Flashcards in Hutchings, 2015 - thresholds for impaired species recovery Deck (7)
What is are the small population & declining population paradigms concerned with?
- correlates of extinction probability
- dynamics of species at such low numbers that probability of extinction is decreased
- due to demographic/environmental/genetic stochasticity
- causes and consequences of population depletion
What happens to depleted populations?
- continue to decline, stabilise, or increase
- SPP & DPP concern themselves with these
- neither concerned with recovery
What's an allee effect?
- positive correlation between population size or density and the mean individual fitness (often measured as per capita population growth rate)
- mean individual fitness/per capita population growth measured as (r realised)
- strong allee effects when r realised is negative at low abundances, leading to extinction
- weak when remaining positive
What is a component allee effect?
- a positive relation between any component of individual fitness and either numbers
or density of members of the same species (conspecifics)
- requires assumptions that increase in one component of fitness = increase in overall fitness
- focusing attention on one aspect of fitness & finding no association with population size can lead to failure detecting Allee effects from other components of fitness
What is an Allee threshold/Allee effect threshold?
- Allee threshold = population size/density at which r realised becomes negative and population isn't going to recover
- Allee threshold = population size or density below which r realised begins to decline relative to the negatively density-dependent pattern exhibited at larger population sizes
What are temporal thresholds for impaired recovery?
- the longer a population remains depleted, the more likely its environment will change & become unfavourable to it persisting
- prolonged recovery times/increased uncertainty in recovery expected for depleted populations suffering Allee effects
- recovery time/uncertainty of recovery predicted to increase in presence of Allee effects