Sunday, 1 April 2012

Conservation Genetics: Can Neutral Molecular Markers Really Help Save Endangered Species?


Human impacts, such as over harvesting, land clearing, pest control measures, introduction of exotic species and waste production, have caused many species to become extinct and are continuing to endanger many more (Hedrick, 2002). Due to the major advances in molecular genetics in recent years, a field of study which was previously theory-based has now taken off with the aid of new technology: conservation genetics (Ouborg, 2010). Previous conservation efforts have mainly been focused on ecological methods based on quantitative results (such as phenology), but the use of neutral molecular markers has enabled a closer study in the gene flow of populations and also the genetic drift on variation (Ouborg, 2010). A neutral molecular marker is a type of code which can be used to compare between populations (Ouborg, 2010). The most commonly used marker is a microsatellite; however mitochondrial DNA and AFLP (amplified fragment length polymorphisms) can also be used (Ouborg, 2010). A microsatellite is especially efficient as a marker as its base sequences reoccur from 5-30 times at any locus, making the genome highly repetitive (Oxford, 2008).  Using PCR (polymerase chain reaction) between individuals, the variability of repeats in the genome is determined using gel electrophoresis (Oxford, 2008). As the DNA of an individual is processed through PCR, the results will be given as varying distinctive bands on the developed gel, which can then be used to compare the individual with others in the population (Oxford, 2008).

Putting this method into practice has yielded mixed results. In the investigation of fish populations, polymorphic neutral molecular markers were used to study the allele frequencies in fish populations (Cifci, 2002). From this data, the population and distribution of various species could be estimated and what was thought to be the weaker species could then be protected against further overharvest (Cifci, 2002). However, when the technique was used in the conservation efforts of the Araucaria araucana (monkey puzzle tree in South America), the results showed inconsistency in the markers and therefore were irrelevant to the level and pattern of genetic variation that was estimated (Bekessy, 2003). There was only one trait examined in this investigation, which suggests that in further studies, more than one trait should be involved to produce more accurate data (Bekessy, 2003). The data collected from neutral molecular markers is valuable, but not useful on its own (Kramer, 2009). Pairing the data with results generated from other methods, such as quantitative experiments, would bring together conclusions that would not be able to form separately (Bekessy, 2003). Neutral molecular markers can also be used in conjunction with equations and analysis to develop patterns in the gene flow, which can then be used to make predictions about how the species will be affected in the future (Cifci, 2002).



References

Bekessy A.B; Ennos R.A; Burgman M.A; Newton A.C; Ades P.K (2003) “Neutral DNA markers fail to detect genetic divergence in an ecologically important trait”, Biological Conservation 110 <http://www.sciencedirect.com/science/article/pii/S0006320702002252>

Ciftci, Y; Okumus, I (2002) “Fish Population Genetics and Applications of Molecular Markers to Fisheries and Aquaculture: I- Basic Principles of Fish Population Genetics”, Turkish Journal of Fisheries and Aquatic Sciences 2: 145-155, Central Fisheries Research Institute, Turkey and Japan Internation Cooperation Agency, <www.trjfas.org/pdf/issue_2_2/145_155.pdf>

Hedrick, P.W (2002), “Conservation Genetics: A Review of ‘Introduction to Conservation Genetics’ by R. Frankham, J.D Ballou and D.A Briscoe”, Department of Biology, Arizona State University <www.tree.trends.com>

Hedrick, P.W (2004), “Recent Developments in Conservation Genetics”, Department of Biology, Arizona State University, Forest Ecology and Management 197, pages 3-19, Elsevier <http://www.fws.gov/filedownloads/ftp_verobeach/Habitat%20Conservation%20Planning/2010%20Orig/2/20091019_release_FWS%20to%20CSWFL/20050926_email_Hartt%20to%20Halupa_%20Re_%20panther%20recovery%20-%20more%20q.pdf>

Kramer, A; Havens, K (2009) “Plan conservation genetics in a changing world”, Trends in Plant Science, Vol 14, Issue 11, pages 599-607 <http://www.sciencedirect.com/science/article/pii/S1360138509002040>

Ouborg, N.J; Pertoldi, C; Loeschcke, V; Bijlsma, R.K; Hedrick, P.W (2010) “Conservation genetics in transition to conservation genomics”, Cell Press, Trends in Genetics , Vol 26, No. 4 <http://www.ncbi.nlm.nih.gov/pubmed/20227782>

Oxford Press (2008) “Dictionary of Biology”, Oxford University Press, 6th Edition

Picture References

Ken Fern and Plants For A Future (2010), sourced from <www.pfaf.org>


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