EVSC30006 Lecture Notes - Lecture 13: Growling Grass Frog, Metapopulation, Patch Dynamics
1 Jun 2018
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LECTURE 13: POPULATION & METAPOPULATION
ECOLOGY IN CITIES
POPULATION ECOLOGY
• Population Dynamics: changes in populations over time as they fluctuate, overall increasing trend but large variation
• Processes: births, deaths, immigration, emigration
• Applications of Population Ecology:
o Conservation of declining & threatened species
o Control/eradicate invasive species
o Management of harvested species
• Biological introductions of plants & animals increases number of species & distances travelled
• Processes of urbanisation impact vital rates of dispersal – leads to pop/metapop growth/decline
BIDE Model
• N (population expected) = N (current pop) + births – deaths + emigration - immigration
o N = RNt (where R = population growth rate)
• Growth rates are decreasing with human population increase
• Factors influencing growth rates:
o Density Dependence: population growth rate varies with pop size or density
▪ Often negative: R declines as pop density increases: carrying capacity as a diminishing resource
▪ When positive (Allee Effects): R declines as pop density reduces, as species need a certain
density of individuals to reproduce
o Demographic Stochasticity: random variation in reproduction & survival of individuals from year to year (birds
& deaths)
o Environmental Stochasticity: random variations in environmental conditions that affect birth and death rates
of individuals in a population
o Catastrophes: disease, natural disaster – large scale environmental perturbations that lead to dramatic pop
declines
• Fragmented populations experience Allee effects
METAPOPULATIONS
• Group of local breeding populations linked together by dispersal
• Types of Metapopulations:
o Classical Metapopulation: frequent extinction & colonisation to maintain same number of occupied habitats
– patch dynamics
o Source-Sink Metapopulation: some large, highly persistent populations
• Effects of Urbanisation: habitat loss, fragmentation, isolation – consequences on metapopulation dynamics
• Growling Grass Frog: live in waterbodies – creeks, wetlands, ponds
o Changes to habitat loss & quality increase probability of extinction with reduced size of corridors as buffer
zones
Pimela spinescens
• Spiny rice flower – plant
• Critically endangered due to loss of grassland habitat under the EPBC Act
• Fragmented populations
• Loss of habitats, fragmentation & isolation – invasive species effect vital rates of the plant
Document Summary
Population dynamics: changes in populations over time as they fluctuate, overall increasing trend but large variation: conservation of declining & threatened species, control/eradicate invasive species, management of harvested species. Biological introductions of plants & animals increases number of species & distances travelled. Processes of urbanisation impact vital rates of dispersal leads to pop/metapop growth/decline. Bide model: n (population expected) = n (current pop) + births deaths + emigration - immigration, n = rnt (where r = population growth rate, growth rates are decreasing with human population increase. Environmental stochasticity: random variations in environmental conditions that affect birth and death rates of individuals in a population: catastrophes: disease, natural disaster large scale environmental perturbations that lead to dramatic pop declines. Fragmented populations experience allee effects: critically endangered due to loss of grassland habitat under the epbc act. Metapopulations: group of local breeding populations linked together by dispersal.
