Loss of Genetic Variation May Harm a Population - Assignment Example

Loss of Genetic Variation May Harm a Population Please answer the following questions based on the reading material for Writing Assignment #3. If you cannot find the answer in the article you read, then simply state that in space provided. As always, make sure that your answers are original and in your own words. 1. What is an extinction vortex? The extinction vortex is a pattern used by the specialists in conservation in order to describe and categorize the extinction process that declining populations undergo. The extinction vortex combines basically two causal factors: environmental conditions (pollution, loss of natural habitat) and genetic traits (a series of factors which, over time, will result in making decreasing populations gradually become extinct: genetic drift, inbreeding depression, and increase in genetic load at small populations). The extinction vortex models forecast that demographic and genetic changes combined increase exponential the extinction rate in smaller populations. 2. Both fitness and genetic diversity declined in the Illinois prairie chickens over a 32 year period. After seeing breeding results following bird translocations, the authors conclude that which is more critical to maintaining populations of prairie chickens – sufficient population size or sufficient genetic diversity? Explain the basis of their conclusion (use direct evidence from the reported data as much as possible, give specific examples from the tables and figures). The genetic material variation of the prairie chickens population is vital, according to the authors, in maintaining both fitness and capacity of this population to constantly adapt to environmental transformations. The Illinois prairies, the natural environment of the greater prairie chickens populations, covered in the first decades of the 19’s century more than 60% of the state’s landscape. In the mid-19th century, the prairie chickens populations were estimated to several million exemplars statewide. By 1962 it was reported that a slender number of 179 groups of prairie chickens were localized spread on a territory of 1500 km2. This alarming decline in number of the prairie chickens populations was documented in southeastern Illinois in a study undertaken by the authors of the article in discussion that covers a period of 35 years. According to the mentioned study, the egg success rate of the Illinois populations of greater prairie chickens, isolated in groups of exemplars because of the gradually loss of grassland, declined rapidly after 1980 (as a comparison, during the 1930s this rate was establish at 93%), when 70% of all successful nests contained at least one unhatched egg. Along with this decline in number of individuals, consisting with progressive loss in habitat for nesting (with a rate of egg success of 93% in 1937 but going on a downward spiral and hitting 50% in 1980) and isolation, the remaining populations of prairie chickens show a concerning reduced genetic variability, considered by geneticists the survival and evolution engine of any species. 3. State why loss of genetic variation may harm a population and why chance events harm small populations more than large populations. (You can base this answer on what you have learned in the course in addition to what you read in the paper). The conservation of genetic variation within species is a necessary element in preserving the biological diversity of the living world, a tool that ensures the preservation of the evolutionary pattern of any species. The genetic dynamics depend on a series of ecological factors: population size, irreversible destruction of the natural ecosystems, water and air pollution etcetera. A smaller a population becomes due to alterations in its natural environment the more vulnerable it gets. Also, as a population becomes smaller it becomes more dependent on the surrounding environment. The distribution of the genetic variation amongst individuals belonging to small populations decreases due to poor reproductive performances, threatening the capacity of the entire species to adapt to a constantly changing environment. Therefore, conservationist efforts focus on enhancing genetic diversity, directly applying the principles of science in order to increase the number of individuals of a population. The authors of the article in discussion themselves point out the necessity of a biodiversity conservation strategy in order to enhance the genetic variation of the populations of greater prairie chickens. Unless a significant amount of natural habitat will become available soon, periodic translocations of the prairie chickens populations become imperative in order to maintain the focal population viable. 4. What, according to the authors, is the single most important factor leading to decline in populations of greater prairie chickens? The focal population may have been condemned to extinction by the demographic changes that occurred in the 1970s in the prairies of Illinois. The smaller prairie chickens populations that orbited as a satellite around the focal population of greater prairie chickens disappeared in the 1980s. That turning point drove the population into isolation and the probability of local extinction grew exponential. The authors think that the loss of the other prairie chickens populations which surrounded the focal population, along with the disappearing of the grassland for nesting and nurturing led the greater prairie chicken to decline in populations. 5. Was there a direct relationship between number of males and number of eggs hatched in this study? (Use direct evidence from the reported data as much as possible, give specific examples from the figures and tables). By interpreting Fig. 2, it can be deduced that the number of hatched eggs per total eggs in incubated clutches for the period 1963-1997 was directly proportional to the number of greater prairie chicken males. According to these statistics, nests from 1993, 1994 and 1997 presented an important increase in the rate of fertility compared to the period 1982-1991. The mean fertility rate for 278 clutches was establish at 93%, maintaining itself at 90% through 1980, but vertiginously declining in the following 12 years with a low of 74% in 1990. The overall egg success rate in the focal population during the 1930s was 93%. In the 1960s, the success rate of hatched eggs varied from 91% to 100%. Despite this percentage, by 1981 were established success rates of hatched eggs lower than 80%. This downward direction achieve climax in 1990, when the success rate of eggs was recorded at an extremely low 38%. Regarding the size of the focal male population in Jasper County, Illinois, the number of greater prairie chicken males oscillated between 84 (in 1963) and 40 (in the 1960s), increasing significantly to a number of 206 males in 1972. Between 1963 and 1994 the local availability of natural habitat for the greater prairie chickens populations increased continuously also. Still, the near extermination of the individuals of the focal group already emerged on the horizon until 1997. Therefore, a conservation strategy (for instance, a periodic translocations of the population is a solution presented by the authors of this article) needs to be implemented in order to prevent total extinction of the greater prairie chickens. Read More