Lecture 24

Question 1

1. How does reduced genetic diversity affect the fitness of a population?

Answer 1

1. There can be reduced adaptability within the population
2. there can be fixation of deleterious mutation
3. there can be inbreeding depression

Question 2

What is the “extinction vortex”?

Answer 2

extinction cotex is the feedback loop between small population size, loss in genetic diversity and reduced survival/reproductiong

Question 3

Define effective population size.

Answer 3

the minimum size of an idealized populatin that would experience the same drift as the actual population

Question 4

Why might the effective population size be different from the census size?

Answer 4

1. if there is a variation in reproductive success amongst individuals in the population
2. If there are fluctuation in past census populations size

—–> a population that was originally small and had a boom in population size will have genetic variation of a small population

Question 5

What is a population bottleneck? Give examples of events that could cause a bottleneck.

Answer 5

population bottlenecks are when populations experience decrease in population size so very few individual’s are contributing to future generations

some events that could cause a bottle neck would be:

a large scale disease outbreak

a smaller group founding a new population in anisolated location

period of verharvesting

sudden loss of habitat

Question 6

How does a population bottleneck affect genetic diversity?

Answer 6

sudden decrease in poulation can result in genetic drift in which gene/allele frequency
shift or disappear.

Question 7

How do populations regain lost genetic diversity?

Answer 7

bottle necks are the result of a population size crashing and recovering however the because genetic drift will be at play ( as some alleles that were not intiialy in high frequency can fix and others than were in high frequency before the crash can get lost) the genetic diversity will recover at much slower rate than the population size.

causes of bottle necks: founder effect subpopulation foujnd new habitat

large scale disease outbreak

period of overharvesting

sudden loss of habitat

Question 8

Define inbreeding depression.

Answer 8

decreased fitness in inbred propulaiton due to the exposure of delterious mutation as a result of 50% heterozygosity being lost every generation as a result of inbreeding. Heterozygosity typically masks these mutations.

Question 9

What are the genetic causes of inbreeding depression?

Answer 9

Inbreeding increases the freequency of homozygous recessive alleles allowing the phenotype of the mutation to be manifested when their are two hits of the mutated allele.

Question 10

How does habitat fragmentation impact genetic diversity, independent of changes in population size?

Answer 10

habitat fragmentation creates small populations in which genetic drift will be substantial and inbreeding will increase.

Question 11

How do corridors connecting habitats benefit natural populations?

Answer 11

corridors allow for gene flow between these populations so they can function as a whole population again and genetic diversity can increase

Question 12

Define genetic rescue.

Answer 12

is a sudden increase in fitness by introducing new genetic variation into the population

Question 13

Under what conditions is assisted gene flow likely to result in genetic rescue?

Answer 13

in highly inbred populations assisted gene flow can help initiate the introduction of genetic variation otherwise known as genetic rescue.

Question 14

Define outbreeding depression.

Answer 14

fitness declines when two individuals that are not closely related reproduce.

this is typically caused by:

genetic incompatibilities between populations

the combination of the alleles from he to populations is less fit in either environment

or introduction of new deleterious variation:

homozygotes are more common in small populations as they are more likely to be inbred
and deleterious mutations appear more in homozygous recessives so NS can select these individuals out of the population

Question 15

When is outbreeding depression more likely, when populations are closely related or more distantly
related?

Answer 15

distantly related

Question 16

Define purging.

Answer 16

purging is the process of deleterious recessive alleles being lost by being selected out of the population by natural selection as there is a greater frequency of recessive homozygotes in smaller populations due to greater inbreeding. so they can therefore be seen by NS better in small populations

Question 17

Which alleles are most likely to be purged when inbreeding is frequent in a population: weakly deleterious
recessive alleles, weakly deleterious dominant alleles, or strongly deleterious recessive alleles? Explain.

Answer 17

strongly deleterious mutaitons

Question 18

Define genetic swamping. Why is this a problem for conservation biology?

Answer 18

When the newly introduced individuals begin to gave greater fitness than the native populations they can be overexpressed to the point of local genotypes disappearing.

This is an issue for conservation biology as methods to mitigate genetic drift through assisted gen flow may deplete the native population instead of increasing genetic variation.

Question 19

Define evolutionary rescue.

Answer 19

evolutionary rescue is when natural selection allows a population to adapt to the conditions that are causing their decline.

However genetic variation must be vast to begin with and it requires ample time for evolution to occur.

Question 20

In what situations would demographic rescue be most likely to work? In what situations would evolutionary
rescue be most likely to work?

Answer 20

genetic rescue would be more likely to work in an already genetic variable populations that simply have a decrease in population size

evolutionary rescue would more likely to work in rapidly reproducing population such as insects. ( e.g: pests developing resistance to pesticides)

Question 21

Why might evolutionary rescue not work well for saving an endangered large mammal like the panda?

Answer 21

Evolutionary rescue would likely not work for pandas as they do not produce many offspring compared to something like insects. As a result natural selection would likely take thousands of years to go into effect.

Question 22

What information does an admixture plot tell us? How is this useful for identifying where a confiscated animal originates from?

Answer 22

admixture plots allows the genetic information of individuals to be group together into common genomic regions. Individuals that are placed in the same genomic region likely have ancestral commonalities. So if the ancestral orgini of an animal is unknown depending on where it is placed on an admixture plot its ancestral origin can be determined.

Question 23

Define a cryptic species and state why they pose a challenge to conserving biodiversity.

Answer 23

cryptic species are species that a re morpholigcally similar and were once considered the same species however they do not share genetic information.

Because these species are “cryptic” it can be hard to evaluate true biodiversity as they will look like others in the population however they will be gentically distinct.

If the conservation efforts are not tailored to the cryptic species because they are overlook as being different from others in the ppulation they could go extinct.

Question 24

Why should zoos keep pedigrees of their animals? Why might they occasionally introduce new individuals
from wild populations into the captive breeding population?

Answer 24

pedigrees ultimaly track relationships between different animals to track what admixture events leed to inbreeding or introduction of disease. This assure that in zoos no inbreeding happens.

Casually introducing new individuals from wild populations into captive breeding populations could allow the genetic material from deceased individuals to be re-introduced.