Age Structured: Equal time intervals • All surviving individuals progress to the next time step t = 0, 1, 2, 3, 4, 5, 6….x

      Deer or humans.

Stage Structured: Individuals are difficult to age • Demographic characteristics (fecundity, survival) are relatively consistent within discrete ‘stages’.

      Salamanders or frogs.

For humans, age is a meaningful descriptor of an individual • For many wild pops, vital rates (i.e. reproduction & survival) depend on developmental, morphological or behavioral stages • Stage is often more easily identified in field than age

Age-Based (Leslie Matrix): Each individual will move on to the next age class no matter what. This means the fecundity will be present each step.

Stage-Based (Lelfovitch Matrix): Each individual may or may not move on to the next stage each time step. And so each amount that does and does not move on needs to be accounted for. Fecundity will only be accounted for at the adult stage.

• Each element in top row represents fecundity (Fx) for that age group – Combination of mj (maternity) and p j (survival) of newborns.

Fecundity = # young produced that survive to next time step

           Fx = # young produced / # adults of age x  OR  Fx = # daughters produced / # females of age x

Maternity (natality, fertility) – average # offspring born/female that reproduces (litter size, clutch size).

Fecundity – average number of offspring born per individual of a given age (or stage) surviving until the next age – product of maternity & proportion of the cohort that breeds.

 Recruitment ‐ net population production after both births & deaths accounted for. May include only female offspring.

Monogamous – population growth declines with a departure from 1:1 ratio for either sex. Skewed sex ratio means some wont get to breed if its not even.

 Polygamous – effect depends on which sex declines because it is a function of number of breeding aged females. Take deer, one male breeds with many females. Drop in females means less young while drop in males inconsequential.

Males and females have different migration patterns for breeding. Males stay while females travel = more mortality in females. Or males leave soon after breeding while females stay = a sample appears that there are more females. Some can change sex later?

Birds : • clutch size • hatching success • young fledged.

Mammals:  • litter size • juvenile numbers • corpora lutea scars.

Herps: • clutch/egg mass size • hatching success • # of larvae/hatchlings • # of metamorphs.

Average # of female offspring produced by each female during her life.

Equation: R0 =  Σ l fx bfx

The sum of lx (proportion of original cohort that survives to start of age x) times bx (# of female offspring produced by adult females of age x).at each time interval.

The relative number of offspring that remain to be born to individuals of a given age

 # offspring produced by individuals of age x or older / # individuals of age x

Age that produces most offspring (highest reproductive value) is the one that should be saved/culled the most.

Cohort – a group of individuals born at the same time: “year class”. Data followed through time. More difficult.

Standing Crop – a count of all individuals by age class at one point in time. Can be used to determine cohort if recruitment and survival rates constant.

Can be used to determine cohort if recruitment and survival rates constant.

Survivorship is the proportion of the original number of individuals in the cohort that are still alive at the beginning of age x.

Survival rate, which is the probability of surviving from a given age to the next, whereas survivorship is the probability of surviving from birth to a given age.

Calculate survivorship by n(x)/n(0).

Calculate survival rate using S(x) = l(x+1) / l(x).

Type I ‐ humans & other mammals that invest much in their offspring

 Type II – rare, some birds but with more mortality at egg & chick stages

Type III – many insects, marine invertebrates & flowering plants

Average age of reproduction or the average age of the parents of all the offspring produced by a single cohort

Stable age distribution ‐ proportions of individuals in each age group are constant

Stationary age distribution ‐ proportions of individuals in each age group are constant AND constant population size

How many nests survived a breeding season? Used to estimate survival from a cohort of nests when data are missing. – Nests typically not found until after incubation begins – Typically not checked daily. How many nests were initiated & failed before you found them? Exact date of failure?

• A “regional” population made up of two or more “local” populations.

 • Discontinuous in distribution – distributed over spatially disjunct habitat (patches)

• Movement among local populations occurs but is not routine, usually due to intervening unsuitable habitat (matrix)

Linking processes: • Extinction • Colonization • Population turnover

Examples are salamanders in vernal pools and spotted owl habitats.

• Supplementation (“rescue effect”)

• Gene flow

 • Re‐colonization

• Number & geographic configuration of habitat patches

• Similarity of environmental conditions for various patches

• Dispersal patterns

• Interaction between environmental conditions & dispersal patterns

1. Local breeding populations occur in “relatively discrete” habitat patches (spatially structured)

2. No local population is so large that its life expectancy is long relative to the metapopulation

3. Dynamics of local populations are sufficiently asynchronous so simultaneous extinction of all local populations is unlikely

4. Habitat patches are not so isolated that recolonization is prevented

‐ occurs when a local population is saved form extinction by immigration from other local populations (e.g. from sources to sinks)

Only a small proportion of the total population may be located in source habitat (measures of population density can be misleading; need to evaluate demographic characteristics of population)

Adding habitat to a reserve may result in a smaller metapopulation if most of the additional land is sink habitat

Greater correlation and dispersal = greater risk of extinction over time.

Greater proximity (farther they are), the less enviro correlation and more survival against natural disasters. BUT farther means more dispersal which means less survival when dispersal needed.

Should a reserve design emphasize a Single Large habitat patch Or Several Small patches. Depends on what species but over all big, less divided, more circular is always better.

Based on three factors and having one will make it rare.

Geographic Range: • Species near the limits of their geographical ranges or habitat spectra

Population Size: • Species that exist at low population densities wherever they occur

Habitat Specificity: • Species that specialize on certain types of patchily‐ distributed habitats

Locally abundant over a large range in specific habitat, Locally abundant in several habitats but restricted geographically, or Locally abundant in a specific habitat but restricted geographically

Habitat Diversity Hypothesis - Larger islands contain a higher diversity of habitats and therefore support more species.

Passive Sampling Model -  • Islands function as passive targets for immigration that randomly accumulate individuals

 • Large islands would be expected to accumulate more species by chance alone.

Equilibrium Theory -  Once an island is at its equilibrium for a particular taxa group, the rate at which species are lost  =  the rate at which unrepresented species colonize the island

Area Effect:  • Smaller islands support smaller populations • The probability of a species going extinct increases with smaller population sizes  

Distance Effect • The more isolated the island, the less likely colonization will occur. • Thus, distance acts through immigration rates to limit the number of species

• Dispersal is greatly enhanced in the flying taxa over the non‐flying taxa

• Lower metabolic rate of ectotherms allows for higher population densities, thus less vulnerability to extinction than endotherms

• Larger body size + higher metabolic demands also lead to lower densities

They can fly, they may use areas between patches, and have more mobility.

Rates of extinction above natural extinction. Current rate 1000 times faster than natural. 

• Population levels decline due to some deterministic factor (e.g. over‐harvesting)

 • Deterministic stressors are eliminated or reversed (e.g. regulation)

 • However, small populations remain vulnerable

Need to prevent deterministic factors from ever happening and is they do happen, then you need to be vigilant even after stressor relieved due to stochastic vulnerability.

The quantitative branch of viability assessment The application of data and models to estimate likelihoods of a population crossing thresholds of viability within various time spans. Generally combine: • Field studies on important demographic parameters • Simulation modeling of the possible effects of various extinction factors.

Components: Criterion for viability (quasi‐extinction threshold) – Extinction threshold – Quasi‐extinction threshold (e.g. based on Allee effects) – Triggers for management action

• Time frame

 • Probability of reaching a threshold

Applications: • Planning research & data collection

• Assessing vulnerability

• Ranking management options

Not an exact science

Criterion for viability (quasi‐extinction threshold) – Extinction threshold – Quasi‐extinction threshold (e.g. based on Allee effects) – Triggers for management action

• Time frame

 • Probability of reaching a threshold

Birds have highest rate of extinction.

• Small restricted ranges – essentially 1 population

• Isolation ↑vulnerability

–       Predation – Disease – Low reproductive rates

A value judgment by society is needed to determine the time frame to use in conservation planning, and the degree of security sought for the population being conserved.

Polymorphism: Occurrence of more than one allele for a gene within the subject population or subpopulation

Heterozygous: An individual having two different alleles for a particular gene.

Homozygous: An individual having two copies of the same allele for a particular gene

Allelic diversity: Average number of alleles per locus (Location of a gene on a chromosome)

• Within individuals – Fitness

 • Among individuals (within a population) – Fitness of progeny – Adaptive capacity

 • Among populations – Adaptation to local environmental conditions – Adaptive capacity

The random changes in gene frequency, including loss of alleles, that is likely to  occur in small populations because each generation retains just a portion of the gene pool of the previous generation and that sample may not be representative.

The loss in heterozygosity arising from mating of closely related individuals. Increases likelihood of recessive, non-desirable traits to be expressed because allele more common.

• Populations may be locally adapted to different environmental conditions – Offspring of parents from different populations are not well adapted to either location

 • Different populations evolve different coadapted gene complexes – Outbreeding can disrupt these gene complexes and decrease fitness

            A dramatic collapse of population numbers – sudden or gradual environmental change

A bottleneck is a sampling event – taking a relatively small sample of items, i.e. genes from a large population

Can recover after if low population numbers do not persist.

Ne = 50 to conserve genetic diversity during the short term (several generations) and to avoid inbreeding depression

Ne = 500 to avoid serious genetic drift in the long term

Decline due to poaching and habitat loss. Captive breeding in home range is best.