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CONSERVATION BIOLOGY - LU 4 1.0 GENETIC CONSERVATION (Major Genetic…
CONSERVATION BIOLOGY -
LU 4 1.0 GENETIC CONSERVATION
WHAT? It deals with genetic factors that affect extinction risks and genetic management regimens to minimize these risks.
Connection between N, Ne and MVP
•The working N for policy issues: 1. N = 50 defines the critical list 2. N = 500 defines the endangered list
•The ratio of effective size to census size Ne/N ratio. Observations from field and laboratory experiments indicate that Ne/N ratios are about 0.25.
•With a Ne/N ratio of 0.25, the census size (N) should be 4 times higher than the simple numbers predicted by "critical“ (N = 50) and "endangered“ (N = 500) estimates.
Major Genetic Issues in Conservation Biology
Fragmentation of populations and reduction in gene flow.
Random processes (genetic drift) overriding natural selection as the main evolutionary process.
Genetic adaptation to captivity and its adverse effects on reintroduction success
Loss of genetic diversity and ability to evolve in response to environmental change
Resolving taxonomic uncertainties
Accumulation of loss (purging) of deleterious mutations
Defining management units within species
Deleterious effects on fitness that sometimes occur as a result of outcrossing (outbreeding depression)
Use of molecular genetic in forensics
The deleterious effects of inbreeding on reproduction and survival (inbreeding depression)
Use of molecular genetic analyses to understand aspects of species biology important to conservation.
Genetic can minimize extinction
. 3. Resolving population structure.
Resolving taxonomic uncertainties
Identifying population concern.
Defining management units within species
Reducing extinction risk by minimizing inbreeding and loss of genetic diversity
Detecting hybridization
Non-intrusive sampling for genetic analysis
Defining sites for reintroduction
Minimum Viable Population (MPV size)
a population size that ensures the persistence of a species for specified period of time.
Model 1
There should be a positive relation between the population carrying capacity, K (population size the local environment can sustain) and the average time to population extinction, t.
Model 2
Extinction times are exponentially distributed so a large proportion of populations will go extinct in a period of time less than the mean time to extinction.
Combination of Model 1 and 2
“The implication from these simulation results is that Larger Populations are Better: It will take longer for a larger population to go extinct, and larger populations will lower the extinction curve.”
If other causes is added with the models
•Environmental variability + models: •MVP should be 500 - 1000.
•Demographic variability + models: •MVP needs to be sustained at higher values (1000 5000).
•Interwoven ecosystem + models: •MVP should probably be higher (i.e more than 1000).
•Inbreeding depression will be likely with an effective population size of Ne < 50: •MVP = 500 will avoid possibility of inbreeding
Single Large or Several Small (SLOSS) System
If the species is subject to demographic fluctuations, it would be better to maintain ONE LARGE SYSTEM. (i.e. the graph plot suggests that extinction is more likely in small populations).
•In systems of species where environmental stochasticity is a general problem, the SEVERAL SMALL approach is probably better: many sub-reserves will reduce the chances of losing the entire system.
Metapopulation System
At some level of migration, metapopulations become 'systems of subpopulations' since in the strict sense the demes of a metapopulation experience little gene flow.
can also contribute to the purging of deleterious recessive alleles.
•One approach is to have semi- isolated subpopulations with corridors for dispersal.
Equal Founder Size (EFS)
retain more genetic variation that populations maintained by random mating.
approaches equalize (balance) the number of founders that contribute to the "captive" population each generation.
Equal Founder Representation (EFR)
studies retain slightly more genetic variation than randomly mating populations.
EFR populations are maintained with a controlled pedigree where the parentage of each contributing female and male is known.
Evolutionarily Significant Units (ESU)
recognized as populations with independent evolutionary histories
Fixed allelic differences or strong phylogenetic support such as multiple synapomorphies distinguishing one population from another are good grounds for the recognition of distinct ESUs.
should be emphasized that mitochondrial DNA markers are maternally inherited and may not reflect the true evolutionary history of the entire populations.
•Hence it is advisable to have additional nuclear markers for ESU recognition such as allozymes, RAPDs or microsatellites.
Management Unit (MU)
defined as populations that have different frequencies of alleles, but do not necessarily show fixed differences between populations.
Genetic Conservation of threatened and endangered species
Assessment of genetic variability to prevent inbreeding depression
Molecular forensics for law enforcement
Recognition of threatened and endangered species