BY: PAULA MARIE M. LLIDOBSED – 3 BIOLOGICAL SCIENCES

CONSERVATION

GENETICS

CHAPTER 24

understand the dynamics of genes in populations principally to avoid extinction.

applies genetic methods to the conservation and restoration of biodiversity.

CONSERVATION GENETICS

CLIMATE CHANGE

THREATENED SPECIESGMOs

INCREASING HUMAN

POPULATION SPECIES EXTINCTION

LEVELS OF GENETIC DIVERSITY

• 2

INTERSPECIFIC DIVERSITY

INTRASPECIFIC DIVERSITY

12Diversity from different species present in an

ecosystem (ex. Rainforest with different plant and animal

species)

INTERSPECIFIC DIVERSITY

INTRASPECIFIC DIVERSITY

diversity within same species(ex. Squirrel population) 2

INTRAPOPULATION DIVERSITY

INTERPOPULATION DIVERSITY

Genetic variation occurring within a single

population of same species

Genetic variation occurring between different

population of same species (ex. Squirrel Pop A and B)

INTRAPOPULATION OR

INTERPOPULATION

DIVERSITY?

INTERSPECIFIC OR INTRASPECIFICDIVERSITY?

LOSS OF GENETIC DIVERSITY

• Excessive hunting or harvesting•Habitat loss cause – human activities effect – POPULATION FRAGMENTATION • In domesticated species, abandoning cultivation of local types, which may disappear

HEEELP!!!

IDENTIFYING GENETIC DIVERSITY

(DNA Analysis Techniques)• Short Tandem Repeats (STRs) / microsatellites(ex. 3 remaining population of endangered plants silversword found only in Hawaii)

•PCR-based DNA fingerprinting(ex. Illegal ivory smuggled and elephant droppings)

•mtDNA(ex. Turtle meat (for consumption) is actually an alligator’s meat!)

Population Size Has a Major Impact on Species Survival

•< 100 individuals – extremely sensitive to genetic drift, inbreeding, and reduction of gene flow.• 100,000 individuals – long-term sustainability.• Effective population size – # of individuals in population having the equal probability of contributing gametes to the next generation

Also influenced by FLUCTUATION

• Population bottleneck –

TYPES OF GENETIC DRIFT

Genetic Effects are More Pronounced in Small, Isolated

Populations Small isolated populations, such as

those found in threatened and endangered species or produced by

population fragmentation, are especially vulnerable to genetic

drift, inbreeding, and reduction in gene flow.

GENETIC DRIFT• variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce.• Loss of genetic variation•Random process•Useful alleles for fitness can be lost

1

INBREEDING•mating between closely related individuals•Greater in small population• Increases proportion of homozygotes • Inbreeding Coefficient (F) – measures the probability that two alleles of a given gene are derived from a common ancestral allele.

2Declining population = decreasing heterozygous in each generation

•Self-pollinating plants – high levels of homozygosity and relatively little genetic variation within single populations (except different).

•Outbreeding species - inbreeding results reduced fitness and lower survival rates among offspring.

• Inbreeding Depression – increased homozygosity for deleterious alleles.

•Genetic load (or genetic burden) – # of deleterious alleles present in the gene pool of a population

REDUCTION IN GENE FLOW•Migration– main route for gene flow (exchange of alleles between populations) in animals •Cross-pollination/ seed dispersal – plants

Isolation and population fragmentation in rare and declining species significantly reduce gene flow

3HINDRANCE

S?

GENETIC EROSION THREATENS SPECIES’ SURVIVAL

•Genetic erosion – The loss of previously existing genetic diversity from a population or species.• Two important effects on a population:

2. Reduction in levels of heterozygosity.

1. it can result in the loss of potentially useful alleles from the gene pool, thus

reducing the ability of the population to adapt to changing environmental conditions

and increasing its risk of extinction.

Conservation of Genetic Diversity

Is Essential to Species SurvivalEX SITU CONSERVATION • Captive –breeding programs• Gene banks

IN SITU CONSERVATION• Establishment of parks and reserves

POPULATION AUGMENTATION

EX SITU CONSERVATION• Ex situ (Latin for off-site) conservation involves removing plants or animals from their original habitat to an artificially maintained location such as a zoo or botanic garden.• Ex. Captive Breeding

EX SITU CONSERVATION• Gene banks – preservation for reproductive components, such as sperm, ova, and frozen embryos in the case of animals, and seeds, pollen, and cultured tissue in the case of plants.

• Disadvantage: large collections cannot contain all the genetic variation that is present in a species. • Solution: Core collection – is a subset of individual genotypes, carefully chosen to contain as much as possible of the species’ genetic variation;

EX SITU CONSERVATION

greatest biological diversity in both domesticated and non domesticated species

is frequently found in underdeveloped countries, most ex situ collections

are situated in developed countries that have the resources to establish and maintain them.

IN SITU CONSERVATION

• In situ (Latin for on-site) conservation – preserve the population size and biological diversity of a species while it remains in its original habitat.

POPULATION AUGMENTATION•Population augmentation—boosting the numbers of a declining population by transplanting and releasing individuals of the same species captured or collected from more numerous populations elsewhere.

•Genetic swamping – gene pool of the original population is overwhelmed by different genotypes from the transplanted individuals and loses its identity.•Outbreeding depression – reduced fitness occurs in the progeny of matings between genetically diverse individuals.

POPULATION AUGMENTATION RISKS

Outbreeding depression that occurs in the F2 and later generations is due to the disruption of Coadapted gene complexes—groups of alleles that have evolved to work togetherto produce the best level of fitness in an individual.

POPULATION AUGMENTATION RISK

Conservation genetics uses a combination of ecology, molecular biology, population genetics, mathematical modeling, and

evolutionary taxonomy. It is both a basic and an applied science. A community rather than

individual effort. First, scientists must understand the genetic relationships among the organisms they're studying. Then wildlife

managers use techniques to preserve biological diversity in these species.

SUMMARY