Wildlife Population Restoration - Session 3 - Lecture Objectives Flashcards
Explain the concept of Metapopulation. How does it relate specifically to restoring wildlife populations?
- Metapopulations = distinct populations that have some crossover in terms of gene flow, extinction, and repopulation
- First identify formerly occupied locations, then determine the factors responsible for loss of linkage/subpopulation
- Identify: The metapopulation structure and estimate abundance within each subpopulation
Explain the concept of ‘minimal viable population’, including ‘thresholds’, 50-500 rule, and 10-50 generation rule.
- Minimal viable population = smallest possible population size that can sustain itself over time and below extinction is inevitable.
- You need at least 50 breeding individuals for short-term viability
- And 500 individuals for long-term viability
- Populations persist for 10 generations for environmental/demographic viability or
50 generations for enhancing genetic variability
Why is density a misleading indicator of habitat quality?
Density does not provide information on:
Reproduction, survival, dispersal rates etc.
How does varying habitat quality affect metapopulation structure?
- Not all suitable habitats will be occupied at any one time
- Need to monitor/conserve unoccupied habitats for many years
- Need an adequate sample size to avoid concluding ‘absence’
How does the distribution pattern influence the approach to restoration?
- Many species have a bull’s-eye distribution
- Greatest areas of abundance are toward the middle of their ranges and peripheral portions of the range in marginal conditions
- Identifying areas of high demography/high environmental suitability are important for management
- Restorationists should consult expert opinion, use literature to enhance chances of success
How does an understanding of each of the following influence restoration planning: dispersal, migration, and home range?
- Need to know: direction/distance animals disperse from natal areas
- How frequently adults change breeding locations
- How animals establish and use home ranges is essential for ER
- Identifying the area used by the animal helps identify:
- Specific resources needed by an animal during specific periods
- Restorationist need detailed info on what animals use to specify the vegetation and habitat features needed
- Home range naturally varies through time; thus, it requires a temporal context
Why is knowing whether your measured population response is a ‘functional’ or ‘numerical’ response essential?
- A habitat disturbance might elicit one or both kinds of responses (functional or numeric)
- Functional response = behavioural changes
- Numerical response = increase in abundance, survival, reproduction
- Restorationists usually want a numerical response
Explain the source-sink dynamics of populations and their impact on restoration.
- Sources (strong contributors) are populations of stable reproductive individuals,
- Sinks (population drains) are habitats predominated by subdominant individuals and young of the year
- Restoring sink habitats will depend on knowing:
- Why habitat is low quality, and
- Why do immigrants keep going into that area? (ecological trap)
- Removing a stressor may turn an ecological trap into a ‘source site’
Describe how exotic species can impact restoration activities.
- Must assess the potential impact that exotic species will have on desired species
- Exotics can quickly negate efforts to enhance native species following restoration
- Sometimes natives rely on exotics (e.g., southwestern willow flycatcher nesting in invasive salt cedar)
Why would you initiate ‘conservation breeding’? (3 goals)
- To provide demographic and genetic support for wild populations
- To establish sources for founding new populations in the wild,
- To prevent species extinction with no immediate chance of survival in the wild
What are the main concerns about captive breeding and restoring rare populations (3). Include concerns around genetic bottlenecks.
- Captive breeding/translocation are not ideal for recovery of rare populations
- Captive breeding –> expensive
- translocation –> problematic
- Captive breeding can induce additional mortality in an already rare species
- There is potential for genetic bottlenecks
- Captive breeding can lead to a loss of genetic variation through random drift
- Captive breeding is often recommended but there usually aren’t enough resources available
Why is genetic variability in a population good? How does conservation breeding compromise this variability?
- Genetic variation determines the ability of populations to persist through changing environments
- Severe genetic problems (e.g., inbreeding, bottlenecks) can occur as a result of conservation breeding
- Captive breeding selection can eliminate alleles that are maladaptive in the captive situation yet important for survival in the wild
- Random genetic drift can cause the cumulative loss of both adaptive and maladaptive alleles
What is the justification for the 50-500 rule, and how does one ensure genetic variability is maintained in captive breeding programs?
- Recall that 50/500 rule called for >500 individuals for long-term genetic programs
- The rationale for long-term criteria was to allow new mutations to restore heterozygosity and add genetic variance as rapidly as possible as it is lost to random genetic drift
Explain the ‘genetic bottleneck’ and ‘founders effect’.
- Genetic bottleneck is when an event causes a significant reduction in the number of individuals; hence, gene variation as well
- Founders effect is when a few individuals drive the direction of genetic composition in a population
How does metapopulation structure enhance genetic variability?
- Metapopulations, being smaller, more varied populations allow:
- The retention of greater gene diversity and
- Greater allelic diversity than would a single, large population
