over unfavoured conditions
Range expansion
Dispersal over favoured conditions
Dispersal movements overtime
- Dispersal - movement from place to place
- Vicariance - split from its parent population by a geographical phenomenon
- Extinction
Why are there Llamas in African and South A. but not in North A.?
- Dispersal of common ancestor in NA to SA and Africa during Pangea
- Vicariance of SA and Africa lands
- Extinction of common ancestor in NA
Metapopulations
Group of subpopulations living on patches of habitat connected by an exchange of species e.g. Alpine butterfly and Lesser Kestrels
there is movement of individuals between patches of populations but what happens at one patch does not affect the other
Commoness and Rarity [3] factors
- Geographical range of species
- Habitat tolerance
- Local population size
Rarity I
Extensive range, broad HT, small population
PEREGRINE FALCON
Rarity II
Extensive range, narrow HT, large population
PASSENGER PIGEON
Rarity III
Restricted Range, narrow HT, small population
