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Hope for Lynx

September 17, 2011
Picture by Programa de Conservación Ex-Situ del Lince Ibérico (Wikipedia) – Iberian Lynx

 

The Lynx, named for its bright, reflective eyes, belongs to the magnificent wildcat family. The Iberian Lynx is found exclusively in isolated pockets of the Iberian peninsula, mainly in Spain. With less than 300 individuals remaining, it is one of the most critically endangered species on earth. Its population has reduced dramatically in the last century, attributed mainly to the decline of its main prey species, the European rabbit, and the loss of its habitat due to human activities.

Current individuals of the Iberian Lynx are unusually similar at the genetic level, with extremely low variation in DNA. DNA is a macromolecule containing a long sequence built out of four basic units – A,G,T,C – and is present in every cell of an organism. It is akin to a software that ‘codes’ the structure and functioning of the entire organism. The DNA sequence of individuals within a species is very similar, but there are notable differences leading to slightly different traits. Most of the DNA resides in a region of the cell called the nucleus, but some of it is also found in the mitochondria, the powerhouse of the cell. Mitochondria break down food to a form which can be used by the cell for energy.

The mitochondrial DNA (mtDNA) has a ‘control region’ which shows the most variation among individuals of a species. However, the current population of Iberian Lynx shows almost no variability in the mtDNA control region sequence. This lack of genetic diversity is generally feared to be detrimental to the future survival of the species, putatively resulting in inbreeding and reduced adaptability to the changing environment. Low genetic diversity is usually attributed to a ‘population bottleneck’ i.e. a period in history where the population was reduced to only a few individuals because of climatic or other environmental conditions.

Such a ‘population bottleneck’ for the Iberian Lynx could have occured about 10,000 years ago, at the end of the last glacial period. Or it could have just occured in the last century, when the population has fallen dramatically. A team of researchers from Spain, Denmark, UK and Sweden have now analyzed bone and teeth samples of 19 different Iberian Lynx individuals, collected from different areas in Spain and spanning a time from 50,000 years ago to the last century. The samples were powdered and dissolved in solution, from which DNA was extracted and its concentration amplified through biochemical reactions.

The scientists compared a region of length 183 units in the mtDNA, and found no variation among the 19 individuals. The sequence is also the same as that found in the contemporary population. The genetic variation within a species is determined by the mutation rate of DNA and the population size. The same variation can be attained with a small mutation rate and a large population size, or a higher mutation rate and a small population size. Mutations in the DNA generally occur at a constant rate, which is known as the ‘molecular clock’. For wildcat species like the Lynx, the DNA is estimated to change at a rate of 5-25% per million years.

The authors combined their data with that of 26 other Iberian Lynx taken previously and performed extensive computer simulations to estimate the evolution of population size over the last 50,000 years. They conclude that there is a very high probability that the population of the Iberian Lynx has remained relatively low throughout the past 50,000 years, comprising of less than 8000 females at any given time. Thus it seems that a lack of genetic diversity may not be such a great threat to the survival of this great cat, and such fears should not dilute conservation efforts.

 

RODRÍGUEZ, R., RAMÍREZ, O., VALDIOSERA, C., GARCÍA, N., ALDA, F., MADURELL-MALAPEIRA, J., MARMI, J., DOADRIO, I., WILLERSLEV, E., GÖTHERSTRÖM, A., ARSUAGA, J., THOMAS, M., LALUEZA-FOX, C., & DALÉN, L. (2011). 50,000 years of genetic uniformity in the critically endangered Iberian lynx Molecular Ecology, 20 (18), 3785-3795 DOI: 10.1111/j.1365-294X.2011.05231.x

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