Climate and BiomesEvolution and AdaptationPopulation Ecology

Population EcologyI.Attributes of Populations

- Population: A group of potentially interbreeding organisms at the same time and place, that share a common gene pool.

- Population size : number of individuals

- Population Growth Rate: change in number over time, as a function of (birth +immigration)- (death + emigration)

- Population density : number per unit area

- Range/distribution: geographic area over which the individuals are dispersed.

- Population Structure: - age class structure - sex ratio - genetic structure - spatial structure (pattern of how individuals are distributed through

the range)

Population EcologyI.Attributes of PopulationsII.Distributions

A. Determining Factors1. Environmental Tolerance – the Niche Concept

Population EcologyI.Attributes of PopulationsII.Distributions

A. Determining Factors1. Environmental Tolerance

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temperatureperf

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Realized and fundamental nichesZones of optima, tolerance, intolerance

Population EcologyI.Attributes of PopulationsII.Distributions

A. Determining Factors1. Environmental Tolerance2. Barriers to Dispersal

A. Determining Factors1. Environmental Tolerance2. Barriers to Dispersal3. Changes thru Time: Seasonal Migration

A. Determining Factors1. Environmental Tolerance2. Barriers to Dispersal3. Changes thru Time: Seasonal Migration4. Changes thru Time: Climate Change

A. Determining Factors1. Environmental Tolerance2. Barriers to Dispersal3. Changes thru Time: Seasonal Migration4. Changes thru Time: Climate Change

Changes in elevational range

cooler warmer

Craig Moritz,1,2* James L. Patton,1,2 Chris J. Conroy,1 Juan L. Parra,1,2 Gary C. White,3 Steven R. Beissinger1,4. 2008. Impact of a Century of Climate Change on Small-Mammal Communities in Yosemite National Park, USA. Science 322:261-264.

Craig Moritz,1,2* James L. Patton,1,2 Chris J. Conroy,1 Juan L. Parra,1,2 Gary C. White,3 Steven R. Beissinger1,4. 2008. Impact of a Century of Climate Change on Small-Mammal Communities in Yosemite National Park, USA. Science 322:261-264.

A. Determining Factors1. Environmental Tolerance2. Barriers to Dispersal3. Changes thru Time: Seasonal Migration4. Changes thru Time: Climate Change5. Niche Modeling and Invasive Species

Probabilities of three Eucalyptus species being found in an area, mapped by climate and soil type.

Probabilities of three Eucalyptus species being found in an area, mapped by climate and soil type.

Probabilities of three Eucalyptus species being found in an area, mapped by climate and soil type.

Problems:

Doesn’t account for biological aspects of the environment - maybe the native range is limited by competition/predation - separated from that competitor/predator, the range may increase

Water Hyacinth

Neochetina eichhorniae

“Biological Control Agent”

Problems:

Doesn’t account for biological aspects of the environment - maybe the native range is limited by competition/predation - separated from that competitor/predator, the range may increase

Doesn’t account for the possibility of adaptation

A. Determining FactorsB. Dispersion – how organisms in a population are spaced

B. Dispersion

- Regular

Low variance

B. Dispersion

- Regular

- intraspecific competition

- allelopathy

- territoriality

B. Dispersion

- Clumped

- patchy resource

- social effects

- limited dispersal

High variance

B. Dispersion

- Random

- canopy trees, later in succession

Normal distribution

B. Dispersion - Complexities

Varies with type of dispersal

B. Dispersion - Complexities

Varies with life-history stage

B. Dispersion - Complexities

Varies with spatial scale and resource distribution

C. Population Density 1. Correlates with Niche Parameters – greatest at center of range

Density of Dickcissel, a prairie songbird

C. Population Density 2. Habitat Selection

Fretwell – Lucas model of habitat selection (1972)

C. Population Density 3. Maintenance of Marginal Populations

Why don’t these adapt to local conditions?

D. Modeling the Spatial Structure of Populations 1. Metapopulation Model

Subpopulation inhabit separate patches of the same habitat type in a “matrix” of inhospitable habitat..

- immigration causes recolonization of habitats in which population went extinct. So, rates of immigration and local extinction are critical to predicting long-term viability of population.

D. Modeling the Spatial Structure of Populations 2. Source-Sink Model

Subpopulations inhabit patches of different habitat quality, so there are ‘source’ populations with surplus populations that disperse to populations in lower quality patches (‘sinks’).

D. Modeling the Spatial Structure of Populations 3. Landscape Model

Subpopulations inhabit patches of different habitat quality, so there are ‘source’ populations with surplus populations that disperse to populations in lower quality patches (‘sinks’). However, the quality of the patches is ALSO affected by the surrounding matrix… alternative resources, predators, etc. And, the rate of migration between patches is also affected by the matrix between patches… with some areas acting as favorable ‘corridors’

E. Macroecology

“Top-down” approach – what can the large scale patterns in abundance, density, and diversity tell us?

E. Macroecology 1. Some General Patterns - Species with high density in center of range often have large ranges

E. Macroecology 1. Some General Patterns - Species of large organisms have smaller populations

E. Macroecology 1. Some General Patterns - And of course, food limits size/density relationships

E. Macroecology 1. Some General Patterns - energy equivalency rule: pop’s of biologically similar organisms consume the same amount of energy/unit area, but process it in different ways depending on body size….LATER

E. Macroecology2. The shapes of ranges - Abundant species have ranges running E-W; rare species have N-S ranges

So, if a species has an E-W range, it will probably cross many habitats; signifying that the species is an abundant generalist.

E. Macroecology2. The shapes of ranges

So, if a species has an E-W range, it will probably cross many habitats; signifying that the species is an abundant generalist.

If a species has a N-S distribution, it may be a rare specialist limited to one habitat zone.

E. Macroecology2. The shapes of ranges

So, if a species has an E-W range, it will probably cross many habitats; signifying that the species is an abundant generalist.

If a species has a N-S distribution, it may be a rare specialist limited to one habitat zone.

An independent test would be to make predictions about Europe.

E. Macroecology2. The shapes of ranges

An independent test would be to make predictions about Europe.

E. Macroecology2. The shapes of ranges

An independent test would be to make predictions about Europe.

Abundant species run N-S, and rare species run E-W, as predicted by topography and the generalist-specialist argument.

E. Macroecology2. The shapes of ranges