Con Bio Lec 8: Genetic Diversity

What is the topic of Lecture 8?

Genetic Diversity.

What does the unique makeup of a species determine besides distinguishing it from other populations?

It determines the species' capacity to adapt to changing conditions.

What is conservation biology's first primary genetic goal?

To preserve a significant amount of inheritable genetic variation, particularly in small populations threatened with extinction.

Why does preserving high heritable variation matter?

It helps retain a population's current reproductive fitness and its capacity to adapt to environmental change over the long term.

What is conservation biology's second primary genetic goal?

To prevent the fixation of deleterious alleles.

What can fixation contribute to?

Fixation can contribute to reduced fitness and the accumulation of harmful mutations.

Why is preventing fixation of deleterious alleles important?

It is intended to prevent declines in survivorship and fecundity that often occur in small populations because of reduced genetic diversity.

What does fecundity mean?

Fecundity is the number of young produced.

What are the three categories of conservation-genetics activities?

Genetic management of small populations; resolving taxonomic uncertainties; and using genetic analyses in forensics, especially to enforce conservation laws.

What is the goal of genetic management of small populations?

To maximize genetic diversity and minimize inbreeding.

What is one conservation-genetics activity involving classification?

Resolving taxonomic uncertainties.

What is one conservation-genetics activity involving law enforcement?

Using genetic analyses in forensics, especially in enforcing conservation laws.

What are the three concerns regarding the genetics of small populations?

Genetic bottlenecks, genetic drift, and inbreeding.

What is a genetic bottleneck?

A genetic bottleneck is an event in which a population declines to very low levels with an accompanying loss of genetic diversity.

After a bottleneck, what do the remaining individuals and genes represent?

They represent only a sample of the original source population.

How does sample size affect representation of the source population after a bottleneck?

The smaller the sample, the more likely it is not representative of the source population.

Which alleles are especially likely to be lost after a bottleneck?

Rarer alleles are especially likely to be lost.

What can the loss of genetic variation mean for a population?

It can mean a loss of heterozygosity in the population.

Why can loss of heterozygosity reduce overall fitness?

It exposes a greater proportion of recessive genes in a homozygous condition.

What happens to traits that were previously masked when homozygosity increases?

They become expressed.

What effects can recessive genes have on organisms?

Many recessive genes have deleterious or even lethal effects.

What are lethal genes?

Lethal genes are genes that are recessive and unexpressed in a heterozygous state but always cause the individual's death in a homozygous condition.

What is lethal load?

Lethal load is the proportion of lethal genes in a population.

When is little overall genetic variation lost after a population decline?

Little overall genetic variation is lost if the reduction in population size is temporary.

When is significant genetic variability removed?

It is removed if the population remains small for many generations.

When can rare alleles be lost quickly?

Rare alleles can be lost quickly in small populations that experience a sudden decline.

What is genetic drift?

Genetic drift is random fluctuation in gene frequencies resulting from nonrepresentative combinations of gametes during breeding.

How is the array of genotypes in a population formed?

It is formed by sampling gametes from the previous generation.

How does population size affect the representativeness of a breeding sample?

The smaller the population, the more likely random matings may represent neither the average nor the range of population characteristics.

What is inbreeding?

Inbreeding is the mating of individuals having any degree of genetic relatedness.

What can inbreeding result in?

Inbreeding can result in inbreeding depression.

What is inbreeding depression?

It is a pattern of reduced reproduction and survival that occurs because of inbreeding.

What did an examination of 47 allozyme loci in 55 cheetahs reveal?

It revealed no polymorphic loci.

What are allozymes?

Allozymes are enzyme variants that differ structurally but not functionally from other allozymes coded for by different alleles at the same locus.

What was the average heterozygosity of the cheetahs studied?

The average heterozygosity was 0.0.

What has cheetah genetic uniformity been attributed to?

It has been attributed to past population bottlenecks followed by severe inbreeding.

How do cheetah sperm counts compare with related felid species?

Cheetah sperm counts are ten times lower than those of related felid species.

What percentage of cheetah sperm are morphologically aberrant?

Seventy percent of cheetah sperm are morphologically aberrant.

Where is conservation genetics especially important?

It is especially important for populations on islands, in fragmented habitats, and in zoos.

What is the Mauritius kestrel?

It is a small falcon found only on the island of Mauritius, east of Madagascar.

What factors were associated with the Mauritius kestrel's population decline?

The decline was associated with pesticide use and habitat deforestation.

How low was the Mauritius kestrel population believed to have fallen?

It was believed to have been reduced to a single breeding pair.

How many Mauritius kestrel breeding pairs are there now?

There are now over 200 breeding pairs because of careful protection and habitat restoration.

What comparison was made in the Mauritius kestrel genetics study?

The DNA of living kestrels was compared with the same DNA loci in museum skins from ancestral populations.

What did the Mauritius kestrel genetics study find about ancestral unique alleles?

A number of unique alleles present in ancestral populations no longer occur in living kestrels.

How has heterozygosity changed in the restored Mauritius kestrel population?

The restored population shows a 57% reduction in heterozygosity compared with ancestral populations.

What has happened to Mauritius kestrel populations despite genetic scars and the end of intensive management?

The populations continue to increase.

What reproductive measure continues to rise in Mauritius kestrels?

The average number of fledglings per nest continues to rise.

What does the Mauritius kestrel case suggest about some wild populations?

Some wild populations may be highly resistant to genetic loss.

What hope does the Mauritius kestrel case provide for conservation?

It provides hope that conservation efforts can succeed even after severe reductions in numbers and a loss of genetic diversity.