genetics chapter 24:conservation genetics
TRANSCRIPT
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