Hutchings, 2015 - thresholds for impaired species recovery Flashcards Preview

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Flashcards in Hutchings, 2015 - thresholds for impaired species recovery Deck (7)
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1

What is are the small population & declining population paradigms concerned with?

SPP:
- correlates of extinction probability
- dynamics of species at such low numbers that probability of extinction is decreased
- due to demographic/environmental/genetic stochasticity

DPP:
- causes and consequences of population depletion

2

What happens to depleted populations?

- continue to decline, stabilise, or increase
- SPP & DPP concern themselves with these
- neither concerned with recovery

3

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

4

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

5

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



6

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

7

What's the recovering population paradigm?

- ultimate goal of conservation = recovery
- rather than extinction focused SPP & DPP

- effort needed to identify thresholds of abundance below which recovery is impaired
- estimating red flags for impaired recovery
- theoretical & empirical template for research on determinants, rate & probability of recovery
- might be expected to differ among broad taxonomic groups