Generosion (alternative notation: gene erosion ) describes the loss of genetic diversity within a wild or domesticated plant or animal population . In addition, the term is used for the decline in biodiversity due to the extinction of plant and animal species.
“Generosion” as a synonym for species decline
The use of the term “generosion” to denote a general, cross-species decline in biodiversity on a global scale or in a specific ecosystem is unsuitable, if not nonsensical, since it is relatively trivial that with a decrease in biodiversity, genetic diversity also decreases.
Above all, however, genetic diversity is of no importance with regard to interspecific (interspecific) relationships, since individuals of different species cannot produce any or at least no reproductive offspring with one another. Therefore, in this case, we should specifically speak of a “decline in biodiversity” or “decline in species diversity” instead of “generosion”. It is true, however, that generosion within a species (i.e. generosion in the strict sense) can ultimately contribute to the extinction of a species (see below).
Generosion in the true sense of the word
The genetic diversity within a species (intraspecific) is of far greater importance, which is why the term “generosion” should only be used in this special context. Generosion in wild plants and animals can have natural causes, but can also result from a more or less direct impact of humans on the affected populations (displacement, hunting). In the case of useful plants and animals, a distinction must be made between generosion within a breeding line through targeted inbreeding , and generosion within a group of useful plants or animals through the displacement of a large variety of local or regional varieties and races by a few supra-regional varieties and races.
If the total population of a species is divided into several individual populations isolated from one another, each comprising only a few individuals, or even if the total population shrinks to only a few individuals, the genetic impoverishment that results from it can be caused by e.g. B. inbreeding depression lead to the complete collapse of the individual sub-populations or the entire remaining population and thus to the extinction of the species. Generosion is thus i. e. S. a mechanism for species extinction.
However, if the species does not die out and the total population recovers, the now larger population is genetically significantly more uniform than the population of almost the same size before the crisis as a result of the generosion that occurred previously. Such a “generosion event” without becoming extinct is called a genetic bottleneck . The recent cheetah ( Acinonyx jubatus ) is a prime example of what is presumably naturally caused erosion in the animal kingdom . Its genetic uniformity is attributed to a “generosion event” at the turn of the Pleistocene to the Holocene . The genetic diversity of the cheetah population, which is already low, and which has been split up into numerous individual populations due to the influence of humans, further worsens the chances of survival of the species, which is currently severely threatened. One species likely to be affected by human erosion is the Iberian lynx ( Lynx pardinus ).
Domesticated plants and animals
The expression " overbreeding ", which is often used in connection with dog breeds , describes, among other things, the negative effects of the generosion in a breeding line brought about by humans through targeted inbreeding.
In the agricultural sciences, the decrease in the diversity of cultivated plants ( landrace agrobiodiversity ) is referred to as generosion. Local (indigenous) varieties that originate from pre-industrial agriculture and are the result of an adaptation to the local natural and anthropogenic conditions have been developed since the introduction of modern agricultural technologies, with the supra-regional distribution of newly bred (or, more recently, genetic engineering ) ), higher-yielding, more robust crops are increasingly displaced. In Europe this concerned and still concerns B. Wheat ( Triticum aestivum , T. durum ), whereby in Italy between 1920 and 1950 about 13% of the local wheat varieties disappeared each year (today the decline is below 1% to 4%) and in Greece the share of local wheat varieties increased over 80% from around 1930 to 10% in the mid-1960s. In the genetic diversity of rice in South and Southeast Asia, however, no significant reduction was found between 1962 and 1995.
The process of generosion in crops is, according to information from non-governmental organizations critical of globalization , such as B. GRAIN , in countries where the industrialization of agriculture is still in its infancy (especially in Asia and Latin America) by seed companies from the industrialized countries, which, supported by UPOV ( Union Internationale pour la Protection des Obtentions Vegetales , German "International Association for the Protection of New Varieties of Plants"), which make small farmers in these countries dependent on themselves with patented seeds and thus bring ever larger areas of food production under their control.
- Species protection , extinction , biodiversity
- Population Biology , Population Genetics , Smallest Viable Population
- ↑ BIOPAT: The importance of biological diversity and "generosion".
- ↑ Rob Bijlsma, Volker Loeschcke: Genetic erosion impedes adaptive responses to stressful environments. Evolutionary Applications. Vol. 5, No. 2, 2012, pp. 117–129, doi : 10.1111 / j.1752-4571.2011.00214.x , PMC 3353342 (free full text)
- ↑ Stephen J. O'Brien, David E. Wildt, David Goldman, Carl R. Merrill, Mitchell Bush: The Cheetah Is Depauperate in Genetic Variation. Science. Vol. 221, 1983, pp. 459-462, doi : 10.1126 / science.221.4609.459
- ↑ K. S. Herring, E. van Marle-Köster, P. Bloomer: Scatology as a potential non-invasive conservation tool for the cheetah ( Acinonyx jubatus ) in South Africa. SA Anim Sci. Vol. 8, No. 1, 2007, pp. 1–5 ( online )
- ↑ M. Casas-Marce, L. Soriano, J.V. López-Bao, J.A. Godoy: Genetics at the verge of extinction: insights from the Iberian lynx. Molecular Ecology. Vol. 22, 2013, pp. 5503–5515, doi : 10.1111 / mec.12498 ( alternative download on Digital.CSIC)
- ↑ Viglaska. Datasheet in the European Wheat Database
- ^ A b Karl Hammer, Gaetano Laghetti: Genetic Erosion - Examples from Italy. Genetic Resources and Crop Evolution. Vol. 52, No. 5, 2005, pp. 629-634, doi : 10.1007 / s10722-005-7902-x
- ^ Brian V. Ford-Lloyd, Darshan Brar, Gurdev S. Khush, Michael T. Jackson, Parminder S. Virk: Genetic erosion over time of rice landrace agrobiodiversity. Plant Genetic Resources. Vol. 7, No. 2, 2009, pp. 163-168, doi : 10.1017 / S1479262108137935
- ↑ GAIA / GRAIN: Ten reasons not to join UPOV. Global Trade and Biodiversity in Conflict. No. 2, May 15, 1998
- What is Genetic Erosion and How Can it Be Managed? Why We Care About Genetics ( USDA Forest Service Genetic Fact Sheet) Volume 11 (PDF, 460 kB), high resolution PDF (2.8 MB)
- Keyword generosion in the glossary of the European wine network Wein-Plus.eu
- Genetic erosion - a global dilemma. on WorldLynx (excerpt from Stephen James O′Brien: Genetic Erosion: A global dilemma. National Geographic, April 1992, p. 136)