Genetics

1. Genetics • The rate of evolutionary change in a population is proportional to the amount of genetic diversity available.

2. Genetic variation has three levels: • heterozygosity- genetic variation within individuals • variation among individuals within a population • variation among populations

3. Results of the loss of genetic diversity: • lower fitness- i.e. lifetime reproductive success relative to other individuals in the population • reduced evolutionary flexibility of populations

4. Causes of declines in genetic diversity: • Founder effect- when a few individuals establish a new population, the genetic composition depends on the founders • Demographic bottlenecks- occurs when a new population experiences a severe, temporary reduction of size • Genetic drift- random change in gene frequencies in small populations. Through chance alone some alleles will not be represented in the next generation.

5. Genetic Diversity: Inbreeding • inbreeding- mating with closely related individuals • results: • increased homozygosity • inbreeding depression- reduced fecundity, offspring size, growth, or survivorship; changes in age of maturation and physical deformities

6. Loss of among-population genetic diversity: • when historically divergent, isolated populations experience unusually high rates of gene flow… • organisms are moved • creation of new corridors

7. Management Concerns • maintenance of viable populations in the short term • maintenance of the ability to adapt • maintenance of the ability for continued “natural” speciation

8. Populations • deme- locally, randomly interbreeding group of individuals • metapopulation- network of populations that have some degree of intermittent or regular gene flow among geographically distinct units. • populations exist along a continuum