Zoo 360 exam 2 unit 4- Conservation of Genetic Diversity

Explain why maintaining genetic diversity is important to populations of species

Ensures adaptability: Some alleles that are not currently important could be important as the environment changes (emerging diseases, pollution, climate change)

Define heterozygosity in populations and calculate it when provided allele frequencies.

the condition of having two different alleles at a locus

Genetic diversity within a population is high if there are many different alleles - heterozygosity is high

to calculate heterozygosity:

H = number of individuals with 2 different alleles over total number of individuals in a population

Describe the three primary processes that determine genetic diversity

Genetic Drift - random change in allele frequencies in a population from generation to generation due to finite population size

More effective on small populations

relatively weak and little genetic diversity is lost when the number of breeders is 2000

Genetic drift is stronger when population size is 200

Genetic drift is stronger and more genetic diversity is lost when population size is 20

mutation

Mutation - an error in the replication of DNA that causes a change in DNA sequence. Only source of new genetic variation in populations (sex cells only)

Point mutation

Structural modification of a chromosome

Irregular number of homologous chromosomes

produce the genetic variation needed for evolution

If mutation increases reproductive success or is beneficial in some other way it may increase in frequency over time

gene flow

the exchange of genes among populations via the movement of individuals

The movement of individuals and therefore the genes they possess to other populations

Fragmentation of habitat impedes gene flow

Isolation increases inhibition to gene flow

Explain the meaning of Effective Population Size (Ne) and describe what can cause Ne and N to differ.

The number of breeders in a population that contribute genes to subsequent generations

The number of individuals that can contribute their genes to future generations

Ne can be reduced by:

- Population fluctuations

- Unequal sex ratios

- Unequal reproductive success among individuals

One male elephant seal mates with many females

➢ Ne is smaller than the population size

Discuss the causes and consequences of inbreeding depression.

causes:

Inbreeding is the mating of related individuals

Necessarily occurs in small (bottlenecked) populations because most individuals are related

Inbreeding depression is a reduction in the survival or reproductive success that can occur because of inbreeding

All organisms have some recessive alleles that are "deleterious"

consequences:

• Low sperm counts • Abnormally shaped sperm • High infant mortality • Low hatching success • Physical deformities • Compromised immune system

Describe the 50/500 Rule

An Ne of ~50 • needed to minimize loss of genetic diversity (heterozygosity) due to inbreeding in the short term • The increase in homozygote individuals occurs rapidly in populations of

define bottleneck events

an event that drastically reduces the size of a population, and therefore reduces genetic variation

Results in a great loss of genetic diversity

An event when a population is greatly reduced in size, rare alleles are lost.

define fixed alleles

it is the only variant at that gene in a population. It is now homozygous

define locus

Location of a gene on a chromosome

Identify the four "wicked problems" of the Anthropocene

CO2 concentration

damming of rivers

extinctions

land use by humans

Provide a definition for "de-extinction"

the controversial process of creating an organism, which is a member of or resembles an extinct species

Compare shallow de-extinction to deep de-extinction

Shallow de-extinction: Resurrecting recently extinct species from preserved genetic material (from no more than a few decades ago)

Deep de-extinction: Resurrecting a longextinct species using advanced genetic engineering to reassemble degraded "ancient DNA" (from centuries to millennia ago

Discuss the pros and cons of de-extinction.

pros:

It is utterly cool - It is a matter of justice - It could reestablish lost value - It could create new value - It could be a new conservation tool of last resort

cons:

It is "unnatural" and possibly unethical - It could reduce the urgency for conservation - It could cause animal suffering - It could be ecologically problematic - It is hubristic

Explain ways in which de-extinction could potentially contribute to goals of conservation.

BY RESTORING THE INTEGRITY OF ECOLOGICAL COMMUNITIES THAT HAVE LOST KEY SPECIES

Reviving recently extinct species that had specific threats we've now overcome

Reviving recently extinct species that were keystone or highly coevolved members of a community

• Explain ways in which de-extinction could undermine the goals of conservation.

Would the current "extinction crisis" be viewed as less calamitous?

Might extinctions be tacitly condoned because "we can always bring them back" later (a moral hazard)?

DE-EXTINCTION MIGHT CONFLICT WITH EFFORTS TO PREVENT EXTINCTIONS

Reviving long-extinct species that could become invasive or even threaten extant species and communities

Reviving long-extinct species for which current environmental conditions would need to be altered

Reviving extinct species that would remain heavily "conservation-dependent"

Define hybridization

mating between different species or two genetically distinct populations that produces offspring, regardless of fertility of offspring

Explain how hybrid zones are maintained.

Hybrids may be less fit than parental taxa and selected against, but dispersal into the zone maintains a narrow band of F1 's - Hybrids may be more "fit" than parental taxa in habitats that are intermediate to parental taxas' native habitat

Describe how hybrids are detected.

Primarily using morphology until the mid-1960's, but not often not effective

Genetic methods have become increasingly important for identifying hybrid individuals

A simple approach: use a locus where each species has completely different alleles

Compare the opposing perspectives on hybridization (i.e., why some see hybridization as negative while others view it as positive).

The negative view: "Hybridization, with or without introgression, frequently threatens populations in a wide variety of plant and animal taxa because of various human activities

Negative Impacts of Hybridization:

Genetic extinction: fertile hybrids displace one or both parental populations or species through the production of hybrid swarms • Hybrid swarm: populations or species in which all individuals are hybrids to various degrees

Retaining genetic diversity among species increases evolutionary potential

Outbreeding depression: hybrid offspring have lower reproductive success or survival than either parent.

The positive view: "We conclude that when viewed over the long-term of millenia, introgressive hybridization may have contributed importantly to the generation of species diversity in birds"

Hybridization occurs more frequently than previously recognized and is an important source of speciation

Hybrid vigor: offspring of different populations species have high "fitness

Discuss some of the philosophical issues with hybridization in terms of how it relates to conservation and management.

How much do we want to control hybridization in the wild? • Should a threatened species be protected if it's hybridized with a common species? • Is it ethical to remove the "guilty" species or their hybrid offspring? • Should hybrids be allowed to persist if they fill an ecological role? • What constitutes a genetically pure species?

introgression

the incorporation of genes from one population or species to another through hybridization that results in fertile offspring

fertile offspring

offspring that will mature and be able to reproduce

backcross

Cross between an F1 individual and one of the parental (P) genotypes.

fertile offspring that further hybridize with parental populations or species ("backcross"

F1 hybrid

The first generation of offspring produced by breeding from two distinct true-breeding populations. All the offspring have the same combinations of characteristics

F2 hybrid

offspring from the f1 generation

hybrid zone

a geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestry

genetic extinction

fertile hybrids displace one or both parental populations or species through the production of hybrid swarms

hybrid swarms

populations or species in which all individuals are hybrids to various degrees

outbreeding depression

hybrid offspring have lower reproductive success or survival than either parent

hybrid vigor

offspring of different populations species have high "fitness"

Describe why identifying taxonomic units for protection is essential for conserving biodiversity.

Pop might provide certain ecosystem services in that particular area

Conserving morphological and genetic differences among groups of individuals is essential for maintaining adaptability and speciation

Groups of individuals can have unique social or economic values

Conservation resources are limited and sometimes only a subset of groups can be protected

Prioritize groups that are distinct from other groups Groups that are not distinct may be redundant

Genetics can help identify units for conservation

List and define groups that can be protected (i.e., listed) under the Endangered Species Act.

1. Species: Groups that cannot interbreed (Biological Species Concept)

2. Subspecies: Groups below the species level that are "on their way to species-hood"

3. Distinct Population Segments: Groups below the species level that are "discrete" and/or "significant" (specific to the ESA)

Provide definitions for distinct population segments, evolutionary significant units, and management units

Evolutionary Significant Units: Groups below the species level with unique adaptations

Management Units: Groups below the species that will not be "rescued" by other groups (little migration occurs)

distinct population segments

DPS are defined under the ESA based on two criteria:

Discreteness: How different is the population (group) from the rest of the species? Differences in genetics, morphology, physiology, ecology, or behavior • International differences in threats and conservation practices

Significance: How important is the population (group) segment to the species to which it belongs? Occurrence in an unusual "ecological setting" • Differs markedly from other populations of the species in its genetic characteristics • Loss of the DPS would result in a significant gap in the range

Describe the traits of turtles that make them particularly vulnerable to extinction.

Life history vulnerabilities Long lives, high adult survival Low hatchling survival

Poor dispersal abilities

Discuss the primary threats facing turtle populations.

overharvesting

1. consumption

2. pet trade

3. overkill

habitat loss

1. Destruction, degradation, and fragmentation of wetlands • Historic losses greatest in the Midwest and California • Continuing losses in the South

exotic species

nest predators

pollution

disease

Explain how genetic diversity and sex ratios of Blanding's turtles are influenced by climate change and land use change, and identify which threat is stronger to this species.

Places with higher road density had a negative relationship with heterozygocity and a poitive relationship with sex ratios

Nest closer to water → less vulnerable to road mortality

Longer terrestrial nesting migrations → more vulnerable to road mortality

Many blanding's occurrences in NHI database may be male-biased

highly susceptible to climate change

Describe how a subspecies can be defined and how they are designated.

Divergent opinions on how to define subspecies, which vary based on the "philosophy" of taxonomists: ‐Some emphasize complete differentiation at key genes ‐Others emphasize the presence of differences at key genes

Compare "lumpers" and "splitters" in terms of approaches to taxonomy.

lumpers group subspecies together while splitters refer to subspecies

Discuss the controversy of designating the CA Gnatcatcher as a subspecies (e.g., why did some people think it should not be classified as a subspecies while others believed it should)

3 subspecies identified based on morphology • Coloration on breast appears different in northern "coastal" subspecies - but the only trait (of dozens) that had strong differences

• New study found no genetic differences among sampled sites across the CGC range using 9 "neutral" loci • Developers sued US Fish Wildlife Service to remove CGC from the threatened species • Re‐analysis (by different scientists) found that 2, maybe 3 loci were different between the northern and the other two subspecies

If the Fish and Wildlife Service agrees, it would open development on 200,000 acres of coastal land (valued at billions of $)

Perhaps the regional extirpation of CGC