Geography 3412 Class Notes

March 7 and 9, 2005

Chap. 5

Lectures by Juan Paritsis

Genetic Diversity in Ecosystem Management

What is genetic diversity?

Provides a mechanism for populations to adapt to their changing environment

The more variation, the better the chance that at least some of the individuals will have an allelic variant that is suited for the new environment, and will produce offspring with the variant that will in turn reproduce and continue the population into subsequent generations.


Why study genetics in Ecosystem Management?



Some useful definitions


Levels of genetic diversity

    1. Within individuals
    2. Among individuals within the same population
    3. Among populations


Within individuals

Every diploid organism has duplicated genetic information (from its mother and father)

It is the same type of information (locus) but the specific forms may differ (alleles)

Among individuals within a population


Different individuals carry different genetic information

The sum of the variation of an interbreeding population is called Gene pool



Among populations






When an organism is referred to as a heterozygote, or being heterozygous for a specific gene, it means that the organism carries two different versions of that gene on the two corresponding chromosomes. Heterozygosity refers to both the state of being a heterozygote, but more commonly in population genetics to the fraction of individuals in a population that are heterozygous for that locus.



Loss of genetic diversity

Two ways of loosing it…

  1. Loss of genetic diversity in small populations
  2. Changes in the natural distribution of genetic diversity among populations (artificial isolation and mixing)


Loss of genetic diversity in small populations





Four factors responsible for genetic diversity loss in small populations:


1.Genetic drift

2.Founder effect

3.Demographic bottleneck



1.Genetic drift

2. Founder effect

"The establishment of a new population by a few original founders which carry only a small fraction of the total genetic variation of the parental population." (Ernst Mayr)





Example: Irish Potato Famine

3. Demographic bottleneck

4. Inbreeding


The other way to loss genetic diversity:

Changes in the natural distribution of genetic diversity among populations

Related with the geographical distribution of the species and therefore with landscape management issues

Artificial isolation

Avoids genetic flux among populations due to barriers such as highways, dams, etc

Artificial mixing

Enhances genetic flux among populations where that flux was not possible due to natural barriers (examples: bridges, tunnels)

Allelic richness


Example: Peppered moth and pollution in Manchester



• Small sized populations are more prone to lose allelic richness

Ecosystem Management and Genetics in Conservation

• Useful in (some examples):

–Endangered small populations

–Captive breeding

–Translocation of individuals

–Determining dispersal patterns