Landscape-level Conservation

Question 1

What is a good population size to ensure long-term persistence of a species?

Answer 1

Minimal Viable Population

Question 2

Define Minimal Viable Population (MPV)

Answer 2

VP for any given species in any given habitat is the smallest isolated population having a 99% chance of remaining extant for 1000 years despite the foreseeable effects of demographic, environmental, and genetic stochasticity*, and natural catastrophes

Question 3

What does a Minimal Viable Population (MVP) do?

Answer 3

• Gives a quantitative estimate of population size needed to insure long-term survival.

-Estimate must plan for both normal and harsh years by assessing potential impact of stochastic events.

Question 4

Define Minimum Dynamic Area (MDA)

Answer 4

Area of suitable habitat necessary for maintaining MVP
- Estimated by studying home-range sizes

Question 5

What are potential consequences of
going below the MVP?

Answer 5

1. Loss of genetic variability
2. Demographic fluctuations
3. Environmental fluctuations and natural catastrophes

Question 6

Define genetic diversity

Answer 6

Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species, it ranges widely from the number of species to differences within species and can be attributed to the span of survival for a species

Question 7

What is polymorphism

Answer 7

forms of the same gene
- the idea that an entity in code such as a variable, function or object can have more than one form

Question 8

Define heterozygosity

Answer 8

The presence of two different alleles at a particular gene locus
- genetic variability!

Question 9

Does the loss of genetic variability occur in small or large populations?

Answer 9

Loss of genetic variability (heterozygosity) occurs faster in smaller populations

Question 10

Why do small populations have a faster loss of genetic variability?

Answer 10

Genetic drift

Question 11

Define genetic drift

Answer 11

allele frequencies within a population change from one generation to the next based on random processes (depending on which individuals survive to maturity, mate, and leave offspring)

Question 12

The math of Genetic Drift notes.

Answer 12

E.g. = rare allele (5% of alleles in gene pool) in population of 1000 vs 10 individuals

1000 individuals X 2 copies per individual X 0.05 allele freq. = 100 copies

10 individuals X 2 copies per individual X 0.05 allele freq. = 1 copy

Question 13

The passing of alleles to future generations depends on what?

Answer 13

reproduction

Question 14

Define Effective Population Size ( Ne)

Answer 14

size of the theoretical population that loses heterozygosity at a rate equal to the rate observed in the real population

= size of the population as estimated by the number of its breeding individuals.

Question 15

What does Define Effective Population Size assume?

Answer 15

• assumes constant number of individuals in population
• assumes equal number of males vs females

Question 16

What does a small (Ne) mean?

Answer 16

• With a small Ne the remaining genetic
  variance decreases in each new
  generation.
• As Ne gets even smaller
  the amount of genetic variance
  decreases more rapidly between
  generations.

Question 17

List factors that can alter the effective populations size and thus, affect the rate of loss of heterozygosity.

Answer 17

A) Unequal Sex Ratio
B) Variation in Reproductive Output
C) Population Fluctuations and Bottlenecks

Question 18

Define or list an example of unequal sex ratio

Answer 18

• Monogamous species (e.g. Scarlet macaws)
• Social systems (e.g. Northern Jacanas)

Question 19

Define or list an example of Variation in Reproductive Output

Answer 19

e.g. Many plants)
- Many individuals produce 1,000,000’s of seeds whereas other individuals will produce 100’s.
- Results in some individuals being disproportionately represented in the next generation

Question 20

Define or list an example of Population Fluctuations and bottlenecks

Answer 20

(e.g. butterflies, amphibians)
-Many species have populations that vary drastically from year to year.
- Ne is then a harmonic mean calculated for a given timeframe
- strongly determined by years that have the smallest populations

Question 21

Define bottleneck

Answer 21

when the population is severely reduced so that rare alleles in the population are lost if no individuals possessing those alleles survive and reproduce.

Question 22

Define or list an example of bottlenecks

Answer 22

(e.g. Ngorongoro lions)
Most damaging when population remains low (<10 individuals) for several generations

Question 23

What are the consequences of reduced variability?

Answer 23

1. inbreeding depression
2. loss of evolutionary flexibility

Question 24

Define inbreeding depression

Answer 24

Offspring receive two identical copies of a defective allele from each of its parents.

Negative effects include higher offspring mortality, fewer offspring, offspring that are weak, sterile, or have low mating success.

Question 25

Define loss of evolutionary flexibility

Answer 25

• The loss of rare alleles or the inability to form unique allele combinations reduces chances of adapting to new/changing environments.
  -Small populations less likely to have genetic variation necessary to adapt to long-term environmental changes, thus are more likely to go extinct.

Question 26

Define demographic fluctuations

Answer 26

Variation in population size due to random variation in reproductive and mortality rates
within a population (or demographic stochasticity)

• Some individuals die young, others old
  -Some individuals don’t reproduce, other reproduce a lot

Question 27

Smaller populations are at greater risk to extinctions due to what?

Answer 27

due to increased probabilities of low/no births, and/or many deaths in one year.

Question 28

Explain environmental fluctuations and natural catastrophes

Answer 28

• Variation in the physical environment (such as rainfall, temperature, cloud immersion
  frequency) can alter food sources, predators, parasites, etc. that can alter birth & death
  rates.
• Natural catastrophes occur at unpredictable intervals and can wipe out a portion or all
  individuals in a population

Question 29

Small populations are more susceptible to what?

Answer 29

1. unequal sex ratios
2. allee effect

Question 30

Define allee effect

Answer 30

occurs when social conditions are not met to continue normal behaviors.