Sinopsis
Extinction is a fact. Ever since organic life fi rst evolved on this planet, life forms have been changing. New species have arisen and old ones have gone extinct (Raup 1992). Speciation, the birth of new species, and extinction, the death of species, are as natural events in evolution as birth and death of individuals in demography. Seen over the entire history of organic life on Earth, biodiversity has generally increased. There has been a build up of life forms. However, five times in the evolutionary past of the planet have mass extinction events taken place. The so-called big fi ve are periods when the rate of extinction of species has become vastly elevated and have outnumbered the level of new species forming (Raup 1994). It is now established that some of the elevated levels of mass extinction coincide with major celestial impacts on the Earth’s surface and their climatic consequences, although some workers advocate more complex scenarios that include a number of factors that may explain mass extinction (Erwin 2006). Today we are witnessing a sixth major mass extinction event and this time celestial impact has nothing to do with it. It is beyond doubt that this event is caused by the activities of one of the species inhabiting the Earth: modern humans. I can think of no other scientifi c activity more important than trying to understand the causes and consequences of this contemporary mass extinction. This book is therefore concerned with a proposition put forward some years ago that extinction of species is somehow related to loss of genetic variation.
It has been suggested that genetic variation is crucial for the persistence of populations (Soulé 1980, 1986, 1987, Frankel and Soulé 1981, Gilpin and Soulé 1986). Two reasons have been given. In the short term, inbreeding and genetic drift leads to lower fi tness of individuals and increased extinction risk of populations. In the long term, populations that lose genetic variation cannot evolve since evolution cannot proceed without genetic variation. In a world of rapid environmental change, any population that is unable to adapt to changing conditions will go extinct (Spielman et al. 2004).
Content
- The extinction vortex, is genetic variation related to extinction?
- How to measure genetic variation
- Inbreeding, geographic subdivision, and gene flow
- Genetic diversity in changing environments
- Genes under selection: Mhc and others
- Local adaptation
- Ecological genomics
- An evolutionary conservation biology
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